玉米-大豆不同宽幅间作对大豆光合特性及群体产量的影响

为探究不同农机作业宽幅条件下玉米-大豆间作对大豆光合特性及群体产量的影响，于2018—2019年采用大田试验，以单作玉米（SM）和单作大豆（SSB）为对照，在玉米-大豆2：1播幅（I₂₁）、2：2播幅（I₂₂）、2：3播幅（I₂₃）间作模式下，测定大豆光合指标、生理生长指标以及群体产量。2年的结果表明：各处理大豆冠层上方的光合有效辐射（PAR）日变化呈现先增后降的单峰曲线变化趋势，随着大豆宽幅的增加，各间作处理大豆冠层上方的光合有效辐射逐渐增加，但均小于单作。相较于单作，间作处理降低了大豆植株的净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）以及地上部生物量，各指标均随着大豆播幅的增加而增加，其中I₂₁处理显著低于I₂₃和SSB处理，I₂₂处理与I₂₃处理之间差异不显著；增加了大豆植株的胞间CO₂浓度（Ci）、叶绿素含量以及株高，各指标均随着大豆播幅的增加而减小，其中I₂₁处理显著高于I₂₃和SSB处理。与单作相比，基于处理总面积的间作玉米产量显著增加，大豆产量显著降低，3种间作处理以籽粒产量为基础的LER（土地当量比）随着大豆播幅的增加而增加。研究表明，玉米-大豆2：2、2：3播幅种植具有间作生产优势。

Effects of maize-soybean intercropping with different widths on photosynthetic characteristics of soybean and population yield

We conducted field experiments in 2018 and 2019 to explore the effects of maize-soybean intercropping, laid out at different widths based on the agricultural machinery used, on the photosynthetic characteristics of soybean and population yield. We measured the photosynthetic and physiological growth indices of soybean and population yield, under maize-soybean intercropping modes in a 2:1 (I₂₁), 2:2 (I₂₂), and 2:3 (I₂₃)ratio, with fields of single maize (SM)and single soybean (SSB)as the controls. The results after two years showed that the diurnal variation in photosynthetic active radiation (PAR)above the canopy of the soybean showed a single-peak curve trend that increased first and then decreased. As the ratio of the soybean planting increased, the PAR above the canopy of intercropping soybean increased gradually, however, all their values were smaller than that of the monoculture. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr)and aboveground biomass of soybean decreased in the intercropping systems compared with the monoculture. All indices increased as the ratio of soybean planting increased, among the treatments, the values for I₂₁ were significantly lower than those for I₂₃ and SSB, and there was no significant difference between I₂₂ and I₂₃. The intercellular CO₂ concentration (Ci), chlorophyll content and height of soybean plants increased in the intercropping systems compared with the monoculture. All the indices decreased with the increase in the ratio of soybean planting, with the values for I₂₁ being significantly higher than those for I₂₃ and SSB. The maize yield increased and soybean yield decreased, both significantly, in the intercropping systems-compared with the monocultures-based on total treatment area. The LER (land equivalent ratio)based on grain yield of the three intercropping treatments increased with the increase in the ratio of soybean planting. The maize-soybean planting ratios of 2:2 and 2:3 demonstrated the advantages of intercropped production.