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

Increasing attention is being paid to the development of control led-release and stabilized fertilizers that seem more efficient and "environment friendly". Fertilizers with nitrification inhibitors (NIs) may potentially reduce NO3- losses by leaching from NH4-N, liberating fertilizers materials, including organic N sources, by maintaining N as NH4+, which is less susceptible to loss from the soil by this route, and NH3 volatilization. The objective of this study was to assess the effects of N fertilizers with the new nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) on the yield and soil quality of two agricultural crops (winter wheat and cotton). From 2002 to 2004 field trials were conducted in Northern Greece. Three treatments (T) with different level of N fertilization with NI were applied, and the control was the conventional fertilization (CF). For wheat: N127P60 (CF), N127,5P37,5 (T1), N102P30 (T2), N102,5P22,5 (T3) and for cotton: N113,5P40K40 (CF), N104,5P52,5K52,5 (T1), N111P20K40 (T2), N109,5P42,5K40 (T3) (subscripts are units ha(-1)). Soil samples were collected before seeding and after harvest, from three different depths (0-15, 15-30, 30-45 cm). Samples were analyzed for pH, EC, organic C, P, K (for cotton), total N as well as the concentrations of NH4+-N and NO3--N. The use of nitrogenous fertilizers with Nis offers several environmental advantages, compared to the application of conventional N fertilizers. Results show that DMPP may increase the mean crop yield of winter wheat between 25.85% and 39.43% under treatment T2 and the mean crop yield of cotton by 5.2% under treatment T3. Significant increase of NO3--N concentration is observed under all treatments in cotton, while in wheat is decreasing under T2. It is worth mentioning that in cotton NO3--N distribution with in the depth of soil is different among treatments. It is realized that in treatments with Nis there exists a retention of NO3--N in surface layers (0-15cm), that indicates a reduction of nitrate leaching. The NH4+-N presents a tendency of reduction in wheat, probably because of its uptake by crop, while in cotton it presents significant increase. P concentrations in wheat are increasing under all treatments while in cotton they show a significant increase in all treatments apart from T2. Finally, K concentrations are increasing in cotton and it is possible that the applied quantities are not assimilating by the crop. The results suggest that the use of fertilizers with Nis have been associated in trials with increased yield and reduced application rates necessary to achieve identical yields. In addition, DMPP could be potential a nitrification inhibitor, increasing fertilizer nitrogen use efficiency in winter wheat and cotton cultivation in this particular area.