四川地区玉米/大豆带状套作对大豆形态、叶绿素荧光特征及系统产量的影响

玉米/大豆带状套作可以充分利用光环境，提高单位土地面积物质产出。为探明玉米/大豆带状复合种植模式下不同空间配置对大豆冠层光环境、形态、产量及系统效益的影响，进而为大豆高产优质栽培提供依据，本研究选用半紧凑型（‘川单418’）和紧凑型（‘荣玉1210’）玉米品种与大豆带状套作，固定带宽为200 cm，玉米采用宽窄行种植，玉米窄行距设置3个处理：20 cm、40 cm、60 cm；并以单作大豆（SS）作为对照。分析透光率、形态、光合色素、荧光参数、生物量和系统产量的变化规律。结果表明：套作大豆冠层透光率、红光/远红光（R/FR）比值随玉米窄行距的增大而逐渐降低；套作下大豆茎粗、节数、茎干重和全叶干重均随玉米窄行距增大呈降低趋势，最大值出现在玉米窄行距20 cm处理下；与单作大豆相比，两个玉米品种下大豆茎粗、节数、茎干重和全叶干重均显著降低，而第2节间长和主茎长显著升高。套作下大豆叶片光合色素含量随玉米窄行距的增大而逐渐降低，各行距处理及不同玉米品种下套作的叶片光合色素含量均低于单作大豆。大豆叶片荧光参数F_v/F_m、NPQ、F_q''F_m''和F_q''/F_v''随玉米窄行距的增大均呈先增大后减小的趋势，而F_o变化趋势与之相反。玉米收获后，大豆光环境得到改善并迅速恢复生长，套作大豆形态生理指标与单作差异减小，但由于前期玉米的遮荫，各套作处理间大豆产量差异仍显著。通过系统效益分析，在玉米窄行距40 cm处理下，套作系统综合产量最高，两玉米品种下玉米、大豆产量平均分别为8 559.52 kg·hm^-2、1 717.60 kg·hm^-2，土地当量比平均达1.57。本试验中大豆与两个株型玉米套作，大豆形态生理指标差异影响不显著。因此，选择紧凑或半紧凑玉米品种，适度缩小玉米窄行距可以显著改善带状套作大豆的生长环境，提高其生物量和产量。

Effect of maize/soybean relay strip intercropping system on soybean morphology, chlorophyll fluorescence, and yield in Sichuan area

Maize/soybean relay strip intercropping can make efficient use of light and land resources to improve yield per unit of land area. The research was conducted to explore the influence of row spacing of maize on the soybean canopy light environment and morphological traits. Two maize varieties, semi-compact (Chuandan 418) and compact (Rongyu 1210), were used to study the efficient utilization of land resources to enhance yield and yield components. Three arrangements of 20 cm, 40 cm, and 60 cm of maize narrow row spacing were set with same width of strip intercropping (SI) belt and soybean row spacing. Solely soybean with a fixed strip width of 200 cm was planted as a control. The light transmittance, morphology, photosynthetic pigment, fluorescence parameters, biomass of soybean and grain yield of both maize and soybean were analyzed. The results showed that the light transmittance and red light/far-red light (R/FR) ratio of the soybean canopy decreased with an increasing narrow row spacing of maize. The same trend was visible in the stem diameter, node number, and dry matter of stem and leaves. The maximum values were measured in the maize narrow row spacing width of 20 cm. Compared with the control, the stem diameter, node number, dry matter of stem and leaves of soybean were significantly reduced under intercropping with two maize varieties, while the second internode length and main stem length of soybean were significantly increased. Photosynthetic pigments contents in intercropped soybean leaves gradually decreased with the increase of narrow row spacing of maize, and were lower than monocultured soybean. The fluorescence parameters of soybean leaves of F_v/F_m, NPQ, F_q''/F_m'', and F_q''/F_v'' first increased and then decreased, while a reverse trend was visible for F_o with the increase of narrow row spacing of maize. The soybean rapidly recovered after exposure to a full light environment by harvesting the maize crop. The difference in soybean morphological and physiological indexes between intercropping and monoculture was reduced. However, owing to the shading effect of maize in the early growth stage, a significant difference in the grain yield was observed between different intercropping treatments. A benefit analysis of the maize/soybean intercropping system demonstrated that the comprehensive yield was the highest for a narrow row spacing arrangement of maize (40 cm). The yield of maize and soybean were on average 8 559.52 kg·hm^-2 and 1 717.60 kg·hm^-2, respectively. The average land equivalent ratio was 1.57. There was no significant effect on soybean morphological and physiological indexes under intercropping conditions between both types of maize in this experiment. It can be concluded that selecting compact or semi-compact maize varieties and moderately reducing the narrow row spacing of maize can significantly improve the growth of soybean in a maize/soybean strip intercropping system, and result in higher biomass and yield.