To evaluate selected models describing nitrate leaching and biological transformations and to quantify the effects of various agricultural practices (irrigation and drainage, conventional or reduced tillage, residues management practices) on nitrate pollution.
The ECC recommendations (91/676/CEE) on good agricultural practices designed to reduce nitrate pollution were published in the "Journal Officiel des Communautes Europennes" No L 375/1. These recommended practices are mainly :1) Matching supply to consumption by adequate optimizing N-fertilization (mineral or organic), 2) Crop residue management, 3) Introduction of catch crops in the rotation, 4) Control of irrigation, and drainage. While the first point has been intensively investigated there have been fewer studies made to assess how these combined techniques can reduce nitrate leaching under real field conditions, which involve different water regimes and water management systems. Any prediction of nitrate pollution requires knowledge of both water and nitrate fluxes in soils. Validated models are the essential tools that can predict these processes on the scale of a field or waterhed. A combination of field experiments and modelling are then required to optimize recommendations in the wide range of agricultural situations currently found in Europe. Several models for nitrogen biotransformations and leaching have been developped but they still need to be validated, and improved. Five research groups, whose fields of expertise include agronomy, soil physics, soil microbiology and modelling, have cooperated to prepare this proposal. They plan to 1)Compare, test, validate and improve a selection of models with which they have a considerable expertise, 2)Conduct relevant field and laboratory experiments to create the databases needed to calibrate the models, 3)Improve and/or develop the methodology for assessing N-fluxes between the various compartments of C-N biotransformation systems, 4)Check the models in the following situations :i)Tile drained polders with a fluctuating water table (Netherlands), ii)Well drained loess soils of the northern Paris basin (France), iii)Irrigated zones in the comunidad de Valencia (Spain). The efficiency of the combined optimized agricultural practices will be assessed under real conditions. Farmers will test these methods in all the fields of a small, confined watershed. The outputs of the selected models will be compared to field measurements and outlet nitrate concentrations.
Funding SchemeCSC - Cost-sharing contracts
9750 RA Haren
46113 Moncada (Valencia)
AL5 2JQ Harpenden, Herts