Studies On Variety Screening Ratoon Rice And The Effect Ofmain Crop Harvesting Model On Ratoon Crop Yield

Rice ratooning is a cultural practice that usually harvested after the first crop season. It takes the advantage of dormant axillary buds exisiting at the rice stubble which then regenerates into new tillers and become a new crop. It has been practiced a long time since the adoption of ratoon rice cultivation. However, factors like high requirement for cultivation techniques, few varieties suitable for planting and low efficiency of manual work etc, restricted the development of ratoon rice. If the main crop harvest by mechanical way, it can effectively solve the technical bottlenecks.Therefore, selecting suitable ratoon rice varieties will prove the effect of mechanical harvesting of main crop on grain yield of ratoon crop. It is of great interest to provide candidate varieties for mechanization of ratoon rice and technologies theoretical guidance. The field experiments were conducted simultaneously in Chidong Town, Qichun county, Huanggang City, Xian’an District of Xianning City and Shakou Town, Honghu City, Jingzhou City of Hubei Province, in 2013 and 2014. Varieties used for screening test were chosen from the rice varieties already planting in Hubei which have been adopted as ratoon rice, where as those for the proven harvesting model of main crop impact on grain yield of ratoon crop, test of ratoon rice harvested by machine are selected from the varieties screening tests. Comparative study was made among the growth duration of main and ratoon crop, crop growth and development condition, yield and qualities of rice, and preliminary exploration of the effects of different main crop harvesting modes on ratoon crop yield. The results are as follows:1. The growth duration of the selected varities, practiced as one-season intermediate rice in Hubei province, is not longer than about 138 days. Seeding done before the March end, growth period of main crop is ranging from 128 days to 149 days, while that of ratoon crop is with in the range from 55 days to 73 days, and the total growth duration may not exceed 221 days.2. Among the varieties tested, grain yield of main crop and ratoon crop showed significant differences. The main grain yield of Tianyouhuazhan, Yiyou673, Zhunliangyou527, Longliangyouhuazhan and Shenliangyou5814 were 3.4% to 20.4% higher than the control(Fengliangyouxiang1), while the ratoon grain yield ofCliangyou4418, Guangliangyou476, Yiyou673, Liangyou6326 and Xinliangyou223 were 3.5% to 58.9% higher as compared to control. Compare the sum of main and ratoon grain yield, Cliangyou4418, Longliangyouhuazhan, Shenliangyou5814, Guangliangyou476, Xinliangyou223, Liangyou6326 and Zhunliangyou527 were 4.4% to 16.3% higher than the control, and can be seen as appropriate candidate varieties for the expansion of ratoon rice in Hubei.3. According to the yield components analysis, panicles per unit area and spikelets per panicle are the major factor affecting the ratoon grain yield, so it is benefical to achieve high grain yield of ratoon rice by selecting cultivas with strong ratoon ability or medium ratoon ability with large spike.4. The ratoon ability and the dry weight of rice stubble was a significant positive correlation. Improvement of the biomass in main crop and the dry weight of rice stubble is conducive to enhance the ratoon ability and panicles per unit area of ratoon rice.5. Rice grain quality of main crop and ratoon crop were significantly different among varieties. The brown rice rate, mill rice rate and head rice rate of ratoon crop were 1.4%, 4.8% and 57.4% higher than those of main crop, respectively. The chalky rice percentage and chalkiness of varieties ratoon crop were 60% and 78.6% lower than those of main crop. Among of them, the ratoon rice quality of Huanghuazhan, Cliangyou4418, Longliangyouhuazhan and Shenliangyou5814 were better.6. Significant differences were found between the grain yield of ratoon crop when main crop was harvested by labor and machine respectively while mechanical harvesting was 13.3% to 33.6% lower than manual harvesting. The lower yield of ratoon crop can be attributed to mechanical harvesting of main crop, for the reason that the wheels of machine rushed the ratoon crop, leading to the reduction of panicles per unit area.