根间作用与密度协同作用对小麦间作玉米产量及产量构成的影响

密植是间作模式下重要的增产增效技术措施,本研究旨在探讨间作适应密植的产量构成响应机制。2014—2015年连续两年在河西绿洲灌区进行田间试验,设计不隔根、尼龙网隔根(阻断根系交叉,仅有水分养分的交流)和塑料布隔根(完全阻断)3种根间作用方式,及2个玉米种植密度(9.0万株hm~(-2)和10.5万株hm~(-2)),测定地上、地下部互作对小麦间作玉米产量及产量构成因素的影响。与单作相比,地上、地下部完全作用时间作优势提高48.3%,密度增加使其间作优势增加9.7%,地下部互作对间作优势的贡献率为21.0%,增加密度使其贡献率提高5.0%,根系交叉叠加对间作优势产生的补偿效应为9.0%,地下部水养分交流互补效应为11.1%。地上、地下部完全互作下混合籽粒产量相对于单作增幅最大,高、低密度下增幅分别达58.8%~62.2%和36.1%~36.8%;间作中地下部分对小麦组分籽粒产量的贡献率为26.5%~31.5%,其中根系穿叉产生的补偿效应为12.9%~13.2%,地下部水分养分交流互补效应为12.2%~16.0%;地下互作对玉米组分籽粒产量的贡献率为9.7%~22.6%,增加密度使地下互作贡献率提高7.0%~11.0%;密度提高对不隔根和尼龙网隔根产量的贡献率分别18.1%~23.3%和12.5%~21.5%,说明根间完全作用有利于密度正效应的发挥。地下互作对小麦穗数贡献率为5.5%~11.4%,密度对小麦地下部贡献率影响差异不显著,地下互作对玉米穗数的贡献率为12.5%~16.3%,增加密度使地下互作贡献率增加3.6%~14.1%。通径分析进一步表明,不同根间作用及密植效应下间作小麦、玉米主要通过提高单位面积穗数来提高籽粒产量。本研究表明,增加密度可显著增加间作优势和地下部贡献率,地上地下完全互作有利于密植效应充分发挥,可为进一步发掘密植条件下的间作优势机理提供理论依据。

Synergistic Effect of Root Interaction and Density on Yield and Yield Components of Wheat/Maize Intercropping System

As planting density is a key strategy for improvement of yield and efficiencies in intercropping, the present study was conducted to explore the mechanism of yield response to close planting in intercropping systems. The field experiment was carried out in Hexi oasis irrigation area from 2014 to 2015, of which, three root partition patterns, i.e. no root barrier, nylon mesh barrier (obstructs overlapping of wheat roots with maize roots, but allows water and nutrients to exchange through the nylon mesh) and plastic sheet barrier (prevents water and nutrients from exchange between the two intercrops and no overlapping of wheat roots with maize roots), were combined with two planting density levels, i.e., 90 000 plants ha-1 and 105 000 plants ha-1. The main objective was to determine the effect of above- and below-ground interrelation on grain yield and yield components. The results showed that a complete effect of above- and below-ground interaction increased the intercropping-advantage (i.e. LER) by 48.3% compared to sole cropping. Besides, increase of maize density would led to the LER increased by 9.7%. Generally, the below-ground interaction attributed 21.0% to the LER, and with maize density increased, the contribution rate was increased by 5%. The compensation effect of root overlapping and the complementary of moisture/nutrient exchange attributed 9.0% and 11.1% to the LER, respectively. A complete effect of below- and above-ground interaction also had the highest grain yield, which was increased by 58.8%–62.2% under the higher density and by 36.1%–36.8% under the lower density, compared to the corresponding monocultures. On average, the below-ground interaction attributed 26.5%–31.5% to the grain yield of intercropped wheat, of which, the compensation effect of root overlapping and the complementary of moisture/nutrient exchange attributed 12.9%–13.2% and 12.2–16.0%, respectively. For maize grain yield in the wheat-maize intercropping, the below-ground interaction attributed 9.7%–22.6%, and with maize density increased, the contribution rate was increased by 7.0–11.0%. Increase of maize density increased grain yield by 18.1%–23.3% and 12.5%–21.5% under no root barrier and nylon mesh barrier, this indicated that a complete root interaction could improve the positive effect of close planting. The below-ground interaction attributed 5.5%–11.4% to wheat era number, but not influenced by the density. Similarly, the below-ground interaction attributed 12.5%–16.3% to maize era number, and was further increased by 3.6% to 14.1% with the increase of the density. Based on the result of path analysis, it could conclude that the improvement of grain yield of wheat and maize was mainly attributable to the increase of era number per area. This study showed that increase of planting density could significantly promote the intercropping advantage and the contribution rate of the below-ground interaction. Furthermore, a complete effect of above- and below-ground interaction would facilitate the positive effect of close planting. Accordingly, the results will provide sound theoretical base for the further exploring of the mechanism in intercropping advantage under close planting.