Effect of nitrification inhibitor 3,4-Dimethylpyrazole Phosphate on Yield and 15N Dynamics of Different Rainfed Wheat Genotypes with different Carbon 13 Isotope Discrimination Indexs

In order to increase yield and nitrogen fertilizer use efficiency in autumn application of fertilizer for rainfed wheat through nitrification inhibitor DMPP, a field experiment was conducted in RCB design in 2014-2015. The treatments were five bread wheat genotypes (with different ∆ value) and nitrogen (control no N, 60 kgN/ha 15N ammonium sulphate and 15N ammonium sulphate with DMPP). The results showed that use of DMPA could delay conversion of ammonium to nitrate for 42 days. DMPP had greatest impact on nitrogen derived from fertilizer and had little effect on nitrogen derived from soil. It seems ammonium ions fixed by exchangeable sites of soil reduce effectiveness of DMPP in the soil. Application of DMPP could increase yield and nitrogen fertilizer use efficiency by 1516 kg/ha and 12.2%, respectively. The interesting point in this regard was complete absorption of ammonium ions in the genotype G5 (Zergan 6) compared with other genotypes. It seems that preferential absorption of ammonium by genotype G5 (with lower Δ index) caused toxicity effects. Thus, a small reduction of nitrogen fertilizer use efficiency (6.5%) appeared. Therefore use of DMPP in fast growing genotypes with ammonium preferential absorption ability (like G5) should be performed with caution.