Abstract
Since the green revolution, excessive utilization of chemical fertilizers has become prevalent due to concerns about the integrity of food production for the growing population. This indiscriminate use harms the fertility of the soil, especially in sandy soils where nutrient leaching, particularly nitrogen, results in yield losses as well as environmental and health problems. A pot experiment was carried out at Gomal University, Pakistan, in March 2022 to assess the nitrogen use efficiency, nitrogen uptake, and yield of okra. There were nine treatments with four replicates and the treatment combinations were established using a completely randomized design (CRD). Urea coated with agrotain (urease inhibitor) was applied each at 120 and 84 kg N ha−1 in 2 or 3 splits. Urea at 84 kg N ha−1 was also used in combination with Farmyard manure (FYM) and compared against the control (100% recommended urea). Obtained results showed that inhibitor-treated urea significantly increased soil concentrations of NO3−N and NH4−N over non-inhibitor-treated urea. The highest NO3−N was recorded where urea alone and urea treated with 3 L (3 L) agrotain was applied to 100%. The highest ammonical-N was recorded, where 70% urea treated with 3 L agrotain was applied. Urea, in combination with FYM, significantly increased the organic matter. Electrical conductivity in extract (ECe), and pH of the soil. The improvement in yield with inhibitor was at par with 70% and 100% urea. The highest improvement of 16% in fruit yield and 7.29% nitrogen use efficiency was obtained in the treatment receiving 120 kg N ha−1 treated with 3 L agrotain compared with non-inhibitor urea. The 2nd highest improvement of 10% in fruit yield on account of increased fruit length, stem diameter, and number of fruits, and 5.97% nitrogen use efficiency (NUE) was obtained in treatment receiving 120 kg N ha−1 in combination with FYM in comparison to control. These results suggested that the use of N inhibitor significantly increased the okra fruit yield on account of enhancing ammonical-N and increased N use efficiency.
•Inhibitors-treated urea significantly increased the concentration of NO3–N and NH4–N in the soil over the non-inhibitor urea.•NO3–N concentration in the soil and plant was improved by urea and urea treated with 3 L agrotain @100%.•Ammonical-N can be enhanced by using 70% urea treated with 3 L agrotain.•Urea, in combination with FYM, also increased the organic matter, ECe, and pH of the soil.•Nitrogen inhibitors remarkably increase the yield by enhancing ammonical-N efficiency in the plants.