RICE RATOONING - IRRI books - International Rice Research Institute

72 RICE RATOONINGANDHRA PRADESHBasumathi, Jeerige sanna, Sugadas, and Kakirekkalu rices studied in 1956 atRajendranagar, Hyderabad, produced ratoon yields 6-111% of the main crop yieldin half the main crop duration, the highest ratoon yield being 1 t/ ha, in Jeerige Sanna(16). Fertilized plots yielded higher than unfertilized ones and the varietiesresponded differentially to N levels.ASSAMDas and Ahmed (4) evaluated 89 photoperiod-insensitive semidwarf varieties atKarimganj, Assam, for main and ratoon crop yields. The main crop receivedcomplete fertilizer at 60 kg N, 13.2 kg P, and 24.90 kg K/ha but the ratoon cropreceived only N at 30 kg/ha, topdressed immediately after cutting the main crop at30 cm stubble height. The ratoon crop yields ranged from 9.4 to 68.1% of main cropyields with an average of 37.2%; the average ratoon crop duration was 39.6% of themain crop. The best performing C 3810 produced the highest main crop yield(4.1 t/ ha in 124 d) and the highest ratoon crop yield (2.1 t/ha in 54 d), followed byCR 220-60 and CR 156-5021-307.BIHARAs reviewed earlier (11), two experiments were carried out to determine the yieldsobtainable from ratoon crops of rice and the effect of date of transplanting and rateof manuring on ratoon crops. In the first experiment, NP 97 rice yielded 1.8 t/ha in120 d (Table 1). The ratoon crop harvested in 60 d yielded 0.6 t/ha without N;addition of 10 and 20 kg of N/ha produced 0.7 and 0.8 t of grain/ha. In a secondexperiment the same year, NP 125 rice was transplanted to manured fields on 1, 15,and 30 Jun. The highest yield from the ratoon crop (0.7 t/ha) was obtained fromplants transplanted on 1 Jun and the lowest (0.4 t/ ha) from those transplanted on30 Jun, indicating regression of ratoon crop yield on the planting time of the maincrop.KARNATAKAIn Karnataka, the first report on ratooning, published in 1943 (1), stated that thevariety S 684 gave a main crop yield of 2.7 t/ha in 174 d and a ratoon crop yield of1 t/ ha in 113 d, the ratoon crop taking 65% of the main crop duration but producing37% of the main crop yield (Table 2). Subsequent reports in the 1970s mostlyemphasized the success of this system on hill valley bottoms and midlands, whereseasonal inadequacies (short interval of rice fallows and moisture) prevented raisingan upland crop or a newly planted rice crop. The excellent ratooning ability of Intan