Seed yield, crude protein and mineral nutrient contents of sesame during a two-year continuous cropping on upland field converted from a paddy

Sesame (Sesamum indicum L.) is an important oilseed crop that is negatively affected by continuous cropping but there is still limited research on this phenomenon. A three-year field experiment was conducted from 2012 to 2014 at Tottori, Japan, on an upland field converted from a paddy to determine the effect of continuous cropping on seed yield, crude protein and mineral nutrient contents of four sesame cultivars ('Maruhime', 'Nishikimaru', 'Gomazou', 'Masekin') and identify cultivars adaptable to continuous cropping obstacle. Seed yield, crude protein and mineral nutrient contents were negatively affected in the second cropping: however, the level of response differed among the cultivars. In the first cropping, the intercultivar yield differences were not significant whereas seed yield showed significant differences among the cultivars in the second cropping. Averaged over years, seed yield was significantly lowest in 'Maruhime' and 'Nishikimaru' compared with 'Gomazou' (588.3 kg ha−1) and 'Masekin' (450.3 kg ha−1). Averaged across cultivars, the seed crude protein and N, P, Fe, Zn and Mn contents decreased by 7.5, 10.0, 19.4, 14.7, and 13.6% in the second cropping compared with the first cropping. Although 'Maruhime' yields in the second cropping were lower than those of the other cultivars, its crude protein, N, P, and Fe contents were generally highest. Changes in the soil nutrients N and available P partially explained the decrease in the yield and seed mineral contents. The variation in the seed yield, crude protein and mineral nutrient contents in the second cropping reflected differences in the cultivar response to continuous cropping that influence the seed composition. To minimize this yield reduction, adoption of two sesame cultivars 'Gomazou' and 'Masekin' could be recommended to overcome continuous cropping obstacle on upland fields converted paddy.