Effect of urease and nitrification inhibitors on wheat yield

A field experiment was conducted to assess the effect of urease and nitrification inhibitors on wheat yield at the Research Farm of the University of Agriculture Peshawar during 2011-12. The experiment was arranged in a randomized complete block design with 3 replications. Urea coated with urease inhibitor (agrotain) or urease combined with nitrification inhibitors (super urea) was applied each at 60 kg and 120 kg N per ha in 2 or 3 splits. The results showed that the inhibitors treated urea significantly increased the yield and yield components of wheat over the non-inhibitor urea treatment. The results further showed that super urea was more effective than agrotain in terms of increased yield. The improvement in yield with inhibitors was more with low (60 kg N per ha) than with high dose of urea (120 kg N per ha). Application of urea in 3 splits was better than 2 splits. The highest improvement of 42.9% in grain yield and 45.1% in total N uptake was obtained in treatment receiving super urea at 60 kg N per ha compared with non-inhibitor treated urea at 60 kg N per ha. The 2nd highest improvement of 37.5% in grain yield and 38.0% in total N uptake was obtained in treatment receiving agrotain (urease inhibitor) treated urea at 60 kg N per ha compared with non-inhibitor treated urea at 60 kg N per ha. These results suggested that the use of N inhibitors significantly increased the yield of wheat. However, the combined use of urease and nitrification inhibitors (super urea) was better than urease inhibitor alone (agrotain). Based on the findings of this study, improvement in wheat yield caused by urease and nitrification inhibitors is likely due to increased N use efficiency.