| Long-term conventional tillage is not conducive to the improvement of farmland crop productivity,and conservation tillage measures play an important role in water storage and soil fertility improvement compared to conventional tillage.However,the drawbacks of single tillage measure is increasingly apparent.Relevant studies have shown that conservation rotation tillage measures can effectively alleviate the drawbacks of single tillage measures and improve crop productivity.Based on the long-term conservation tillage positioning experiment that began in 2007,this study continued to carry out experiments in 2021-2022.Six tillage treatments were set up,including ploughing tillage(CT),subsoiling tillage(ST),no-tillage(NT),no-tillage/subsoiling rotation(NT/ST),subsoiling/ploughing rotation(ST/CT),and ploughing/no-tillage rotation(CT/NT),with ploughing tillage(CT)as the control treatment(CT).Through measuring soil physical and chemical properties,root morphology,photosynthetic performance,and crop yield of spring maize further explore the mechanism of soil-root-canopy synergistic effects of long-term conservation rotation tillage on improving productivity of spring maize in dryland.The main conclusions of the study are as follows:1.Long term NT and CT respectively lead to higher and lower soil bulk density.ST and rotation tillage can significantly improve soil bulk density,create suitable soil structure,promote soil water storage,moisture conservation,and regulate crop water use.Compared with CT treatment,ST,ST/CT,and NT/ST treatments reduced the soil bulk density of20-60 cm soil layer by 1.36% to 4.67%.The soil water storage capacity of spring maize before sowing under NT/ST,CT/NT,NT,ST/CT,and ST treatments was higher than that of CT treatment.Three rotation tillage treatments were beneficial for increasing the soil water storage of 0-200 cm soil layer during the jointing,tasseling,and grouting stages,while the soil water storage capacity during the growth period of spring maize under NT treatment was generally lower than that under CT treatment.Compared with CT treatment,the organic matter content,total nitrogen content,and available phosphorus content of 0-20 cm soil layer under NT,NT/ST,CT/NT,and ST treatments increased by 9.07%-24.3%,9.81%-10.89%,and 8.94%-28.8%,respectively.The total phosphorus content of 0-20 cm soil layer under NT/ST,ST,and CT/NT treatments increased by 12.26%-26.07% compared to CT treatment,respectively.2.Different tillage treatments significantly affected the root length growth characteristics of spring maize,and were closely related to the physical and chemical environmental effects of soil.In 0-80 cm soil layer,the root length density and root surface area density of NT/ST,ST/CT,ST,CT/NT treatments increased by 8.96%-13.6%,11.07%-22.87%,3.83%-13.09%,4.61%-21.72%,respectively,compared to CT treatment during the tasseling and grouting stages,while NT treatment decreased by 12.29%,11.86%,24.74%,and 27.77%,respectively.Compared with CT treatment,the root dry weight density of 0-20 cm soil layer at jointing stage and grouting stage under CT/NT treatment increased significantly by 17.1% and 18.86%,respectively.The root dry weight density of0-10 cm soil layer under NT/ST treatment significantly increased by 14.36% compared to CT treatment during tasseling.Correlation analysis showed that there was a significant negative correlation between soil bulk density and root morphology,while there was a significant positive correlation between soil organic matter content,available phosphorus content,and root morphology.The regression equation shows that there is a significant linear relationship between soil water content and root length density and root surface area density in 0-20 cm soil layer during the tasseling stage,and a very significant linear relationship between soil water content and root dry weight density in 20-60 cm soil layer.3.There were significant differences in photosynthetic characteristics of spring maize ear leaves under different tillage treatments.The net photosynthetic rate and chlorophyll content of CT/NT,NT/ST,and ST/CT treatments increased by 1.78%-4.53% and 1.89%-4.84%,respectively,compared to CT treatments during the tasseling stage.Compared with CT treatment,the net photosynthetic rate of ST treatment increased by 4.54% and 2.43%during jointing and tasseling stages,respectively.The transpiration rates of the three rotation tillage treatments increased by 15.3%-28.57%,4.84%-11.55%,and 1.97%-7.97%during jointing,tasseling,and filling stages compared to CT treatments,respectively.Compared with CT treatment,the net photosynthetic rate of NT treatment decreased by2.37%-7.47% during jointing,tasseling,and filling stages.The dry matter accumulation under the three rotation tillage treatments increased by 2.97%-7.18% compared to the CT treatment during the tasseling stage,and the dry matter accumulation under the ST treatment during the mature stage increased by 0.68% compared to the CT treatment.Compared with CT treatment,the three rotation tillage treatments increased nitrogen accumulation in stems and leaves before flowering and in grains during late growth.Correlation analysis showed that root morphology was significantly positively correlated with net photosynthetic rate of leaves and nitrogen accumulation in plants.4.Conservation tillage treatment has a significant impact on spring maize yield and water and fertilizer utilization efficiency.The grain yield of CT/NT,NT/ST,ST/CT,and ST treatments increased by 5.21%-20.16% compared to CT treatments.The water use efficiency of CT/NT and NT/ST treatments increased by 9.56% and 5.73% compared with CT treatments,respectively.The yield and water use efficiency of NT treatment were3.73% and 12.73% lower than those of CT treatment,respectively.Under CT/NT,NT/ST,and ST treatments,the radiation utilization efficiency and nitrogen fertilizer partial productivity increased by 0.85%-7.23% and 5.21%-20.16%,respectively,compared to CT treatment.The regression equation showed that there was a significant linear relationship between net photosynthetic rate and grain yield,water use efficiency,and nitrogen partial productivity,while there was a very significant linear relationship between transpiration rate and grain yield,nitrogen partial productivity.In summary,combining the effects of different tillage measures on soil physical and chemical properties,root morphology,canopy photosynthetic performance,yield,and resource utilization efficiency,it can be concluded that the improved soil physical and chemical properties of long-term protective rotation tillage affect the root growth configuration of dryland maize,effectively promote functional leaf photosynthetic characteristics,and ultimately significantly increase grain yield.In this study,the NT/ST rotation tillage model and the CT/NT rotation tillage model have a good overall regulatory effect on soil-root-canopy-yield,and can be used as suitable tillage models for this region to promote and apply. |
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