Abstract

Rice-rice-fallow is the most common rice-based farming system in northern Kerala, particularly in the districts of Kasaragod, Kannur and Kozhikode. Therefore, a field study was undertaken during the summer, 2018 at Regional Agricultural Research Station, Pilicode, Kerala, India to find the suitability of different pulse crops (cowpea, black gram, green gram and red gram) for summer fallows of double cropped lowland rice fields under varying nitrogen doses. Height at 100% Recommended Dose of Nitrogen (RDN) (38.73 cm), number of branches per plant at 100 and 75% RDN (9.40 and 9.93, respectively), leaf area index (LAI) at 100 and 50% RDN (1.16 and 1.28, respectively), crop growth rate (CGR) (4.57 g m−2 per day) and yield at 50% RDN (1681.16 kg/ha) was significant for cowpea. Cowpea and red gram performed better among the different pulses, in terms of yield. At 100 and 50% RDN, the nitrogen (N) (46.2 kg/ha and 60.0 kg/ha, respectively) and phosphorous (P) uptakes (7.3 kg/ha and 9.9 kg/ha, respectively) were on par in cowpea. At 75 and 50% RDN, the nitrogen (N) (52.6 kg/ha and 42.9 kg/ha respectively) and phosphorous (P) uptakes (4.6 kg/ha and 4.4 kg/ha, respectively) were on par in green gram. The potassium (K) uptake (25.0 kg/ha) was higher in cowpea (50% RDN). The available soil nutrients showed no difference after summer crop. Gross income (Rs.1,52,269.20/ha), net income (Rs. 70,902.20/ha) and B:C (benefit: cost) ratio (1.87) were higher for red gram. Under varied amounts of N in the same crop, there was no significant change in yield, gross revenue, or B:C ratio of pulses, indicating that the lower level of N (50% RDN) will suffice. It's also reasonable to assume that the residual impact of the previous two rice crops helped to lower N exposure when pulses were cultivated in double-cropped lowlands during the summer.