Effectiveness of catch crops on soil nitrogen retention and subsequent crop growth

Kristian Thorup Kristensen, University of Copenhagen, Denmark

Denmark is an intensively farmed country and is surrounded by shallow coastal waters, sensitive to nitrate pollution. Due to this, nitrogen (N) regulation in agriculture has been earlier and stricter than in most other countries. Catch crops have been an important part of this regulation for the last 30 years, leading to substantial research, testing and experience in catch crops.

This paper deals with research directed into understanding and improving catch crop effects. I will focus on three aspects of catch crop optimisation:

1) catch crop root growth,

2) the catch crop N effect on the succeeding crop through N mineralisation and pre-emptive competition, and

3) the effect of catch crop placement in crop rotations.

The challenge with N is that it leaches down the soil profile, and therefore it is obvious that fast deep rooting will be beneficial. Early sowing promotes deep rooting, but the choice of catch crop species is even more important. Among common catch crops, the rate of root depth penetration by oilseed radish is almost three times higher than that of ryegrass, and such differences have been shown to have a great effect on the ability of catch crops to catch N and reduce nitrate leaching loss.

Much work has gone into understanding N mineralisation from catch crop residues, in order to predict their N effect for succeeding crops. However, mineralisation is only “half the story”. When catch crops take up N, which would otherwise have remained as available N in the soil, catch crop N uptake occurs in a pre-emptive competition with the succeeding crop. The total N effect of a catch crop on the succeeding crop is the combined effect of mineralisation and pre-emptive competition. Especially in retentive environments, with loamy soils and low precipitation surplus, the N effect of catch crops often becomes negative, due to pre-emptive competition.

Placement of catch crops within crop rotations is important, taking into account both what was grown previously and what is to be grown after the catch crop. It is obviously advantageous to grow them where the pre-crop is harvested early, and where it leaves much N in the soil, but this is also a good rotational position, where farmers often prefer to establish e.g. winter wheat. Catch crops lift N in the soil, so more is available in the topsoil and less in the subsoil after growing a catch crop. Due to this effect, catch crops should preferably be grown before shallow rooted crops, as this will optimise their overall effects on N leaching and N supply for succeeding crops.

There will be a written paper accompanying this webinar.

Reduction of nutrient losses from vegetable cropping in water protection zones

Karin Rather, State Horticultural College and Research Institute (LVG), Heidelberg, Germany

This paper describes work to measure N residues from vegetable growing sites in relation to water quality protection legislation.

In Germany the Fertilizer Ordinance (Düngeverordnung, DüV) specifies the standards of good agricultural practice of fertilisation, and implements the EU-Nitrate Directive in national law. These basic rules are strengthened in water protection areas (WPAs) in each of the 16 states of Germany.

In Baden-Württemberg (BW) the establishment of these regulations and the settlement of claims in WPAs is centrally managed by the state government. This was due to the fact that WPAs account for 26% of the state area, with 1,250 independent water supply companies. Thus agriculture and horticultural practice in BW is subject to the centrally organized decree of SchALVO (Schutzgebiets- und Ausgleichsverordnung). The SchALVO fulfils the Water Framework Directive as ‘additional program of measures’. The SchALVO is compulsory in WPAs with 359,500 ha in agricultural use.

The constraints on farmers depend on soil type, distance to water source and the nitrate concentration of groundwater in three classes (I <35-50, II 35-50, III >50 mg NO₃ L^-1). Measures covering vegetable cropping include fertiliser use, fertiliser splitting, crop choice, dates for establishment of catch crops, time windows for tillage, and other factors.

In 2019 a detailed analysis of nitrate-N residues on roughly 150 vegetable growing sites was carried out, and the results presented. Generally the effect of measures according to SchALVO is influenced by site specific characteristics as well as weather conditions. The results of this monitoring program are used to check compliance with the requirements and are a valuable instrument for the extension services to derive recommendations for good practice.

There will be a written paper accompanying this webinar.

Origin Fertilisers is delighted to support the IFS webinar series.
Learning and education are integral in transferring knowledge into best practice on farm.

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Phosphorus (P) availability during the depletion of soil P

Sophie Nawara^a, Fien Amery^b, Hilde Vandendriessche^a,c,  Roel Merckx^d and Erik Smolders^d

^a Soil Service of Belgium, Heverlee, Belgium
^b Institute for Agricultural and Fisheries Research, Plant Sciences Unit – Crop Husbandry and Environment, Merelbeke, Belgium
^c KU Leuven, Department of Biosystems, Division of Crop Biotechnics, KU Leuven, Heverlee, Belgium
^d Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU Leuven, Heverlee, Belgium

As an essential element for crop growth, phosphorus (P) has been added excessively to many agricultural soils during the last decades. This created an imbalance between P input (P fertilisation) and crop P offtake, which caused an accumulation of P in soils in some regions of western and southern Europe. Currently, a more sustainable and stricter P fertiliser use is promoted, which led to negative soil P balances in some European regions (i.e. depletion). It is expected that the availability of P in a soil P depleting scenario is smaller than in a P accumulation scenario, due to the hysteresis of the sorption-desorption processes.

This webinar will focus on determining crop and soil factors affecting the availability of soil P in a soil P depleting scenario, and the identification of a soil test which adequately predicts this P availability in a P depleting scenario. The following will be discussed during the webinar:

• An evaluation of soil P tests in their capacity to quantify the plant-available P. For this, soils from eleven European long-term field trials, with contrasting soil properties and different P application rates, were used. The following established soil P tests were evaluated: extraction with ammonium oxalate, extraction with ammonium lactate, extraction with 0.5 M NaHCO₃ (Olsen), extraction with 0.01 M CaCl₂, and the diffusive gradient in thin film technique.
• The effect of the crop growth rate on the critical available P before P deficiency occurs in a soil P depleting scenario. This was based on eight Flemish soils which were subjected to a P mining experiment in a greenhouse to obtain depleted soils. Different amounts of nitrogen fertilisers were applied, thereby creating different crop growth rates.

The role of the P desorption rate on soil P availability in a soil P depleting scenario. This was determined by modelling, via a mechanistic nutrient uptake model based on classic nutrient uptake models, but extended with P desorption kinetics and including the plant’s P demand rate as an important factor in determining the P uptake by roots.

Integrating new bio-based fertilisers with mineral fertilisers to meet crop and soil nutrient requirements: challenges and opportunities

Patrick Forrestal, Teagasc, Ireland

The use of conventional nitrogen (N), phosphorus (P) and potassium (K) mineral fertilisers along with advances in plant breeding, pest, weed and disease control has underpinned growth in agricultural productivity over the past century. At an EU level a decline in the reliance on conventional mineral fertilisers and a growing focus on bioeconomy opportunities such as the recovery and recycling of nutrients to produce renewable bio-fertilisers is envisaged as part of the Farm to Fork Strategy. The recycling of nutrients from organic sources has been a feature of agriculture for generations particularly where animal and crop agriculture are geographically in close proximity making transport of low nutrient density materials feasible. However, concentration of animal agriculture and human populations in recent decades has led to pronounced regional imbalances in nutrient distribution. Recapture and concentration of these nutrients for transport and integration into fertiliser programmes presents a host of challenges but also opportunities.

At Teagasc, as part of the EU INTEREG funded ReNu2Farm and H2020 funded Nutri2Cycle projects, we are developing the solutions and knowledge needed for successful integration of new bio-based fertilisers along with organic manures and conventional mineral fertiliser in arable and grassland fertiliser programmes. Insights from this on-going work including mineral N and P replacement values of new bio-based fertilisers and their performance in fertiliser programmes will be shared in the forthcoming presentation.

This webinar will be worth 2 BASIS FACTS CPD PN points.

This webinar is supported by the Agricultural Industries Confederation – supporting a sustainable food chain.

Accurate spreading of fertiliser and manure: lessons from UK practice

Ian Richards, Ecopt, UK

Based on training material for the BASIS FACTS Continual Professional Development scheme in the UK, this paper provides practical good practice for accurate spreading of fertiliser, slurry and manure. It discusses the consequences of the two main problems that can occur during spreading fertiliser, namely the wrong rate of application and uneven spreading, and discusses in detail the specific actions needed to minimise these. Data is shown on current spreading practices in the UK. The impact of evolving spreader capability is reviewed, along with the opportunities being provided by emerging digital technologies.

Current UK practices regarding the spreading of organic manures and slurry are outlined, and the requirements for accurate application are compared to these practices. The detailed requirements and good practice for even application are described. The particular requirement to minimise ammonia losses are discussed, and good practice explained. Finally, developing spreader capabilities and technological aids for even spreading are covered.

There will be a written paper accompanying this webinar.

This webinar will be worth 1 BASIS FACTS CPD E point and 1 AP point.

This webinar is supported by Omex

OMEX is a UK-based supplier of solution and suspension fertilisers and is committed to the accurate application of crop nutrients in all forms. More information here.

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Exploring variations in demand for fertilisers derived from recycling in NW Europe

Romke Postma and Imke Harms, Wageningen University and Research

The nutrients N, P and K are often applied to agricultural fields as mineral fertilisers. Currently, fertiliser production in the EU depends on imported raw materials (P, K) and energy (N). Each year about 2,392 Gg of P is imported into the EU-27, mostly in the form of mined rock phosphate or as animal feed. Within the scope of sustainable agriculture and a circular, bio based economy, it is crucial to find ways to reduce quantities of non-recycled nutrients and to decrease the dependency on nutrient imports.

Within north west Europe (NWE), regional differences can be identified with respect to nutrient supply and demand. Hot-spots with a surplus of P in animal manure in the NWE territory are the Netherlands, Flanders in Belgium and Brittany in France. At the same time, there are regions with potential to replace mineral P fertilisers: areas with the highest levels of usage are Northern France, Wallonia in Belgium, Eastern England and Ireland. Within the scope of the NWE Interreg project ReNu2Farm, the opportunities for the replacement of nutrients from traditional mineral fertilisers by recycled nutrients from regions with a nutrient surplus is explored. Recycling-derived fertilisers (RDF’s) could be made from animal manure, food waste, sewage sludge, etc. The objective of this paper is to quantify the requirement of N, P and K in various regions within the NWE territory and to formulate the desired properties of the RDF’s, from an agronomic perspective.

In a desk study we quantified the demand for nutrients and organic matter in regions within NW Europe. This demand is quantified at the basis of the area of crops grown per region, the yield levels, the fertiliser recommendations, the soil types (clay, silt, loam, sand), the soil quality (bioavailability of the nutrients in the soil), the current legislation and the common fertiliser practice.

In addition, the regional availability of nutrients in animal manure and other organic fertilisers is affecting the fertiliser choice and the additional demand for recycled nutrients in each region. For this reason, the current use of animal manure per region is also quantified.

From these two factors, the net potential demand for nutrients in RDF’s is quantified. In broad terms, the regional differences in potential demand for nutrients in RDF’s could be characterised by the main crops, soil types and quality and the availability of animal manure in that region. Regional variations in demand for external inputs of organic matter are also considered.

There will be a written paper accompanying this webinar.

New developments in the production of plant-available phosphorus from abattoir waste

Martin Blackwell and Tegan Darch, North Wyke, Rothamsted Research, UK

Our long-term food security depends on finding a sustainable alternative to the finite and unevenly distributed rock phosphate deposits that are used to make the vast majority of our phosphorus fertilisers, on which global food production relies. More urgently, there is a need to reduce the quantities of phosphate that are released into the environment and which are reported to have exceeded the limits of sustainability. Furthermore, over 2 billion people worldwide are currently affected by micronutrient deficiencies, and crop concentrations of essential minerals are declining. There is unlikely to be a single solution to these issues at a global scale, and so a range of solutions are required.

This paper examines whether a novel, recycled, multi-element fertiliser can contribute towards solving these problems by producing crop yields comparable to conventional rock phosphate derived fertilisers, and have an additional benefit of increasing essential mineral concentrations. This fertiliser is produced from abattoir and recycled industrial by-products, and as part of its novel production process, it increases the quantity of human edible protein recovered from a single animal by around 15%, compared to typical carcass processing.

It was tested against conventional mineral fertilisers in a pot trial with wheat and grass. In soil, yields were comparable between the fertiliser types, but, in a low nutrient substrate, it showed a yield benefit. Elemental concentrations in the plant material typically reflected the relative concentrations in the fertiliser, and plants fertilised by it contained significantly more of some essential elements, such as selenium and zinc. Furthermore, concentrations of the toxic element cadmium were significantly lower in crops fertilised by this new fertiliser. Among the fertilisers, manganese concentrations were greatest in the new recycled fertiliser, but within the fertilised plants, they were greatest under the mineral fertiliser, showing the complexity of assessing whether nutrients will be taken up by crops.

In summary, fertilisers from livestock waste have the potential to improve wheat and grass concentrations of essential elements while maintaining yields. Their ability to make a significant impact on the fertiliser market is frequently questioned, but if all global beef cattle by-products were processed in this way, it is estimated that 50 million tons per annum of fertiliser could be produced, representing ca. 20% of the current global fertiliser use.

There will be a written paper accompanying this webinar.

This webinar will be worth 2 BASIS FACTS CPD PN points.

ICL Fertilizers are proud to be a sponsor for this IFS presentation, your global partner for your nutrient needs, ICL Fertilizers.

Challenges and opportunities for farming in the Digital Age

Shamal Mohammed, Agri-EPI Centre Ltd, UK

The increasing global population, climate change, dwindling natural resources and unprecedented political events are placing the food supply chain under tremendous and intractable pressure. Digital technology offers one critical solution to the required transformation of global food systems. But along with great potential, the growth of new and effective data-driven advances comes with challenges.

The advent of Global Positioning Systems (GPS) has transformed many industries by connecting information and location and was the basis for the concept of Precision Agriculture. While still prone to errors, it currently provides an accuracy of 4-5 metres, but this can be enhanced using Real-Time Kinematic (RTK) to 1m. The availability of GPS services allowed farmers to apply yield mapping, soil management zoning for site-specific management, using variable rate application of inputs, using auto-steering systems and Controlled Traffic Farming (CTF).

In the past two-decades agriculture, and other industries, have seen an explosion due to the advancement in digitisation tools and easily captured data, with a reduction in data acquisition and storage cost, and improvements in connectivity. Earth Observations technologies improved significantly in term of coverage, availability, and cost. These can now be obtained to cover larger area with better spatial and temporal resolutions.

Data capture by other sensors and farm machinery has opened new opportunities for the concept of big data, which can be collected and stored quickly. Its analysis allows complex questions to be answered and there are extensive opportunities for adding value in agriculture, including benchmarking, predictive modelling, and improvements in system efficiency. The key enabler for big data is connectivity. It is essential that, without human intervention, data can be collected from all connected devices, shared and ana-lysed. This process is known as the Internet of Things (IoT).

Current developments and advancement in the data analytic and digital capabilities such as artificial intelligence and machine learning, robotics and autonomous systems (RAS), and blockchain technology will play a critical role in transforming the food supply chain in the next decade. Specifically, digital technology can increase efficiency (reduce waste), provide a true picture of the value of food, including its economic and natural capital costs, help to redesign a diverse agricultural system, and provide a route to multifunctional landscapes and create space for bio-energy capture and storage.

However, there are many factors which may limit the application of digital technologies for transformative changes in agriculture industry, including:

• Data ownership issues.
• Moving from the traditional supplier-customer transaction to a new business model based on co-creation and partnership.
• The need for technology providers to engage farmers and understand their pain points at an early stage of technology development.
• The need to integrate the various technologies, machinery, and farmer-collected data to create effective digital solutions.
• Connectivity across all the sources and players, at a time when rural connectivity is still poor across much of the UK.

There will be a written paper accompanying this webinar.

Applications and limitations of soil nutrient sensor technology

Christy van Beek , AgroCares, The Netherlands

Fertilisers are a major cost item for almost all farmers all over the world. The vast majority of farmers apply fertilisers, but only a fraction have access to information about the crop needs in relation to their soils’ fertility. This problem is particularly evident in Sub-Saharan Africa, where farmers are often barred from soil testing services because of financial constraints (too expensive), logistic constraints (too far away), or simply because it is unavailable. In developed countries, a transition is occurring towards circularity and precision farming, where insights into soil fertility variations in space and time are required. In both cases, the use of sensor technology may be relevant because of its mobility, affordability and lack of consumables.

Near Infrared (NIR) spectroscopy has been known to soil scientists for years, especially in the area of soil carbon monitoring (e.g. Viscarra Rossel and Bouma, 2016). This is because NIR directly measures chemical bonds in organic matter. To use NIR spectroscopy in the field to additionally measure nutrients in moist soils several building blocks are required:

• A high-quality sensor in a fool proof device;
• A clean, and sufficiently large database;
• Advanced statistical models to convert spectral readings into desired parameters;
• Quality checks and corrections, e.g. for moisture content;
• Translation of results into reports based on user needs.

In practice, a number of constraints and limitations have been found to exist in the deployment of this technology, which are still in the process of being overcome. AgroCares has developed a NIR based operational system called the SoilCares Scanner, which was introduced to the market in early 2017, and which overcomes several of these limitations. The sensor and lightsource generate a spectral signal which is transmitted to an application on a smartphone. This application sends the signal to the AgroCares cloud where it is converted into soil characteristics using the calibration database and deep learning models. Key aspects of the AgroCares system will be described.

This webinar will be worth 2 BASIS FACTS CPD PN points.

This webinar is supported by Yara.

Review of digital tools for farmers and advisors arising from the EU Fairshare project

John Hyland, Teagasc, Ireland

This presentation will describe the work and findings, so far, of the EU H2020 FAIRshare CSA project , which aims to enable a more digitally active farm and farm advisory community. As one aim of this project, a digital platform has been developed to collect and distribute information on digital tools and services used by advisors with a view to improving the acquisition, exchange and dissemination of Digital Tools and Services (DATS). The project will identify good practices associated with digital tools as well as the identification of high impact tools. Furthermore, the project will fund user cases where groups of advisors will select and adopt DATS that meet their needs and objectives.

The recent SCAR-AKIS policy brief on the Future of Farm Advisory Services (2017) recognises the opportunity for farm advisors to use new digital technologies and data flows to add value to their work through more open data exchange and digital services. It proposes the strengthening of those support systems which enable advisors to do their job more effectively; and improved connections for knowledge to be shared and developed further.

Enhanced decision making around fertiliser application requires the effective use of data related to fertiliser input options, recommendations, limits, crop type and responsiveness to fertilisers, field specifications, environmental risk, climate, machinery, etc. Agricultural advisors play an important role as an intermediately to assist farmers interpret data pertaining to fertiliser application decisions. Advisors using DATS can identify key periods where data is required and where quick decision making is paramount. Additionally, advisors are able to illustrate to farmers the value in collected data pertinent to fertiliser application. Increased use of data and decision making tools will therefore help many advisors provide better, more informed and targeted advice to their clients.

As one aim of the FAIRshare project, a digital platform has been developed to collect and distribute information on digital tools and services used by advisors with a view to improving the acquisition, exchange and dissemination of DATS. The objective is to collect DATS related to all sectors and aspects of agriculture that are used by European advisors; many of these DATS are directly related to fertiliser application. The overall goal of the project is to support the sharing of digital tools, experiences and motivations  within the farm adviser community and the farmers they serve. This will include a multi-lingual, web-based catalogue and semantic search tool, (‘Digital Advisor’) which itself takes digital services and tools for farmers and advisers as its core domain.

There will be a written paper accompanying this webinar.

The availability and use of digital tools for grassland fertilisation

David Parsons, Swedish University of Agricultural Sciences, Sweden; Julien Morel, Swedish University of Agricultural Sciences, Sweden; Zhenjiang Zhou, Zhejiang University, China; Thomas Astor, University of Kassel, Germany; René Gislum, Aarhus University, Denmark; Jakob Geipel, Norwegian Institute of Bioeconomy Research, Norway

Various remote sensing technologies have been developed for monitoring grasslands, including handheld, tractor-, air-, and space-borne sensing systems. This paper will discuss the various types of remote sensing systems for assessment of grassland nutrition, their characteristics, examples of practical applications, and possible future development.  

For the specific goal of nutrition management of grasslands, the most important agronomic parameters to estimate include biomass, nutrient concentrations (particularly N concentration) and botanical composition. The proportion of legumes is particularly relevant for informing nitrogen fertiliser recommendations.

A remote sensing system includes a combination of a sensor and a platform to deploy and control the sensor. The operational parameters of remote sensing systems differ in various important ways, including i) the sensor technology, e.g. whether the sensor is imaging or non-imaging, ii) the spatial resolution, describing the size and level of detail of an object, iii) the spectral resolution, characterised by the position, number and width of wavebands, iv) the temporal resolution, a measure for the data acquisition frequency, v) the radiometric resolution, indicating the system’s sensitivity to small changes in signal intensity, and vi) costs of purchase and maintenance.

There are additional steps before data retrieved from a remote sensing system can be used for decision support. Agronomic parameters are estimated from sensor data using mathematical models. The ensuing issue is what to do with this often voluminous information. To use the estimated agronomic parameters as a basis for decision support, it is important to understand both the goals of the producer, and the effect of potential management practices on the grassland. Ultimately, useful decision support systems in crop management depend on localised understanding of agronomic interactions and practices.

There will be a written paper accompanying this webinar.

This webinar will be worth 1 BASIS FACTS CPD PN point and 1 PD point.

This webinar is supported by Fertiizers Europe.

Fertilizers Europe represents the interests of the majority of mineral fertiliser manufacturers in the European Union. Our vision for the future of EU agriculture is ‘Applying more knowledge per hectare’. In concrete terms this means best fertilisation practices and innovative fertiliser products targeted to specific crops combined with new tools, smart farming application methods and real time data. Discover more.

Discovery and application of a generalised nitrogen response function for global cereals

Hans J.M. van Grinsven¹, Renske Hijbeek² and Hein F.M. ten Berge²

¹Department of Water, Agriculture and Food, PBL Netherlands Environmental Assessment Agency, The Netherlands.
²Wageningen Plant Research, The Netherlands.

A crucial relationship for agronomic and food system analysis is the response of crop yield (Y) to the addition of nitrogen fertiliser (Nrate). Long-term field experiments (LTEs) are essential for correctly determining the economic and environmental performance of alternative agricultural practices. However, the vast majority of N response data are derived from trials lasting only one or two years (STEs). Typically, marginal N response from STEs is about twice as low as for LTEs, implying that caution is justified when basing regional agronomic and environmental effects of changing N regimes on STEs.

In view of the generic principles governing N transformations and uptake when N input, crop yield and soil N pools are in a near steady state, we hypothesised the existence of a generic LT N response relationship for global cereals. To test this hypothesis, we scaled N response by using indexed yield (Y/Ymax) and total N availability (sum of N input from fertiliser and non-fertiliser sources – here referred to as SN), and fitted scaled N response by 2^nd order polynomials with zero intercept (curve referred to as SNR).

We first derived SNRs for winter wheat between 1985 and 2018 at Rothamsted experimental station in the UK (running for >150 years: R² 0.954 for wheat in rotation and R² 0.903 for continuous wheat), and for continuous corn between 2000 and 2010 at the Southwest Research-Extension Center in Kansas, USA (running for >50 years; R² 0.934). Next we found similar SNRs (R² 0.818) for the combined results of 25 less extensive LTEs (running >15 years) for winter wheat, barley and corn in Europe, USA and Asia, with maximum yields between 2.8 to 12.8 t/ha, N rates from 0 to 300 kgN/ha and under a wide range of practice, soils and climate. We did not find LTEs for Africa, but could demonstrate applicability of our SNRs. For paddy rice we had 4 LTEs but the resulting SNR was different.

SNRs can be transformed back to unscaled N response curves for common situations where no LTEs  are available, by using site specific estimates of specific SN (mainly from N deposition biological N fixation) and Ymax. The scaled, generalised N response relationship was used to construct a globally applicable function and diagram between agronomic efficiency and Ymax. This can be used to support the development of strategies to increase regional cereal sufficiency, balancing efforts to increase Nrate and Ymax.

Finally, we developed LT N response approaches, including N removal and N losses, to assess economically optimum N rates from the farm perspective, accounting for the cost of N fertiliser use, and the societal perspective by also accounting for the cost of N pollution. For this we could only use N data from the LTEs at Rothamsted. Ranges of these optimum N rates show that the safe operating space of N fertiliser application narrows when aiming at the combined ambitions of adequate farm income, regional cereal sufficiency and acceptable levels of N pollution.

A new method to predict grain protein in milling wheat during the growing season

Mechteld Blake-Kalff ¹, Laurence Blake ¹ and Allison Grundy ²

¹Hill Court Farm Research, UK
²CF Fertilisers UK Ltd., UK

Growers receive a premium on their milling wheat if they reach protein levels above 12.5%. Usually the larger the yield, the lower the protein levels will be, unless extra Nitrogen is applied. It is difficult to ascertain mid-season whether more N is necessary to achieve the required protein level, because relatively small differences in N nutrition are involved; 30-40 kg of N might be enough to push protein over the threshold.

In this paper we describe the development of an accurate test to predict final protein in grain, using samples taken mid-May to mid-June, so that it is possible to add extra fertiliser if necessary. The test measures signals in the roots that are involved in the regulation of N uptake in response to the external N supply. Generally, when plenty of nitrogen is available, the N uptake efficiency will decrease and vice versa.

Measuring these regulatory signals provides a reliable assessment of the N status of the plant, and from this the final grain protein level can be predicted. Despite the difficult growing conditions in 2019, we were able to correctly predict protein levels as being < 12%, between 12 – 12.5%, and > 12.5% in 72% of samples, which all received between 180 and 360 kg/ha N fertiliser. Further field experiments have been conducted in 2019 and 2020, so that additional results can be presented in this webinar.

There will be a written paper accompanying this webinar.

This webinar will be worth 2 BASIS FACTS CPD PN points.

CF values are to listen, challenge, evolve and look to the future. So we are proud to support forums like these that strive for efficiency and best practice.

Impact of multiple sources of abiotic stress on nitrate availability and the growth of wheat

Richard Whalley, Rothamsted Research, UK

In the field, wheat experiences a combination of physical and nutrient stresses. There has been a tendency to study root impedance and water stress in separation, and less is known about how they might interact. In this study, we investigated the effect of root impedance on the growth of three wheat varieties (Cadenza, Xi19 and Battalion) at different levels of nitrate availability, from 0–20 mM nitrate, in sand culture. This model system allows soil strength to be increased while maintaining adequate water availability. In a separate pot experiment, we grew the same wheat varieties in a loamy sand, where soil was allowed to dry sufficiently to both reduce water potential and increase root impedance. This pot experiment also had a range of nitrate availabilities 0–20 mM nitrate. Once the seedlings were established, we limited water supply to apply a matric potential of approximately −200 kPa to the roots. Soil drying increased the penetrometer resistance from approximately 300 kPa to more than 1 MPa.

There were differences between the two experimental systems; growth was smaller in the soil-based experiment compared to the sand culture. However, the effects of the experimental treatment, root impedance or water withholding, relative to the control were comparable. Our data confirmed that leaf elongation in Cadenza (carrying the tall Rht allele) was the most sensitive to root impedance. Leaf stunting occurred irrespective of nitrate availability. Leaf elongation in the Xi19 and Battalion (carrying the semi-dwarf Rht allele) was less sensitive to root impedance and drought than Candenza. We suggest that the critical stress in a pot experiment where the soil was allowed to dry to approximately −200 kPa was root impedance and not water availability.

There will be a written paper accompanying this webinar.

Evidence-based review of the primary soil properties limiting crop yields in Sweden

Holger Kirchmann, Gunnar Börjesson, Martin A. Bolinder, Thomas Kätterer and Faruk Djodjic.

Swedish University of Agricultural Sciences, Sweden

Yield statistics and national soil inventory data representing 90 yield survey districts, and results from Swedish long-term soil fertility experiments, were evaluated with the aim of identifying the most yield-limiting soil properties. The same soil variables affecting yields were identified in the national and experimental datasets. Crop yields were significantly affected by plant-available soil phosphorus (P-AL), soil organic matter (SOM) and soil pH. The levels present in the soil of plant-available potassium and magnesium had no significant impact on yield, except in potatoes. Soil pH was found to have the greatest potential to affect crop yields, even at values >6.5 (pH_(H2O)). Surprisingly, increasing soil organic matter (SOM) reduced yields, probably due to lower pH in soils that are richer in SOM.

To fully exploit the known benefits of SOM, liming requires more attention. The demand of plant-available soil P by high-yielding crops has increased since the 1990s, now ranging from 60-100 mg P-AL kg^-1 soil. Furthermore, yields increased significantly with a pH of up to 7.0.  Current Swedish recommendations require updating with new target values for soil P and pH.

This webinar will be worth 2 BASIS FACTS CPD E points.

CF values are to listen, challenge, evolve and look to the future. So we are proud to support forums like these that strive for efficiency and best practice.

Soil microbial dead zones induced by N fertilisation application

S. Ruiz¹, D. McKay Fletcher¹, A. Boghi^1,5, K. Williams¹, S. Duncan¹, C. Scotson¹, C. Petroselli¹, T. Dias¹, D.R. Chadwick^2,3, D.L. Jones^2,4, T. Roose¹

¹Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, UK
²School of Natural Sciences, Bangor University, Bangor LL57 2UW, UK
³Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Southwest University, Chongqing, China.
⁴SoilsWest, UWA School of Agriculture and Environment, The University of Western Australia, Perth, WA 6009, Australia
⁵Computational Science Ltd, 30a Bedford Place, Southampton SO15 2DG, UK

Nitrogen (N) released into soils from fertiliser pellets is prone to loss via volatilization, leaching, denitrification, and surface run-off. These loss pathways result in low N use efficiency (NUE), environmental degradation, and negative effects on human health. While multiple field and farm-scale models describe N flows and losses in the plant-soil system, these fail to adequately capture spatial heterogeneity in N reactions surrounding fertiliser pellets and impacts on soil function.

Our aim was therefore to develop a mathematical model to describe N transport and reactions in soil at the pore-scale. Using X-ray Computed Tomography (XRCT) scans, we reconstructed a microscale description of a dry soil-pore geometry as a computational mesh. Solving two-phase water/air models produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The model considers ammonium (NH₄⁺), nitrate (NO₃^–) and dissolved organic N (DON), and includes N immobilisation, ammonification and nitrification processes, as well as diffusion in soil-solution. We simulated the dissolution of a fertiliser pellet and a pore scale N cycle at the three different water saturation conditions. To aid interpretation of the model results, microbial activity at a range of N concentrations was measured experimentally.

The model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predicted that the maximum NH₄⁺ and NO₃^– concentrations in soil solution around the pellet under dry conditions are in the order of 110³ and 110⁴ mol m^-3 respectively (1-10 M), and under wet conditions 210² and 110³ mol m^-3, respectively (0.1-1 M). Supporting experimental evidence suggests that these concentrations would be sufficient to reduce microbial activity in the zone immediately around the fertiliser pellet (ranging from 0.9 to 3.8 mm depending on soil moisture status), causing a major loss of soil biological functioning.

This model demonstrates the importance of transport processes in regulating N movement in soil with special capability to predict the effects of fertilisers on soil processes and the root microbiome. We will also discuss and expand what this study means for the field scale fertiliser application and resulting soil microbiome dynamics.Nitrogen (N) released into soils from fertiliser pellets is prone to loss via volatilisation, leaching, denitrification, and surface run-off. These loss pathways result in low N use efficiency (NUE), environmental degradation, and negative effects on human health.

While multiple field and farm-scale models describe N flows and losses in the plant-soil system, these fail to adequately capture spatial heterogeneity in N reactions surrounding fertiliser pellets and impacts on soil function. Our aim was therefore to develop a mathematical model to describe N transport and reactions in soil at the pore-scale. Using X-ray Computed Tomography (XRCT) scans, we reconstructed a microscale description of a dry soil-pore geometry as a computational mesh. Solving two-phase water/air models produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The model considers ammonium (NH₄⁺), nitrate (NO₃^–) and dissolved organic N (DON), and includes N immobilisation, ammonification and nitrification processes, as well as diffusion in soil-solution. We simulated the dissolution of a fertiliser pellet and a pore scale N cycle at the three different water saturation conditions. To aid interpretation of the model results, microbial activity at a range of N concentrations was measured experimentally. The model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predicted that the maximum NH₄⁺ and NO₃^– concentrations in soil solution around the pellet under dry conditions are in the order of 110³ and 110⁴ mol m^-3 respectively (1-10 M), and under wet conditions 210² and 110³ mol m^-3, respectively (0.1-1 M). Supporting experimental evidence suggests that these concentrations would be sufficient to reduce microbial activity in the zone immediately around the fertiliser pellet (ranging from 0.9 to 3.8 mm depending on soil moisture status), causing a major loss of soil biological functioning. This model demonstrates the importance of transport processes in regulating N movement in soil with special capability to predict the effects of fertilisers on soil processes and the root microbiome. We will also discuss and expand what this study means for the field scale fertiliser application and resulting soil microbiome dynamics.

Boron in the soil and plant: a review

Philip White, James Hutton Institute, UK (UNFORTUNATELY PHILIP IS INDISPOSED, AND SO THIS PRESENTATION HAS BEEN POSTPONED)

Boron (B) is a plant micronutrient. It is essential for plant growth and reproduction. Commelinid monocots, such as cereals and grasses, require tissue B concentrations greater than about 10 mg kg^-1 dry weight (DW), whereas non-grasslike monocots and eudicots require tissue B concentrations greater than 20-30 mg kg^-1 DW. In general, the tissue B requirements of plant species parallel the amounts of B in their cell walls. Frequent symptoms of B deficiency in plants include impaired root and shoot elongation, chlorosis of developing leaves, necrosis of meristems and aberrant reproductive growth, reflecting the physiological role of B in cell walls.

Soils differ greatly in their phytoavailable B concentrations. The main factors affecting B availability to plants include the B content of the soil’s parent material, soil texture, soil organic matter content, clay mineralogy and pH. Boron deficiency is often considered one of the most common micronutrient deficiencies in crops and generally occurs on deep sandy soils in regions of high rainfall, through which B readily leaches. Boron deficiency in crops can be addressed through the application of soil or foliar B fertilisers. Boron toxicity to plants occurs in arid regions where the B content of the soil’s parent material is high, such as the Middle East, Southern Australia, parts of California, Chile and the Eastern Mediterranean. It has been addressed both by improved soil management and by the development of crop genotypes with greater abilities to prevent B uptake or tolerate high tissue B concentrations.

In the soil solution, most B is present as boric acid, B(OH)₃. In the cytoplasm of plants cells some B (about 2%) is present as borate, B(OH)₄^–. Plant root cells can control B uptake by regulating the entry of boric acid and the efflux of borate through the expression of genes encoding the B transport proteins in their plasma membranes. Boron is relatively immobile in the phloem of most plant species, with the exception of plants that transport sugar alcohols (polyols) in the phloem. Thus, a constant B supply is required to prevent the occurrence of B deficiency symptoms, which will occur first in developing tissues. There is considerable variation among species, and among genotypes of a species, in the ability to control B uptake, the efficiency by which B is utilised physiologically, and the ability to tolerate large tissue B concentrations. This variation has been used to develop crops for soils with low or high B phytoavailability.

This talk will describe the occurrence of B in soils and factors affecting B availability to plants, the molecular mechanisms by which plants control B uptake and its distribution between organs, and the agronomic and genetic strategies that are being used to mitigate B deficiencies and B toxicities in agriculture.

There will be a written paper accompanying this webinar.

This webinar will be worth 1 BASIS FACTS CPD E point and 1 PN point.

ICL Fertilizers are proud to be a sponsor for this IFS presentation, your global partner for your nutrient needs, ICL Fertilizers.

Swedish trial results investigating different sources and levels of potash and phosphate

Ingemar Gruvaeus, Yara, Sweden

Trials to compare the effect of NPS and NPKS fertilisers on spring barley in Sweden have shown surprisingly large yield benefits for NPK, even when grown on potassium rich clay soils. This has been puzzling, and attempts to explain the effect, such as being due to a low K/Mg ratio in the soil, have been discounted.

In a series of trials conducted during 2010-2011 by Yara Sweden we investigated the effect of both potassium chloride and calcium chloride. Compared to combi drilled NPS we gained the same yield increase with MOP based NPKS, and also with NPS + Calcium chloride.

In leaf analysis carried out at Growth Stage 31, calcium chloride did not affect any other analysed nutrient except for the chloride content, while MOP also affected N, P, K, Cl, Ca and Mg.

Multi-nutrient management for increased yield and quality on barley in South of England

Scott Garnett, ICL, UK

This presentation will present and discuss the first year’s results from a three year trial to look at the relationship between nitrogen and different potassium sources. In the trial two rates of nitrogen are applied to spring barley, with the timings of the nitrogen applications also being split.

The trial is comparing the application of potassium chloride with magnesium sulphate to that of potassium chloride and polyhalite.

In each year, three different varieties of barley will be included within the trial.

This webinar will be worth 2 BASIS FACTS CPD PN points

Field-specific nutrient management in smallholder farming systems: the future or a pipe-dream?

Tom Schut, Wageningen University and Research, Netherlands

Co-authors – S.K. Njoroge and K.E. Giller

Fertilizer recommendations are key for farmers: the investment is relatively large for smallholders and risky with unknown yield responses and variable fertiliser prices. Are agronomists able to provide useful site-specific fertiliser recommendations that reduce these uncertainties? We evaluated the influence of errors introduced due to soil sampling and chemical analysis procedures both within- and among laboratories on fertilizer recommendations. Using what we consider to be conservative estimates of the uncertainty in estimating soil supply of N, P and K in a single composite soil sample, the resulting 90% confidence interval of fertilizer recommendations ranged from 86 to 186, 0–58 and 38–114 kg N, P and K ha⁻¹ respectively. The numerous laboratory services and digital applications providing field-specific recommendations appear to promise more accuracy than soil analysis can realistically deliver.

African fields are known for their variability. Yet, this variability is due to past management. On-farm experiments in Western-Kenya with long-term nutrient omission trials, provide strong evidence of the long-lasting influence of manure applications on especially soil P and K status. Unbalanced fertiliser applications quickly mined the soil and increased spatial variability, whereas balanced fertilizer maintained soil fertility and reduced spatial variability. On all strongly nutrient depleted fields, balanced and placed NPK application resulted in a strong yield response. We observed the same on depleted fields with cassava crops with a strong response to balanced NPK. Based on models, we expect that a fertiliser strategy focussing on a regional balanced supply is more robust and sustainable than site-specific fertilizer strategies.

We conclude that a field-specific fertiliser recommendation based on a single composite soil sample is indeed a pipe-dream. However, balanced fertiliser applications provide a robust alternative when combined with farmer knowledge.

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Site-specific nutrient management recommendations for smallholder farms in sub-Saharan Africa

Shamie Zingore, African Plant Nutrition Institute, Morocco

Fertilizer recommendations tailored to specific climate, soil, crop, and farmer’s socio-economic status can increase farm-input use efficiency, productivity, and reduce climate-related production risks in highly heterogenous smallholder maize-based farming systems in sub-Saharan Africa (SSA). The scope for wide-scale use of soil testing in smallholder farming systems in SSA is curtailed by several challenges that include high costs of soil sampling and analysis, difficulty in taking representative soil samples, ill-equipped laboratories and considerable amount of time required to produce results. There are also limitations associated with standards of soil testing and interpretation of soil test results.

The site-specific nutrient management concept (SSNM) provides an alternative crop-based approach that is more practical for resource-constrained smallholder farming systems. The SSNM integrates soil and climate information to make field-specific decisions based on a set of nutrient management principles, which aims to supply a crop’s nutrient requirements tailored to a specific field or growing environment. Nutrient Expert for Maize (NE) was developed as an extension-based decision support tool using the SSNM concept to support cost-effective delivery of nutrient management recommendations.

The algorithms for calculating fertilizer requirements in NE is determined from a set of on-farm nutrient omission trial data under representative conditions. The N, P, and K requirements are based on the relationship between the balanced uptake of nutrients at harvest and grain yield, called internal nutrient efficiency, which are predicted using the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model. The nutrient requirement for a field or location is estimated from the expected yield response to each fertilizer nutrient, which is the difference between the attainable yield and the nutrient-limited yield. Evaluation of NE across five countries showed strong utility for guiding improved nutrient management.

The recommendations generated using NE were effective in maintaining high yields, but at a lower fertilizer input cost compared with current recommendation approaches. Agronomic nutrient use efficiencies were also increased with NE recommendations. Socio-economic and soil fertility diversity between smallholder farms had profound effects on crop productivity and nutrient management recommendations to optimize yields and profits, therefore, refinement of technologies to suit different types of farmers is essential for sustainable maize production intensification. Further improvement of NE by integration with geo-spatial soil and agronomic will enable rapid development and dissemination of recommendations for larger areas to reach millions of smallholder farmers at scale.

Anglo American is delighted to support the IFS webinar. Anglo American product POLY4 is a multi-nutrient, low-chloride fertiliser that offers season-long crop nutrition.

Can sub-Saharan Africa feed itself? Tripling cereal production with minimum fertilizer use and emissions

Martin van Ittersum, Wageningen University and Research, Netherlands

Demand for five cereals (maize, millet, rice, sorghum and wheat) is projected to increase between 2015 and 2050 by a factor 2.8 in sub-Saharan Africa (SSA) due to population increase and dietary changes. In theory, SSA could meet this demand, but only just so, on existing cereal cropland area. Yields would have to increase between 2015 and 2050 from current levels, which are about 20-40% of the agronomic yield potential under rainfed conditions, to ca. 80% of that potential. This is an unprecedented rate of yield increase for rainfed systems in the world.

To enable the required yield increases, crop nutrient requirements will have to increase enormously, to – for example – an average minimum requirement of 140 kg nitrogen (N)/ha for maize, which is the most widely planted cereal in SSA. This is equivalent to a 15-fold increase between 2015 and 2050. If cereal demand will be fulfilled in SSA, by 2050, greenhouse gas emissions from cereal production will be at least 50% higher than in 2015 due to the larger production, regardless whether scenarios of intensification or crop area expansion will be followed. Intensification of cereal production with sufficient and efficient use of fertilizers will lead to lowest GHG emissions, but requires excellent agronomy. .

Can maize variety influence the mineralisation of soil organic matter and supplement inorganic fertilisers for nitrogen supply in soil?

Lumbani Mwafulirwa, University of Reading, UK

Plant species and genotypes vary with respect to the degree to which they mediate soil organic matter mineralisation. For example, as a consequence of rhizodeposition amount and composition shaping rhizosphere microbial community structure and increasing microbial activities, including mineralisation of soil organic matter. A consequence of soil organic matter mineralisation is the mobilisation of ammonium and subsequent nitrification, both providing N available for plant uptake. Therefore, there is the potential for manipulating this root-soil interaction through breeding to help meet soil nitrogen supply in cropping systems, especially in low input systems of tropical and subtropical areas.

As part of the project “Exploiting the potential of genotype microbiome interactions to promote sustainable soil health in southern Africa”, the University of Edinburgh and partners explored maize genotype-specific influences on soil organic matter mineralisation and gross nitrification under conventional management versus no-tillage with crop residue retention. Using microcosm experiments, root traits linked to enhanced soil organic matter mineralisation and gross nitrification were revealed. Candidate genes related most closely to these root traits have been identified. These results and implications for breeding, soil organic matter/nutrient management and sustainable production will be shared in this presentation.

Co-researchers: Prof Liz Baggs, University of Edinburgh, UK; Dr Eric Paterson, The James Hutton Institute, UK; Prof Tim Daniell, University of Sheffield, UK; Dr Jill Cairns, CIMMYT, Zimbabwe; Dr Christian Thierfelder, CIMMYT, Zimbabwe; Dr Manje Gowda, CIMMYT, Kenya.

Locally-relevant agronomy at scale: Experiences from the African Cassava Agronomy Initiative

Bernard Vanlauwe and the African Cassava Agronomy Initiative team, Nairobi, Kenya

Agronomy is delivering fertilizer and best agronomic practice recommendations for different crops and agro-ecologies. Scaling recommendations to a larger area has been challenging because of significant spatio-temporal variation in soil, rainfall and other climatic factors resulting in a substantial risk of under-performance on farmers’ field.

The African Cassava Agronomy Initiative (ACAI) with its flagship product ‘AKILIMO’ has developed a strategy delivering tailored agronomic advice at scale. AKILIMO’s Agronomy @ Scale principles comprise several components where partners demand and capacity play a central role. First it has toolboxes to source existing and new data at scale from field trials and surveys. Using in-house developed Smart Agronomic Data management (SAnDMan), the project worked with over 20,000 farmers and collected over 50,000 yield measurements. Advanced data analytics, crop modelling and machine learning techniques are used to determine the apparent soil nutrient supply from field observations and geospatial data layers. Because of substantial soil fertility variation within short distances and the limitations of available geospatial data, we understood that field-level soil fertility indicators are key to model yield responses at this scale. The prediction engine estimated apparent soil NPK supply with R² values of 0.82, 0.70 and 0.60, respectively. Yield response to additional nutrients is translated to fertilizer advice with an economic module optimizing profit based on available fertilizers and fertilizer/crop prices.

In on-farm validation trials, where AKILIMO advice was compared with farmers’ practice, over 75% of the 5,000 farmers realized increases in yield and profit. Beyond tailored advice, AKILIMO is also working on packaging the advice in several interfaces, developing training materials, understanding factors driving use and uptake, and bundling agronomic advice with other relevant services. In this context, the importance of evaluating user experiences is documented. ACAI has thus been pioneering the development and delivery of local relevant agronomy solutions at scale, which formed the basis to the upcoming Excellence in Agronomy Initiative of the One CGIAR research system.

A new paradigm for responsible plant nutrition to improve human, soil and environmental health

Achim Dobermann, Scientific Panel on responsible Plant Nutrition

During 2020 the International Fertiliser Association, in response to prompting by the United Nations, established a Scientific Panel on Responsible Plant Nutrition. Its mission is to provide a sound scientific basis for the principles and practices of responsible plant nutrition in farming systems. It will achieve this by better understanding the links between plant nutrition practices and sustainability outcomes, and providing the scientific evidence to support a transition in practices to achieve these outcomes.

In October 2020 the Scientific Panel published a major report outlining how this vision can be achieved, defining a new paradigm for plant nutrition. This defines five interconnected aims of responsible plant nutrition, along with ten high level questions that the industry must address over the next 5-10 years. These lead to the six key action areas in which progress must be achieved. The report also identifies the contributions that various parts of the industry need to deliver, and explains what ‘success’ will look like.

This presentation will explain these components of the new paradigm, along with the thinking behind them.

EU Green Deal and Farm-to-Fork Strategy: Opportunity or Threat for nutrient related businesses?

Ludwig Hermann, European Sustainable Phosphorus Platform

The European Green Deal is a bundle of strategies aiming to make Europe the first climate-neutral continent by 2050. It is intended as a new, sustainable and inclusive growth strategy to boost the economy, improve people’s health and quality of life, care for nature, and leave no one behind.

The Farm-to-Fork Strategy is, next to the Climate Action Plan, one of the core elements of the European Green Deal. It addresses the challenges of accelerating the transition to sustainable food systems without compromising the economic, social and environmental foundations of food and nutrition security for current and future generations. It aims at enabling a “just transition” for all actors of the food systems, in which also social inequalities are reduced, food poverty is addressed, and a fair income for all actors is ensured. The Farm-to-Fork Strategy builds on innovative solutions that can be scaled up, such as agro-ecological and organic practices, alternative sources of protein (e.g. plant-based, ocean-based, insect-based, etc.), sustainable food from the oceans and aquaculture, and personalised advice relating to sustainable healthy diets.

Among other ambitious targets, bold objectives are set for crop nutrients: reduce nutrient losses by 50% by 2030 (assumed to lead to 20% less fertiliser use) towards zero pollution of water, soil and air. The objectives address two of the main challenges of industrial agriculture: biodiversity loss and continued low water quality status in Europe. Both challenges are closely linked with prevailing agricultural practices causing extinction of insects, bird-, terrestrial- and soil-life and oversupply of nutrients to ground- and surface waters.

The nutrient loss related problems could be tackled by solutions readily available for implementation: precision agriculture following the 4R Principles (right source, right rate, right time, and right place), by using digital tools and high efficiency delivery (e.g., fertigation) and fertilisers releasing nutrients at times and in quantities plants can absorb (controlled release fertilisers), soil improvers averting soil erosion and surface run-off (the main routes for phosphorus losses to water) and biodiversity enhancing farming practices providing improved conditions for fertiliser use efficiency.

The talk will cover the policies and the opportunities and threats for industries serving the crop nutrition and soil improvement markets, and discuss responses that the author considers to be appropriate.

Anglo American is delighted to support the IFS webinar. Anglo American product POLY4 is a multi-nutrient, low-chloride fertiliser that offers season-long crop nutrition.