Abstract
Several field experiments were conducted over six seasons on fine loamy, mixed, hyperthermic, Aquic Ustorthent soil in the flood plain soil of Punjab, India, to evaluate the effect of intercropping of sesbania (Sesbania aculeata) and summer mungbean (Vigna radiata) straw as green manures in plant as well as ratoon crops of sugar cane (Saccharum spp). There were six rates of urea fertilizer N (0, 37.5, 75, 112.5, 150, and 187.5 kg N ha-1) in pure-stand sugar cane plots and four rates of N (37.5, 75, 112.5, and 150 kg N ha-1) in plots intercropped with mungbean and sesbania as green manure (GM). Total N addition from sesbania averaged 102 kg N ha-1 under plant crop and 90 kg N ha-1 under the ratoon crop, whereas mungbean residues contributed only 30 kg N ha-1 in both plant and ratoon crops. In addition, mungbean yielded 550 kg ha-1 of pulse grains under plant crop and 390 kg ha-1 in ratoon crop of sugar cane. The cane yield decreased significantly by intercropping with sesbania or mungbean in plant sugar cane, but increased significantly over no GM treatment at N rates up to 112.5 kg in both summer mungbean and sesbania in the ratoon crop. The N uptake was lower in GM treatments than in no GM treatment, but it increased significantly with N application up to 112.5 kg N ha-1, irrespective of GM incorporation in the plant crop. It was significantly more under GM treatments than no GM up to 112.5 kg N ha-1 in the ratoon crop. The results of this study showed that intercropping of sesbania as GM and mungbean for grain and GM in ratoon sugar cane be practised for getting higher cane yield. However, in planted sugar cane, the growing of mungbean as an intercrop can also be recommended for obtaining additional income from pulse grains. There was a saving of 75 kg N ha-1 from the incorporation of sesbania GM and 37.5 kg N ha-1 from the incorporation of mungbean straw in sugar cane.
