| Nowadays,more than one-third of the population feed on rice as the staple food in the world,and more than two-thirds of the people who feed on rice as the staple food in China.’High input,high output’ intensive agriculture in China has contributed greatly to food security,but caused heavy agricultural nitrogen(N)loss.Modern agriculture faces the dual challenge of increasing food supply and protecting the environment for sustainable agriculture.It is essential to reduce nitrogen loss and pollution without sacrificing rice yield especially in the case of high yield and high N input.Cultivation measures to promote high-yield,high-efficiency and high-quality rice have become the key to cultivation research.Therefore,in this study,two super rice cultivars,Yongyou 2640 and Wuyunjing 24,were used as the research objects,and the local farmers’ practices measures in the Yangtze River Basin were used as controls.Nitrogen blank area,local farmers’ practices,reduce nitrogen,densification and nitrogen reduction,alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,application of silicon and zinc fertilizer,etc.Based on yield and nitrogen utilization efficiency,the impact of cultivation measures on the growth and development of the two super rice cultivars,nitrogen absorption and transport,soil structure and properties,soil nutrient content,soil enzyme activity,rice root activity and other indicators is analyzed,in order to clarify the high-yield,high-efficiency and high-quality cultivation measures of super rice cultivar and its physiological mechanisms.The main findings are as follows:1.Rice yield,population growth and development characteristics,and nitrogen fertilizer use efficiency indicatorsThe grain yield of the Yongyou 2640 cultivar under the measures of densification and nitrogen reduction,alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,application of silicon and zinc fertilizer cultivation measures were 12.8 t hm-2,13.4 t hm-2,13.6 t hm-2,14.1 t hm-2,14.7 t hm-2,and the local farmers’practices(control)yield is 12 t hm-2,compared with the control,the yield of these treatments increased by 6.3%,11.4%,13.4%,17.0%,and 22.4%,respectively;The grain yield of Yunjing 24 under the measures of densification and nitrogen reduction,alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,and application of silicon and zinc fertilizer cultivation measures were 10.1 t hm-2,11.0 t hm-2,11.6 t hm-2,12.0 t hm-2,and 12.3 t hm-2,respectively,and the control treatment yield was 9.9 t hm-2.which increased by 2.6%,11.6%,17.8%,21.7%,and 25.1%,when compared with the local farmers’ practices(control).During the panicle differentiation period,the number of tillers of rice reached the maximum value.The densification and nitrogen reduction,alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,and application of silicon and zinc fertilizer cultivation measures showed an increasing trend when compared with the control.Yongyou 2640 increased 6.4-22.5%,and Wuyunjing 24 increased by 7.9-23.9%.Yongyou 2640 accumulated 45.2-58.8%of the nitrogen in the whole growth period from the panicle differentiation period to the heading stage,and Wuyunjing 24 accumulated 44.4-54.3%of the nitrogen.Compared with the control,the effective Leaf area index(LAI)of Yongyou 2640 at the heading stage increased by 9.8-22.0%,and the high-efficiency LAI increased by 8.7-21.4%under the treatments of densification and nitrogen reduction,alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,and application of silicon and zinc fertilizer cultivation measures.Compared with the control,the effective LAI of Wuyunjing 24 increased by 18.6-33.4%,and the high effective LAI increased by 19.1-36.7%.Under the above five cultivation measures,the dry matter weight of Yongyou 2640 was 7.7-35.7%higher than that of the control during the whole growth period,and Wuyunjing 24 increased by 12.7-37.1%,respectively.Compared with the control,the nitrogen fertilizer input was reduced by 10%,and the Agronomic N use efficiency(AE)of Yongyou 2640 under the treatments of Compared with the control,increased by an average of 45.6%,when compared with the control,PE(Physiological N use efficiency)increased by 14.0%on average,Apparent Recovery N use efficiency(RE)increased by 27.9%on average,and Partial factor productivity of applied N(PFP)increased by 25.7%on average;The AE of Wuyunjing 24 increased by 41.1%,PE increased by 18.8%on average,RE increased by 17.7%on average,and PFP increased 16.7%on average.The result indicate that the optimization of cultivation measures can improve the population quality,optimize the relationship between source and sink,increase the accumulation and transfer of nitrogen in the ground,increase the utilization of nitrogen fertilizer,and increase the grain yield of rice.2.The influence of cultivation measures on soil physical and chemical properties and soil nutrient supplyCompared with local farmers’ practices,the alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,application of silicon and zinc fertilizer,the soil nitrate nitrogen content increased by 5.4-56.3%.The soil organic matter content increased by 4.4-39.2%.The soil ammonium nitrogen content decreased by 8.7-39.9%.The optimization of cultivation measures also increased the activities of soil urease,invertase,catalase and invertase activity.The results of the experiment show that nitrogen in the soil is not the main factor limiting yield under high-yield conditions.The more nitrogen absorbed by the rice plant,the higher the yield.Therefore,the content of ammonium nitrogen and alkali-hydrolyzable nitrogen in soil is negatively correlated with yield.The optimization of cultivation measures reduced the content of nitrogen in soil and reduced the loss of soil nitrogen.Compared with local farmers’ practices,the alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,application of silicon and zinc fertilizer,the soil nitrogen loss decreased by 35.9-38.1%,45.2-51.6%,52-66.4%and 61.3-67.3%,respectively.The above results show that the alternate wetting and soil drying irrigation measures can not only increase the content of nitrate nitrogen and organic matter in the soil,but also increase the enzyme activity in the soil;the combined application of organic fertilizer and chemical fertilizer can not only significantly improve the physical properties of the soil,but also improve the soil Chemical properties,increase soil nutrient content and reduce soil nitrogen loss;increased tillage depth cultivation can effectively improve soil nutrient content and promote soil enzyme activity.The optimization of cultivation measures can improve soil texture and reduce soil nitrogen loss,so as to achieve the purpose of increasing grain rice yield.3.The effect of cultivation measures on the vitality of rice rootsCompared with local farmers’ practices,the alternate wetting and soil drying irrigation,increased application of cake fertilizer,increased tillage depth cultivation,application of silicon and zinc fertilizer,the rice root oxidation activity increased by 8.3-15.9%,11.1-20.4%,15.8-29.8%and 25.4-40.2%,respectively.The rice root oxidation activity increased by 8.3-15.9%,11.1-20.4%,15.8-29.8%and 25.4-40.2%,respectively.The root total absorbing surface area increased by 4.3-17.4%,9-24.8%,11.3-28.7%and 17.4-37.9%,respectively.The root active absorbing surface area increased by 1.7-6.7%,7.6-17.4%,10.9-25,2%and 2 1.1-45%,respectively.The above research results show that the extension of the rice root system in the soil layer can be improved through the optimization of cultivation measures,thereby increasing the absorption and utilization of soil nutrients by the rice,and promoting the high yield of rice. |
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