Effect of fertilizers with the new nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) on yield and quality of agricultural and horticultural crops

In 1997–1999, 136 field trials were conducted under various soil-climatic conditions in western and southern Europe in order to assess the effects of N fertilizers with the new nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) on the yield and quality of various agricultural and horticultural crops. Results show that DMPP may increase the mean crop yield (grain yield, winter wheat +0.25 t ha–1, wetland rice +0.29 t ha–1, grain maize +0.24 t ha–1; tuber yield, potatoes +1.9 t ha–1; corrected sugar yield, sugar beets +0.24 t ha–1; biomass, carrots +4.9 t ha–1, lambs' lettuce +1.9 t ha–1, onions +0.5 t ha–1, radish +4.6 t ha–1, lettuce +1.4 t ha–1, cauliflower +5.2 t ha–1, leek +1.7 t ha–1, celeriac +2.2 t ha–1) and/or improve crop quality (e.g. reduced NO3– concentration in leafy vegetables). In some crops, the same yield level as obtained with the control (fertilizer without DMPP) was achieved with one fewer applications of N, or with a reduced N application rate. The positive effect of DMPP on crop yield was especially pronounced at sites with a high precipitation rate or intensive irrigation, and/or light sandy soil. DMPP had a negative effect on the crude protein concentration of winter wheat and on the biomass yield of spring-grown spinach.