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Nutrient requirements of horticultural crops - HH3505SFV

Large amounts of N are applied to agricultural land to support profitable and competitive farm enterprises. However, abilities to effectively manage this N over the long-term are lacking, with the result that agriculture is a key contributor of greenhouse gases arising from denitrification, and nitrate leaching, which results in pollution of drinking water and freshwater habitats. The use of computer models offers great potential to improve the prediction and management of N fluxes in soil. However, such models are limited in 1. The accuracy with which they predict mineralization, particularly in the winter 2. The number of crops which they represent.

In a range of agricultural systems incorporating both conventional and organic practices, serious seasonal and site discrepencies occur between computer simulated and actual rates of net N mineralization. There is a need to consider the impact of soil variability in the models, and to develop a mechanistic understanding of soil microbial mineralization-immobilization processes, in order to improve their reliability.

The growth of overwinter crops is not well represented in current computer models, which overpredict the amount of autumn growth. Resultant fertilizer recommendations are therefore skewed towards the autumn which are not justified in the light of measured plant growth or N uptake. New algorithms are needed to take account of these phases of growth so that predictions of fertilizer requirement can be improved.

In addition there has been increasing concern about the need for sulphur fertilization to field crops. Levels of wet and dry deposition of sulphur have declined by 42 and 62% between 1986 and 1997.. Already crops such as oilseed rape and grass grown for silage have been shown to be exhibiting S deficiency symptoms in the field (MAFF 1999). Vegetable brassicas particularly have a large requirement for sulphur. Current methods used to assess soil S status have been found to be unreliable and there is a need to develop alternative techniques which provide an accurate assessment of soil S availability.

The aims of this project are to:
1. To determine how key soil characteristics control mineralization of N from crop residues, and to use the data to develop new algorithms for computer models
2. To develop new tools with which to provide a mechanistic understanding of microbial N immobilization-mineralization processes in soil
3. To improve simulation of the growth and nitrogen requirement of overwinter crops in order to provide the basis for more precise use of nitrogen
4. To optimise methods for assessing available soil sulphur status for field vegetable crops with a view to recommending further research on methods for improving the balance between S demand and supplies from the soil for field vegetable crops

This project would address the DEFRA HH35 Sustainable Crop Nutrition Roame objective of "Forecasting the fate and impact of added nutrients in soil". The results would add considerable value to the research being carried out in the EUROTATE_N project (Funded by Framework V ending December 2006) which aims to develop a Europe-wide decision support system to improve the efficiency of nitrogen use by field vegetable crops. This system will be of use to Policy makers, farmers and consultants.


1) Identify the effect of variation of soil properties within a field on the decomposition of crop residues

2) Develop stable isotope probing as a practical tool to trace flows of C and N from crop residues to the soil microbial community inorder to determine how crop residue quality controls N flows through biomass.

3) Develop subroutines to simulate the growth and nitrogen uptake of overwinter crops particularly brassicas which can be used to improve nitrogen fertiliser recommendations in EUROTATE_N

4) Evaluate methods to assess the available sulphur content of soils supporting horticultural crops.

Project Documents
• Final Report : Nutrient requirements of horticultural crops   (978k)
Time-Scale and Cost
From: 2003

To: 2004

Cost: £173,045
Contractor / Funded Organisations
Horticulture Research International
Organic Farming              
Fields of Study