Enhancing crop production and carbon sequestration of wheat in arid areas by green manure with reduced nitrogen fertilizer.

Green manure with appropriate amount of chemical nitrogen fertilizer can increase crop yield, but also aggravate soil carbon emissions. However, it is unclear whether incorporation of green manure into the cropping pattern with reduced nitrogen amount can alleviate this situation and enhance carbon sequestration potential. So, a field experiment with split-plot design was set up in 2018 of northwest China, and studied the effects of nitrogen reduction on crop productivity, carbon emissions, and carbon sequestration potential in 2021-2023. The main plots were two cropping patterns, including multiple cropped green manure after wheat harvest (W-G) and fallow after wheat harvest (W). Three nitrogen application levels formed the split-plots, including local conventional nitrogen amount (N3, 180 kg ha-1), nitrogen amount reduced by 15% (N2, 153 kg ha-1) and 30% (N3, 126 kg ha-1). The results showed that W-G increased grain yield of wheat and energy yield of wheat multiple cropped green manure pattern. The multiple cropped green manure after wheat harvest with local conventional nitrogen amount reduced by 15% (W-GN2) had the significant increasing-effect, and increased grain yield of wheat by 9.6% and increased total energy yields by 39.3% compared to fallow after wheat harvest with local conventional nitrogen amount (W-N3). Relative to W-N3, W-GN2 did not significantly increase carbon emissions of wheat season, and increased total carbon emissions of cropping pattern by 11.1%. Compared to multiple cropped green manure after wheat harvest with local conventional nitrogen amount (W-GN3), W-GN2 decreased carbon emissions by 5.8% in wheat season and decreased by 3.9% in the whole cropping pattern. Therefore, W-GN2 gained high carbon emission efficiency based on grain yield, and were 9.9% and 11.2% higher than W-N3 and W-GN3, respectively. In addition, W-GN2 enhanced soil total nitrogen, carbon, and organic carbon contents, compared with W-N3, thus increasing soil carbon sequestration potential index (net primary productivity/carbon emissions). We conclude that multiple cropped leguminous green manure after wheat harvest with local conventional nitrogen amount reduced by 15% can enhance crop productivity and carbon sequestration potential of farmland in arid areas.

Blue light regulated lignin and cellulose content of soybean petioles and stems under low light intensity.

To improve light harvest and plant structural support under low light intensity, it is useful to investigate the effects of different ratios of blue light on petiole and stem growth. Two true leaves of soybean seedlings were exposed to a total light intensity of 200µmolm-2 s-1 , presented as either white light or three levels of blue light (40µmolm-2 s-1 , 67µmolm-2 s-1 and 100µmolm-2 s-1 ) for 15days. Soybean petioles under the low blue light treatment upregulated expression of genes relating to lignin metabolism, enhancing lignin content compared with the white light treatment. The low blue light treatment had high petiole length, increased plant height and improved petiole strength arising from high lignin content, thus significantly increasing leaf dry weight relative to the white light treatment. Compared with white light, the treatment with the highest blue light ratio reduced plant height and enhanced plant support through increased cellulose and hemicellulose content in the stem. Under low light intensity, 20% blue light enhanced petiole length and strength to improve photosynthate biomass; whereas 50% blue light lowered plants' centre of gravity, preventing lodging and conserving carbohydrate allocation.

Beneficial effects of red and blue light on potato leaf antioxidant capacity and tuber bulking.

Artificial light application is an effective method for promoting potato production in indoor facilities. In this study, we assessed the effects of different combinations of red (R) and blue (B) light application on potato leaf and tuber growth. Potato plantlets were transplanted under W (white light, control), RB5-5 (50% R + 50% B), RB3-7 (30% R + 70% B to 70% R + 30% B) and RB1-9 (10% R + 90% B to 90% R + 10% B), and ascorbic acid (AsA) metabolism in leaves and cytokinin (CTK), auxin (indole-3-acetic acid, IAA), abscisic acid (ABA), and gibberellin (GA) levels in tubers were measured. At 50 days of treatment, potato leaves had significantly higher L-galactono-1,4-lactone dehydrogenase (GalLDH) activity and utilized AsA faster under RB1-9 treatment than under RB3-7 treatment. CTK/IAA and ABA/GA ratios in large tubers under W treatment did not differ significantly from those under RB1-9 treatment, which had higher levels than those under RB5-5 and RB3-7 treatment at 50 days. However, under RB1-9 treatment, total leaf area decreased rapidly from 60 to 75 days compared with plants under RB3-7 treatment. Tuber dry weight per plant under W and RB5-5 treatment approached a plateau at 75 days. At 80 days, RB3-7 treatment significantly improved ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase activity compared with RB1-9 treatment. RB1-9 treatment with a high ratio of blue light increased CTK/IAA and ABA/GA to improve tuber bulking at 50 days, while RB3-7 treatment with a high ratio of red light stimulated AsA metabolic pathway to delay leaf oxidation and maintain tuber biomass accumulation at 80 days. For the indoor potato cultivation, RB3-7 treatment had a higher proportion of medium-sized tubers, thus being a suitable light treatment.

Delayed application of N fertilizer mitigates the carbon emissions of pea/maize intercropping via altering soil microbial diversity.

Strategies to reduce carbon emissions have been a hotspot in sustainable agriculture production. The delayed N fertilizer application had the potential to reduce carbon emissions in pea (Pisum sativum L.)/maize (Zea mays L.) intercropping, but its microbial mechanism remains unclear. In this study, we investigated the effects of delayed N fertilizer application on CO2 emissions and soil microbial diversity in pea/maize intercropping. The soil respiration (Rs) rates of intercropped pea and intercropped maize were decreased by 24.7% and 25.0% with delayed application of N fertilizer, respectively. The total carbon emissions (TCE) of the pea/maize intercropping system were also decreased by 21.1% compared with that of the traditional N fertilizer. Proteobacteria, Bacteroidota, and Chloroflexi were dominant bacteria in pea and maize strips. Heatmap analysis showed that the soil catalase activity at the pea flowering stage and the soil Ν Η 4 + - Ν at the maize silking stage contributed more to the variations of bacterial relative abundances than other soil properties. Network analysis demonstrated that Rs was positively related to the relative abundance of Proteobacteria and Bacteroidota, while negatively related to the relative abundance of Chloroflexi in the pea/maize intercropping system. Overall, our results suggested that the delayed application of N fertilizer combined with the pea/maize intercropping system altered soil bacterial community diversity, thereby providing novel insights into connections between soil microorganisms and agricultural carbon emissions.

No-till and nitrogen fertilizer reduction improve nitrogen translocation and productivity of spring wheat (Triticum aestivum L.) via promotion of plant transpiration.

Excessive nitrogen (N) fertilizer has threatened the survivability and sustainability of agriculture. Improving N productivity is promising to address the above issue. Therefore, the field experiment, which investigated the effect of no-till and N fertilizer reduction on water use and N productivity of spring wheat (Triticum aestivum L.), was conducted at Wuwei experimental station in northwestern China. There were two tillage practices (conventional tillage, CT; and no-till with previous plastic film mulching, NT) and three N fertilizer rates (135 kg N ha-1, N1; 180 kg N ha-1, N2; and 225 kg N ha-1, N3). The results showed that NT lowered soil evaporation (SE) by 22.4% while increasing the ratio of transpiration to evapotranspiration (T/ET) by 13.6%, compared with CT. In addition, NT improved the total N accumulation by 11.5% and enhanced N translocation (NT) quantity, rate, and contribution by a range of 6.2-23.3%. Ultimately, NT increased grain yield (GY), N partial factor productivity, and N harvest index by 13.4, 13.1, and 26.0%, respectively. Overall, N1 increased SE (13.6%) but decreased T/ET (6.1%) compared with N3. While, N2 enhanced NT quantity, rate, and contribution by a range of 6.0-15.2%. With the integration of NT, N2 achieved the same level of GY and N harvest index as N3 and promoted N partial factor productivity by 11.7%. The significant positive correlation of NT relative to T/ET and GY indicated that improving T/ET was essential for achieving higher NT. Therefore, we concluded that no-till coupled with N fertilizer rate at 180 kg N ha-1 was a preferable management option to boost the N productivity of spring wheat in arid areas.

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.

Optimized nitrogen rate, plant density, and irrigation level reduced ammonia emission and nitrate leaching on maize farmland in the oasis area of China.

Nitrogen fertilizers play a key role in crop production to meet global food demand. Inappropriate application of nitrogen fertilizer coupled with poor irrigation and other crop management practices threaten agriculture and environmental sustainability. Over application of nitrogen fertilizer increases nitrogen gas emission and nitrate leaching. A field experiment was conducted in China's oasis irrigation area in 2018 and 2019 to determine which nitrogen rate, plant density, and irrigation level in sole maize (Zea mays L.) cropping system reduce ammonia emission and nitrate leaching. Three nitrogen rates of urea (46-0-0 of N-P2O5-K2O), at (N0 = 0 kg N ha-1, N1 = 270 kg N ha-1, and N2 = 360 kg N ha-1) were combined with three plant densities (D1 = 75,000 plants/ha-1, D2 = 97,500 plants/ha-1, and D3 = 120,000 plants/ha-1) with two irrigation levels (W1 = 5,250 m3/hm2 and W2 = 4,740 m3/hm2) using a randomized complete block design. The results showed that, both the main and interaction effects of nitrogen rate, plant density, and irrigation level reduced nitrate leaching (p < 0.05). In addition, irrigation level × nitrogen rate significantly (p < 0.05) reduced ammonia emission. Nitrate leaching and ammonia emission decreased with higher irrigation level and higher plant density. However, high nitrogen rates increased both nitrate leaching and ammonia emission. The study found lowest leaching (0.35 mg kg-1) occurring at the interaction of 270 kg N ha-1 × 120,000 plants/ha-1 × 4,740 m3/hm2, and higher plant density of 120,000 plants/ha-1 combined with 0 kg N ha-1 and irrigation level of 5,250 m3/hm2 recorded the lowest ammonia emission (0.001 kg N)-1. Overall, ammonia emission increased as days after planting increased while nitrate leaching decreased in deeper soil depths. These findings show that, though the contributory roles of days after planting, soil depth, amount of nitrogen fertilizer applied and year of cultivation cannot be undermined, it is possible to reduce nitrate leaching and ammonia emission through optimized nitrogen rate, plant density and regulated irrigation for agricultural and environmental sustainability.

N-fertilizer postponing application improves dry matter translocation and increases system productivity of wheat/maize intercropping.

Intercropping increases the grain yield to feed the ever-growing population in the world by cultivating two crop species on the same area of land. It has been proven that N-fertilizer postponed topdressing can boost the productivity of cereal/legume intercropping. However, whether the application of this technology to cereal/cereal intercropping can still increase grain yield is unclear. A field experiment was conducted from 2018 to 2020 in the arid region of northwestern China to investigate the accumulation and distribution of dry matter and yield performance of wheat/maize intercropping in response to N-fertilizer postponed topdressing application. There were three N application treatments (referred as N1, N2, N3) for maize and the total amount were all 360 kg N ha-1. N fertilizer were applied at four time, i.e. prior to sowing, at jointing stage, at pre-tasseling stage, and at 15 days post-silking stage, respectively. The N3 treatment was traditionally used for maize production and allocations subjected to these four stages were 2:3:4:1. The N1 and N2 were postponed topdressing treatments which allocations were 2:1:4:3 and 2:2:4:2, respectively. The results showed that the postponed topdressing N fertilizer treatments boosted the maximum average crop growth rate (CGR) of wheat/maize intercropping. The N1 and N2 treatments increased the average maximum CGR by 32.9% and 16.4% during the co-growth period, respectively, and the second average maximum CGR was increased by 29.8% and 12.6% during the maize recovery growth stage, respectively, compared with the N3 treatment. The N1 treatment was superior to other treatments, since it increased the CGR of intercropped wheat by 44.7% during the co-growth period and accelerated the CGR of intercropped maize by 29.8% after the wheat had been harvested. This treatment also increased the biomass and grain yield of intercropping by 8.6% and 33.7%, respectively, compared with the current N management practice. This yield gain was primarily attributable to the higher total translocation of dry matter. The N1 treatment increased the transfer amount of intercropped wheat by 28.4% from leaf and by 51.6% from stem, as well as increased the intercropped maize by 49.0% of leaf, 36.6% of stem, and 103.6% of husk, compared to N3 treatment, respectively. Integrated the N fertilizer postponed topdressing to the wheat/maize intercropping system have a promotion effect on increasing the translocation of dry matter to grain in vegetative organs. Therefore, the harvest index of intercropped wheat and maize with N1 was 5.9% and 5.3% greater than that of N3, respectively. This demonstrated that optimizing the management of N fertilizer can increase the grain yield from wheat/maize intercropping via the promotion of accumulation and translocation of dry matter.

Photosynthetic Physiological Characteristics of Water and Nitrogen Coupling for Enhanced High-Density Tolerance and Increased Yield of Maize in Arid Irrigation Regions.

To some extent, the photosynthetic traits of developing leaves of maize are regulated systemically by water and nitrogen. However, it remains unclear whether photosynthesis is systematically regulated via water and nitrogen when maize crops are grown under close (high density) planting conditions. To address this, a field experiment that had a split-split plot arrangement of treatments was designed. Two irrigation levels on local traditional irrigation level (high, I2, 4,050 m3 ha-1) and reduced by 20% (low, I1, 3,240 m3 ha-1) formed the main plots; two levels of nitrogen fertilizer at a local traditional nitrogen level (high, N2, 360 kg ha-1) and reduced by 25% (low, N1, 270 kg ha-1) formed the split plots; three planting densities of low (D1, 7.5 plants m-2), medium (D2, 9.75 plants m-2), and high (D3, 12 plants m-2) formed the split-split plots. The grain yield, gas exchange, and chlorophyll a fluorescence of the closely planted maize crops were assessed. The results showed that water-nitrogen coupling regulated their net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), quantum yield of non-regulated non-photochemical energy loss [Y(NO)], actual photochemical efficiency of PSII [Y(II)], and quantum yield of regulated non-photochemical energy loss [Y(NPQ)]. When maize plants were grown at low irrigation with traditional nitrogen and at a medium density (i.e., I1N2D2), they had Pn, Gs, and Tr higher than those of grown under traditional treatment conditions (i.e., I2N2D1). Moreover, the increased photosynthesis in the leaves of maize in the I1N2D2 treatment was mainly caused by decreased Y(NO), and increased Y(II) and Y(NPQ). The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize, whose Pn, Gs, Tr, Y(II), and Y(NPQ) were enhanced, and its Y(NO) was reduced. Redundancy analysis revealed that both Y(II) and SPAD were the most important physiological factors affecting maize yield performance, followed by Y(NPQ) and NPQ. Using the 20% reduction in irrigation and traditional nitrogen application at a medium density of planting (I1N2D2) could thus be considered as feasible management practices, which could provide technical guidance for further exploring high yields of closely planted maize plants in arid irrigation regions.

Improving wheat grain yield via promotion of water and nitrogen utilization in arid areas.

Crop yield is limited by water and nitrogen (N) availability. However, in Hexi Corridor of northwestern China, water scarcity and excessive fertilizer N in wheat (Triticum aestivum L.) production causes serious conflicts between water and N supply and crop demand. A field experiment was conducted from 2016 to 2018 to evaluate whether reducing of irrigation and fertilizer N will reduce grain yield of wheat. There were two irrigation quotas (192 and 240 mm) and three fertilizer N rates (135, 180, and 225 kg N ha-1). The results showed that reducing irrigation to 192 mm and N rate to 180 kg N ha-1 reduced water uptake, water uptake efficiency, and N uptake of spring wheat as compared to local practice (i.e., 240 mm irrigation and 225 kg N ha-1 fertilizer). Whereas, it improved water and N utilization efficiency, and water and N productivity. Consequently, the irrigation and N rate reduced treatment achieved the same quantity of grain yield as local practice. The path analysis showed that interaction effect between irrigation and N fertilization may attributable to the improvement of grain yield with lower irrigation and N rate. The enhanced water and N utilization allows us to conclude that irrigation quota at 192 mm coupled with fertilizer N rate at 180 kg N ha-1 can be used as an efficient practice for wheat production in arid irrigation areas.

No Tillage With Plastic Re-mulching Maintains High Maize Productivity via Regulating Hydrothermal Effects in an Arid Region.

Plastic is a valuable mulching measure for increasing crop productivity in arid environments; however, little is known about the main mechanism by which this valuable technology actuates spatial-temporal changes in soil hydrothermal effect. So a 3-year field experiment was conducted to optimize soil hydrothermal effect of maize field with three plastic mulched management treatments: (1) no tillage with plastic re-mulching (NM), (2) reduced tillage with plastic mulching (RM), and (3) conventional tillage with annual new plastic mulching (CM). The results showed that NM treatment increased soil water content by 6.6-8.4% from maize sowing to seedling stage, than did CM, and it created a good soil moisture environment for sowing of maize. Also, NM had greater soil water content by 4.8-5.6% from maize silking to early-filling stage than had CM, and it made up for the abundant demand of soil moisture for the vigorous growth of maize filling stage. The NM treatment increased water consumption (WC) before maize big-flare stage, decreased WC from big-flare to early-filling stage, and increased WC after early-filling stage. So NM treatment effectively coordinated water demand contradiction of maize at entire growing season. NM decreased soil accumulated temperature (SAT) by 7.0-13.0% at maize sowing to early-filling stage than did CM, but NM had little influence on the SAT during filling stage. In particular, the treatment on NM had smaller absolute values of air-soil temperature differences than RM and CM treatments during maize filling stage, indicating that NM treatment maintains the relative stability of soil temperature for ensuring grain filling of maize. The NM treatment allowed the maize to grow in a suitable hydrothermal status and still maintained high yield. In addition, NM treatment obtained higher net income and rate of return by 6.4-11.0% and 44.1-54.5%, respectively, than did CM, because NM treatment mainly decreased the input costs for plastic and machine operations. Therefore, the NM treatment can be recommended as a promising technique to overcome simultaneous heat stress and water shortage in arid environments.

Strip width ratio expansion with lowered N fertilizer rate enhances N complementary use between intercropped pea and maize.

Maize (Zea mays L.)/pea (Pisum sativum L.) strip intercropping is considered a promising cropping system to boost crop productivity. The 3-year (2009-2011) field experiment was conducted at Wuwei, northwest China, with two maize to pea strip width ratios (80:80 cm and 120:80 cm), each under three N fertilizer rates (0, 90 and 135 kg N ha-1 for pea, and 0, 300, and 450 kg N ha-1 for maize). The results showed that expanding maize to pea strip width ratio from 80:80 cm to 120:80 cm coupled with a reduction of N fertilizer rate intensified N competition and improved N compensation. The apparent N recovery and N utilization efficiency of intercropped pea with strip width ratio of 120:80 cm were increased by 8.0% and 8.9% compared to strip width ratio of 80:80 cm. Compared to high N rate, the two indicators of intercropped pea with lowered N rate were increased by 10.0% and 6.0%. For intercropped maize, the two indicators were increased by 6.8% and 5.1%, with strip width ratio of 120:80 cm compared to 80:80 cm. Also, they were improved by 9.7% and 11.5%, with lowered N rate compared to high N rate. Consequently, the grain yield of pea and maize in the 120:80 cm pattern was improved by 11.9% and 7.7% compared to 80:80 cm. We concluded that expanding maize to pea strip ratio coupled with N fertilizer reduction can optimize N complementary use.

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Dryland agriculture, with wide distribution and high yield potential, plays an important role in ensuring food security in China. It is currently limited by water scarcity, soil depletion, water and soil loss, and low non-renewable resource-use efficiency. Green manure has the potential to improve growth environment of crops and promote sustainable high-yield crops by increasing soil quality, balancing soil nutrients, and enhancing soil water-storage capacity. In addition, green manure has ecological benefits, including enhancing agroecosystem biodiversity, increasing soil surface cover degree, reducing ineffective nutrient loss to environment, improving air balance of farmland systems, and biological control of diseases, insect pests, and weeds. Under current scenario of intensified global climate change, environmental deterioration, and agricultural product demand changes, the traditional agronomic techniques of using green manure as a fertilizer cannot satisfy the requirements of agricultural development. Thus, it is necessary to strengthen the selection and bree-ding of green manure genetic resources for dryland agriculture, to develop a new regionalization of green manure, and to establish a cropping pattern based on green manure suitable for different regions. Furthermore, it is important to study and optimize the tillage and cultivation techniques to satisfy modern production and to establish an evaluation system for the comprehensive benefits of green manure. It is needed to establish a green manure application pattern that enables resource and ecological protection for improving ecological environment and economic efficiency of dryland agriculture and provides theoretical basis and technical support for exploiting green manure benefits.

Synchrony of nitrogen supply and crop demand are driven via high maize density in maize/pea strip intercropping.

Cereal density may influence the balance between nitrogen (N) supply and crop N demand in cereal/legume intercrop systems. The effect of maize (Zea mays L.) plant density on N utilization and N fertilizer supply in maize/pea (Pisum sativum L.) strip intercropping was evaluated in a field study with sole maize, sole pea, and intercropped maize/pea with three maize densities (D1, 45,000 plants ha-1; D2, 52,500 plants ha-1; D3, 60,000 plants ha-1) and two N treatments (N0, 0 kg N ha-1; N1, 450 kg N ha-1 for maize and 225 kg N ha-1 for pea). Soil mineral N in intercropped strips decreased with increased maize density. Increased maize density decreased N accumulation for intercropped pea but increased it for maize and the sum of both intercrops. The land equivalent ratio for grain yield (LER grain) showed a 24-30% advantage for intercrops than corresponding sole crops, and was greater with D3 than D1 and D2. Maize/pea intercropping had 4-113% greater nitrogen use efficiency (NUE) than sole maize, which was enhanced with increased maize density. Increasing maize density improved the synchrony of N supply and crop demand in maize/pea strip intercropping.

Source-to-Sink Translocation of Carbon and Nitrogen Is Regulated by Fertilization and Plant Population in Maize-Pea Intercropping.

Translocation of carbon (C) and nitrogen (N) from vegetative tissues to the grain sinks is critical for grain yield (GY). However, it is unclear how these processes respond to crop management practices when two crops are planted in relay-planting system. In this study, we characterized the C and N accumulation and translocation and their effects on yield formation in a pea (Pisum sativum L.)-maize (Zea mays L.) relay-planting system under different levels of source availabilities. Field experiment was conducted at Wuwei, northwest China, in 2012, 2013, and 2014. Two N fertilizer rates (low - N0 and high - N1) and three maize plant densities (low - D1, medium - D2, and high - D3) were designed to create the different levels of source availabilities. During the co-growth period, the rate of C accumulation in intercropped maize was 7.4-10.8%, 13.8-22.9%, and 13.5-32.0% lower than those in monoculture maize, respectively, under the D1, D2, and D3 treatments; however, after pea harvest, these values were 1.1-23.7%, 33.5-78.9%, and 36.8-123.7% greater than those in monoculture maize. At maturity, intercropped maize accumulated 11.4, 11.5, and 19.4% more N than monoculture maize, respectively, under the D1, D2, and D3 treatments. Compared to the monoculture crops, intercropped pea increased C accumulation in stems by 40.3% with N-application and by 19.5% without N application; intercropping maize increased these values by 16 and 11%, respectively. Overall, increasing N fertilization improved the rates of C and N remobilization from the vegetative tissues to the grain sinks across the different density treatments. In intercropped maize, the stems contributed 22, 33, and 44% more photosynthate to the grain sinks than the leaves, respectively, under the D1, D2, and D3 treatments. Quantitative assessments showed that the enhanced C and N remobilization due to high N fertilization and high plant density led to an increase of GY in the intercropping system by 35% compared with monoculture. We conclude that the enhanced productivity in maize-pea intercropping is a function of the source availability which is regulated by plant density and N fertilization.

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.

Low N Fertilizer Application and Intercropping Increases N Concentration in Pea (Pisum sativum L.) Grains.

Sustainable intensification of pulses needs reduced input of nitrogen (N) fertilizer with enhanced crop nutritional quality and yield. Therefore, increasing N harvest in grains (sink organs) by improving N remobilization is of key importance. Previous research has shown that a lower dose of N fertilizer effectively increases the rate of N remobilization, while intercropping improves the grain N concentration in pea (Pisum sativum L.). However, it is unknown whether intercropping can facilitate this N fertilizer effect to increase N remobilization, and thereby enhance the N harvest index (NHI). In this study, we determined N allocation among different organs of pea plants, N translocation from leaf and stem tissues to pods, N2 fixation, N utilization efficiency, and NHI of pea plants grown alone or intercropped with maize (Zea mays L.) with different N fertilization treatments in a field experiment in northwestern China from 2012 to 2014. A base application of 90 kg N ha-1 at sowing and top-dress application of 45 kg N ha-1 at flowering integrated with maize-pea intercropping increased N allocation to pod tissues, N translocation to grains, and NHI of pea plants. Compared with the application of 90 kg N ha-1 at sowing and 135 kg N ha-1 top-dressed at flowering, reducing the top-dress application of N fertilizer to 45 kg N ha-1 increased N allocation to intercropped pea plants by 8%. Similarly, N translocation to grains from leaf and stem tissues was increased by 37.9 and 43.2%, respectively, enhancing the NHI by 40.1%. A positive correlation between N2 fixation and NHI was observed, implying that N2 fixation improves N concentration in grain sinks. Thus, our data show that growing pulses in an intercropping system with reduced N fertilization are essential for maximizing N translocation, improving nutritional quality, and preventing the loss of N through leaching, thereby avoiding potential groundwater contamination.

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.