Experimental Research On Rice Rainfed Irrigation In Sub-humid Areas

With the global warming and the rapid development of economy, Water shortage has become a global issue of common concern.China is the largest rice production and consuming countries of the world.The research on rice rainfed irrigation can take full advantage of natural precipitation, ease the drought in China, reduce agricultural nonpoint source pollution generated by rice cultivation, reduce greenhouse gas emissions and reduce irrigation times.It has a certain practical significance.Based on the domestic and international research of rainfed irrigation on rice, rainfed irrigation methods are presented. Upper limit is the maximum field water holding rate and the lower limit is60%of the maximum field water holding.According to the established irrigation program model for rice rainfed irrigation, a calculation procedure of rice rainfed irrigation system is developed which is used Matlab as a platform and is visual.Using the collected dates1991-2010rice rainfed irrigation programs of Gaoyou region are calculated.Under the rice rainfed irrigation system, the average annual amount of the whole growth period irrigation is2920.50m3/hm2. The average irrigation times are3.15times. An annual average of the whole growth period drainage is453.00m3/hm2. The average irrigation times are0.95times.Deep percolation capacity of the average annual amount of deep percolation is1206.00m3/hm2. The calculation of the irrigation program can meet the requirements of the non-fully irrigated rice.Through the comparison of rice grown with traditional irrigation mode, there are a lot of fluctuations in the soil moisture of rice rainfed irrigation around the maximum field water holding rate.In the entire growth period irrigation quota of rice rainfed irrigation model is1770m3/hm2. In the entire growth period irrigation quota of rice rainfed irrigation model is4800m3/hm2.3030m3m3/hm2is saved.Water-saving effect is obvious.Compared with the controlled trial, weeds of rice rainfed irrigation are more serious. Rainfed irrigation treatment weed density is greater than the flooding irrigation treatment; and is about five times more than the flooding irrigation treatment. The main reason is the changes of soil moisture.The existing control methods will not achieve the desired effect.In the early growth stage, the two treatments basically have the same plant height. The difference is very small. In Fertility medium-term, two plant heights respectively are37.16cm and33.60cm. The rainfed treatment is3.22cm higher than the flooding treatment.After ripening of the rice, the productions of the tow treaments are measured.The rainfed treament has average of42.80plants in1m2,2.53plants lower than the flooding irrigation treatment. The average per plant has average7.15spikes.An spike has108.72grain,8.24higher than the flooding irrigation treament. Seed setting rate is97.39%,1.02%higher than the flooding irrigation treatment, grain weight mean for the27.65g,1.39g higher than the flooding irrigation. The theoretical production of rainfed treament is8918.55kg/hm2. The theoretical production of flooding irrigation treatment is8532.75kg/hm2. The theoretical yield of rainfed treament is significantly higher than the flooding irrigation treatment.the main reason is that the average number of grains per panicle, seed setting rate and grain weight are all higher than the flooding irrigation treatment.rice rainfed irrigation can take full advantage of natural precipitation, ease the drought in China, reduce agricultural nonpoint source pollution generated by rice cultivation, reduce greenhouse gas emissions and reduce irrigation times.it is worth to be popularized.