RICE RATOONING - IRRI books - International Rice Research Institute

140 RICE RATOONINGTable 7. Comparison of photoperiod-sensitive ratoon crop and normal aman ricecrop.Aman-sown riceRatoon cropVariety Plant Panicle Tiller Yield Plant Panicle Tiller Yieldht length (no.) (t/ha) ht length (no.) (t/ha)(cm) (cm) (cm) (cm)SR26B 146 22 7 3.7 158 24 11FR13A 113 22 8 3.8 146 25 11Tiliakkachari 142 24 9 3.8 170 26 13Achra108/1 132 25 7 3.9 170 27 11Mean 133 23 8 3.7 161 26 122.53.05.04.83.8FERTILIZER RESPONSE OF MAIN AND RATOON CROPSA field experiment was conducted at Bidhan Chandra Krishi Viswa Vidyalaya, WestBengal, in dry season (ratoon crop in 1983-84), to study the effect of major nutrientson growth and yield of the main crop and the ratoon crop of some photoperiodsensitivetraditional types and photoperiod-insensitive HYVs.GrowthThe varieties IR36, IR50, CR1014, and Kumargore were transplanted in Januarywith four fertilizer treatments: 100 kg N/ha, 100 kg N and 22 kg P/ha, 100 kg N and42 kg K/ha, and 100 kg N, 22 kg P, and 42 kg K/ha. Immediately after main cropharvest, all plots received 20 kg N/ha followed by an additional 10 kg N/ha 60 dlater.Main crop yields of Kumargore and CR1014 were appreciably lower thanthose of IR50 and IR36 in the dry season (Table 8). This was because the number ofmatured panicles was lower in the photoperiod-sensitive Kumargore and CR1014than in the photoperiod-insensitive IR36 and IR50. The ratoon crop yields of IR36and IR50 were appreciably lower than their main crop yields but the ratoon yields ofCR1014 and Kumargore were only slightly lower. The IR50 ratoon crop yieldedmore than IR36; on par with Kumargore and CR1014. Panicle initiation in IR50and IR36 was 30 d after main crop harvest. Yield was recorded as the sum total ofmatured panicles collected at 15-20 d intervals. Kumargore and CR1014 partiallylodged in wet season after 30 kg N/ha was applied after main crop harvest. Thenumber of grains per panicle and 1,000-grain wt of IR36 and IR50 were appreciablyreduced in the ratoon crop, but not as much as in the CR1014 and Kumargoreratoon crop.Ratoon cropping of the dry season crop of IR36 and IR50 was not feasibleagronomically because of staggered maturity of the panicles. The yields ofKumargore and CR1014 were also less than those of the HYVs. The residual effectof phosphorus was not significant in the dry-season crop. There is, however, a needfor varieties and management practices to raise total yield of the ratoon and the maincrops in West Bengal lowlands, where fields are waterlogged for long periods in thewet season and a dry season crop is possible by tapping nearby water resources.