Cai Zhao

Enhancing the systems productivity and water use efficiency through coordinated soil water sharing and compensation in strip-intercropping

In arid areas, water shortage is threating agricultural sustainability, and strip-intercropping may serve as a strategy to alleviate the challenge. Here we show that strip-intercropping enhances the spatial distributions of soil water across the 0–110 cm rooting zones, improves the coordination of soil water sharing during the co-growth period, and provides compensatory effect for available soil water. In a three-year (2009–2011) experiment, shorter-season pea (Pisum sativum L.) was sown in alternate strips with longer-season maize (Zea mays L.) without or with an artificially-inserted root barrier (a solid plastic sheet) between the strips. The intercropped pea used soil water mostly in the top 20-cm layers, whereas maize plants were able to absorb water from deeper-layers of the neighboring pea strips. After pea harvest, the intercropped maize obtained compensatory soil water from the pea strips. The pea-maize intercropping without the root barrier increased grain yield by 25% and enhanced water use efficiency by 24% compared with the intercropping with the root barrier. The improvement in crop yield and water use efficiency was partly attributable to the coordinated soil water sharing between the inter-strips and the compensatory effect from the early-maturing pea to the late-maturing maize.

Wheat-maize intercropping with reduced tillage and straw retention can enhance economic and environmental benefits in arid areas

Intercropping is considered a promising system for boosting crop productivity. However, intercropping usually requires higher inputs of resources that emit more CO2. It is unclear whether an improved agricultural pattern could relieve this issue and enhance agricultural sustainability in an arid irrigation area. A field experiment using a well-designed agricultural practice was carried out in northwest China; reduced tillage, coupled with wheat straw residue retention measures, was integrated with a strip intercropping pattern. We determined the crop productivity, water use, economic benefits, and carbon emissions (CEs). The wheat-maize intercropping coupled with straw covering (i.e., NTSI treatment), boosted grain yield by 27–38% and 153–160% more than the conventional monoculture of maize and wheat, respectively, and it also increased by 9.9–11.9% over the conventional intercropping treatment. Similarly, this pattern also improved the water use efficiency by 15.4–22.4% in comparison with the conventional monoculture of maize by 45.7–48.3% in comparison with the conventional monoculture of wheat and by 14.7–15.9% in comparison with the conventional intercropping treatment. Meanwhile, NTSI treatment caused 7.4–13.7% and 37.0–47.7% greater solar energy use efficiency than the conventional monoculture of maize and wheat, respectively. Furthermore, the NTSI treatment had a higher net return (NR) by 54–71% and 281–338% and a higher benefit per cubic meter of water (BPW) by 35–51% and 119–147% more than the conventional monoculture of maize and wheat, respectively. Similarly, it increased the NR and BPW by 8–14% and 14–16% in comparison with the conventional intercropping treatment, respectively. An additional feature of the NTSI treatment is that it reduced CEs by 13.4–23.8% and 7.3–17.5% while improving CE efficiency by 62.6–66.9% and 23.2–33.2% more than the conventional monoculture maize and intercropping treatments, respectively. We can draw a conclusion that intercropping maize and wheat, with a straw covering soil surface, can be used to enhance crop production and NRs while effectively lowering CO2 emissions in arid oasis irrigation region.

Interspecies Interactions in Relation to Root Distribution Across the Rooting Profile in Wheat-Maize Intercropping Under Different Plant Densities

In wheat-maize intercropping systems, the maize is often disadvantageous over the wheat during the co-growth period. It is unknown whether the impaired growth of maize can be recovered through the enhancement of the belowground interspecies interactions. In this study, we (i) determined the mechanism of the belowground interaction in relation to root growth and distribution under different maize plant densities, and (ii) quantified the “recovery effect” of maize after wheat harvest. The three-year (2014–2016) field experiment was conducted at the Oasis Agriculture Research Station of Gansu Agricultural University, Wuwei, Northwest China. Root weight density (RWD), root length density (RLD), and root surface area density (RSAD), were measured in single-cropped maize (M), single-cropped wheat (W), and three intercropping systems (i) wheat-maize intercropping with no root barrier (i.e., complete belowground interaction, IC), (ii) nylon mesh root barrier (partial belowground interaction, IC-PRI), and (iii) plastic sheet root barrier (no belowground interaction, IC-NRI). The intercropped maize was planted at low (45,000 plants ha−1) and high (52,000 plants ha−1) densities. During the wheat/maize co-growth period, the IC treatment increased the RWD, RLD, and RSAD of the intercropped wheat in the 20–100 cm soil depth compared to the IC-PRI and IC-NRI systems; intercropped maize had 53% lower RWD, 81% lower RLD, and 70% lower RSAD than single-cropped maize. After wheat harvest, the intercropped maize recovered the growth with the increase of RWD by 40%, RLD by 44% and RSAD by 11%, compared to the single-cropped maize. Comparisons among the three intercropping systems revealed that the “recovery effect” of the intercropped maize was attributable to complete belowground interspecies interaction by 143%, the compensational effect due to root overlap by 35%, and the compensational effect due to water and nutrient exchange (CWN) by 80%. The higher maize plant density provided a greater recovery effect due to increased RWD and RLD. Higher maize plant density stimulated greater belowground interspecies interaction that promoted root growth and development, strengthened the recovery effect, and increased crop productivity.

Effects of Postponing Nitrogen Topdressing on Water Use Characteristics of Maize-Pea Intercropping System

In oasis irrigation agricultural region, water resources deficit is one of the most penetrating constraints for developing intercropping. However, these was neither sufficient academic basis for enhancing water utilization rate through optimizing chemical nitrogen application, nor available practices for increasing yield and water use efficiency (WUE) of crops in developing cereal/legume intercropping. Here, we carried out a field experiment in Hexi Corridor, a typical arid oasis irrigation area in 20122013, and the effect of postponing nitrogen topdressing on yield and water use characteristics of soleand intercropping maize, pea systems was investigated. The total nitrogen application level for the same cropping system was equal. On the basis of 10% basal N fertilizer plus 50% pre-tasseling N fertilizer, three N treatments were managed with different topdressing amounts postponed: N1, N postponing application with 30%; N2, N postponing application with 15%; and N3, traditional nitrogen application. The purpose of the study focused on providing academic and practical evidence for increasing yield and WUE through optimizing nitrogen fertilizer management. The results showed that, N postponing application had no significant influence on total water consumption (ET) of maize-pea intercropping in the whole growing stage, but the soil evaporation (E) and E/ET were significantly decreased. As compared with traditional nitrogen application treatment, evaporation and E/ET in 15% N postponing application maize-pea intercropping were reduced by 6% and 4%, respectively, while those in maize-pea intercropping with 30% N postponing application both by 2%. In maize-pea intercropping systems, average soil evaporation in pea strips was 329 mm, but 第 3期 滕园园等: 氮肥后移对玉米间作豌豆耗水特性的调控效应 447 that in maize strips was 232 mm, showing that invalid water consumption in pea strip is significantly higher than that in maize strips. Mixed grain yield of maize-pea intercropping under N postponing application with 15% was 6% higher than that of the traditional nitrogen application treatment. And WUE of pea-maize intercropping systems was also significantly higher than that of the traditional nitrogen by 5%. As well as mixed grain yield and WUE of pea-maize intercropping under N postponing application with 30% was 3% and 2% higher than that of the traditional nitrogen application treatment respectively. Consequently, the 15% N postponing application (topdressing fertilizer with 67.5 kg N ha at pea flower pod period/maize jointing period, topdressing fertilizer with 225 kg N ha at maize pre-tasseling period and topdressing fertilizer with 112.5 kg N ha at maize 15 days after flowering period) combined with maize-pea intercropping could be one of the effective strategies to promote grain yield and WUE of cereal-legume intercropping in Oasis irrigation region.