Preliminary Study On High-Efficient Management Of Water In Cultivated Rice

China is a country with serious shortage of water resources.Irrigation water for rice production alone consumes nearly 50%of the total water consumption in China. Therefore,screening and using rice vareities with more efficient use of water in rice production and carrying out water-saving irrigation have strategic significance for the national food security and water resources conservation in China.Cultiveted in pots under rainout shelter,10 common rice(Oryza sativa) and 4 African rice(Oryza glaberrima) varieties were used as materials in the experiment and studied the quick,simple,initial screening indices and methods of efficient use of water varieties in rice.And different water management measures were tested to improve water use efficiency(WUE) using a high-WUE rice variety(Yangdao 6.).The main results were as follows:1.The quick simple initial indices and methods for screening high WUE rice varieties(1) Preliminary screening for high WUE according to root number and the whole plant WUE from sowing to boot stagePositive correlations(r=0.578^*,0.633^*,0.646^* respectively) were found between root number at the boot stage and WUE of grain yield,whole plant or above-ground part during whole growth period.And a positive correlation(r=0.537^*,) was found between yield WUE and whole plant WUE at boot stage.Therefore,root number and whole plant WUE could be used as an index and method for quick,simple,preliminary screening high WUE.(2) Preliminary screening for high WUE according to the WUE of above-ground part during tillering stage to boot stageThere was a significant positive correlation(r=0.627^*) between yield WUE and whole plant WUE during tillering stage to boot stage.And a positive correlation(r= 0.684^**) was found between yield WUE and the WUE of above-ground part during tillering stage to boot stage.All the correlation coefficients between the WUE of above-ground part and whole plant at the same growth stage were positive and significant at 0.01 probability level.(3) Preliminary screening for high WUE based on correlated indices of certain growth periodsPositive correlations(r=0.685^**,0.557^*,0.563^*,0.593^*,0.608^*,0.598^*respectively) were found between green leaf area,number of green leaves,tiller number,seedling height,root number,root volume and WUE of whole plant at tillering stage.Positive correlations(r=0.675^**,0.707^** respectively) were also found between green leaf area, seedling height and WUE of above-ground part.A significant positive correlation was found between specific leaf weight and WUE of whole plant or above-ground part at boot stage.And there was a significant negative correlation between root-shoot ratio,leaf water loss rate and whole plant WUE at grain filling period.And significant negative correlations were found between root dry weight,root-shoot ratio and above-ground part WUE at grain filling stage.Therefore,each correlation indices could be used as indices for screening water use efficiency in each corresponding period,respectively.2.Water management measures for improving water use efficiency of rice(1) Moderat water deficit treatment could improve WUE of rice in certain growth stagesThe yield WUE of Yangdao changed with irrigation water volumes in the same growth stages.Yield WUE changed with growth and development process on condition of the same irrigation water volumes.In the whole growth period of Yangdao 6,the WUE increased with irrigation water volumes except 65-80 stage.However,the WUE all had single-peak curve changes with increasing irrigation water volumes.The highest WUE value had a U curve changes with growing periods and irrigation water volumes in the whole period.(2) More times of irrigation with same volume of total water supply under moderate water deficit at tillering stage could increase the WUE and yield of riceYield and yield WUE of rice all increased with increasing irrigation times on condition of the same irrigation water volumes.Yield and yield WUE first increased and then decreased with increasing irrigation water volumes on condition of the same irrigation times that is one irrigation every two days and one irrigation every four days.Yield and yield WUE achieved the highest value under 70%-80%of the water supply.However,Yield and yield WUE increased with irrigation water volumes on condition of the same irrigation times that is one irrigation every six days.In this test, under 70%of the water supply,the yield WUE(1.303g/kg) of one irrigation every two days was 7.42%and 53.47%higher than that of one irrigation every four days and one irrigation every six days respectively,and 20.43%higher than that of control treatment (1.082g/kg).70%of the water supply with one irrigation in every two days achieved highest grain yield(50.16g/plant) among all treatments.The differences in yields between this treatment and the control as well as other treatments were significant at 0.01 probability level.The results indicated that the water management measure of frequent irrigations under moderate water deficit at tillering stage could increase the grain yield of rice.