A field experiment was conducted in alpha lattice design in subtropical region of Nepal in the wheat crop to determine the association between yield and yield attributing traits through correlation and path analysis. The result showed highly significant variations among the genotypes for all the traits under study. Simple correlation coefficients revealed that the association of grain yield with biological yield followed by harvest index, plant height, thousand grain weight and Area Under SPAD Retread Curve (AUSRC) at anthesis were positive and highly significant (at 1% level of significance). The positive and significant (at 5% level of significance) association of grains per spike followed by flag leaf area with grain yield was also found. Path analysis showed that biological yield and harvest index had the highest positive direct effect on grain yield. While other traits contribute to the grain yield significantly indirectly via biological yield and harvest index. This suggests that biological yield and harvest index having significant positive correlation and high direct effect on grain yield explained the true relationship and the direct selection of the genotypes through these traits is effective for improving yield potentiality. SAARC J. Agri., 15(1): 1-12 (2017)

The optimum dose of fertilizers for crops varies with soil, agro-ecology, and crop management practices. Optimizing application dose is critical to reduce nutrient loss to the environment and increase nitrogen use efficiency (NUE), crop yields, and economic return to farmers. An experiment was conducted to determine the optimum N dose for increasing maize (Zea mays L. cv, Manakamana-3) yield, NUE, and farm profits under rainfed conditions. Five levels of N (0, 60, 120, 180, and 240 kg ha⁻¹), and a non-fertilized treatment were tested in a randomized complete block design with three replications. Effects of each treatment on yield and yield attributing traits, plant lodging and Sterility (plants with no cob or grain formation), NUE, and stay green trait of maize were recorded. Application of N above 120 kg ha⁻¹ (N120) did not have any significant effects on yield and yield components. Nitrogen, at N120 and above, produced highly fertile plants (though sterility slightly increased at N180 and N240), higher N uptake, and lower dead leaf area (18–27%). N120 produced the highest agronomic; yield increase per unit of N application (AEN—26.89 kg grain kg⁻¹ N) and physiological efficiency of N (PEN—42.67 kg grain kg⁻¹ N uptake), and net benefit (USD 500.43). Considering agronomic, economic, and NUE factors, an N dose of 120 kg ha⁻¹ was found optimum for the cultivation of rainfed maize (Manakamana-3) under sandy loam soil.

Several innovative fertilizers and application methods, along with different decision support tools have been developed to improve nitrogen use efficiency (NUE) and crop yields, but their comparative study in maize is yet to be done in Nepal. Thus, we evaluated different slow-release N fertilizers and decision-making tools for real-time N management compared with the common urea on their effectiveness in increasing NUE, grain yield and economic return of spring maize (Zea mays L. cv. Rampur Hybrid-10). A field trial was conducted at Dang Valley of Nepal in a Randomized complete block design with three replications and seven treatments; N omission- (0 kg N ha⁻¹), normal urea at 120 kg N ha⁻¹ (recommended dose, N120), and 180 kg N ha⁻¹(N180), Polymer Coated Urea (PCU- 90 kg N ha⁻¹), Urea Briquette-deep placement (UDP- 90 kg N ha⁻¹), GreenSeeker (GS- 143 kg N ha⁻¹) and Leaf Color Chart based N management (LCC- 143 kg N ha⁻¹). N application based on decision support tools (LCC and GS) and innovative fertilizers (UDP, PCU) yielded 17.35–45.81% more grain yield than recommended dose (RDF). The real time nitrogen application through LCC and GreenSeeker and slow release N fertilizer (PCU and UDP) resulted in higher agronomic efficiency of nitrogen- AEN (21.30–27.82 kg grain kg⁻¹ N) compared to RDF (12.15 kg grain kg⁻¹ N) and N180 (19.87 kg grain kg⁻¹ N). UDP, with 25% less N compared to RDF, resulted in higher grain yield (5.25 t ha⁻¹), partial factor productivity of N– PFPN (58.37 kg grain kg⁻¹ N) and AEN (27.82 kg grain kg⁻¹ N). Based on the economic return and ease in the application, both UDP and LCC based N application seem promising in Nepalese conditions. However, their effectiveness should be validated across diverse agro-ecologies, soil types and climatic conditions for a general recommendation.

In Nepal, blanket fertilizer recommendations without considering diverse soil types, nutrient status, climate and crop management practices along with imbalanced fertilization practices by farmers, mainly “urea fertilizer,” have resulted in reduced nitrogen use efficiency (NUE) and productivity in tomato production. Optimizing the rate of nitrogen (N) fertilizer, application time and improved application methods could increase crop yields and NUE and reduce environmental costs. This study was conducted to identify the optimum N rate and application method for increased tomato yield and NUE. Multilocation trials (n = 28) conducted in a randomized complete block design with nine treatments across five districts included the omission of N, P and K (N0, P0, K0), variable N rates of 100, 150, 200 and 250 kg ha⁻¹ (N-100, N-150, N-200 and N-250), use of urea briquettes (UB) with deep placement (UBN-150) and a control (CK). N input in UB was reduced by 25% from the recommended N rate of 200 kg ha⁻¹ considering its expected higher NUE. Yield responses from an NPK omission plot revealed N as the most limiting plant nutrient. Applications of fertilizer at N-100, N-150, N-200 and N-250 increased tomato yield by 27%, 35%, 43% and 27%, respectively, over N0. Tomato yields responded quadratically to the added N fertilizers with optimum rates ranging from 150 to 200 kg ha⁻¹ across districts. UBN-150 significantly increased tomato yield by 12% over N-150 and produced a similar yield to N-200 (the recommended rate). The highest partial factor productivity of nitrogen (PFPN) was observed at N-100 and the highest agronomic efficiency of N (AEN) was at N-200. Deep placement of UB at-150 increased PFPN by 8% and 21% and AEN by 27% and 21% compared with N-150 and N-200, respectively. These results have positive implications for developing efficient N fertilization strategies to increase tomato yields and reduce environmental impacts in Nepal.

The present study was performed in a randomized complete block design with three replications to identify higher yielding genotypes and putative traits for grain yield improvement under a rainfed environment. Genotypes recorded highly significant variation for most of the observed agro- morphological traits except the number of effective tillers/m2. IR102774-31-21-2-4-7 (5.40 t/ha) followed by IR99739: 2-1-1-2-1 (5.22 t/ha), and IR103587-23-2-1-B (5.05 t/ha) respectively were the higher grain yielders. These high yielders were among the sets of early flowering (85-96 days) and maturing (120-130 days) genotypes. Plant height (PHT- 86.62% and 25.69%), harvest index (HI-87.17% and 44.66%), and thousand-grain weight (TGW- 71.06% and 30.05%) recorded high heritability values coupled with higher genetic advance as a percentage of the mean (GAM). IR102774-31-21-2-4-7 produced superior agro-morphological character for several traits like grain yield, thousand-grain weight, biological yield, plant height, and days to flowering and maturity. Plant height, biological yield, harvest index, days to flowering, and maturity were highly associated with grain yield and had medium to high heritability and GAM values. Therefore, these traits might be of importance for selection in grain yield improvement of rice under rainfed lowland conditions.