Growth, yield and nutrient content of mungbean (Vigna radiata (L.) Wilczek), soybean (Glycine max (L.) Merrill) and cowpea (Vigna unguiculata (L.) Walp.) under different levels of salinity and nitrogen

In both experiments, the crop species were stunted under high salinity levels. During vegetative stage, plant height, root length and dry matter production of cowpea, mungbean, and soybean were reduced under Ec 7 dS/m. Root length of mungbean and plant height and dry matter of cowpea were drastically reduced compared to those of soybean at higher salinity during harvest (flowering). Nitrogen and P concentrations in the straw were reduced at Ec 7 dS/m. K concentration of mungbean was reduced at Ec 7 dS/m. Sodium and Cl increased salinity levels in mungbean but not in soybean and cowpea. In contrast, Na and Cl increased with salinity and this reduced the K/Na in mungbean. In cowpea and soybean, higher K/ha ratio were maintained. Chloride was lower in cowpea and soybean than in mungbean. In the second experiment, increased salinity level decreased the different growth parameters, and delayed both flowering and days to harvest (maturity). Mungbean seedlings were drastically affected by Ec 9 dS/m causing death of one sixth of the plant population within the first week. On the other hand, soybean germination was delayed by 5 days. Ec above 6 dS/m reduced the dry matter production of both crops; mungbean was more affected before flowering. Increase in salinity increased the N concentration in the straw and reduced that in the pods for both crops. Soybean P content in the straw increased at Ec 9 dS/m while that in the pods remained constant for both crops. Salinity did not affect the K concentration. However, the total nutrient content decreased with salinity. The K/Na ratio and nitrogen utilization efficiency was greatly reduced in soybean than in mungbean with increase in salinity level. Yield and yield components were reduced with increased salinity. Soybean and mungbean grain yields were reduced at Ec 9 dS/m by 72 and 28%, respectively when compared to those at Ec 2 dS/m. The nitrogen at 0.66 g/pot increased root length, root and leaf dry matter, LA [leaf area], LAR [leaf area ratio], RGR [relative growth rate], N concentration, K concentration in soybean pods, and pod yield of soybean and mungbean.