| As an important food crop in Shandong Province,summer maize occupies an important position in the North China Plain and even in the whole China.However,the problem of agricultural water consumption is becoming more and more serious.Global climate change and long-term traditional rotary tillage have had negative effects on the topsoil.As an effective conservation tillage measure,subsoiling can improve the soil environment,construct a reasonable tillage layer structure,and increase crop yield.However,most of the previous studies focused on the comparison of several different conservation tillage techniques,setting a single depth of subsoiling,and the selection of depth of subsoiling in actual production was not standardized to some extent.Combined with the field experiment of summer maize,this study compared the effects of different depth of subsoiling on the yield formation and water consumption characteristics of summer maize compared with traditional rotary tillage under the wheat-maize two-cropping cropping system in Shandong Province,in order to determine the more suitable depth of subsoiling for the actual production in Shandong Province.At the same time,due to the limitations of field experiments,it has been difficult to continuously characterize soil water consumption and loss under different tillage management schemes.The field test results were combined with the root zone water quality model(RZWQM2),and the RZWQM2 model was calibrated and verified by using the test data of summer maize growth period from 2017 to 2019.In order to verify the applicability of the RZWQM2 model in this experimental situation,and use the RZWQM2 model as a computing tool to further analyze the process of farmland water consumption and loss.There are three treatments in this experiment: rotary tillage 15 cm(R15);subsoiling 35cm(S35);subsoiling 40 cm(S40)was carried out before sowing of winter wheat,and the frequency of subsoiling was once every two years.Each treatment was repeated for 3 times,and the test site was divided into 9 plots.The results show that:1.Compared with rotary tillage(15cm),35 cm and 40 cm of subsoiling can effectively increase the soil volume water content and soil water storage capacity within 0–130 cm soil layer.Meanwhile,the effect of 35 cm of subsoiling on soil water is not as good as that of 40 cm of subsoiling.Under the better soil moisture conditions,35 cm subsoiling and 40 cm subsoiling show better leaf area index and aboveground dry matter accumulation,ear leaf chlorophyll content is relatively increased,at the same time delayed the leaf area index and the declining rate of ear leaf chlorophyll content,physiological basis for assimilation and yield formation of organic matter.2.In terms of summer maize water consumption and yield formation,35 cm of subsoiling and 40 cm of subsoiling and rotary tillage compared to 15 cm,can absorb more effective use of deep soil moisture,using supply crop growth,the 35 cm of subsoiling in yield and yield components to liquidate the optimal,relative to the rotary tillage 15 cm function to the promotion of production reach significance level,therefore,the grain yield and WUE were significantly improved.The results of field experiment showed that the treatment of 35 cm subsoiling was a reasonable conservation tillage measure in the North China plain,and could improve the yield and WUE of summer maize under the cropping system of two crops a year.3.Field test results showed that the soil moisture content(SWC)and evapotranspiration(ET)of 35 cm and 40 cm of subsoiling increased compared with that of 15 cm rotary tillage.RZWQM2 shows good applicability in this scenario,and successfully simulates dynamic changes of soil water caused by rainfall distribution of 15 cm in rotary tillage,35 cm in subsoiling and 40 cm in subsoiling.The normalized root mean square error(n RMSE)of soil water storage(SWS)and farmland evapotranspiration(ET)were 11.31–19.65% and 11.99%–16.57%,respectively,with n RMSE values below 20%.Therefore,it can be considered that the model has a good simulation effect on such indicators.4.The calibrated model is used for supplementary calculation of actual transpiration(AT),actual evaporation(AE)and deep drainage.According to the model calculation,35 cm of subsoiling can effectively reduce the actual evapotranspiration in the early growth stage and maintain the higher transpiration in the later growth stage.However,the depth of 40 cm resulted in a high leakage rate and cumulative water leakage.In terms of soil water balance,35 cm of subsoiling is closer to summer maize production with high water use efficiency,which is conducive to the establishment of summer maize production model with high water efficiency.Through the field experiment combined with the RZWQM2 model simulation,the experimental results showed that 35 cm of subsoiling had a better performance in improving soil moisture,reducing soil evaporation,promoting the growth and development of summer maize and yield formation,etc.,and could better balance the relationship between yield and evapotranspiration in farmland,and reached the highest WUE in the 3 treatments of this experiment.35 cm can be used as a suitable subsoiling depth for the Shandong Province.The RZWQM2 model has a good calibration condition,and its calculation results suggest that increasing the depth of subsoiling may lead to more drainage water. |
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