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 c onditions in western and southern Europe in order to assess the effects of N fertilizers with the new nitrification inhibitor (NI) 3,4-dimethylpyrazol e phosphate (DMPP) on the yield and quality of various agricultural and hor ticultural 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), grai n maize +0.24 t ha(-1); tuber yield, potatoes +1.9 t ha(-1); corrected suga r 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 th e control (fertilizer without DMPP) was achieved with one fewer application s of N, or with a reduced N application rate. The positive effect of DMPP o n crop yield was especially pronounced at sites with a high precipitation r ate or intensive irrigation, and/or light sandy soil. DMPP had a negative e ffect on the crude protein concentration of winter wheat and on the biomass yield of spring-grown spinach.