This webinar will be comprised of two presentations: Phosphorus (P) availability during the depletion of soil P, by Sophie Nawara, Soil Service of Belgium; and Integrating new bio-based and mineral fertilisers to meet nutrient requirements, Patrick Forrestal, Teagasc, Ireland.
Phosphorus (P) availability during the depletion of soil P
Sophie Nawaraa, Fien Ameryb, Hilde Vandendriesscheac, Roel Merckxd and Erik Smoldersd
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.
There will be a written paper accompanying this webinar.
Integrating new bio-based and mineral fertilisers to meet nutrient requirements
Patrick Forrestal, Teagasc, Ireland
Abstract will be available shortly.