Improving soil health and crop productivity through conservation agriculture and nitrogen management in rice-mustard-maize systems

Context Conventional crop production practices, including crop establishment using intensive soil tillage, low use of fertilization, low-yielding varieties, and the removal or burning of crop residues, in the Terai region of Nepal have led to low crop yields and nutrient imbalances. Conservation agriculture (CA) offers a potential solution by integrating no-tillage, residue retention, and optimized nitrogen (N) management, yet its impact in this region remains underexplored. Objectives This study investigated the effects of CA practices combined with varying N rates on soil physico-chemical properties, nutrient uptake, and crop yields in rice-mustard-maize- systems. Methodologies A two-year field experiment (2011–2013) was conducted in farmers’ fields in the Western Terai region using a strip-split plot design. Treatments included: (i) two establishment methods (CA: no-till with residue retention vs. conventional tillage (CT): conventional tillage without residue retention, (ii) two crop varieties (improved or hybrid vs. local), and (iii) four N rates (0, 60, 120, and 180 kg ha−1 for rice and 0, 30, 60, and 90 kg ha−1 for mustard in both years whereas for maize, 0, 60, 120, and 180 kg ha−1 in the first year and 0, 80, 160, and 240 kg ha−1 in the second year). Soil properties, crop yields, and crop nutrient uptake were assessed. Results and discussion CA enhanced soil fertility and structure, with significant increase in soil organic carbon (15.4 %) and total nitrogen (14.6 %) at 0–10 cm depth, reduced bulk density, and improved moisture retention. In CA, Nitrogen uptake increased by 3 % in rice and 11 % in maize, while yield increased by 7 % and 9 %, respectively. Hybrid maize and rice outperformed local varieties, yielding 47 % and 3 % higher, respectively. Mustard performed variably, with ‘Bikash’ yielding 44 % more than ‘Goldie’. System productivity increased by 5 % under CA. Optimal yields were achieved with 180 kg ha−1 for rice and maize and 90 kg ha−1 for mustard. Increased N application reduced barrenness and sterility percentage across varieties. Conclusions CA combined with optimized N management significantly improves soil health, nutrient dynamics, and crop productivity in intensive rice-based systems. Hybrid varieties exhibit higher productivity under CA than open-pollinated or inbred types. Thus, adopting CA with appropriate N management and variety can sustainably intensify cropping systems, bridging yield gaps while preserving soil health. These findings have implications for broader adoption across Nepal's Terai and similar agroecological zones of Indo-Gangetic Plains, addressing food security and environmental challenges.