Abstract Interspecific interactions in intercropping can affect the yield of component crops, but little attention has been given to the dynamics of interspecific competition based on biomass accumulation in various management practices. A field experiment with wheat ( Triticum aestivum L.)–maize ( Zea mays L.) intercropping was conducted to evaluate the interspecific competition with four types of straw management for wheat (no‐tillage with straw standing or mulched soil and conventional tillage with straw incorporation or no straw retained) and two methods of plastic mulching for maize (no‐tillage with residual plastic mulching [i.e., new at the beginning of the previous crop, old plastic mulched in season] and conventional tillage with annual new plastic mulching). Aboveground biomass of intercrops was sampled throughout the growing season and fit to a logistic growth model. Compared with sole‐cropping, intercropping significantly increased maximum biomass and maximum growth rate of wheat but suppressed vegetative and maximum growth rates of maize. Maize growth recovered after wheat was harvested when maize was blister kernel stage (R2). Straw mulching in wheat strips and residual plastic mulching in maize strips produced greater maximum biomass amount or rates of wheat and maize than that with conventional intercropping (conventional tillage with no straw retention in wheat strips and annual new plastic mulching in maize strips). Straw mulching in wheat strips and residual plastic mulching in maize strips enhanced total grain yields by 14.9% compared with conventional intercropping. Straw mulching in wheat strips and residual plastic mulch in maize strips are suitable for coordinating interspecies interactions and increasing the productivity of wheat–maize intercropping.
The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs. Increased planting density can maintain higher yields, but also consumes more restrictive resources. However, it is unknown whether increased maize density could compensate the negative effects for reduced water and N supply on grain yield and N uptake in the arid irrigated areas. This study is a long-term positioning trial started in 2016. A split-split plot field experiment of maize was implemented with two irrigation levels: local conventional irrigation reduced by 20% (W1, 3240 m3 ha-1) and local conventional irrigation (W2, 4050 m3 ha-1), two levels of N application rates: local conventional N reduced by 25% (N1, 270 kg ha-1) and local conventional N (360 kg ha-1), and three planting density: local conventional density (D1, 75000 plants ha-1), increased density by 30% (D2, 97500 plants ha-1), and increased density by 60% (D3, 120000 plants ha-1) in the arid irrigated area of northwestern China in the 2020 to 2021. Our results showed that grain yield and aboveground N accumulation of maize were decreased under reduced water and N inputs, but increased maize density by 30% can compensate for the reduction of grain yield and aboveground N accumulation caused by reduced water and N supply of maize. When water was reduced while N application rate was unchanged, increased planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%. Under reduced water and N inputs, increased maize density by 30% enhanced N uptake efficiency and N partial factor productivity, as well as compensated for N harvest index and N metabolism related enzyme activity. Compared with W2N2D1, N uptake efficiency and N partial factor productivity were increased by 28.6 and 17.6% with W1N1D2. W1N2D2 was 8.4% of N uptake efficiency and 13.9% of N partial factor productivity higher than W2N2D1. W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at R2 stage and 19.6% at V6 stage, increased net income and benefit: cost ratio by 22.1 and 16.7%. W1N1D2 and W1N2D2 decreased nitrate nitrogen and ammoniacal nitrogen contents at R6 stage in 40-100 cm, compared with W2N2D1. In summary, increased planting density by 30% can compensate the loss of grain yield and aboveground N accumulation under water and N inputs. Meanwhile, increased maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while constant N application rate in arid irrigation areas.
<p class="2">Knowledge on effect of yield formation under straw combined with plastic film mulch is important in highlighting the importance of cultivating high-efficient and high-yield crops in the arid environments. In this study, we developed a ‘double-mulching’ system, i.e., plastic film coupled with straw mulch, integrated together with intensified strip intercropping. We determined (i) the responses of leaf area index improvement to the integrated double mulching system, and (ii) Its effects on yield formation process and mechanism of intercropped wheat and maize under the integrated systems. Experiments were carried out in northwest China in 2009 to 2011. Results showed that wheat-maize strip intercropping in combination with plastic film and straw covering on the soil surface (i.e., NTS) increased maize yield by 27 to 42% compared to conventional monoculture maize, and increased wheat yield by 149 to 160% compared to conventional monoculture wheat. The crops on NTS had higher harvest index of maize, an increase of 8.2 to 21.6% than that of conventional monoculture maize. NTS system increased spike number (i.e., SN) by an average of 30.4%, increased kernel number per spike (i.e., KNS) by an average of 10.8%, and increased thousand-kernel weight (i.e., TKW) by an average of 7.0% of intercropped wheat in comparison with conventional monoculture wheat. Similarly, there was an average increase of 5.7% of SN, 23.8% of KNS, and 7.5% of TKW under intercropped maize in comparison with conventional monoculture maize. Moreover, the treatment on NTS had greater leaf area index (i.e., LAI) an average increase of 64.1% than that in conventional monoculture maize. Similarly, LAI had an average increase of 29.3% than conventional monoculture wheat. Path analysis exhibited that straw mulching combined with reduced tillage increased the grain yield of intercropped wheat by improving KNS, and increased the grain yield of intercropped maize by improving SN. We conclude that the intercropping system in combination with plastic film and straw mulching can be an effective system for boosting crop productivity via improving yield components and LAI under limited resources in arid enviroments.</p>
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