| This experiment was carried out in 2022 in Key Laboratory Test Base of Water Physiology and Drought-Resistant Germplasm Improvement of Shandong Agricultural University.A total of 7 treatments were set in the experiment(all of the maize straw was returned to the field in full):the maize straw was crushed 1 cm with a mixing depth of 5 cm(M1D1),the maize straw was crushed 1 cm with a mixing depth of 10 cm(M1D2),the maize straw was crushed 3 cm with a mixing depth of 5 cm(M2D1),the maize straw was crushed 3 cm with a mixing depth of 10 cm(M2D2),the maize straw was cut into 5 cm vertical pole with a mixing depth of 7cm(M3D3),the maize straw was cut into 10 cm vertical pole with a mixing depth of 12cm(M4D4),the straw wasn’t returned to the field(M0).By combining the method and depth of straw ditch-buried returning,analyzed the influences on water and nitrogen utilization efficiency,photosynthetic characteristics and yield of maize,and proposed the control methods of straw returning for high-yield and efficient cultivation of maize.There are the main research results:1.Effects of straw deeply-buried methods on water absorption and utilization and the analysis of water sourceThe soil moisture content in each soil layer decreased gradually after anthesis.At tasseling stage,the difference was the most significant in 20-40 cm soil layer and the most significant in40-60 cm soil layer at filling stage.In the tasseling stage,the soil moisture of 10-20 cm,20-30cm and 30-40 cm soil layer under the treatment of M4D4 was significantly higher than that of the treatment of M0 by 13.47%,16.22%,13.96%,respectively.In the whole growth period of maize,the shallow soil water of 20-40 cm was mainly used,while the deep-buried straw returning treatment could effectively enhance the soil water retention capacity,increase soil water content and promote the growth and development of maize.2.Effects of straw deeply-buried methods on photosynthetic characteristics of maizeThe leaf area per plant and SPAD value of each treatment increased firstly and then decreased with the growth period of maize.Compared with M1D1,M1D2,M2D1 and M2D2treatments,the leaf area per plant of M4D4 treatment increased on average in each growth period after anthesis by 13.51%、19.17%、6.63%and 10.31%,and SPAD value increased on average by 5.23%、5.91%、3.63%、4.17%.The stomatal conductance,transpiration rate and photosynthetic rate of summer maize ear leaf under different treatments showed a unimodal trend with the prolongation of the post-anthesis time,then peaked at the grain-filling stage,and the change trend of intercellular carbon dioxide concentration was opposite to the trend of photosynthetic rate.Compared with M1D1,M1D2,M2D1,M2D2 treatments,T_r under M4D4 treatment increased by 27.90%,26.90%,11.56%,6.66%in each growth period after anthesis.Compared with M0 treatment,P_n and T_r of M4D4 treatment increased by 30.24%and 42.06%in each growth period after anthesis,respectively.Among the after-effects of straw returning to the field in maize season,the maize straw cut into 10cm vertical pole returning to the field improved the photosynthetic rate,transpiration rate and stomatal conductance of leaves after anthesis,at the same time reduced the intercellular carbon dioxide concentration and improved the photosynthetic capacity of maize.3.Effects of straw deeply-buried methods on maize yieldStraw returning to the field playing the after-effect in the maize season,which is conducive to the increase of dry matter in maize organs,improved the ability of dry matter accumulation and transportation after anthesis,and promote the accumulation of dry matter into grains.The grain yield of M4D4 was 3.79%higher than that of M3D3.Between straw crushing and returning treatment,the grain yield was significantly increased by crushing 3 cm compared with1 cm under the same returning depth.M4D4 treatment was 13.99%at average higher than that of straw crushing and returning treatment.M4D4 treatment was significantly higher than M0by 27.48%.The yield of maize could be significantly increased by the maize straw cut into 10cm vertical pole returning to the field.4.Effects of straw deeply-buried methods on water utilization of maizeIn the after-effect of straw returning in maize season,compared with M1D1,M1D2,M2D1and M2D2,the water utilization of the maize straw cut into 10 cm vertical pole returning to the field increased significantly by 19.64%,20.46%,13.61%and 13.89%.Compared with non-returning straw of M0 treatment M4D4 significantly increased by 32.25%.The results indicated that the maize straw cut into 10 cm vertical pole returning to the field played the after-effect on the maize season and significantly improved the water use efficiency.The maize straw cut into10 cm vertical pole returning to the field was significantly superior to the straw crushing and returning treatment of the straw non-returning treatment.5.Effects of straw deeply-buried methods on nitrogen utilization of maizeStraw returning can significantly reduce the nitrate and ammonium nitrogen contents in soil,increase the total nitrogen content in soil,improve the nitrogen supply capacity of soil,and promote the transformation among nitrogen forms.Compared to straw crushing and returning to the field,soil total nitrogen content significantly increased by 6.01%under M4D4 treatment,and significantly increased by 9.52%compared with M0 treatment.M4D4 treatment significantly increased nitrogen use efficiency,which was significantly higher than straw crushing and returning to the field treatments by 7.20%,and significantly higher than straw non-returning of M0 treatment by 14.15%.Among the after-effects of straw returning to the field,the maize straw cut into 10cm vertical pole returning to the field treatment could significantly improve nitrogen use efficiency and further promote the increase of maize yield.In summary,in the after-effect study of straw returning method of ditch-buried returning on maize,the maize straw cut into 10 cm vertical pole returning to the field treatment significantly increased the soil moisture content in the after anthesis growth period of maize compared with other treatments.The soil water holding capacity was enhanced and water use efficiency was improved compared with other treatments.The content of nitrate and ammonium nitrogen in soil was decreased,and the content of total nitrogen in soil was increased,meanwhile the transformation of nitrogen form in soil was promoted,and the efficiency of nitrogen use was improved compared with other treatments.In addition,photosynthesis of maize leaves was enhanced,and the transportation of dry matter production to grains were promoted compared with other treatments.Finally,the yield of maize was significantly increased,which provided a theoretical basis for maize cultivation with high yield and high efficiency. |
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