Leached nitrate under fertilised loamy soil originates mainly from mineralisation of soil organic N

Animal manures are suspected to be a major source of nitrate leaching due their low nitrogen use efficiency (NUE) by crops. However, actual measurements from animal manure under field conditions scarce. In an on-farm trial in Switzerland over 2.5 years, we used 15 N labelling trace the fate cattle slurry soil-plant system and test whether more was leached than mineral fertiliser. The experiment conducted on two neighbouring fields with loamy soil agricultural area Swiss midlands, where levels groundwater persistently high. Both followed same crop rotation (silage maize – winter wheat grass-clover), but shifted one year. We compared three fertiliser treatments: Control (Con), (Min), (Slu). order provide comprehensive balance several traced labelled fertilisers into biomass, soil, nitrate. year application, recovery crops 45–47% for Min, only 19–23% Slu. Complementary this finding, recoveries were greater Slu despite NH 3 emissions Fertiliser succeeding small (< 4.6% originally applied first residual < 2.4% second) similar both fertilisers. Depth translocation marginal, majority still top 0.3 m after years. Along higher Slu, found significantly lost through leaching. less 5% cumulated amounts crops, which reached up 205 kg nitrate-N ha -1 , originated direct Our findings suggest that most mineralisation N. • On-farm study quantifying NO losses slurry. fertiliser, overall small. During recent additions. Mineral release rates or similar.