Keywords:. fertiliser blending, segregation, prescription fertilisation.
The demand for multi-nutrient, prescription compound fertilisers is growing rapidly across the UK and many European countries as farmers and their advisors increasingly realise the benefits of precise and complete fertilisation. There are various agronomic, economic and environmental factors driving this change in fertiliser practice including imbalances in soil nutrient status, more integrated nutrient management planning, a focus on environmental protection and rising fertiliser costs.
Traditionally, fertiliser manufacturers produced limited ranges of compound fertilisers with standard nutrient ratios from which farmers and their advisors would select the one that gave the closest fit to their requirements. Conversely, prescription compounds can be defined as fertilisers in which the nutrient analysis is specific to a particular farm or even individual field, having been determined by a combination of integrated analyses and nutrient management planning. The required quantity of each individual nutrient is ‘prescribed’ in kg per hectare and fertilisers are then formulated to match these requirements.
From both practical and economic perspectives, prescription fertilisers are made as blended compounds rather than complex compounds (refer to the Definitions section for definitions). Fertiliser blenders can produce an infinite range of nutrient analyses in relatively small quantities without having to make any operational changes to their production plant other than amending the formulations. This level of production flexibility is ideally suited to making prescription compound fertilisers.
The main challenge in producing quality blended compound fertilisers is avoiding nutrient segregation, which can happen during production, storage, transport and spreading. Uneven distribution of nutrients during spreading can impact crop yield and quality and would negate the potential advantages of prescription nutrition. Using ‘best practice’ blending procedures as detailed by the European Fertilizer Blenders Association, it is possible to produce non-segregating blends as demonstrated by data from fertiliser sampling, nutrient analyses across spread widths and agronomic trials.