RICE RATOONING - IRRI books - International Rice Research Institute

RICE RATOON CROP MANAGEMENT IN KARNATAKA 89The main crop seeded in June 1978 was harvested in December and the ratoonwas topdressed 40 d later at 40 kg urea/ ha. The ratoon was harvested on 21 Apr1979. Other practices followed were local. All 3 experimental crops lost an estimated35% to birds because there were no rice plots around the experiments.Neither cutting time nor cutting height influenced grain yield (Table 2). A 5-dinterval after harvest seems to be too short to cause significant yield differencebecause the main and ratoon crops have long growth durations (171 and 130 d);longer cutting intervals may improve ratoon yields. Similarly, yield differencesattributable to cutting height were not significant. But treatments differing by 10 cmor more may produce large differences. With the late-maturing variety Intan, minordifferences in cutting time and height of the main crop appear to have no significantinfluence on yield. Cutting heights with larger differences might induce variation, ashas been observed in nonreplicated experiments where no yield data could berecorded systematically. Studies on varieties suitable for ratoon cropping, with virusresistance and good regrowth ability, are needed.The ratoon crop yields (Table 3) in the third experiment were attractive, anaverage 2.9 t/ ha, ranging from 42 to 61% of the main crop. But their yields weremuch lower than those of 1977-78. Bird damage contributed to some extent to theobserved discrepancy.Table 2. Effect of cutting time (days after 50% flowering) and cutting height ofthe main crop on grain yield of ratoon crop of rice variety Intan.Days after50% floweringGrainyield(t/ha)Cutting htfrom ground(cm)Grainyield(t/ha)354045CV %3.03.13.11381318–2.82.92.621Table 3. Yield of main and ratoon crops of rice variety Intan at Balehonnur, Karnataka,India, at different fertilizer levels, 1978-79.Main crop treatmentMain cropGrain yield (t/ha)Ratoon crop aN 0 P 0 K 0N 40 P 0 K 0N 80 P 0 K 0N 120 P 0 K 0N 40 P 20 K 0N 80 P 40 K 0N 120 P 60 K 0N 40 P 20 K 20N 80 P 40 K 40N 120 P 60 K 60N 120 P 60 K 40N 120 P 60 K 40 + ZnSO 4Mean4.22.1 (50)5.22.6 (50)5.32.7 (51)5.92.5 (42)5.32.7 (51)5.76.02.8 (49)2.9 (48)5.4 2.8 152)5.72.8 (49)5.76.13.5 (61)3.4 (56)6.2 3.1 (50)5.6 2.8 (50)a Figures in parentheses are percentages of main crop yield.