Low nitrogen inputs, low crop yield, and low land productivity are major challenges associated with cereal-based sole cropping systems in Nepal. Crop intensification and diversification by introducing legumes as intercrops could help alleviate these challenges. With the presence of diverse crops and cropping systems, particularly in hilly topographies, a range of intercrop options is required. We compared 10 intercrop combinations to native sole cropping systems in the mid-hills of Nepal for two cropping seasons (2015–2017) to identify the most productive and economic intercrop combinations for smallholder terrace agriculture. In the spring-summer season (i.e., mid-March to mid-July), cowpea (var. Makaibodi and Suryabodi) and bean were intercropped with maize in 1:1 rows, whereas soybean, blackgram, and horsegram were broadcast with millet (30:70 ratios) during the rainy-autumn season (i.e., mid-July to mid-November). Pea and lentil were used as pre-winter/winter intercrops (i.e., mid-November to mid-March) in mustard (30:70 ratios), while wheat was planted with pea. Ginger was planted with maize in 1:1 rows during the spring-summer season in which the maize rows were replaced by soybean and lentil during the rainy-autumn and pre-winter/winter season, respectively. Plots were analyzed for yields of individual crops as well as other agronomic indicators including land equivalent ratio (LER), total land output (TLO), harvest index (HI), and potential economic return.
Maize+cowpea var. Makaibodi appeared to be the most productive and economic intercrop combination for the spring-summer season (LER – 1.58 and TLO – 4.26 t ha−1, 21% higher than the maize sole crop with an increase in potential economic return by 67%) whereas millet+soybean appeared to be the best combination for the rainy-autumn season (LER – 1.40 and TLO – 2.21 t ha−1, 26% higher than the millet sole crop with a 288% increase in potential income). For the pre-winter/winter season, wheat+pea and mustard+pea combinations appeared to be productive (wheat+pea: LER – 1.31 and TLO – 2.90 t ha-1 i.e., 16% higher than sole wheat with a 54% increase in potential income; mustard+pea: LER – 1.36 and TLO – 2.14 t ha−1 i.e., 30% higher than sole mustard with a 15% increase in potential income). The year round intercrop system (i.e., ginger+maize-soybean) displayed a LER value of 2.45 with increased TLO (21.8 t ha−1 i.e., 2% higher compared to sole ginger) which increased potential economic return by 6%. We conclude that legume intercropping was a robust option across seasons and locations confirming that it could be a promising ecological practice for intensification of cereal-based sole cropping systems on smallholder terraces. Also, it is important to note that soybean and pea provided higher potential net income to farmers as sole crops compared to when they were grown with millet and wheat as intercrops, respectively. It is important that we promote these options to smallholder farmers and disseminate the advantages of legume integration on land productivity, soil fertility management, and income.