Agronomic manipulation in main season and ratoon rice influences growth, productivity, and regeneration ability in tropical lowlands

Rice ratooning is an efficient technology with minimal input requirements and can increase the total rice pro-ductivity of eastern India, where, resources are considerably more than a single rice crop but not sufficient for a double rice crop. Although ratooning is an age-old practice, farmer acceptance is low mainly due to the lack of availability of suitable cultivars and agronomic management. Therefore, this study was undertaken to optimize the major agro-techniques necessary for ratoon cultivation, viz., cultivars, establishment method, planting time of the main crop, cutting height of stubbles, root pruning through cono-weeding, and nitrogen (N) fertilization in the ratoon crop. Three experiments were conducted from 2013 to 2017, each for 2 consecutive years. In experiment 1, rice establishment methods followed in the main rice crop i.e. conventional transplanted rice (CTPR), surface-seeded rice on puddled soil (Wet-DSR), and system of rice intensification (SRI) and two levels on N fertilization in the ratoon crop. In experiment 2, we evaluated 10 rice cultivars of different durations ranging from 110 to 160 d, including hybrids under three different planting times. In experiment 3, stubble height (10, 20, 30 cm) and root pruning through cono-weeding was studied. The regeneration rate, panicle density and ratoon yield (44 % higher than inbreds) were significantly higher in hybrids. Among the inbreds, long-duration cultivars ratooned better than short-duration cultivars. Higher stem non-structural carbohydrates in stubbles, basal panicle weight and stubble dry weight resulted in higher regeneration ability, especially in the 30 cm stubble height and normal planting time treatments. Conventional transplanting of the main crop and an additional dose of N to the ratoon crop gave the most favorable ratooning results. It is suggested from these findings that to achieve better ratooning, hybrid cultivars or long duration inbreds should be planted on time by transplanting, and the main crop should be harvested at a 30 cm height; root pruning can be performed through cono-weeding, and an additional dose of N is beneficial for higher regeneration of the ratoons and their growth and development. Proper agronomic management in the main and ratoon crop is recommended to augment the productivity and sustainability of rice-ratoon systems.