Effects Of Rice Yield And Nutrient Balance Of Paddy Field System Under Rice-Duck And Biogas Slurry

Rice-ducking farming, which originated from the the killing locust during the Spring and Autumn and Warring Stage period, was the essence of chinese ancient agriculture. It then forms the planting-breeding combined mode of agriculture. As for feeding ducks in paddy fields, it is far from enough that sufficient nutrition could support the lowest level of need of paddy rice. This research is based on the rice-duck farming and aims at remedy the inefficiency of nutrition absorbed during the paddy rice’s growth by providing biogas slurry. Through the field and pot experiment, the paper critically analyzes the relationship between the growth dynamics of rice plant, yield components and the nutrient flux and balance of paddy ecosystem, under the condition of providing biogas slurry to rice-duck farming system. The aim of the paper is to provide reasonable foundation of promotion in integrated rice-duck farming system and the use effective use of biogas slurry. Major results of the research are listed as below:1. Effects of biogas slurry and rice-duck on growth dynamics and yieldIn normal nitrogen application, only applying biogas slurry not advantages for rice growth,and can reduce the yield, but if add rice-duck in the base of biogas slurry can improve the situation.Pot experiment shows that the plant height, tillering, chlorophyll content and yield of check treatment (applying chemical fertilizer, the nitrogen amount applied as top dressing is 198kg-hm’2) is better than N1 (the nitrogen amount applied as top dressing is the same as check treatment); Field test shows that the tiller number and yield of "biogas slurry+rice-duck" can be improved significantly, compared with that of biogas slurry treatment. N2 (the nitrogen amount applied as top dressing is doubled the check treatment), N3 (the nitrogen amount applied as top dressing is triple the check treatment) can promote the rice growth, increase the effective tillering number and chlorophyll content, but have no significant influence on yield.By faciliating with N2 and N3, the ability of tillers could increase by 9% and 16%, but have no significant influence on yield, compared with that of chemical fertilizer.2. Effects of biogas slurry and rice-duck on nitrogen and phosphorus content in plantsAppling biogas slurry clearly increased the nitrogen and phosphorus content in plants,and compared with nitrogen the increasing of phosphorus content in plants of "biogas slurry+rice-duck" was more significant. By faciliating with the treatment of biogas slurry and "biogas slurry+rice-duck", the ability of phosphorus content in root could increase by 22% and 41%,and the phosphorus content in stem and leaf could increase by 13% and 27%, compared with that of using chemical fertilizer treatment.The nitrogen content in root, stem and leaf, grain and phosphorus content in root, stem and leaf increase,but the phosphorus content in grain increases first and then start to drop,as with enhancement of biogas slurry utilization.3. Effects of biogas slurry and rice-duck on concentration of nitrogen and phosphorus of soil surface waterThe concentration of nitrogen and phosphorus in soil surface water of the treatment of biogas slurry decreased rapidly first and then decreased slowly, and the decrease rapidly period appeared in the first 3 to 5 days. The decrease rapidly period is the crucial time to control the runoff pollution of nitrogen and phosphorus of soil surface water. In the range of biogas slurry irrigation,the concentration of nitrogen and phosphorus of soil surface water increases,and the nitrogen and phosphorus digestion cycle extend, as with enhancement of biogas slurry utilization. The digestion cycle of N1 is about 11 days, and the activities of ducks can shorten it.4. The balance of nitrogen and phosphorus of rice-duck ecosystemFeeding ducks in paddy fields can make paddy field system less dependent on fertilizer, improve the return rate of nitrogen and phosphorus, maintain the balance of nutrient and reduce inputs of nitrogen and phosphorus of paddy field system. In the rice-duck ecosystem, fertilizer is the most important part of nutrient input. The percentage of nutrient of nitrogen in total input of using chemical fertilizer, biogas slurry, "biogas slurry+rice-duck"and rice-duck treatment was 86%,87%,70%,70% respectively. The nitrogen and phosphorus return rate of rice-duck treatment is 4.5,3.7 times higher than using chemical fertilizer, respectively.