Maize-soybean Intercropping System Research Articles

The effect of strip orientation and width on radiation interception in maize–soybean strip intercropping systems

AbstractMaize–soybean intercropping systems are widely used in developing countries, but few studies have been performed to optimize such systems. The effects of strip width and orientation on photosynthetically active radiation (PAR) distribution characteristics were therefore determined to gain a better understanding of crop productivity in maize–soybean intercropping systems. A series of intercropping experiments incorporating different strip orientations and widths were conducted. In addition, an improved radiation transmission model was used to simulate PAR interception by the maize and soybean crops. We found that more PAR was intercepted by the soybean plants than by the maize plants when the strip orientation angle increased from 0° to 90° in the maize–soybean intercropping systems. This result was obtained in most of the main maize production areas, including those with different latitudes. The effect of strip widths within the intercropping systems also had a significant effect on PAR interception. The relative fraction of PAR intercepted ranged from 39.4% to 86% for soybean and 105.8% to 169.3% for maize. The effect of soybean strip width on leaf PAR interception was greater than that of maize strip width. These results are not only of fundamental biological importance but they also have important implications for agriculture in terms of the optimization of production in intercropping systems.

Growth responses of maize-soybean intercropping system and its potential for cattle feed in Bali

There had been a 2.145 ha fields transition in Bali which had a major impact on the loss of food production. However, there was raise in the population annually, therefore it disrupts local food security. Effort to raise the effectiveness and agricultural productivity areas through changing cropping system from monoculture to intercropping. This study aimed to find out the growth responses of maize and soybean crops cultivated by monoculture and intercropping planting systems and its carrying capacity for cattle feed. The study was arranged using a randomized block design with 3 treatments and 3 replications, namely: T1: Bima 20 URI VUB maize seeds in monoculture (40cm x 20cm x 80cm; 1 seed/hole or 70cm x 40cm x 100cm; 2 seeds/hole); T2: Anjasmoro, Deja 2 and Devon soybean VUB seeds in monoculture system (40cm x 20cm; 2-3 seeds/hole); T3: maize-soybean intercropping; Maize (2 rows; 40cm x 12.5; 2 seeds/hole); Soybeans (4 rows; 30cm x 10cm; 2-3 seeds/hole); both distance: 40cm. Data collected were growth performance, yield components and yield capacity of both maize and soybean crops also competition and profit value of maize and soybeans crops cultivated by intercropping planting system. The results showed that monoculture maize crops cultivated by monoculture planting system were better than it intercropped with soybean crops in terms of growth parameters. However, intercropping maize and soybean were produced greater yield components on cobs number, cobs and grains weight than monoculture (P<0.05), except grains weight per cobs. The monoculture soybean plant in growth, components and yield parameters were greater than intercropping (P>0.05). The ATER, LER, RCC, CR, and AYL values were 3.24; 1.28; -2.69; 4.58; -0.098 on maize and 2.52; 0.84; 1.82; 0.21; -0.158 on soybean. Those result was followed by carrying capacity in intercropping system by 30% usage can be used for 1.804 AU meanwhile 40% usage was sufficient for 1.353 AU. Intercropping system can be recommended to farmers to increase growth responses of maize-soybean and its potential carrying capacity for cattle feed.

Film mulching affects root growth and function in dryland maize-soybean intercropping

• Maize roots morphological behaviors respond to soybean roots presence in dry and wet conditions. • Intercropped maize roots were shallower compared to sole maize. • More active root-diameter strategy for intercropped maize to adapt to varied water conditions. • Film mulching improved the overlap of interspecific roots. • Film mulching greatly increased maize grain yield with a lesser decline of soybean grain yield relative to sole soybean. Understanding the morphological response of maize roots in the presence of soybeans in fields under varied water conditions is vital for identifying maize-dominant intercropping systems suitable for climate change. In this study, two maize-soybean intercropping systems (maize with and without film mulching) were compared with maize and soybean sole crops in rainfed farmland on the Loess Plateau. Different features, including the maize root morphological traits, root vertical distribution, shoot traits, interspecific root overlap, and grain yield of intercrops, were determined after silking in 2017 (dry year) and 2018 (wet year). The intercropped maize (without film mulching) employed a thin root system under dry conditions and a profuse root system under wet conditions, with shallow roots and active root-diameter strategy to adapt to varied water conditions. These features resulted in higher grain yield in per unit area for the intercropped maize (16.97 % overyielding) than sole maize without film mulching. Film mulching of intercropped maize modified the roots with confined growth under dry conditions and inhibited the roots with excessive growth under wet conditions; as a consequence, the two morphologies of intercropped maize root system were reshaped into the optimal one (less profuse but not thin), with S-type vertical distribution (1 m soil profile) for root length and more beneficial root-diameter strategy. Besides, film mulching improved interspecific root interaction through an evident increase in root length or mass in the interspecific overlap regions. Finally, film mulching improved the maize overyielding dramatically (84 %) due to high leaf adaptability and efficient root-shoot synergy in maize plants. Importantly, the maize mulching did not decrease intercropped soybean yield significantly when compared with sole soybean due to the benefits from interspecific facilitation, while it enhanced total grain yield (10.67 %) for the intercropping system. Thus, film mulching improved maize root morphology and balanced soil resource exploitation and shoot development, consequently strengthening the attainable grain yield in the intercropping system. To conclude, the research elucidates the plant root mechanisms (root morphological changes) underlying overyielding of intercropped maize in varied water conditions. It identifies film mulching of maize as a strategy to optimize root growth and function for higher intercropping yield advantage in dryland.

Growth promotion ability of phosphate-solubilizing bacteria from the soybean rhizosphere under maize-soybean intercropping systems.

Optimum cultivation and management measures are needed to increase the phosphorus (P) absorption efficiency of crops for sustainable agricultural production. Previous studies indicated that leguminous crops can promote P absorption by neighboring gramineous crops. In this study, we isolated and screened the phosphate-solubilizing bacteria (PSB) from soybean rhizosphere under a maize-soybean intercropping system in Southwest China, and nine PSBs with high P-solubilizing ability were identified. 16S rDNA sequencing and phylogenetic analysis showed that these PSBs belong mainly to Bacillus and Pseudomonas. The phosphate solubility of Bacillus aryabhattai B8W22 reached 388.62 μg mL-1 . High-performance liquid chromatographic analysis showed that each strain could secrete a large quantity of organic acids, including oxalic acid, malonic acid, citric acid and succinic acid. In addition, all strains produced indole acetic acid (IAA) and siderophores that could promote plant growth. Seed germination experiments testified that PSBs isolated in this study have an innate ability to promote plant growth. The plant culture pot experiment further illustrated that soil acid phosphatase (ACP) activity and available P content, as well as plant P uptake, increased significantly with PSBs inoculation. PSBs from the rhizosphere soil of intercropped soybean could secrete organic acids that increase the solubilization of unavailable P, improve soil ACP activity and P availability, and produce IAA and siderophores that promote maize seed germination and seedling growth. Our findings indicate the PSBs from soybean rhizosphere have significant potential to reduce the application of chemical phosphate fertilizers and to promote sustainable agricultural development. © 2021 Society of Chemical Industry.

Crop diversification practice faces a tradeoff between increasing productivity and reducing carbon footprints

Increasing crop biodiversity often increases agro-ecosystem services, however, the effects of crop biodiversity on crop yield and environmental benefits are still unclear. Thus, we conducted a 4-yr field experiment in northeastern China including continuous maize (CM), continuous soybean (CS), maize and soybean rotation (M-S), and maize and soybean intercropping (M/S) to evaluate the crop productivity, economic returns, carbon footprint (CF) and carbon sustainability index (CSI) among the cropping system regimes. Compared with CM treatment, M-S and M/S achieved lower energy yield (EY) and maize equivalent economic yield (MEEY), but higher economic returns. The mean annual net revenue of M-S treatment was 7.2% higher, and the mean annual benefit: cost ratio of M-S and M/S treatments were 12.0% and 8.8% higher than those of CM treatment. Based on the life cycle assessment (LCA), lower CFs were observed in the M-S and M/S systems. The CF per unit of area (CFA) of M-S and M/S treatments was 21.4% and 51.3% lower than that of the CM treatment, respectively. The CF per kg of energy yield (CFEY) of M/S treatment was 35.4% lower, compared with that of the CM treatment. The CF per kg of maize equivalent economic yield (CFMEEY) under M/S treatment was 44.0% lower, than that of the CM treatment. Moreover, CF per unit of economic output (CFE) of M/S treatment was 45.0% lower than that of the CM treatment. The highest CSI was observed in M-S treatment, and it was 61.4% higher than that of CM treatment. Our findings indicate that diversified crop practice (e.g. maize-soybean intercropping and rotation systems) could achieve lesser carbon footprint and higher profitability, however, might compromise grain or energy yield.

Effects of interspecific competition on crop yield and nitrogen utilisation in maize-soybean intercropping system

Intercropping system plays a crucial role in improving crop yield, nitrogen utilisation efficiency (NUE) and economic benefit. The difference in crop yield and interspecific relationship under different bandwidth and row ratio allocation patterns are still unclear. A field experiment was carried out to explore change regularities between crop yield and interspecific relationships under maize soybean intercropping with different bandwidths and row ratios. The results showed that the yield of intercropped crops was lower than that of the sole crop. The nitrogen accumulation (NA), NUE and nitrogen competition ratio was the highest under the intercropping mode with a bandwidth of 2.0 m, which indicated that this mode was more conducive to the N uptake and utilisation in crops. In all intercropping systems, nitrogen equivalent ratio (NER) and land equivalent ratio (LER) were all greater than one, indicating that intercropping systems were conducive to improving land utilisation efficiency and NUE. Under the same bandwidth pattern, expanding the maize soybean row ratio from 2 : 4 to 3 : 4 was beneficial to the improvement of LER, NER, NUE, crop group yield. In conclusion, it was preferable in the NA, NUE, crop group yield under the system of bandwidth 2.0 m and row ratio 2 : 2, which could be a reference for maize soybean intercropping system.

Effects of Baby Corn Density on the Crop and Weed Performance under Different Maize-Soybean Intercropping Systems

This study was conducted to examine the effects of baby corn density on the crop and weed performance under two different maize-soybean intercropping systems. Treatments included four baby corn densities (D1= 138,888 plants ha-1, D2 = 111,111 plants ha-1, D3 = 92,592 plants ha-1, and D4 = 79,365 plants ha-1), and three intercropping methods (P0 = a sole cropping of baby corn, P1 = 1 row of soybean + 1 row of baby corn (density of soybean, 10 plant m-2), and P2 = 2 rows of soybean + 1 row of baby corn (density of soybean, 20 plants m-2)). Physiological characteristics and yield were measured for the baby corn and soybean. The weed species, weed frequency, and the growth of the weeds were recorded at the final harvesting time of the baby corn. The results showed that the yield of soybean and the growth of the weeds were statistically different under the different maize-soybean intercropping systems. Increasing the baby corn density increased the leaf area index, dry matter accumulation, and cob yield, but did not have a clear effect on the soybean yield under both intercropping methods. In addition, the P2 intercropping method produced significantly higher soybean yield and gave better results of weed growth reduction in comparison with the P1 intercropping method. In the P2 intercropping method, baby corn should be grown at a density of 111,111 plants ha-1 to optimize the population productivity and achieve reasonable weed control for the sustainability of agriculture.

Effects of Different Planting Patterns on the Growth and Yield of Maize and Soybean in Northwest China

Aboveground and belowground interactions are crucial in the over-yielding of intercropping systems. However, the relative effects of aboveground and belowground interactions on yields in maize (Zea mays L.) and soybean (Glycine max) intercropping systems are still unclear. Field experiments, including measurements of plant height, soil-plant analysis development (SPAD) value, photosynthetically active radiation (PAR), root length density (RLD), root volume density (RVD), and grain yield, were conducted in 2018-2019 to analyze the advantages and effects of above-ground and belowground inter-species interactions. This study adopted three different planting patterns: mono-cropping maize (MM), mono-cropping soybeans (MS), and maize-soybean intercropping (IM and IS). This study showed that intercropping promotes the growth of maize and makes maize have a better photosynthetic environment, while the growth of intercropping soybeans is inhibited and the photosynthetic environment becomes worse. In the upper layer (0-40 cm) and close to the plants, the root growth and distribution of intercropped maize increased, resulting in greater root length density and volume density, while the root growth and distribution of intercropped soybean decreased, resulting in lower root length density and volume density. The intercropping increased the maize yield by 18.52-19.8%, and reduced the soybean yield by 55.87-57.44%. The results indicated that intercropping improves the competitiveness of maize and reduces the competitiveness of soybeans. The increase in maize yield made up for the loss of soybean yield and led to an overall significant advantage in the maize-soybean intercropping system.

Optimal NH4 + /NO3 - ratios enhance the shade tolerance of soybean seedlings under low light conditions.

In the maize-soybean intercropping system, shade is the major chronic restraint that affects normal growth of soybean. Different spatial patterns of this system affect the microclimate of soybean through shading from maize plants. However, the negative impacts of shading stress can be mitigated by providing optimal ratios of different fertilizers. Therefore, to test this hypothesis, soybean plants were grown under different light conditions (normal light or shade) to evaluate the response to varying NH4 + /NO3 - ratios. Seeds of soybean (Glycine max L. cv. Nan-99-6) were grown in nutrient solution with a total concentration of 5mMN using different NH4 + /NO3 - ratios (T0 =0:0, T1 =0:100, T2 =25:75, T3 =50:50 and T4 =75:25) for 40days in a greenhouse at PPFD 320.95μmolm-2 s-1 (low light) or 967.53μmolm-2 s-1 (normal light). Under low light, growth and photosynthesis of soybean seedlings significantly decreased as compared to normal light conditions. However, the optimal ratios of NH4 + / NO3 - improved growth and photosynthesis of soybean seedlings under both light conditions. Our results indicated that soybean seedlings supplied with optimal NH4 + /NO3 - ratios (25:75 and 50:50) have maximum biomass yield, chlorophyll pigments, leaf gas exchange, photochemical activity and root growth as compared to low and high NH4 + /NO3 - ratios (T1 and T4 ). High ratios of NH4 + /NO3 - (T4 ) resulted in reduced plant growth due to nutrient accumulation in plant tissues; therefore, we suggest that optimal ratios of NH4 + /NO3 - (T2 and T3 ) can enhance the shade tolerance of soybean seedlings.

Agro-Techniques for Lodging Stress Management in Maize-Soybean Intercropping System-A Review.

Lodging is one of the most chronic restraints of the maize-soybean intercropping system, which causes a serious threat to agriculture development and sustainability. In the maize-soybean intercropping system, shade is a major causative agent that is triggered by the higher stem length of a maize plant. Many morphological and anatomical characteristics are involved in the lodging phenomenon, along with the chemical configuration of the stem. Due to maize shading, soybean stem evolves the shade avoidance response and resulting in the stem elongation that leads to severe lodging stress. However, the major agro-techniques that are required to explore the lodging stress in the maize-soybean intercropping system for sustainable agriculture have not been precisely elucidated yet. Therefore, the present review is tempted to compare the conceptual insights with preceding published researches and proposed the important techniques which could be applied to overcome the devastating effects of lodging. We further explored that, lodging stress management is dependent on multiple approaches such as agronomical, chemical and genetics which could be helpful to reduce the lodging threats in the maize-soybean intercropping system. Nonetheless, many queries needed to explicate the complex phenomenon of lodging. Henceforth, the agronomists, physiologists, molecular actors and breeders require further exploration to fix this challenging problem.

BIOMASS YIELD FOR SILAGE AND GRAIN YIELD OF MAIZE INTERCROPPED WITH SOYBEAN

Maize is one of the main cereals produced worldwide and, in association withsoybean crop, can result in benefits to the production system. The objective of this study was to evaluate the biomass yield for silage and grain yield in maize crop, in the maizesoybean intercropping system. The study was conducted in the municipality of Dois Vizinhos - PR, Brazil, using a randomized block design, with nine treatments and four replicates. The treatments were composed of three maize hybrids grown in monoculture and in intercropping with two soybean cultivars (P1630+TMG7062, P1630+P95R51, P1630, LG6030+TMG7062, LG6030+P95R51, LG6030, P30F53+TMG7062, P30F53+P95R51 and P30F53). The data were subjected to analysis of variance and, when there was significance, Scott-Knott test was applied. Maize biomass yield for silage was approximately 4,000 kg ha-1 higher when the hybrids LG6030 and/or P30F53 were used. The cultivar TMG7062 stands out from P95R51 in terms of dry biomass yield for silage. The higher the percentage of soybean biomass added to the silage, the higher its crude protein content. However, crude protein yield per area was similar for the evaluated treatments. Some yield components (number of grains per row and thousand-grain weight) and grain yield of maize differ according to the hybrid used, but similarity is observed between intercropping and monoculture. There is evidence that the soybean cultivar TMG7062, intercropped with P1630, has the potential to reduce the grain yield of the cereal.

Effects of Multiple Planting Densities on Lignin Metabolism and Lodging Resistance of the Strip Intercropped Soybean Stem

The shading of maize and self-shading are the key factors affecting the stem lignin biosynthesis and lodging resistance of soybean at middle and later growth stages in the strip intercropping system. A study was designed to explore the regulation mechanism of lignin metabolism and different planting densities; PD1, PD2, and PD3 were used having a total number of 17 plants m−2, 20 plants m−2, and 25 plants m−2, respectively, on the lodging resistance of strip intercropped soybean stem. Our results depicted that the lower planting density (PD1) appropriately promoted the leaf photosynthesis activities (Pn), increase the activity of lignin-related enzymes and the accumulation of carbohydrates in stems, and eventually enhanced the lodging resistance of the strip intercropped soybean stem. Correlation analysis also showed that the lodging resistance index of soybean stem was significantly correlated with the available light for soybean canopy and Pn strip intercropped soybean stem characteristics and activities of enzymes related to lignin synthesis among the different planting densities. The findings of our research will be useful in future studies to understand the relationship between different light environment, planting densities, and lodging resistance of intercropped soybean and also guide the optimum planting density in maize–soybean intercropping system.

Evaluation of maize-soybean intercropping systems and fertilizer rates on maize grain yield using competitive indices

Field trials were conducted in savanna ecologies of Nigeria during the 2015 and 2016 seasons using maize (PVA8) and soybean (TGX 1448-2E) intercropping systems with different fertilizer rates to evaluate the yield of maize and assess the best intercropping system for resource management. Single plant stands and two plants/stand and 2 arrangements of rows (one row on a ridge and two rows on a ridge) were used to impose maize plant densities evaluated in strip inter-crop with soybean. The trial was factorial, laid out in a randomized complete block design and replicated three times. Thus, 8 maize-soybean strip cropping systems and application of 3 NPK rates were evaluated at Saki-Oyo, Ilorin, and Nasarawa (southern Guinea savanna), Kaduna in the northern Guinea savanna, Funtua (Katsina) and Gusau (Zamfara) located within Sudan savanna ecologies of Nigeria. Data on yields and yield components were collected. The intercropping systems were assessed using existing intercropping indices such as Land Equivalent Ratio (LER), Relative Crowding Coefficient (K), Aggressivity (A), Competitive Ratio (CR), Actual Yield Loss (AYL), Intercropping Advantage (IA) and Monetary Advantage Index (MAI). The result showed that Nasarawa and Kaduna were most ideal locations for maize production in the Nigeria savannas. The highest grain yield of 4.04 tons/ha maize and 1.36 tons/ha soybean were obtained from seeding 1 plant/stand in 2-rows per ridge x 4 ridges of maize alternated with 2 rows of soybean with the application of NPK at 100:50:50. The LER was 1.11, AYL (1.10) and MAI (208) gave a profit of ₦312,102.00 (US$990.80) ha-1 with a benefit-cost ratio of 2.38 and production efficiency of 29.56%. The study concluded that, seeding 80% maize and 20% soybean per ha will lead to sustainable maize crop production with limited use of fertilizer. It can be adopted by the farmers in Nigeria savannas as a relatively profitable intercropping system.&#x0D; Keywords: Maize production, Ideal location, Fertilizer rate, Competitive indices, Savanna ecologies, Nigeria

Nutrient Accumulation and Distribution Assessment in Response to Potassium Application under Maize–Soybean Intercropping System

Intercropping is an intensive agricultural cropping system widely practiced for enhanced yield and nutrient acquisition advantages. A two-year maize–soybean intercropping (MSI) field study was performed in 2018 and 2019 to assess the effects of potassium (K) fertilizer application on biomass accumulation and distribution of essential nutrients in the various plant parts (root, green biomass and seed) of maize–soybean intercropping (MSI). Three different treatments of K fertilizer applications (T0: no potassium application; T1: maize 40, soybeans 30 and T2: maize 80, soybeans 60 kg ha−1) were designed with 2 rows of maize by wide, narrow row planting in row arrangements of 160 cm + 40 cm. Soybeans were grown in 2 wide rows at a width of 40 cm and a row spacing of 60 cm between the rows of maize and soybeans, while the sole maize (SM) and sole soybean (SS) were grown with 70-cm and 50-cm row spacing, respectively. The results of the two-year study confirmed that, as compared to T0, T2 significantly increased nitrogen, phosphate and potassium (NPK) accumulation in all maize parts by 27%, 16% and 20% grain, 23%, 22% and 14% green biomass and 30%, 17% and 15% root, respectively. In soybean treatments, T2 significantly increased NPK accumulation by 23%, 22% and 24% grain, 16%, 15% and 12% green biomass and 18%, 19% and 20% root, respectively. The increased accumulation of nutrients under T2 raised the overall biomass and its distribution to root, green biomass and grain in maize and soybeans by 11% and 18% and 16% and 19%, 20% and 12%, respectively, compared to T0. On average, after two years of experiments, the T2 intercropped maize and the soybeans showed 103% and 64% of the sole yield and attained the maximum LER of 1.66 and 1.68, respectively. Our results reveal that managing optimum K level application (80:60 kg ha−1) can accelerate biomass accumulation and distribution of other essential nutrients in the plant parts of intercropped maize and soybeans. Therefore, it is immensely important to concern potassium application levels in developing a sustainable maize–soybean intercropping systems for achieving higher productivity and land equivalent ratio (LER).

Biological Nitrogen Fixation and Productivity of Soybean in Maize-Soybean Intercrop under Tillage and Bradyrhizobium Inoculation on Alfisols of Northern Guinea Savanna, Nigeria

A field study was conducted in the 2011 cropping season to investigate the effect of tillage and bradyrhizobium inoculation of soybean on biological nitrogen fixation (BNF) and yield components in maize-soybean intercropping systems. Treatments comprised of two tillage practices (conventional tillage (CT) and reduced tillage (RT)) as the main plot and bradyrhizobium inoculation at four levels (inoculated sole soybean, inoculated soybean/maize intercrop, uninoculated sole soybean, and uninoculated soybean/maize intercrop) as sub-plot. The treatments were laid in a split-plot under a randomized complete block design with three replications. Results showed that BNF and nitrogen derived from atmospheric (Ndfa) were significantly higher under RT than CT by 4.18 and 0.10 %, respectively. The BNF was consistently higher in the maize-soybean intercropping system with soybean inoculated with bradyrhizobium than in the uninoculated. BNF was 28.0 % higher in inoculated sole soybean and 80.2 % higher in inoculated maize-soybean intercrop than the uninoculated sole and intercropping system. Similarly, grain yield was 31.0 % higher in the inoculated sole soybean than the uninoculated sole and 33.7 % higher in inoculated maize/soybean intercrop than in the uninoculated intercrop. Biomass yields under inoculatedsole soybean and maize-soybean intercrop, respectively, were significantly higher than in uninoculated sole soybean and maize-soybean intercrop by 30.99and 33.66% for inoculated and uninoculated soybean sole and 34.44 and 30.40 % for inoculated and uninoculated intercrop. The results demonstrated that integrating bradyrhizobium inoculants and tillage will improve N fixation and productivity in maize-soybeanbased intercropping systems in Alfisols of Northern savannah.

Optimum leaf defoliation: A new agronomic approach for increasing nutrient uptake and land equivalent ratio of maize soybean relay intercropping system

Upper canopy leaves of maize decrease the light-transmittance at middle-strata-leaves of maize and soybean canopy in maize-soybean relay-intercropping systems (MS). This affects the uptake of nutrients and distribution patterns in various plant organs of intercrop species in MS. Judicious defoliation of maize plants in MS could help to alleviate this problem and improve nutrient uptake and intercrop yields. In a two-year field experiment with MS, including the measurements of biomass production, nutrients uptake, and distribution at the organ level, and grain yields of intercrop species, maize plants were subjected to four-leaf defoliation treatments to improve the light-transmittance of maize and soybean plants. Defoliation of the topmost two-leaves (T2), four-leaves (T4), six-leaves (T6) was compared to no defoliation (T0).Compared to T0, treatment T2 improved the uptake of nitrogen (N), phosphorus (P), and potassium (K) in each plant part of maize by 23, 12, and 11% (grain), 22, 19, and 13% (straw), and 28, 14, and 18% (root), respectively. Defoliation also enhanced the uptake of N, P, and K in each plant part of soybean by 5, 5, and 10% (grain), 10, 17, and 13% (straw), and 14, 11, and 11% (root), respectively. The improved nutrient uptake in T2 increased the total biomass and its distribution in the root, straw, and grain of soybean and maize by 15 and 13%, and 21 and 15%, 20 and 14%, 7 and 10%, respectively compared to T0. On average, over two years, under T2, relay-cropped maize obtained 107% of the sole-yield, and relay-cropped soybean obtained 65% of the sole-yield. The T2 defoliation treatment also achieved the highest land equivalent ratio of 1.69 and 1.77, with a net profit of 1301.6 $ ha−1 and 1293.4 $ ha−1 in 2017 and 2018, respectively.Following the optimum defoliation treatment of maize in maize-soybean intercrops, i.e., defoliation of the topmost two-leaves, the nutrient uptake can be increased, and the nutrient partitioning over plant organs be better balanced. Optimum defoliation, therefore, enhances the productivity of maize-soybean intercropping systems.

Co-benefits of sustainable farming methods to safeguard food security and environmental health in China: a modelling study

BackgroundModernised farming has contributed significantly to the increased global food supply over the past half-century, albeit while creating severe threats to the environment. Excessive application of chemical fertiliser has in particular led to massive release of reactive nitrogen compounds into the atmosphere, where they become major components of fine particulate matter (PM2·5) pollution, with detrimental effects on human health. Various sustainable farming methods with lower environmental impacts have been experimented with and practised in many countries, but their wider benefits beyond the farm scale have rarely been examined. One such method is intercropping with soybeans, which takes advantage of the nitrogen fixing ability of soybeans to improve nutrient use efficiency and reduce fertiliser use. MethodsWe developed a computational modelling framework using the GEOS-Chem and DNDC models, revising the representation for soil nitrogen processes and crop-crop interaction. We did model experiments to quantify the benefits of nationwide adoption of maize-soybean intercropping systems in China in terms of gains in crop production, decreases in fertiliser consumption, and reductions in ammonia (NH3) emissions. We further examined how the decline in NH3 emissions could reduce the downwind formation of PM2·5 and the associated public health costs. FindingsAnnual mean PM2·5 concentrations can be reduced by up to 1·5 μg/m3 with the nationwide adoption of maize-soybean intercropping, with a corresponding annual net economic benefit of US$67 billion, of which $13 billion arises from saved health costs from reduced air pollution. InterpretationOur study shows the wider economic and environmental value of intercropping systems for promoting both food security and public health, serving as a basis for policy consideration by governments and stakeholders. The same modelling framework can likewise be used to investigate the large-scale impacts of other sustainable farming methods. FundingGeneral Research Fund the Hong Kong Research Grants Council, the Area of Excellence Scheme, and the CUHK Vice- Chancellor Discretionary Fund.

Carbon footprint of different agricultural systems in China estimated by different evaluation metrics

Increase of concentrations of greenhouse gases (GHGs) in atmosphere have garnered lots of attention due to the associated risk of global warming. Carbon footprint (CF) is a measure that is extensively used to assess the contribution of an individual, event, organization, or product to global climate change. In the current study, the CF of five agricultural systems with different crop systems in different regions in China was evaluated in terms of CO2 eq per hectare, per kg crop yield, and per unit economic output, association with soil GHGs, agrochemical production and soil organic carbon (SOC) change. The results showed that direct nitrous oxide accounted for 61.9–97.8% of total soil GHG emissions in upland fields (agroforestry system, summer maize-winter wheat rotation tillage system, maize-soybean intercropping system, and continuous maize tillage system), while soil methane accounted for 89.9–95.1% of total soil GHG emissions in the paddy field (double rice-winter crop rotation system). GHGs produced from agricultural inputs varied from 2698.7 to 9781.5 kg CO2 eq ha−1 yr−1 among different agricultural systems. Nitrogen fertilizer was the dominant source of GHGs, which accounted for 47.4–92.4% of the total emission. Annual SOC increase ranged from −639.9–13823.9 kg CO2 eq ha−1 yr−1 in the five agricultural systems. Increases of SOC in the treatment of “reduced tillage with straw return” offset all of the total GHG emissions while “conventional tillage without straw return” decreased SOC storage in the continuous maize tillage system. An increase of SOC in crop systems of the other four agricultural systems could offset 23.2–66.7% of the total GHG emissions. Carbon emissions per hectare in the double rice-winter crop rotation system (7339.93–22994.17 kg CO2 eq ha−1 yr−1) were higher than the other four agricultural systems (−744.96–6523.12 kg CO2 eq ha−1 yr−1). In terms of crop yield, CFs of the summer maize-winter wheat rotation tillage system (0.28–0.34 kg CO2 eq kg−1 yr−1) were lower than those from the other four agricultural systems (0.39–2.83 kg CO2 eq kg−1 yr−1), except for the treatment with reduced tillage and residue return in the continuous maize tillage system. Similarly, CFs, as quantified via per unit economic output of the agroforestry system (0.12–0.19 kg CO2 eq ¥−1 yr−1), were lower than those in other the four systems (0.26–0.89 kg CO2 eq ¥−1 yr−1).Different evaluation methodology greatly affected the CF of different crop systems and mostly likely contributed to the contrary evaluation results, especially in the complex system of various crop systems (agroforestry and double rice-winter crop rotation system) in current study. Evaluation results of the CF of an agricultural system depends highly on the methodology used and may suggest different management decisions for lowering CF to promote the development of cleaner production.

Responses of photosynthetic characteristics to low light stress in ear leaves of high photosynthetic efficiency maize at narrow row of maize-soybean strip in-tercropping system

Responses of photosynthetic characteristics to low light stress in ear leaves of high photosynthetic efficiency maize at narrow row of maize-soybean strip in-tercropping system

Sustainability Evaluation of the Maize–Soybean Intercropping System and Maize Monocropping System in the North China Plain Based on Field Experiments

Monocropping systems, which currently dominate China’s major grain production regions, contribute to resource scarcity and environmental pollution. Intercropping has the potential to improve resource use efficiency. However, prior studies of intercropping systems have generally focused on ecological, economic, and social consequences. Here, we make a comparative ecological sustainability analysis on energy capture and efficiency of maize monocropping and maize–soybean intercropping systems through emergy evaluation based on field experiments performed from 2012 to 2014. We find that maize monocropping shows higher sustainability than maize–soybean intercropping in the North China Plain at present. Quantitative results indicate that for maize monocropping, the emergy yield ratio (EYR) and emergy sustainability index (ESI) are 13.7% and 21.1% higher than that of intercropping systems, and the environmental loading ratio (ELR) is 7.3% lower than that of intercropping systems. To further test, we applied three levels of nitrogen fertilizer in intercropping systems (120 kg ha−1, 180 kg ha−1, 240 kg ha−1), and find that a reduced rate of N fertilizer for intercropped system leads to higher sustainability (ESI 5.3% higher) but still lower sustainability than maize monocropping. Key drivers of the different sustainability outcomes are decreased energy output and a larger proportion of labor input associated with intercropping systems.