Enhanced-efficiency nitrogen fertilizer boosts cauliflower productivity and farmers’ income: Multi-location and multi-year field trials across Nepal

Summary Enhanced-efficiency nitrogen (N) fertilizers (EENFs) such as slow-release polymer-coated urea (PCU) and deep placement of urea briquettes (UBs) improve nitrogen use efficiency (NUE) by reducing N losses and increasing nitrogen uptake by plants. Multilocation field trials (81) with cauliflower were conducted across two agroecological regions covering seven districts during two crop-growing seasons between 2018 and 2020 to assess the potential of three EENFs, i.e., PCU, sulphur-coated urea (SCU) and UB for increasing curd yields, agronomic NUE (AEN) and economic benefits over conventional urea (CU). Results were compared with farmers’ current nutrient management practice (FP): applying CU at 58.5 kg N ha−1 (ranging from 33 to 88 kg N ha−1). The N rates in three EENF treatments were 33% lower (100 kg N ha−1), considering their higher N use efficiency, than for CU (150 kg N ha−1). We hypothesize that EENFs produce similar or even higher yields compared with CU. For both years, all three EENFs resulted in significantly (p < 0.05) higher curd yields than CU (36.7 ± 1.1 t ha−1). PCU, SCU and UB increased yields by 21, 21 and 24% over those for CU. The yield increment was much higher (PCU, 44%; SCU, 43%; UB, 46%) than for FP. Similarly, PCU, SCU and UB increased the partial factor productivity of N (PFPN) by 91, 90 and 94% and the AEN by 133, 129 and 138%, respectively, compared with CU. The gross margins of all three EENFs were similar: an average 25% more than with CU and 51% more than with FP. These results suggest that EENFs could help increase productivity and farmer income while considerably reducing N input, compared to use of CU. The government of Nepal should promote these EENFs by removing barriers to access for the associated fertilizers and foster their use through extension.