Effects Of Different Irrigation Methods On Yield And Water Use Efficiency Of Middle Indica Rice Varieties

Rice is one of the most important food crops in my country.More than half of the population feeds on rice as the staple food.At the same time,rice is a major water user.The amount of water used for irrigation in rice planting each year accounts for more than two-thirds of my country’s agricultural water.Therefore,,Realizing high rice yield and efficient use of water is of great significance to my country’s food security and resource utilization.For this reason,a total of 12 middle-maturing indica rice varieties,which are representative in the rice variety improvement process in Jiangsu Province in the past 80 years,were selected for this experiment,and these varieties were divided into early high-stalk varieties,dwarf varieties,and dwarf varieties based on the planting age and plant type and genotype.There are 4 types of semi-dwarf varieties and hybrid rice varieties.They are planted in the field for 2 consecutive years and set up 2 irrigation methods:conventional irrigation(CI),that is,maintain a shallow water layer of 2-3 cm throughout the growth period until one week before harvest.Alternate light-dry-wet irrigation(AWD)throughout the growth period,that is,from the shallow water layer to dry naturally until the soil water potential reaches-15 kPa,and then irrigate 1-2 cm,and so on.By analyzing the effects of different irrigation methods on yield formation,water use efficiency,agronomic and physiological characteristics in the process of variety improvement,in order to clarify the differences in the response of medium indica rice varieties to water and their agronomic and physiological characteristics,it is proposed to achieve high rice yield and water content.Efficient use of cultivation techniques.The main results are as follows:1.Output and composition factorsUnder the two irrigation methods,the yield of each type of variety gradually increased with the improvement of the variety.Under CI,the average yield of each type of variety was 4.91,7.15,7.95 and 10.23 t hm-2 in order.Under AWD,the average yield of each type of variety was 5.43,8.02,9.49 and 11.23 t hm-2 in order.The increase in yield is mainly due to the increase in total spikelets(number of spikes × grains per spike),of which the increase in the number of grains per spike is particularly significant.Compared with Cl,AWD has significantly increased the output of all types of varieties,with output increases of 11%,12%,19%and 10%respectively.The increase in yield is mainly due to the increase in the number of grains per panicle,seed setting rate and thousand-grain weight.2.Water use efficiencyUnder the two irrigation methods,the water use efficiency(WUEY)of the yield level of each type of variety gradually increased as the variety improved.Under CI,the WUEY of each type of variety is 0.65,0.95,1.06 and 1.36 kg m-3,respectively.Under AWD,the WUEY of each type of variety were 1.02,1.51,1.79 and 2.12 kg m-3,respectively.Compared with CI,AWD increased the WUEY of all types of varieties by 57%,58%,69%and 55%respectively.Under the two irrigation methods,the leaf-level water use efficiency(WUEL)of each type of varieties at the beginning of panicle differentiation and heading stage gradually increased with the variety improvement,and the WUEL of semi-dwarf varieties was the highest in the middle of grain filling.Compared with CI,AWD has increased WUEL of various types.At the beginning of ear differentiation,WUEL increased by 11%,7%,7%,and 5%;at heading stage,WUEL increased by 12%,8%,21%,and 18%;in the middle of grain filling,WUEL increased by 13%.%,12%,17%and 18%.It shows that water use efficiency can be effectively improved through variety improvement and reasonable irrigation.3.Agronomic and physiological traits of the aerial part Under the two irrigation methods,the rate of tiller and panicle formation,dry matter accumulation of shoots,number of secondary branches,leaf area index,grain-to-leaf ratio,and antioxidant enzyme activity of each type of variety during the main growth period gradually increased with the variety improvement.In the initial stage of panicle differentiation and heading stage,the leaf photosynthetic rate and transpiration rate gradually increased with the variety improvement,while in the middle stage of filling,the semi-dwarf variety was the highest.The angle of leaf implantation gradually decreased with the improvement of the variety.Compared with CI,AWD improved the above-mentioned above-ground agronomic and physiological traits.It shows that the improvement of population quality of modern semi-dwarf varieties and hybrid rice varieties,good plant type and leaf photosynthetic performance,and strong antioxidant enzyme activity under AWD are important reasons for achieving high rice yield and efficient water use.4.Root morphological and physiological characteristicsUnder the two irrigation methods,the dry root weight,root-to-shoot ratio,root length,root bleeding rate,root oxidation capacity,total root absorption surface area and active absorption surface area of each type of variety increased gradually during the main growth period.Compared with CI,AWD improved the above-mentioned root morphological and physiological characteristics.It shows that the improved root growth of modern semi-dwarf varieties and hybrid rice varieties under AWD can promote the increase of rice yield and water use efficiency.