Experimental Study On Compensatory Effects Of Water Deficit And Rewatering In Black Soil Of Cold Region On Rice

China is a big agricultural country with insufficient water resources.The increasingly serious water shortage problem restricts the country's rapid development.Heilongjiang Province,which is located in the black soil region of the cold region,is a major agricultural province,and rice is the main crop in Heilongjiang Province.The traditional rice flooding method has huge water consumption and low water use efficiency.Therefore,exploring the suitable rice water-saving irrigation mode under the current water shortage is of great significance for the development of rice planting in Heilongjiang.In order to explore the effects of water deficit and rewatering at different growth stages on the physiological and ecological characteristics of black soil in cold regions,and understand the appropriate water status in different growth stages of rice,and provide a theoretical basis for determining the appropriate water management model for different growth stages in rice production practice,this study used Longqing No.3 rice as the experimental material,and the pot experiment to set the water deficit state in single growth period and two continuous growth periods,setted Light(soil moisture content controlled at 80% to 90% soil saturated water content),Medium(soil moisture content controlled at 70% to 80% soil saturated water content)and Heavy(soil moisture content controlled at 60%~70% soil saturated water content)3 water deficit levels,and used normal irrigation as a control(CK),which total treatments were 22,analyzed rice growth,chlorophyll fluorescence parameters,water consumption,yield and water use efficiency.The results showed that:Plant Height: During the single-growth-period water deficit treatment,all treatments in the tillering stage and all heavy water deficit treatments had a great impact on the plant height of the rice.in the 2-continuous-growth-period water deficit treatments,continuous heavy water deficit treatments had a greater impact.Only the water deficit treatment in the tillering stage and jointing stage had obvious compensatory effects;Tillering: Water deficit treatment in the tillering stage can significantly increase the effective tillering rate of rice,and the heavier the degree of water deficit was,the higher the effective tillering rate would be;Dry Matter Accumulation: During the singlegrowth-period water deficit treatment,the water deficit treatment in the tillering stage and milk stage had the greatest impact on the dry matter accumulation of rice,and the heavier the degree of water deficit was,the lower the dry matter accumulation would be.The dry matter accumulation of rice was only affect by heavy drought treatment at jointing stage and heading stage.The water deficit treatment in the tillering and jointing stages showed compensation effect.In the 2-continuous-growth-period water deficit treatments,the water deficit treatments during the tilleringjointing period and continuous heavy water deficit treatments had a great impact on the dry matter accumulation of rice.And only the tillering-jointing water deficit treatment showed a compensatory effect.Chlorophyll SPAD Value: The SPAD values of rice leaves in different water deficit treatments were higher than the control in varying degrees.After rehydrating in the latter stage of growth,the SPAD values reached or were close to the control level,and after 10 days,they showed the same change with the control,which indicated that the SPAD value of rice leaves could return to normal level after rehydration,showing a certain compensation effect;Chlorophyll Fluorescence Parameters: Water deficit had little effect on Fv/Fm in rice leaves,and only all treatments in the tillering stage and all continuous heavy water deficit treatment will significantly reduce it;The effect of water deficit on Fv'/Fm',?PSII and q P in rice leaves is related to the degree of drought,the heavier the degree of water deficit was,the lower the value woul be,and the 2-continuousgrowth-period water deficit treatments would further reduce them than in the single growth period.The effect of water deficit in tillering stage and milky stage on q N in rice leaves was related to the degree of drought.the heavier the degree of water deficit was,the lower the value woul be.Water deficit at jointing stage and heading stage did not have a significant impact on q N in rice leaves,and only continuous heavy water deficit treatment had a significant impact on it.After rehydration,almost all treatments could be restored to or even exceed the control level,showing a certain compensation effect.Daily Water Consumption: Affter all the single-growth-period water deficit treatment and the 2-continuous-growth-period water deficit treatments,the daily water consumption in the first 5 days after rehydrating were higher than the control,showing a certain compensation effect,and the medium and heavy water deficit treatments also showed a compensatory effect in the heading period.The medium and heavy water deficit treatments in the tillering and jointing stages had compensatory effects,and the heavier water deficit degree were,the later the compensation effect would occur;Yield and WUE: The single-growth-period light water deficit treatment had little effect on rice yield,and due to the compensatory effect,rice yields in the heading stage and milky stage were slightly improved compared with the control.All single-growth-period light water deficit treatment could improve water use efficiency,and the increase in heading stage and milk stage were much more great.In the 2-continuous-growth-period water deficit treatments,only continuous light and medium water deficit treatment in the tillering-jointing period and continuous light water deficit treatment in the heading-milk period can slightly improve the water use efficiency.According to the effects of different water deficit treatments on rice growth status,chlorophyll fluorescence parameters,daily water consumption,yield and WUE,and the results of compensation effects: 2-continuous-growth-period water deficit treatments were longer than single-growth-period light water deficit treatments in the during time,which is harmful to rice plants.In the singlegrowth-period light water deficit treatments,the treatments of medium and heavy water deficit were more serious than those of light water deficit,which also had different degrees of damage to rice plants.Therefore,light water deficit in single growth period is a suitable water state for rice growth.