玉米播期对大豆/玉米间作产量及种间竞争力的影响

在间作系统中,间作作物间合理的共生期可有效提高间作系统作物对时空资源的高效利用。而间作作物播期直接影响间作作物间共生期的长短,由此导致的时空生态位分离会直接影响到作物生产力和种间相互作用。为明确大豆/玉米间作系统中玉米播期对间作作物产量、系统生产力及间作作物间资源竞争力的影响,本研究设置3个玉米播期处理——M1(4月24日与大豆同时播种,与大豆共生期165 d)、M2(5月4日播种,与大豆共生期150 d)、M3(5月14日播种,与大豆共生期140 d),通过对单间作条件下作物产量、干物质累积的测定,研究了玉米不同播期下大豆/玉米间作系统作物产量、系统生产力、共生期内种间竞争力变化。结果表明:3个播期处理不影响间作产量优势,土地当量比(land equivalent ratio,LER)均大于1;但随播期延迟,LER变小,M1处理LER最大,达1.37。玉米播期变化对间作大豆产量无显著影响;随玉米播期延迟,间作玉米产量下降,间作系统生产力随之下降。玉米播期对间作大豆产量构成无显著影响;随玉米播期延迟,间作玉米的百粒重随之减小,M3的百粒重(26.1 g)仅为M1(36.6 g)的71%。玉米播期延迟抑制了大豆玉米共生后期玉米资源竞争力的恢复,在大豆和玉米共生前期,大豆的资源竞争力强于玉米,而共生后期(9月至收获),玉米的资源竞争力显著提升;M3处理大豆相对于玉米的资源竞争力(aggressivity,A_(sm))始终高于M1和M2,玉米相对拥挤指数随播期延迟而降低,表现为M1M2M3,而竞争比率为M3M2M1。因此,就本研究而言,甘肃河西灌区大豆/玉米间作系统中4月24日大豆和玉米同时播种是此系统间作作物的适宜播期,两作物同时播种可有效稳定间作作物产量及系统生产力,间作玉米播种延迟会导致间作系统生产力下降。

Effect of maize sowing date on yield and interspecific competition in soybean/maize intercropping system

A reasonable co-growth period between intercrop species can effectively improve the use efficiency of soil resources in time-space fabric. However, sowing date of intercrop plants directly determines the length of co-growth period of intercrop plants. This can directly affect intercropped plant productivity and interspecific interaction due to niche differentiation over time. Thus, a study was carried out to determine the effect of sowing date of intercropped maize on yield, productivity and interspecific competitiveness of crops of soybean/maize intercropping system. A total of three sowing dates of maize were set up, which were 24^th April (M1, co-growth period of maize and soybean was 165 days), 4^th May (M2, co-growth period of maize and soybean was 150 days) and 14^th May (M3, co-growth period of maize and soybean was 140 days). Then yield and dry matter accumulation of crops were investigated in both intercropping and sole systems, and system productivity and interspecific competitiveness also analyzed. The result showed that yield of soybean/maize intercropping was not affected by maize sowing date. Land equivalent ratio (LER) of all intercropping systems was greater than 1. However, LER value decreased with delay of sowing date of intercropped maize. The largest LER was for M1 (1.37) treatment. There were no significant differences in yields and yield components of intercropped soybeans with different maize sowing dates. Yield of intercropped maize and productivity of intercropping system decreased with delay of sowing date of intercropped maize. The 100-grain weight of intercropped maize decreased with delay of sowing date, 100-grain weight of M3 (26.1 g) was 71% that of M1 (36.6 g) treatment. The competitive ability of intercropped maize decreased during later co-growth period due to delay in sowing date. During early co-growth period, the competitive ability of soybean for growth resources was stronger than that of maize. However, in later co-growth period (from September to harvest), the competitive ability of maize significantly increased and was greater than that of soybean. However, the aggressiveness of soybean relative to maize (A_sm) under M3 was significantly higher than those under M1 and M2. Meanwhile, relative crowding coefficient of maize also was higher than that of soybean. This decreased with delay in sowing date of intercropped maize in the order of M1 > M2 > M3 and with competitive ratio values of M1 > M2 > M3. Therefore, the most reasonable sowing date of maize in soybean/maize intercropping system in Hexi Corridor of Gansu Province was on 24^th April. Here, yield of intercropped plants and the productivity of intercropping systems were maintained. The delayed sowing dates of maize decreased yield and productivity of intercropping system.