| The northern part of the Tianshan Mountains in Xinjiang is an important livestock production area in China,and the shortage of forage severely restricts the high-quality development of its animal husbandry.The mixed silage can be harvested at the same time after the strip intercropping of silage maize and soybean,which effectively combines the advantages of high yield of maize and high quality of soybean.It is an efficient planting mode to improve the quality of silage,and reasonable planting density is the primary condition for obtaining high yield and high quality.This study used Denghai 618,a high-yield maize variety with a compact plant type that can be used for both food and feed,and Jiyu 441,a high-yield soybean variety that is tolerant to shade and lodging,as experimental materials.A two factor split plot design was adopted,and three maize densities of 67500,82500,and 97500plants/hm~2,as well as three soybean densities of 120000,150000,and 18000plants/hm~2,were set in 2021.In 2022,the density level was further optimized based on the first year,with maize density of 90000,105000,and 120000 plants/hm~2,and soybean density of 150000,18000,and 210000 plants/hm~2.The same density of net maize was used as the control.By studying the effects of planting density on the light distribution characteristics,lodging characteristics,material accumulation,and comprehensive evaluation of population yield and mixed silage quality in the silage maize soybean intercropping community,the optimal density configuration is determined,in order to provide technical support for the field configuration of high yield and quality in the silage maize soybean intercropping community in the drip irrigation area of northern Xinjiang.The main research findings are as follows:1.The effect of maize and soybean density interaction on the light transmittance of strip compound planting population and crop photosynthetic responseThe light transmittance of intercropping maize ear layer decreases with the increase of maize density,with a decrease of 29.14%and 25.50%.The light transmittance at the bottom of soybean canopy decreases with the increase of soybean density.Compared to the shading generated by high-altitude maize on low-altitude soybean,soybean has a greater degree of mutual shading caused by its own density increase,resulting in a higher light transmittance of edge row soybeans than that of inner row soybeans.The photosynthetic potential of maize soybean population reaches its maximum during the filling to milky stage,and shows a trend of first increasing and then decreasing with the increase of maize density.It significantly increases with the increase of soybean density and is significantly higher than that of net maize.When maize increased from low density to medium density,there was no significant difference in leaf senescence index during the milk ripening stage.However,when it increased to high density,it significantly increased by 25.19%and was significantly lower than the corresponding density of net cropping maize.The soybean leaf senescence index is significantly affected by maize density and soybean density.Under low soybean density,the soybean leaf senescence index increases with the increase of maize density,with an increase of 22.36%and 12.30%,respectively.2.The effect of density interaction between maize and soybean on the population structure of strip compound planting and the characteristics of high yield population structureThe LAI of the strip intercropping population was significantly affected by maize density and soybean density.Maize increased from low density to medium density,and the LAI of the population significantly increased during the filling stage.As soybean density increased,the LAI of the population gradually increased.The LAI of the population reached 7.02 under the treatment of 105000 maize plants/hm~2 and 210000 soybean plants/hm~2,which was significantly increased by 70.24%compared to medium density net cropping maize.The total dry matter accumulation of maize with a medium density of 105000 plants/hm~2 and soybean with a high density of 210000 plants/hm~2 is the highest,which is 14.42%and 20.89%higher than the lowest intercropping treatment and the corresponding net cropping treatment,respectively.The average growth rate of intercropping maize was lower at medium density and increased by 8.98%and 34.09%at high density,respectively.With the increase of soybean density,the average growth rate and active growth period of maize showed a first increase and then a decrease.Under the medium density and high density treatments of maize and soybean,soybean reached its maximum growth rate at the earliest,but its active growth period was relatively short.With the increase of maize density,the puncture strength of intercropping maize stalks decreased by 20.94%and 11.30%respectively,and the lodging rate increased by 35.60%and 33.83%respectively.The interaction between maize density and soybean density has a significant impact on the lodging rate of soybean.The lodging rate of soybean first increases and then decreases with the increase of maize density.As the soybean density increases,the bending resistance of intercropped soybean gradually decreases,with a decrease of 18.83%and 24.24%,and the lodging rate increases by 41.23%and 6.41%respectively.The structural characteristics of high-yield population in maize soybean strip intercropping include a maize plant height of 280-305 cm,a maize ear height of 85-100 cm,a soybean plant height of 90-105 cm,and 8-11 branches on the soybean main stem.The LAI of each growth stage population is 1.67(maize 1.08,soybeans 0.59),4.63(maize 2.67,soybeans 1.96),7.02(maize 4.62,soybeans 2.40),7.15(maize 4.08,soybeans 3.07),and 5.04(maize 3.51,soybeans 1.88)during the elongation stage.The light transmittance of maize ear layer reached 28.06%,and the total photosynthetic potential of the population reached 320.93 m~2·d/m~2。The dry matter quality of the population at each growth stage is 5.54(maize 3.68,soybean 1.87),8.75(maize 6.15,soybean 2.60),15.58(maize 11.89,soybean 3.69),20.57(maize 15.16,soybean 5.41),and 35.24(maize 26.70,soybean 8.54)during the elongation stage.3.The impact and comprehensive evaluation of the density interaction between maize and soybean on the yield and quality of strip compound planting populationThe yield of maize intercropped with medium density was significantly increased by 23.44%and 10.56%,respectively,compared to that of maize intercropped with high density.Due to the mild shading of maize on soybeans,the yield of intercropped soybeans gradually increases with the increase of maize density at low and medium density levels;At a high density level of soybean,internal competition intensifies,and intercropping soybean yield first decreases and then increases with increasing maize density.Under low maize density,soybean yield significantly increases with increasing soybean density;Under the medium and high density of maize,as the soybean density increases,the soybean yield first increases and then decreases.The yield of strip intercropping population shows a trend of first increasing and then decreasing with the increase of maize density,and is not significantly affected by soybean density.The population yield of maize with a medium density of 105000plants/hm~2 and soybean with a high density of 210000 plants/hm~2 reached a maximum of 64.98 t/hm~2,which increased by 11.97 t/hm~2 compared to the lowest intercropping treatment and 3.49 t/hm~2 compared to net cropping maize with the same density.The crude protein content of maize with a medium density of 105000 plants/hm~2 and soybean with a low density of 150000 plants/hm~2 reached the highest of 12.23%,and the GI reached the highest of 36.52.Compared with net maize under the same density,the crude protein content increased by 2.39 percentage points,and the GI increased by 22.55%.The ADF content,NDF content,and RFV of each intercropping treatment were not significantly different from those of net maize under the corresponding density.The grey correlation analysis method was used to comprehensively evaluate the biological yield and silage nutritional quality of each treatment.Finally,the high-yield and high-quality density combinations of silage maize soybean intercropping in the northern Xinjiang irrigation area were selected as follows:105000 maize plants/hm~2 and 150000 soybean plants/hm~2,which can be promoted and applied in suitable regions. |
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