Effects Of Irrigation Decision-making Methods On Growth And Yield Of Drip-irrigated Spring Maize In The Hexi Region

The Hexi Region was characterized by water shortage and low water use efficiency,and a suitable irrigation scheduling is of great significance for the local spring maize production.In this paper,the effects of three irrigation decision-making methods（based on soil moisture,evapotranspiration,and soil water potential）on the growth,yield,and water and nitrogen use efficiency of drip-irrigated spring maize in the Hexi Region were studied.The irrigation decision-making method based on soil moisture set 90%,70%and 50%of the available soil water content as the upper irrigation limit（represented by CK,W1,and W2,respectively）,and the upper irrigation limit was the field water capacity.The irrigation decision-making method based on evapotranspiration set weekly irrigation（EP100 and EP80 represented 100%and 80%of the actual evapotranspiration over the past week,and EF100 and EF80represented 100%and 80%of the predicted evapotranspiration over the coming week,respectively）,and the difference between the weekly evapotranspiration and rainfall was set as the irrigation quota.The irrigation decision-making method based on soil water potential set three low irrigation limits of-25k Pa,-45k Pa and-65k Pa（represented by P25,P45,P65）,and the upper irrigation limit was-5k Pa.The main findings are as follows:（1）Irrigation decision-making methods had a significant impact on the growth indicators of spring maize.Under the same irrigation decision-making method,maize plant height,leaf area and dry matter accumulation increased with increasing irrigation amount.Appropriately reducing the irrigation frequency and increasing the irrigation quota was more beneficial to the growth of spring maize stem diameter.The optimal dry matter accumulation treatments for each irrigation decision were W1,EP100 and P25,and they had no significant difference compared with each other,while the EP100 treatment had the smallest amount of irrigation water.The grain filling rate of the optimal treatment in each irrigation decision-making method was ranked as W1>EP100>P25,and there was no significant difference among them.（2）The physiological indicators of spring maize were sensitive to water.The SPAD value under the irrigation treatment based on past evapotranspiration regulation was best overall,and the accumulation of SPAD was inhibited when the irrigation amount was too high or too low.The net photosynthetic rate of spring maize under different irrigation decisions also had a similar trend.During the tasseling period,the optimal treatments under each irrigation decision were W1,EP100 and P65,respectively,while the net photosynthetic rates under the CK and P25 treatments with a large amount of irrigation water were relatively lower.The leaf water potential at noon was proportional to the irrigation amount in this period,and the optimal treatments in each method were CK,EP100 and P25 respectively during the grain filling period.（3）The yield and WUE of spring maize under different irrigation decision-making treatments were significantly different.Under different irrigation decision-making methods,spring maize yield basically increased with the increase of irrigation quota.Crop water consumption was also proportional to the irrigation quota;however,the relationship between yield and water consumption was not a simple linear relationship.The yields of CK and W1treatment were 2.34%and 6.90%higher than that of EP100,but the water consumption was26.13%and 27.35%higher than that of EP100,respectively.The water use efficiency of EP100 and EP80 treatments was significantly higher than that of CK,W1 and P25treatments.The water use efficiency of EP100 treatments was 23.32%,19.08%and 14.28%higher than that of CK,W1 and P25,respectively.The irrigation based on evapotranspiration regulation was superior to other irrigation decision-making methods in terms of water distribution,which was conducive to the use of more water by spring maize plants in the formation of yield.The nitrogen use efficiency of spring maize first increased and then decreased with the irrigation quota in each method.Under each irrigation decision-making treatment,the nitrogen use efficiency of EP100 treatment was highest,while the nitrogen use efficiency of EF80 treatment was lowest.（4）Different irrigation decision-making methods have their advantages,disadvantages and applicability.The irrigation decision-making method based on soil moisture and soil water potential are limited by the precision,accuracy,cost and monitoring area of monitoring instruments,while the method based on evapotranspiration has the advantages of accurate and easy data acquisition,high efficiency,low labor cost,and a wide range of applications.In addition,the accuracy and efficiency of irrigation methods based on past evapotranspiration are higher than those based on future evapotranspiration.Based on the comparison of past evapotranspiration treatments,there was no significant difference in yield and water use efficiency between EP100 and EP80 treatments,while the total irrigation water consumption under EP80 treatment was smaller and the irrigation water use efficiency was higher.（5）Considering various factors,based on the past evapotranspiration control irrigation,a weekly irrigation quota of 80%ET₀ was recommended as the most suitable irrigation decision-making method for high-efficiency and stable production of spring maize in the Hexi Region.