Whilst significant improvements have been made to the fertiliser recommendations for field vegetable crops in the new fertiliser manual, there are still many areas that require updating and improving. For example, nitrogen (N) recommendations relate to single crops in static environments, and for phosphorus (P) there was little readily available data upon which revisions to the recommendations could be made. Future research must be targeted at these two areas:
Modifications to the fertiliser recommendations in the new fertiliser manual represent a major step forward in field vegetable crops, but they provide static recommendations that apply to single crops and are un-reactive to local field conditions and crop rotations.
Work in project HH3506SFV (Making more efficient use of nitrogen in crop rotations of Horticultural crops) demonstrated the importance of considering rotations of crops in order to minimise N losses A parallel European funded project developed the . EU-Rotate_N decision support system to optimise nitrogen use in horticultural crop rotations across Europe. (QLK5-2002-01100). This model was developed as a tool to manage N inputs over rotations and can indicate the presence of periods with a high risk of leaching in crop rotations. (Rahn et al 2010e “EU-Rotate_N – A decision support system to predict environmental and economic consequences of the management of Nitrogen fertiliser in crop rotation”).
Once these high risk periods have been identified, further model runs can be carried out to identify strategies to mitigate them with minimal effect on the economic sustainability, whilst takking account of local field conditions.
Development of the EU-Rotate_N model as part of IF0176 (Fertiliser Manual Decision support Gap Filling (Field Vegetables) and facilitating the next steps in decision support systems.) demonstrated the benefits of using the model to compare alternative strategies for fertilising field vegetable crops with N. A scoping study IF0177 (Low carbon and low input production systems – scoping study) also indicated the importance of managing N for low carbon farming, particularly over rotations.
Within this project the usability of the model will be improved with access to a wider range of input and weather data scenarios. The results of the simulations will be available via a graphical interface which will allow easier utilisation of the EU-Rotate_N model, increasing its potential to answer policy related questions on the appropriate fertilisation of field vegetable crops grown in rotations. Once developed this model could be considered as a tool for forecasting nitrogen losses in catchment studies such as those recently funded by EA/Defra and WAG.
Current fertiliser recommendations for phosphorus (P) are based on work conducted by Duncan Greenwood in the 1960s and 70s with vegetable crops grown at Wellesbourne. Since then production methods, cultural practices, and yields have changed markedly. Some work has been done on P fertiliser requirements of vegetable brassica crops (Defra HH3501SFV), but not on mature field crops. Increased pressures on P fertiliser usage and costs, due to the depletion of non-renewable natural resources, their potential negative impacts on local environments and water quality, and the energy required and carbon dioxide evolved in their production and use, will also increase the need to manage P fertiliser inputs more carefully. With over 85% of mined P is used in food production, and field vegetable crops being very responsive to P supply there is a need to identify future research requirements to ensure its efficient use.
We will conduct an in depth review of literature on the P response of field vegetables, which will support proposals to HDC and Defra on both practical and strategic research and development to support more effective P use by vegetable crops and benefit future revisions of the fertiliser manual.