Effects Of Lower Limit-controlled Irrigation Of Soil Moisture On Growth Characteristics And Yield Of Rice

The traditional irrigation method of rice will not only consume a lot of water,but the yield and quality will not be improved.At the same time,the current situation of my country’s water crisis is getting worse.Therefore,water-saving irrigation must not only achieve the goal of saving water,but also achieve stable or even high yield,which has become a strategic countermeasure for the development of water-saving agriculture.In order to explore the regularity of rice growth traits,above-ground biomass and yield under the controlled irrigation mode,a study will be carried out at Tuanbo Experimental Base in Jinghai District in 2020.In the experiment,the rice variety "Jinyuan 89" was selected,and the plot test was used.The submerged irrigation was used as a control.Three groups of different levels of soil moisture control upper and lower limits were set.They were respectively expressed as controlled irrigation 1(the upper limit is 10 cm deep water layer and the lower limit is 80% of soil saturated water content),controlled irrigation 2(the upper limit is 80% of soil saturated water content),controlled irrigation 3(the upper limit is soil saturated water content and the lower limit is 65% of soil saturated water content).The results were tested based on the Aqua Crop model by observing rice growth traits,yield and other indicators.Finally,it was concluded that controlled irrigation is a water-saving irrigation technology suitable for further research and promotion in the experimental area.The main conclusions of the experiment are as follows:(1)Different levels of irrigation control rice plant height and its increasing change trend are the same,and the plant height reached the maximum in the milk maturity stage.Compared with the three groups of controlled irrigation,the plant height of flooded irrigation has always been in the lead;the effect of controlled irrigation on plant height was reflected in the whole growth period.Therefore,controlling soil moisture can slow down and limit the plant height of rice.The number of tillers all rose to the highest peak in the late tiller stage,and the largest number of tillers during this period was flooded irrigation;the number of tillers showed a downward trend from the late tiller stage to the yellow maturity stage,until the number of tillers no longer changed in the yellow maturity stage.In order to control irrigation 1(43plants)> control irrigation 2(39 plants)= flooding irrigation(39 plants)> control irrigation 3(37 plants),at this stage,the change in the reduction amplitude of flooding irrigation was the largest,that was,the number of ineffective tillers was the largest,and the water was flooded.The effective tillering rate of irrigation was the lowest.(2)The leaf area index of rice controlled by different levels of irrigation rose to the highest peak during the heading and flowering stage.The largest one was controlled irrigation1 and the lowest was controlled irrigation 3 at this stage.Control Irrigation 1 and Control Irrigation 2 can better regulate the cooperative ability of nutrients and increase the photosynthetic rate of leaves,thus providing a material basis for increasing yield.(3)The aboveground biomass of rice in different irrigation treatments reached the maximum in the yellow maturity period,and the controlled irrigation 1 and controlled irrigation 2 were the best.The growth rates of the controlled irrigation 1 and controlled irrigation 2 in the yellow maturity period were 10.9% and respectively.6.9%.Control irrigation 1 and control irrigation 2 treatments were more conducive to the extraction of nutrients,making the above-ground biomass better.Control Irrigation 1 and Control Irrigation2 achieved the effect of increasing production,increasing production by 8.5% and 4.14%respectively;Control Irrigation 3 reduced production by 2.28%.It shows that proper control of the upper and lower limits of water content can not only achieve water-saving effects,but also increase yields;under severe water shortages,rice yields will actually decrease.Combined with irrigation water use efficiency and comprehensive consideration,the effect of irrigation control 2 was the best.(4)Based on the AquaCrop model to simulate the above-ground biomass and yield of rice,it can be seen that the measured and simulated values of above-ground biomass show the same trend.R2 is greater than 0.87,and the RMSE is in the range of 27%-30%.The results were good;the overall R2 of the four treatments was 0.97;the water production efficiency RE of different irrigation treatments ranged from 0.29% to 1.62%.Judging from the simulation results of the 4 groups of treatments,the control irrigation 2 has the best effect,which was consistent with the measured results,indicating that the simulation results are better.