Peer review

Open Access

The imbalanced use of fertilizers, particularly the inefficient application of nitrogen (N), has led to reduced nitrogen use efficiency (NUE), lowered crop yields and increased N losses in Nepal. This study aimed to enhance yields, NUE and farm profitability by optimizing N fertilizer rates, application timing and methods through multilocation trials and demonstrations. In 2017, 57 field trials were conducted in two mid-hill districts using a completely randomized block design. The treatments included control (CK), NPK omission (N0, P0 and K0), variable N rates (60, 120, 180 and 210 kg N ha-1) and top-dressing timings (120 kg N ha-1 applied at knee height and shoulder height, V6, V10 and V8 stages). A full dose of recommended P (60 kg ha-1) and K (40 kg ha-1) were applied at planting, while N was top-dressed in two equal splits at knee-height and shoulder-height growth stages for P and K omission treatments, as well as for treatment with variable N rates. Grain yields responded quadratically, with optimum N rates ranging from 120 to 180 kg ha-1 across the districts. N applied at 120 kg ha-1 and top-dressed at V6 and V10 increased maize yield by 20-25%, partial factor productivity of nitrogen (PFPN) by 12%, agronomic efficiency of nitrogen (AEN) by 21% and gross margin by 10% compared to conventional knee and shoulder height application. In 2018 and 2019, fertilizer BMPs, including V6 and V10 top-dressing and the urea briquette deep placement (UDP) were demonstrated on 102 farmers' fields across five mid-hill districts to compare their agronomic and economic significance over traditional farmers' practice (FP). UDP, validated in 2018 field trials, increased yields by 34% (8.8 t ha-1) and urea top-dressing at V6 and V10 increased yield by 33% (8.7 t ha-1) compared to FP (5.8 t ha-1), reducing the average yield gap by 3.0 t ha-1. Moreover, the gross margin was increased by 39% (V6 and V10) and 40% (UDP) over FP. The findings highlight the need for widespread adoption of fertilizer BMPs to close the yield gap and maximize profitability with minimal nitrogen footprint.

Text in English

Pandit, N.R. : Not in IRS staff list but CIMMYT Affiliation

Shiva Adhikari : Not in IRS staff list but CIMMYT Affiliation

United States Agency for International Development (USAID) Feed the Future Nepal Seed an Fertilizer Project (NSAF)