Measuring nitrogen fixation in different groundnut cultivars and the residual effects on a following maize crop

Number of nodule and nodule dry weight of the groundnut cultivars were significantly different at 60 DAP. Groundnut cultivar Khon Kaen 60-3 had the highest nodule number and nodule dry weight. Shoot dry weight and N contents of the nodulating cultivars were not different but significantly different from those of Non-nod. Groundnut cultivar Tainan 9 gave the highest pod yield while Khon kaen 60-3 gave the highest dry stover yield. Total dry matter yield was also observed in Khon Kaen 60-3. Groundnut cultivars Khon Kaen 60-3 also gave the highest N yield in stover, pod shell and total N yield but seed N yield was the lowest among the nodulating cultivars. Tainan 9 had the highest seed N yield but stover N yield was the lowest among the nodulating cultivars. Percentages of nitrogen derived from atmosphere (% Ndfa) of the fixing cultivars ranged from 55.79-66.94. Groundnut cultivar Khon Kaen 60-2 had the lowest % Ndfa and significantly different from those of other cultivars. The amount of nitrogen fixed was highest in Khon Kaen 60-3 (132 kg/ha), fallowed by Khon Kaen 60-1 (123.51 kg/ha) Tainan 9 (120.09 kg/ha) and Khon Kaen 60-2 (95.54 kg/ha) respectively. Seed and total dry matter yeilds of maize grown after different groundnut cultivars were statistically different. Both yields were highest in maize grown after groundnut cultivar Khon Kaen 60-3 while the lowest yields were observed in maize grown after Non-nod. These agreed well with the amount of N2 fixed which was highest in Khon Kaen 60-3 and as nil in Non-nod. Stover returned treatment significantly gave higher seed and total dry matter yields over the stover removed treatment. The degree of responses varied depending on groundnut varieties, being highest in Tainan 9, followed by Khon Kaen 60-1, Khon Kaen 60-3, Khon Kaen 60-2 and Non-nod. Seed N yields of maized grown after different groundnut cultivars were not significantly different but total N yields were. Stover returned treatment signficantly gave higher N yield in seed and toal N yields than the stover removed treatment. No significant interation was found between cultivar and stover treatment in terms of seed N yield and total N yield.