Effect Of Different Cultivation Patterns On Rice Yield And Nitrogen Use Efficiency

Rice is one of the most important food crops in China.With the development of economics and urbanization,the population is increasing and the area of cultivated land is being reduced.It is necessary to increase more crop yield.Meanwhile,this increase needs to be accomplished under high input of water and fertilizer resources.It remains debates whether it is necessary to input more water and fertilizer resources for more food,and whether higher grain yield and higher nutrient use efficiency can be coordinately achieved?In this study,two rice cultivars,Yongyou 2640(an japonica hybrid)and Wuyunjing 24(a conventional japonica inbred),were field-grown with seven cultivation patterns including no nitrogen(N)application(ON),local farmers' practice(control),increasing plant density and reducing N rate(IPRN),precision irrigation(PI),applying organic fertilizer(AOF),deep plowing(DP),applying earthworm feces fertilizer(AEF).The effect of cultivation patterns on grain yield and its components,growth and development,physiological traits,N absorption and utilization efficiency,grain quality of rice and the emission of greenhouse gases from paddy field were investigated.The main results are as follows:1.Growth and development characteristics and physiology of riceThe average grain yield of the two cultivars under IPRN,PI,AOF,DP and AEF was 12.23,11.47,12.1,12.77and 10.77 t ha-1,respectively,and was 10.5-37.8%higher than that of control.Compared with control,IPRN,PI,AOF,DP and AEF significantly increased the percentage of productive tillers,leaf area index(LAI),efficient LAI and high efficient LAI,photosynthetic rate and chlorophyll content of the flag leaf,biomass from heading to maturity,grain-leaf ratio,and root weight and root oxidation activity,indicating that the population quality of rice could be improved and higher yield could be achieved through the improvement of cultivation techniques.2.Nitrogen absorption and utilization efficiency of riceCompared with those of the control,nitrogen recovery efficiency was increased by 15.6%,23.48%,52.9%,30.3%and 46%,and nitrogen agronomic efficiency increased by 50.9%,122.1%,152.3%,114.8%and 166.4%,respectively,under IPRN,PI,AOF,DP and AEF.The percentage of N translocation from heading to maturity under PI and AOF was also increased.The results suggest that higher yield and higher NUE can be achieved through integrating and optimizing cultivation techniques in rice production.3.Grain filling characteristicsThe PI promoted grain filling,increased the maximum rate,advanced the peak time of the the maximum rate,and significantly increased grain weight of inferior spikelets when compared with control,suggesting that integrating and optimizing cultivation techniques can improve grain filling and increase filled grain percentage of inferior spikelets in rice.4.Emission of greenhouse gases from paddy fieldThe emission of methane(CH4),and nitrous oxide(N2O)was decreased under PI,AOF and DP,leading to decreases in global warming potential(GWP)and GWP per unit grain yield(amount of GWP/grain yield),relative to that under control.The reduction in GWP under PI,AOF and DP was mainly due to the decrease in CH4 emission.The results imply that higher grain yield,higher nutrient use efficiency and higher environmental efficiency would be achieved through integrating and optimizing cultivation techniques.5.Grain qualityCompared with control,both DP and AOF significantly increased the milled rice rate,head rice rate and protein content,and reduced chalk rice rate,chalky area and chalkiness.Amylose content showed no significant difference among cultivation patterns.The results indicate that both DP and AOF can improve the milling quality,appearance quality and nutrient quality of rice.In summary,Both DP and AOF can optimize the quality of population such as the increases in sink capacity,photosynthetic potential of the leaves,root activity and remobilization of pre-stored non structural carbohydrates from stems to grain,and thereby increase grain yield,grain quality and N use efficiency and reduce enviromental risk in rice.