| The synergistic improvement of yield,quality,and nutrient utilization could be archeieved with the reasonable application of phosphorus and potassium fertilizer.Rice-wheat rotation is mainly distributed in the middle and lower reaches of the Yangtze River in China,with large planting areas and high proportions in Jiangsu,Anhui and other areas.At present,there are few reports on the high-quality,high-yield and efficient-application technology of phosphorus and potassium fertilizer under the conditions of long-term rice straw returning.In this study,different phosphorus and potassium fertilizer application periods(one-time basal application and half at basal application and half at jointing stage)and application rates(0,72,144 kg/hm2)were set up in the plots with long-term rice-wheat rotation and full straw returning in the cropping seasons of 2020-2021 and 2021-2022.The effects on the grain yield,quality,nutrient utilization,population quality,and lodging resistance in Ningmai 33 were analyzed,aiming to propose high-quality,high-yield,and efficient-application technology of phosphorus and potassium fertilizer,providing a reference for large-scale green and efficient production of rice-wheat cropping system.The main results were as follows:1.Compared with no phosphorus application,phosphorus fertilizer application significantly increased wheat grain yield,improved nitrogen and phosphorus utilization efficiency,absorption efficiency,physiological utilization efficiency,and also significantly increased grain bulk density,protein content,and wet gluten content.High phosphorus application rate(144 kg/hm2)showed no significant difference in grain yield,nitrogen,and potassium efficiency,lodging resistance index,grain protein content,and sedimentation value compared with low phosphorus application rate(72 kg/hm2),while the content of branched starch,while reducing phosphorus utilization efficiency,absorption efficiency,physiological utilization efficiency,and wet gluten content were increased.Compared with one-time basal application of 144 kg/hm2 phosphorus,the basal application and jointing stage application improved the absorption efficiency of nitrogen fertilizer,sedimentation value,and wet gluten content.Compared with other phosphorus application treatments,the treatment of 72 kg/hm2 phosphorus application still had a higher number of spikes,spikelets,higher leaf area index during the main growth period,higher dry matter accumulation,flag leaf SPAD value,and net photosynthesis rate after flowering,promoting the utilization efficiency of nitrogen and phosphorus fertilizers.In summary,moderate phosphorus fertilizer application(72 kg/hm2)is conducive to the synergistic improvement of wheat yield,quality,and efficiency,while the gain effect of high phosphorus application rate(144 kg/hm2)is not significant and even has negative effects on fertilizer utilization efficiency and grain quality.2.Compared with no potassium application,potassium application significantly increased wheat grain yield,lodging resistance index,nitrogen,phosphorus,and potassium utilization efficiency,absorption efficiency and physiological utilization efficiency,as well as grain hardness,bulk density,sedimentation value,wet gluten content,protein content and branched starch content.High potassium application rate(144 kg/hm2)significantly increased grain yield,nitrogen,phosphorus,and potassium accumulation,and utilization efficiency,as well as grain hardness,bulk density,sedimentation value,wet gluten content,protein content.and branched starch content compared with low potassium application rate(72 kg/hm2).Under the condition of 144 kg/hm2 potassium application,there was no significant difference between basal application and jointing stage application in terms of yield and fertilizer efficiency;However,resistance index,branched starch content,and CAT and SS enzyme activity were significantly increased.Compared with other potassium application treatments.the application of 144 kg/hm2 potassium significantly increased the leaf area index during the main growth stage,promoted the accumulation of dry matter,as well as the activities of GS,NR enzymes,and antioxidant enzymes,and improved the post-flowering photosynthesis capacity,which also promoted the utilization efficiency of nitrogen and potassium fertilizers.In summary,moderate potassium application rate(144 kg/hm2)is conducive to the synergistic improvement of wheat yield,quality,and efficiency.3.Under different phosphorus application levels,the influence of potassium application on wheat grain yield,quality,and nutrient utilization was not the same.Under relatively low phosphorus soil fertility(2021),potassium fertilizer did not significantly increase grain yield,nitrogen and phosphorus absorption efficiency,and nitrogen partial productivity under no phosphorus condition.When phosphorus fertilizer was applied,grain yield,nitrogen fertilizer absorption efficiency,and nitrogen fertilizer partial productivity were the highest at 144 kg/hm2.The potassium application rate,and potassium absorption and physiological utilization efficiency were the highest at 72 kg/hm2 potassium application rate,while there was no significant difference between one-time basal application and jointing stage application.Under relatively high phosphorus soil fertility(2022),potassium fertilizer did not increase grain yield,nitrogen fertilizer partial productivity,and phosphorus fertilizer utilization efficiency under no phosphorus condition.When the phosphorus fertilizer was applied,grain yield,nitrogen utilization efficiency,nitrogen fertilizer partial productivity,phosphorus fertilizer utilization efficiency,and phosphorus fertilizer partial productivity were the highest at 144 kg/hm2 potassium application rate,and there was no significant difference between onetime basal application and jointing stage application.In the two cropping seasons,potassium fertilizer did not increase the wet gluten content under no phosphorus condition,while under phosphorus fertilizer application,flour sedimentation value and wet gluten content were highest at 144 kg/hm2 potassium application rate.Therefore,under no phosphorus condition,the effect of potassium fertilizer on production indicators is not significant,and moderate potassium application could promote wheat yield and quality under excessive or insufficient phosphorus application conditions.Under moderate phosphorus application conditions,potassium application promised synergistic improvement of wheat yield,quality,and fertilizer utilization efficiency.4.Overall,there is a suitable combination of phosphorus and potassium fertilizer application for high-yield,high-efficiency,and high-quality wheat production in the ricewheat cropping system.The combination of one-time basal application of 72 kg/hm2 phosphorus fertilizer,basal and jointing stage application of 72 kg/hm2 potassium fertilizer is conducive to improving population quality,enhancing post-flowering antioxidant capacity,delaying leaf senescence,improving sugar-nitrogen-phosphorus metabolism,maintaining high photosynthetic production capacity.The high spike numbers,spikelet numbers,and thousand-grain weight was archeived,which facilitiates synergistic improvement of grain yield,grain quality,fertilizer utilization,and lodging resistance.Therefore,this combination of phosphorus and potassium fertilizer application could be recommended as a high-quality and efficient application technology for phosphorus and potassium fertilizer under the conditions of long-term rice straw returning,ensuring large-scale green and efficient production and sustainable development of the wheat industry.The specific application rates of phosphorus and potassium in this experiment were only combined between 0,72,and 144 kg/hm2,and further detailed research is needed for the effects of different combinations of application rates on the improvement of yield,quality,and efficiency. |
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