Effects Of Seeding Stage On Source-Sink Relation In A Ratoon Rice Cropping System With Labor Reduced Cultivation In Northearstern Jiangxi Province

The number of famers was becoming less and less in most areas, because the rural population went gradually to the town and city in China with the development of social and economic and so on. This led that the shortage of famers was serious in many areas, and then food production and the national food security were threaten. So labor reduced cultivation was developed rapidly in recent years. Rice (Oryza sativa L.) ratooning is the production of a second rice crop from the stubble left after the main crop harvesting. It has the advantage which could be harvested twice when seeded once. However, compared with direct-seeding and seedling-throwing, the development of ratoon rice was limited seriously by the disadvantaged aspects that were artificial planting and harvesting of main rice. Therefore, the objective of this study was to establish a ratoon rice cropping system with labor reduced cultivationin northeastern Jiangxi province.1) Influencing factors of ratooning buds were researched through investigating the ability of ratooning buds.2). Source-sink relations were analyzed in labor reduced cultivation and different seeding stages,3) thus, evaluation the development of ratoon rice with labor reduced cultivation according to the regional climate conditions and social economic benefits in northeastern jiangxi province. The results of this study in 2008,2009 and 2010 are presented as follows:Influencing factors of ratooning buds:The temperature and solar radiation could meet the growth of main and ratoon rice in northeastern Jiangxi province. Main rice should be harvested by manual labour because ratooning buds would be destroyed in mechanical harvesting. Ratooning buds were mainly in the third and fourth quarter, and they were 54.4%-60.5% in total ratooning buds. Ratooning buds of direct-seeding and seedling-throwing were lower than transplanting, and seeding earlier was more than later. This suggested that main rice was seeded in later March and earlier April which could improve the ratooning buds ability.Source-sink relations in labor reduced cultivation:Leaf area index of directed-seeding and seedling-throwing was lower than transporting by 37.4% and 29.5% when effective accumulated temperature was more than 1700℃in main rice, but they were not significant different in ratoon rice. In main rice, grain numbers were decreased than transplanting by 41.8% and 26.6% in directed-seeding and seedling-throwing, and they were reduced by 47.2% and 16.3% in ratoon rice. This indicted source and sink of directed-seeding and seedling-throwing were lower than transporting.Yield and its compontents in labor reduced cultivation:In 2009, the yield of main rice in ditect-seeding and seedling-throwing were reduced than transplanting by 15.8 and 6.7 percent, respectively, but there was no significant difference in ratoon rice. In 2010, the yield of main rice was no significant differences in three cultivations, but in ratoon rice, compared with transplanting, yield of ditect-seeding and seedling-throwing were decreased 35.1% and 30.1%.The spike numbers and length and grain number per spike were different significantly among three cultivations in,main rice. Spike number and length and grain number per spike in direct-seeding were reduced than transplanting by 36.8%,2.1% and 8.2%, respectively. in ratoon rice, spike numbers in directed-seeding and seedling-throwing were decreased 35.8% and 10.7%, compared with transplanting, and spike length and grain number per spike of direct-seeding were reduced than transplanting by 6.5% and 14.8%. This suggests that the ratoon rice crooping system with labor reduced cultivation was weaker than transplanting, and spike numbers and grain number per spike were limit factor in the yield formation.Effection of seeding stages:Ratooning buds ability, source-sink relations, yield and its compontents, stubble dry matter and nitrogen translocation efficiency were better when main rice was seeded in later March and earlier April. Their yield in main rice was about 8000 kg hm2 which was increased 27.5% than latter (4000 kg/hm2 round), and the increases of ratoon rice was 33.4%. This showed earlier seeding could increase yield of main and ratoon rice.Evaluation of economical profits:Economical profit of three cultivations in main and ratoon rice was not different significantly in 2009, however, in 2010, profit of direct-seeding and seedling-throwing in main rice were more than transplanting by 61.9% and 44.8%, but they were decreased 45.4% and 36.4% than transplanting in ratoon rice due to their yield of ratoon rice were lower significantly, so their annual benefit were down 699.2 and 787.1 RMB/hm2 than transplanting. The economical profit of ratoon rice cropping system with labor reduced cultivationin could improved scolding seeding earlier in northeastern Jiangxi province.To sum up, the climatic resources was better for the development of main and ratoon rice in northeast Jiangxi province, and the main rice was seeded in later March and earlier April could meet the growth of demand in ratoon rice. Seeding earlier could improve their yield and profits, although economic benefits of directed-seeding and seedling-throwing were lower than transporting, Therefore, ratoon rice cropping system with labor reduced cultivation could promot in northeastern Jiangxi province, therefore, harvesting mechanization of main rice and breeding and improving varieties of ratoon rice are key points in the future.