Wheat-maize Intercropping Research Articles

Agricultural management could reduce soil N2O emissions while increasing grain yields via enhancing soil moisture harvesting and improving soil nutrient status

Intercropping can improve system productivity, but the effect of intercropping integrated with conservation tillage practices on soil N2O emissions remains unclear at the present stage. A 4-yr field experiment was performed in northwest China to examine soil moisture harvesting, soil nutrient status, and soil N2O emissions of wheat-maize intercropping with stubble residues and films management. We found that intercropping increased crop yields and reduced soil N2O emissions over monocultures. Across the intercropping treatments, NTSMFI (no-tillage with mulching stubbles and re-using residual films) and NTSSFI (no-tillage with standing stubbles and re-using residual films) boosted grain-yields by 13.8–17.1 % and 12.9–15.4 % over CTFI (conventional tillage without returning stubbles and mulching new films). NTSMFI and NTSSFI reduced soil N2O emissions by 18.4–28.7 % and 15.5–24.9 % compared to CTFI, respectively. So, NTSMFI and NTSSFI obtained a higher soil N2O emission efficiency than CTFI. The greater effect on soil N2O emissions reduction was detected in NTSMFI, and decreased by 5.1–5.4 % over NTSSFI. The main reason for NTSMFI to improve grain-yields and reduce soil N2O emissions was to enhance soil moisture harvesting and optimize the soil nutrient status. Compared to CTFI, NTSMFI increased the ratio of transpiration to evaporation by 14.4–32.0 %, improved soil organic carbon and total nitrogen concentrations, and soil C:N ratio of 0 to 60 cm soil depth by 14.1 %, 7.1 %, and 6.5 %, respectively. Adopting an environmentally clean strategy exemplified by NTSMFI was recommended as an effective technique for increasing-yields and reducing soil N2O emissions in arid irrigated regions.

Synergistic effects of diazotrophs and arbuscular mycorrhizal fungi on soil biological nitrogen fixation after three decades of fertilization.

Biological nitrogen (N) fixation (BNF) via diazotrophs is an important ecological process for the conversion of atmospheric N to biologically available N. Although soil diazotrophs play a dominant role in BNF and arbuscular mycorrhizal fungi (AMF) serve as helpers to favor BNF, the response of soil BNF and diazotrophic communities to different long-term fertilizations and the role of AMF in diazotrophs-driven BNF are poorly understood. Herein, a 33-year fertilization experiment in a wheat-maize intercropping system was conducted to investigate the changes in soil BNF rates, diazotrophic and AMF communities, and their interactions after long-term representative fertilization (chemical fertilizer, cow manure, wheat straw, and green manure). We found a remarkable increase in soil BNF rates after more than three decades of fertilization compared with nonfertilized soil, and the green manure treatment rendered the highest enhancement. The functionality strengthening was mainly associated with the increase in the absolute abundance of diazotrophs and AMF and the relative abundance of the key ecological cluster of Module #0 (gained from the co-occurrence network of diazotrophic and AMF species) with dominant diazotrophs such as Skermanella and Azospirillum. Furthermore, although the positive correlations between diazotrophs and AMF were reduced under long-term organic fertilization regimes, green manuring could reverse the decline within Module #0, and this had a positive relationship with the BNF rate. This study suggests that long-term fertilization could promote N fixation and select specific groups of N fixers and their helpers in certain areas. Our work provides solid evidence that N fixation and certain groups of diazotrophic and AMF taxa and their interspecies relationship will be largely favored after the fertilized strategy of green manure.

No-tillage with straw mulching and re-using old film boost crop yields and mitigate soil N2O emissions in wheat-maize intercropping at arid irrigated regions

Water shortage and heavy greenhouse gas emissions are threatening agricultural sustainability with food security severely, and becoming a major issue in arid areas. It is unclear whether improved farming systems on strip-intercropping integrated with no-tillage with straw returning and re-using old film practices can be developed to reduce soil nitrous oxide (N 2 O) emissions and boost crop yields for tackling those issues. A four-year field experiment for wheat-maize intercropping was carried on straw residue and film management of northwestern China in 2014–2017 and aimed to comprehensively assess crop yields and soil N 2 O emissions. The results showed that NTSMF (no-tillage with straw mulching and re-using old film), NTSSF (no-tillage with straw standing and re-using old film), and CTSF (conventional tillage with straw incorporation and mulching new film every year) treatments increased grain yields by 15.1%, 13.7%, and 12.8% respectively, compared to CTF (conventional tillage with no straw returning and mulching new film every year, the control treatment). NTSMF, NTSSF, and CTSF treatments had greater water use efficiency by 15.7%, 13.1%, and 14.2% than CTF, respectively. On the contrary, NTSMF and NTSSF treatments had lower soil N 2 O emissions (NE) by 23.9% and 20.4% than CTF, and lower by 19.8% and 16.0% than CTSF, respectively. No-tillage practice used more soil moisture and produced more grain yields but emitted less N 2 O than conventional tillage, NTSMF and NTSSF treatments reduced soil N 2 O emission per volume of evapotranspiration (WUE NE ) by 23.6% and 20.9%, and reduced soil N 2 O emission intensity (NEI) by 33.9% and 30.0% in comparison to CTF. The better effect on the reduction of NE, WUE NE , and SEI was found in NTSMF, and the three indicators were successively decreased by 5.3%, 4.4%, and 6.9% over NTSSF in 2016–2017. NTSMF reduced NE and boosted GY was attributed to increased synchronicity of water demand and reduced adverse effects of soil temperature variations of both intercrops’ strips. Our study concluded that grain yields were enhanced and soil N 2 O emissions were reduced by NTSMF treatment, and NTSMF treatment is a practical cropping production system for environmentally clean in an arid irrigated region. • The improved treatment on NTSMF with straw mulching in wheat strips and re-using old film in maize strips. • The improved treatment reduced soil N 2 O emissions (NE) and boosted grain yields (GY). • NTSMF reduced NE and boosted GY was attributed to increased synchronicity of water demand and reduced adverse effects of soil temperature variations. • NTSMF treatment is a practical cropping system for environmentally clean in arid irrigated areas.

Photophysiological Mechanism of Dense Planting to Increase the Grain Yield of Intercropped Maize with Nitrogen-Reduction Application in Arid Conditions

Leaf photophysiological characteristics are the main indexes that determine crop yield formation. However, it remains unclear whether photosynthesis is systematically regulated via the cropping pattern and nitrogen supply when maize crops are planted with a high density. So, a field experiment that had a three-factor split-plot arrangement of treatments was conducted from 2020 to 2021. The main plot was two cropping patterns that included the sole cropping of maize and wheat–maize intercropping. The split plot had two nitrogen application rates: a traditional nitrogen application rate (N2, 360 kg ha−1) and one reduced by 25% (N1, 270 kg ha−1) for maize. The split–split plot had three planting densities: a traditional density (M1, 78,000 plant ha−1), a medium density (M2, 10,400 plant ha−1), and a high density (M3, 129,000 plant ha−1) for sole maize; the corresponding densities of intercropped maize were 45,000, 60,000, and 75,000 plant ha−1, respectively. The grain yield, the photosynthetic traits, and chlorophyll a fluorescence of the maize were assessed. The results showed that a 25% nitrogen reduction and dense planting had a negative impact on the individual maize’s photosynthesis. However, intercropping could alleviate these drawbacks. When the maize was grown in the intercropping system at a lower nitrogen level and a medium planting density (IN1M2), the photosynthetic traits were better or similar to those of the traditional treatment (SN2M1) at the reproductive growth stage. Moreover, IN1M2 improved the light energy distribution among photochemistry, photo-protective and heat dissipation process of maize compared with SN2M1. A grey relation analysis demonstrated that the Pn and Tr of the individual maize played the most significant role in the group’s productivity. Thus, the IN1M2 treatment achieved the highest grain yield and can be recommended as a feasible agronomic practice in oasis-irrigated regions.

Water use of intercropped species: Maize-soybean, soybean-wheat and wheat-maize

Plant-plant interactions in the intercropping system can significantly affect crop productivity. However, it is poorly understood how the interactions affect the land equivalent ratios (LER) in the cereal-legumes and cereal-cereal intercropping systems in semi-arid agroecosystems. A two-year (2019–2020) field experiment was conducted in the Dryland Agricultural Experimental Station of Lanzhou University, a semiarid rainfed site of northwest China, to quantify the impact of crop diversification on land equivalent ratio, and its moisture-dependent mechanisms in three intercropping systems of maize-wheat, maize-soybean and wheat-soybean. The soybean-involved intercropping systems showed positive interactions, which substantially promoted crop productivity of maize and wheat by 18.1–20.9%. The soil water in soybean strips can be used by intercropped wheat or maize, which in turn promoted soil water storage (SWS) in maize or wheat strips by 0.6% and 11.0% respectively, during the co-growth period. This further improved the photosynthetic rate (Pn), instantaneous growth rate (IGR), and water use efficiency (WUE) for each species and thereafter elevated the land equivalence ratio (LER>1). However, in the wheat-maize intercropping system, interspecific competition was dominated with wheat as dominant species and maize as inferior one respectively. The competition plundered available water of maize strips (SWS decreased by 10.5%), and thus decreased its Pn and WUE by 12.7% and 20.0% (P < 0.05), respectively. Importantly, maize yield and LER were not improved via the compensation effect during the post-harvest period of wheat. While soil water was to some extent restored, the Pn and IGR of intercropped maize were still lower than those of monoculture maize. This trend resulted in maize yield loss during the reproductive period, and ultimately lower LER. For the first time, we found a rarely reported phenomenon, i.e. negative relationships between crop diversity and land equivalent ratios in semiarid agroecosystem, since the yield loss caused by competition was not compensated during the co-growth period. Therefore, a positive relationship between crop diversification and land equivalent ratio required rational crop species configuration, in terms of the tradeoff between crop diversity and its productivity at agricultural landscape scale.

Energy budgeting, carbon budgeting, and carbon footprints of straw and plastic film management for environmentally clean of wheat-maize intercropping system in northwestern China

Modern agricultural production is an energy- and carbon-intensive system. Enhancing energy and carbon efficiencies and reducing carbon footprints are important issues of sustainable development in modern agriculture. This study aimed to comprehensively assess energy and carbon budgeting and carbon footprints in wheat-maize intercropping, monoculture maize, and monoculture wheat with straw and plastic film management approaches, as based on a field experiment conducted in northwestern China. The results showed that intercropping had a greater grain yield by 12.8% and 131.0% than monoculture maize and wheat, respectively. Intercropping decreased energy and carbon inputs, increased energy and carbon outputs, thus improving energy and carbon efficiency, compared to monoculture maize. Intercropping reduced carbon footprint (CF) and yield-scale on the carbon footprint (CFy) via decreasing soil CO2 equivalent emissions over monoculture maize. For the intercropping treatments, NTSMw/NTm (no-tillage with straw mulching and residual plastic film re-mulching) and NTSSw/NTm (no-tillage with straw standing and residual plastic film re-mulching) treatments increased grain yields by 14.9% and 13.8% over CTw/CTm (conventional tillage with no straw returning and annual new plastic film mulching). The lower energy inputs and higher energy outputs were observed in NTSMw/NTm and NTSSw/NTm treatments, thus, NTSMw/NTm and NTSSw/NTm had greater energy use efficiency by 36.9% and 34.9% than CTw/CTm. NTSMw/NTm and NTSSw/NTm treatments decreased carbon inputs and increased carbon outputs, thus improving carbon efficiency by 56.6% and 53.1%, compared to CTw/CTm. NTSMw/NTm and NTSSw/NTm treatments decreased CF by 16.8% and 14.3%, and decreased CFy by 27.6% and 24.8% compared to CTw/CTm, respectively, because of the decrease in soil CO2 equivalent emissions. Our study indicated that system productivity, as well as energy and carbon efficiencies were enhanced, and carbon footprints were reduced by NTSMw/NTm and NTSSw/NTm treatments, and NTSMw/NTm had a more robust effect, indicating this treatment is the most sustainable cropping system in arid areas.

Interspecies interaction intensity influences water consumption in wheat–maize intercropping by regulating root length density

AbstractIn intercropping systems, interspecies interaction intensity has an important effect on water consumption. However, how interspecies interaction intensity reduces water consumption in intercropping is still unclear. The effects of interspecies interaction intensity in wheat (Triticum aestivum)–maize (Zea mays) intercropping system on water consumption characteristics, root length density, and grain yield were examined. A 3‐yr field experiment was conducted to evaluate three root interaction intensities: complete belowground interaction (W/M, without root barrier), partial belowground interaction (NW/M, nylon mesh barrier), and without belowground interaction (PW/M, plastic sheet barrier), with two plant densities of maize (45,000 plants ha−1, M1, and 52,500 plants ha−1, M2) in wheat–maize intercropping system. During co‐growth period of wheat and maize and independent growth of maize, evaporation was reduced by W/M and with increased maize plant density. Root length density of maize was inhibited by intercropped wheat during the co‐growth period. Root length density of maize in the W/M treatment was increased by 14% in 2014 and 45% in 2015, compared with the NW/M treatment, and increased by 26% in 2014 and 119% in 2015, compared with the PW/M treatment, expect for 2016, during maize independent growth. Moreover, there was a negative correlation between evaporation and root length density of maize. Grain yield was increased by W/M2 treatment. Increasing interspecies interaction intensity can decrease evaporation by increasing the root length density of intercropping crops.

The physiological and ecological traits of strip management with straw and plastic film to increase grain yield of intercropping wheat and maize in arid conditions

Strip intercropping is a feasible cropping pattern to improve crop productivity via enhancing the stability of farmland ecosystem. Straw returning and plastic film mulch are effective and valuable measures to boost crop productivity in arid or semi-arid regions. It is unknown whether the yield advantage of strip intercropping can be further enhanced by improving photosynthetic characteristics when applied synchronously with straw returning and plastic film mulch measures. A field experiment on wheat-maize intercropping system was conducted at strip management with straw and plastic film, and photosynthetic characteristics, leaf and soil water potential, and grain yield were determined. The results showed that the SPAD value of wheat and maize leaves with NTSM/NTP (no-tillage with wheat straw mulch in wheat strips and previous residual plastic film mulch in maize strips) was decreased at the vegetative growth period, a higher SPAD value was maintained at the reproductive growth period, compared to CT/CTP (conventional tillage with no straw returning in wheat strips and annual new plastic film mulch in maize strips), it indicated that NTSM/NTP treatment can maintain high physiological activity of intercropped wheat and maize at their reproductive growth period. NTSM/NTP treatment raised net photosynthetic rate (Pn) and leaf water use efficiency (WUEL) of wheat by 9.0–15.8 % and 4.9–8.8 % from filling (Feekes 11.0) to doughing (Feekes 11.2) stage, and raised both indexes of maize by 11.5–25.5 % and 4.7–14.8 % from milking (R3) to doughing (R4) stage, with little effect on transpiration rate (Tr), in comparison to CT/CTP, respectively. NTSM/NTP treatment kept relatively high leaf and soil water potential of intercropped strips, and favorably created a suitable soil moisture environment for enhancing the drought resistance on intercrops. In addition, the value of difference between leaf and soil water potential of wheat and maize in NTSM/NTP treatment was lower than that in CT/CTP treatment at given determining stages, it indicated that NTSM/NTP treatment was beneficial to maintaining the stability of crop water demand and soil water supply for growth of two intercrops. Thus, NTSM/NTP treatment obtained high grain yields, increased by 8.6–11.1 % for intercropped wheat, increased by 16.0–20.2 % for intercropped maize, and increased by 13.8–17.1 % for intercropped wheat plus maize, in comparison to CT/CTP treatment. The improved photosynthetic capacity, optimized leaf and soil water potential, and increased grain yields for intercropped wheat and maize in NTSM/NTP treatment. Therefore, strip intercropping integrated of no tillage with wheat straw and previous residual plastic film mulch can be recommended as the excellent technique to coordinate the contradiction between water shortage and high grain yield in arid irrigated regions.

Growth trajectories of wheat–maize intercropping with straw and plastic management in arid conditions

AbstractInterspecific 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 aestivumL.)–maize (Zea maysL.) 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.

Dynamic process-based modelling of crop growth and competitive water extraction in relay strip intercropping: Model development and application to wheat-maize intercropping

Strip intercropping increases land use efficiency but the effect on water use efficiency is less well-known. Here we develop a modelling method to simulate the growth of an intercrop taking into account the acquisition of light and water by the component species in order to calculate the efficacy of light and water acquisition in an intercropping system as compared to sole crops. The model is parameterized, calibrated and validated using data on wheat-maize intercropping in Gansu province, Northwest China. Observed above-ground biomass was 1630 g m−2 for sole wheat and 1334 g m−2 for intercropped wheat while it was 3023 g m−2 for sole maize and 2259 g m−2 for intercropped maize. The average water use was 405 mm in sole wheat, 595 mm in sole maize and 711 mm in wheat-maize intercropping. Based on observed yields, the land equivalent ratio (LER) was 1.59 and the water equivalent ratio (WER) was 1.14, where LER and WER express the relative amounts of land and water needed to achieve the yields obtained in a unit area of intercrop using sole crops. These results indicate that relay strip intercropping of wheat and maize achieves an increase of land use efficiency of 59% and of water use efficiency of 14%. Overall the intercrop model gave satisfactory predictions, with coefficients of efficiency (CE) in validation of 0.86–0.97, 0.90–0.95, 0.85–0.91 and 0.98 for biomass of sole wheat, sole maize, intercropped wheat, and intercropped maize, respectively. Overall CE of water use was 0.95. Simulated LER and WER were similar to observed LER and WER. The results show that intercropping could be used to obtain more yield on less land with less water. Policies that limit water use per unit land and prohibit the use of intercropping on the basis of its high water use per unit area may therefore be counter-productive. The model for intercrop growth and development under water limitation may be used for exploring production possibilities under land and water constraints.

Straw and Plastic Mulching Enhances Crop Productivity via Optimizing Interspecific Interactions of Wheat–Maize Intercropping in Arid Areas

Intercropping is considered as a promising system for improving crop productivity. In arid environments, it is unknown whether the coordinated interspecific interaction can be improved via optimizing agronomic management measures. In this study, we quantified the competitiveness of the intercrops in response to straw and plastic management during both co‐growth periods, and the compensation effect of each intercrop. A late‐maturing maize (Zea mays L.) was alternately planted in field strips with an early‐maturing wheat (Triticum aestivum L.) under four straw and plastic management patterns in northwestern China from 2014 to 2016. Intercropped wheat was the dominant species, and the average index of competitiveness of wheat to maize (AWM) was 0.403. Integration of straw and plastic mulching application in wheat–maize intercropping reduced the interspecific competition and improved the compensation effect of intercropped maize. On average, no tillage with straw covering the soil in wheat strip combined with 2‐yr plastic mulching in maize strip (i.e., NTSI2) decreased the AWM by 30.9%, increased the growth rate of the intercropped maize by 23.4%, boosted grain yield of intercropped wheat and maize by 9.7 and 17.6%, and boosted total grain yields by 14.9% compared with the conventional intercropping treatment (i.e., CTI). The grain yields of intercrops are a quadratic regression with AWM, and AWM values of 0.354 to 0.375 are the most beneficial to boost the grain yields of the intercropped components. The NTSI2 treatment provided the greatest benefits for weakening the relative competitiveness of the intercrops while strengthening the compensation effect, and boosting the productivity of a wheat–maize intercropping pattern.

Innovation in alternate mulch with straw and plastic management bolsters yield and water use efficiency in wheat-maize intercropping in arid conditions

In arid regions, higher irrigation quota for conventional farming causes substantial conflict between water supply and demand for crop production. Innovations in cropping systems are needed to alleviate this issue. A field experiment was conducted in northwestern China to assess whether straw and plastic managements in wheat/maize intercropping could alleviate these issues. Integrating no tillage with two-year plastic and straw mulching (NTMI2) improved grain yields by 13.8–17.1%, compared to conventional tillage without straw residue and annual new plastic mulching (CTI). The NTMI2 treatment reduced soil evaporation by 9.0–17.3% and the proportion of evaporation to evapotranspiration (E/ET) by 8.6–17.5%, compared to CTI. The NTMI2 treatment weakened wheat competition of soil moisture from maize strip during wheat growth period, and enhanced wheat compensation of soil moisture for maize growth after wheat harvest, compared with CTI. Thus, soil water movement potential of NTMI2 was lowest during wheat growth period, but it was highest during maize-independent growth stage after wheat harvest. The NTMI2 treatment increased evapotranspiration before maize silking, decreased from maize silking to early-filling stage, and increased after the early-filling stage of maize, this effectively coordinated water demand contradiction of intercrops at early and late stages. The NTMI2 treatment improved WUE by 12.4–17.2%, compared with CTI. The improved crop yields and WUE was attributed to the coordinated water competition and compensation, and the decreased soil evaporation and E/ET.

Emergy analysis, water-heat utilization, and carbon emission of typical cropping patterns in the oasis irrigation area.

Reasonable cropping pattern can improve resource utilization efficiency, reduce environmental risks in agricultural production, and achieve the goal of resource saving coupled with high production and efficiency. We evaluated the production effects of typical cropping patterns in an arid irrigation region from several aspects, including resource utilization, carbon emissions, economic benefit, emergy self-sufficiency ratio and net emergy yield ratio, with the method of emergy theory, to provide theoretical and practical basis for the establishment of efficient cropping with lower resource investment and carbon emissions but higher yield and resource utilization efficiency combined with the sustainability of agricultural production. The results showed that, high-efficient wheat-maize intercropping production pattern (integration of no tillage with 25 to 30 cm height of wheat straw covering in the wheat strip and two-year plastic mulching in the maize strip, NTSI) had the best performance in grain yield boosting, with the yields 13.5% to 16.9% and 13.8% to 17.1% higher than that in local traditional production patterns (i.e., wheat-maize intercropping, CTI, and monoculture maize, CTM), respectively. Moreover, NTSI increased water use efficiency and solar energy use efficiency by 12.4% to 17.2% and 6.1% to 8.1%, compared to CTI, respectively. Compared to CTI and CTM, NTSI improved the effect on carbon emission reduction by decreasing total soil CO2 emission by 618 to 895 kg·hm-2 and 1804 to 2002 kg·hm-2 with the ratio of 12.1% to 16.4% and 28.6% to 31.0%, but increased carbon emission efficiency by 29.3% to 40.1% and 58.9 to 71.4%, respectively. Meanwhile, the NTSI pattern had obvious resources saving potential. Compared with CTI and CTM, NTSI reduced total input by 1424 to 1431 yuan·hm-2 and 501 to 1547 yuan·hm-2, with the proportional reduction being 12.6% to 13.6% and 4.9% to 14.6%; however, increased total output by 4309 to 4603 yuan·hm-2 and 8439 to 11057 yuan·hm-2, the increased ratio was 11.2% to 11.8% and 24.4% to 36.3%; also, increased net return by 5740 to 6027 yuan·hm-2 and 9544 to 11558 yuan·hm-2, and the improved percentage was 19.6% to 22.4% and 40.1% to 57.7%, respectively. Therefore, the high-efficient NTSI pattern had greater input-output ratio by 27.9% to 29.0% and 40.5% to 45.6% than CTI and CTM, respectively, similarly, greater benefit per cubic meter of water by 19.9% to 23.2% and 27.7% to 39.3%, respectively. The emergy self-sufficiency ratio of NTSI pattern was 57.2%, being 4.0% and 12.2% higher than CTI and CTM, respectively. NTSI pattern's net emergy yield ratio was 0.173, being 10.0% greater than CTI but 11.7% lower than CTM. With respect to resource utilization, carbon emission reduction, economic benefits and the sustainable development of high-efficient intercropping pattern, the integration of no tillage with straw covering and two-year plastic film mulching measures had higher economic activity, better function of agricultural system, greater production efficiency, and higher returns on energy value. We concluded that NTSI could be a high-efficiency farming system pattern on resources saving, carbon emission reduction, high yield and efficiency in arid oasis irrigation areas.

Wheat-Maize Intercropping With Reduced Tillage and Straw Retention: A Step Towards Enhancing 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.

Straw retention and plastic mulching enhance water use via synergistic regulation of water competition and compensation in wheat-maize intercropping systems

Synergistic regulation of water competition and compensation is critical for the effective use of water in sustainable intercropping systems. A field experiment was conducted on different measures of plastic mulching and straw retention (no-tillage with straw standing in wheat strip and two-year plastic mulching in maize strip, NTSSI2; no-tillage with straw covering in wheat strip and two-year plastic mulching in maize strip, NTSI2; conventional tillage with straw incorporation in wheat strip and annual new plastic mulching in maize strip, TSI; and conventional tillage without straw retention in wheat strip and annual new plastic mulching in maize strip, CTI), which were used in strip intercropping from 2014 to 2016. We determined the effects of integrated measures on coordinating water competition and compensation between inter-strips. The intercropped wheat competed for soil water from the maize strips during the wheat growth period. After wheat harvest, the intercropped maize obtained compensatory soil water from the wheat strips. The results showed that the NTSI2 treatment favorably weakened wheat competition of soil water from the maize strip and strengthened wheat strip compensation of soil water for maize growth compared with CTI treatment. Thus, compared to the CTI treatment, the potential movement amount of soil water in NTSI2 was lowest, decreased by 25.8–58.9% during wheat growth period, but it arrived at the highest, increased by 42.2–60.8% after wheat harvest. The NTSI2 treatment improved grain yield by 13.8–17.1% and enhanced WUE by 12.4–17.2% compared with CTI. The improvement in crop yield and WUE was partly attributed to the coordinated water competition between the inter-strips and the water compensation effect from the early-maturing wheat to the late-maturing maize.

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 Wheat-Maize Intercropping on Population Dynamics of Wheat Aphids and Their Natural Enemies

To study the effects of wheat-maize intercropping on the population dynamics of wheat aphids and their natural enemies, wheat-maize intercropping patterns were divided into four levels: 8:2, 6:2, and 4:2 intercropping, and monoculture wheat. The results showed that as the wheat coverage rate decreased, the quantities of immigrating winged aphids and their natural enemies significantly differed; the population densities of the natural enemies of wheat aphids continuously rose and reached the highest levels in the 4:2 intercropping. During the stable periods, the maximum population density of wheat aphids was the highest in monoculture wheat. With a reduction in the wheat coverage ratio, the maximum population density of wheat aphids showed a decreasing trend. The control imposed by predatory natural enemies in intercropped wheat was higher than that in monoculture wheat; it was strongest in the 8:2 intercropping and the lowest in wheat monoculture. With an increase in the proportion of wheat, the parasitism rate of parasitic wasps increased gradually and reached the highest level in 4:2 intercropping. The effect of host density on hyperparasitism was significant in the intercropped wheat. The intercropping pattern had a great effect on the wheat aphids’ natural enemies. In different agricultural landscapes, the diversity of wheat aphids’ natural enemies differed significantly between intercropped wheat and monoculture wheat; in the heterogeneous landscape, the natural enemy diversity was highest in intercropped wheat, and it was far higher than that in the other wheat cultivation patterns. The natural enemy diversity was also slightly different between monoculture wheat in the heterogeneous landscape and intercropped wheat in the homogeneous agricultural landscape.

Integration of wheat-maize intercropping with conservation practices reduces CO2 emissions and enhances water use in dry areas

Crop intensification has been used as a mean to increase crop yield and secure food supplies in developing countries. However, issues about CO2 mitigation, water consumption, and the overall viability associated with the crop intensification have become a concern. The main objective of this study was to investigate how the yield related environmental factors, i.e. soil CO2 emission and crop water use would responsed to wheat-maize intercropping with conservation practices. Here we determined crop yield, plant biomass carbon, soil CO2 emission, and crop water use in various cropping systems. The field experiment was conducted at Wuwei Experimental Station in an arid oasis region (37°57′N, 102°37′E), in 2011 and 2012. Four tillage and crop residue options were applied to wheat-maize intercropping. They were (a) no-till with stubble standing (NTS), (b) no-till with stubble mulching (NTM), (c) reduced tillage with stubble incorporated into the soil (RTS), and (d) conventional tillage without stubble retention (CT). Averaged across two years, wheat-maize intercropping integrated with no-till and stubble mulching yielded 1.6tha−1 more grains and 7.1MJha−1 more energy, while emitted 1.2tha−1 less soil CO2 than conventional wheat-maize intercropping; at the same time, the system increased plant biomass carbon by 16%, and enhanced CO2 emission efficiency per unit of grain yield by 39%, compared with the conventional system. Also, the integrated system decreased soil evaporation by 11%, increased energy yield per unit of water by 19%, and lowered CO2 emission per unit of water by 9%. Among the wheat-maize intercropping systems evaluated, the treatment with no-till and crop residue mulched on the soil surface had the highest evaluation index at 0.82; this was attributable to the increases of carbon emission efficiency by 48% and water use efficiency by 22%, compared with the conventional system. Wheat-maize intercropping integrated with no-till and stubble retention can be used to increase crop yield efficiently while reducing soil CO2 emission and enhancing crop water use effectively in dry areas.

Intercropping wheat and maize increases total radiation interception and wheat RUE but lowers maize RUE

Row configuration has a large influence on the intensity of species interactions in intercrops. Row configuration affects how many crop rows interact with the same species and how many rows interact with the other species, shaping the expression of plasticity, resource capture, and growth. This study aims to determine how row configuration influences radiation interception and productivity in wheat-maize intercropping under western European growing conditions. Field experiments with different row configurations were carried out in 2013 and 2014 in the Netherlands. We compared seven treatments, comprising sole crops of wheat and maize (SW and SM), a replacement intercrop (6:2WM), skip-row designs (6:0WM, 0:2WM) and add-row designs (6:3WM, 8:2WM). We determined leaf area and biomass dynamics over time, and developed a simple geometry-based model to estimate light capture in these different row configurations. The model was tested with light measurements in the field. Crop radiation use efficiency (RUE) was estimated by linear regression of above-ground biomass on the calculated cumulative intercepted light (photosynthetically active radiation – PAR). This study showed that: 1) wheat-maize intercropping had significantly higher PAR interception than sole wheat in 2013 and 2014, and sole maize in 2013, but not in 2014; 2) intercropping significantly increased RUE of wheat, whereas it significantly decreased RUE of maize; 3) both light interception and light use efficiency changed with planting configuration. Thus we showed that the row configuration of the intercrop affected light interception as well as light use efficiency by modulating the strength of competitive and compensatory interactions within and between crop species.

Yield and yield components of wheat and maize in wheat–maize intercropping in the Netherlands

Abstract Intercropping is widely used by smallholder farmers in developing countries, and attracting attention in the context of ecological intensification of agriculture in developed countries. There is little experience with intercropping of food crops in Western Europe. Yields in intercrops depend on planting patterns of the mixed species in interaction with local growing conditions. Here we present data of two years field experimentation on yield and yield components of a wheat–maize intercrop system in different planting configurations in the Netherlands. Treatments included sole crops of wheat (SW) and maize (SM), a replacement intercrop consisting of strips of six wheat rows alternating with two maize rows (6:2WM), as well as subtractive or additive designs, based on skip-row (6:0WM, 0:2WM) and add-row (8:2WM, 6:3WM) configurations. The land equivalent ratio (LER) of intercrops varied from 1.18 to 1.30 in 2013 and from 0.97 to 1.08 in 2014. Wheat grown in the border rows of wheat strips had higher ear number per meter row, greater kernel number per ear, and greater yield per meter row than wheat in inner rows and sole wheat, indicating reduced competition. Wheat in the border rows in the intercrops had, however, reduced thousand kernel weight and harvest index, indicating that competition in border rows intensified over time. Intercropping negatively affected maize biomass and thousand kernel weight, especially in add-row treatments. This study indicates that there is a potential yield benefit for the wheat–maize intercropping system under Western European growing conditions. However, the LER was affected by yearly variation in weather conditions and significantly greater than one in only one of the two years of the study.