Effects Of Fertilizations On Growth,physiology And Quality Of Rice And Wheat Under Shading At Different Growth Stages

The weakening of solar radiation is one of the main characteristics of global climate change.Rice and wheat are the main food crops in China.Under the background of weakening solar radiation,how to ensure the food security is an important issue that people are generally concerned about.It is not clear how different fertilizer types and fertilization amounts affect the growth,physiological metabolism,yield and quality of rice and wheat under the condition of reduced solar radiation,and whether fertilization can reduce the adverse impact of solar radiation weakening on crop production.This study through field simulation experiment to investigate the effects of applying different levels of compound fertilizer and silicate fertilizer under shading conditions with different growth stages on the growth,photosynthetic physiological characteristics,dry matter accumulation,yield and quality in rice and wheat,to provide experimental basis for regional rice and wheat sustainable production to cope with climate change and ensure food security.The field experiment adopts an orthogonal experimental design with 3 factors and 3 levels.The shading was set at three levels,i.e.no shading（S0,0%of shading rate）,shading at flowering-mature stage（S1,68%of average shading rate）,shading at tiller-mature stage（S2,68%of average shading rate）;The N-P-K compound fertilizers set three levels（N-P₂O₅-K₂O）,i.e.100 kg·ha^-1（F1）,200 kg·ha^-1（F2）,300 kg·ha^-1（F3）;The silicate fertilizer set at 3 levels,no silicate fertilizer（R0）,200 kg·ha^-1（R1）,400 kg·ha^-1（R2）.The experiment was carried out from May2020 to June 2021 at the Agrometeorological Experimental Station,Nanjing University of Information Science and Technology.The tested soil is stagnant paddy soil.The tested cultivars of rice and wheat were Nanjing 5055 and Jimai 211.The main results as follows:（1）The growth of rice and wheatS1 significantly increased plant height,LAI and SPAD value in rice,but inhibited rice tillers.S2 reduced the plant height,tiller number,LAI and chlorophyll content.F2 increased plant height,F3 increased tiller number,LAI and SPAD value.R2 increased plant height,tiller number and SPAD value,R1 and R2 significantly reduced LAI.For wheat,S1and S2reduced plant height,tiller number and LAI,but S1 increased SPAD value.F2 increased plant height and LAI,and F3 increased tiller number and SPAD value.R1 increased increased tiller numbers and R2 increased plant height,LAI and tiller numbers,but R1and R2 reduced SPAD value.The best treatment combinations for rice and wheat growth were suggested as S1F3R2and S0F2R2.（2）The photosynthetic,fluorescence characteristics in rice and wheat at filling stagesS1 and S2 reduced the net Photosynthetic rate（Pn）,Stomatal conductance（Gs）,Transpiration rate（Tr）and Water Use Efficiency（WUE）,but increased the intercellular CO₂concentration（Ci）of rice.F2,F3 increased Pn,Gs,Tr and WUE,but F1 increased Ci.R2increased Pn,Gs,Tr and WUE,but inhibited Ci.For wheat,S1 increased Pn,Gs,Ci,Tr and WUE.S2 increased Ci and Tr,but decreased Pn,Gs and WUE.F1increased Pn,Gs,Tr and WUE,but F3 increased Ci.R2 increased WUE,but decreased Tr.R1 was more suitable to promote Pn,Gs,Ci.For rice,S1 and S2 enhanced the potential active light energy conversion efficiency of PSII,improved the performance index and photosynthetic driving force at the filling stage of rice and wheat.For rice and wheat,F2,R2 and F1,R1 increased the maximum photochemical quantum yield of PSⅡ,improved the photoenergy conversion efficiency and potential activity and enhanced the performance index and photosynthetic driving force.The best combinations to enhance the photosynthetic capacity in rice and wheat were suggested as S0F2R2 and S1F1R1.（3）The dry matter accumulation,yield and quality in rice and wheatFor rice,S1 increased dry matter accumulation after flowering,but S2 inhibited.S1 and S2 reduced the seed setting rate,1000-grain weight and yield of rice,with reducing yield by43.99%and 54.24%.F1 increased the total dry matter accumulation after anthesis,seed setting rate,1000-grain weight and yield in rice.R1 increased 1000-grain weight,seed setting rate and yield,with increasing production by 27.18%.R2 increased the total dry matter accumulation after anthesis,the 1000-grain weight and yield,with increasing production by14.04%.For wheat,S1 and S2 reduced the total dry matter accumulation after anthesis,1000-grain weight,seed setting rate and yield,with droping production by 47.33%and 22.10%.F3increased the total dry matter accumulation after anthesis,yield,1000-grain weight and seed setting rate,and increased production by 6.70%.R1 increased the 1000-grain weight and seed setting rate,and increased yield by 0.32%.R2 increased the total dry matter accumulation after anthesis.Shading decreased yield in rice and wheat,and appropriate fertilization increased yield.The best combinations for the yield of rice and wheat were suggested as S0F1R1 and S0F3R1.S1and S2 reduced processing quality,amylose content,amylopectin content and total starch content,but increased protein content in rice.F1 improved the processing quality in rice.F2 improved the amylose content,amylopectin content and total starch content,and F3increased protein content.R1 and R2 reduced the content of amylopectin,total starch and protein,but R1 improved the processing quality and amylose content in rice.For wheat,S1and S2 decreased the amylose content and total starch content,but S2 increased the grain protein content.F3 increased the grain amylose content and total starch content,but decreased the protein content.R1,R2 reduced grain amylose content,total starch content and protein content.Shading reduced the quality in rice and wheat,and appropriate applications of compound fertilizer and silicate fertilizer improved the quality.The best combination for improving rice processing quality was suggested as S0F1R1,the best combination for improving rice and wheat nutritional quality was recommended as S0F2R0 and S0F3R0.