Soybean Cropping Systems Research Articles

Cereal rye (Secale cereale L.) cover crop improves soil physico-chemical properties with no influence on soybean (Glycine max L.) root growth parameters

Planting winter cover crops (CC) in soybean cropping systems is expected to offer various environmental benefits including soil health and fertility besides enhanced cash crop productivity. In a three-year study (2018–2021) conducted on a Dundee silt loam, we assessed the impact of introducing rye (Secale cereale L.) CC during the winter fallow period on soil organic carbon (SOC), soil organic matter (SOM), soil total nitrogen (STN), bulk density (BD), saturated hydraulic conductivity (Kfs), soil penetration resistance (SPR), and water-stable aggregates (WSA). Three treatments evaluated were: i) no cover crop (NC), ii) winter rye as CC rolled when green and desiccated after soybean planting (GR), and iii) winter rye CC desiccated and rolled before planting soybean (BR) in a randomized complete block design with six replications. The depth of the soil sampling in 2019 was 0-15 and 15-30 cm while 0-10, 10-20 and 20-30 cm depth soil sampling was done in 2020 and 2021. Effects of BR and GR on soybean root growth characteristics (number of roots, root length and root angle) were measured using a CID 600 root scanner. The results showed that CC (both BR and GR) improved SOC by 7 to 12.5%, soil organic matter by 9 to 15%, STN by 13 to 29%, WSA by 26 to 68%, Kfs by 5 to 9% and reduced BD by 8% and SPR by 14 to 18% compared to NC (P<0.05). However, there were no differences between BR and GR treatments. Root characteristics of soybean in the NC, BR and GR treatments were similar. Rye CC fits into the existing soybean production system in the Lower Mississippi Delta with a potential to augment soil-physico chemical properties, thus offering agro-ecosystem services which may not necessarily lead to an impact on soybean root growth traits.

Mechanism underlying the response of fungi and their Fusarium symbiotic networks to the rotations of soybean and corn

Fusarium oxysporum and Fusarium solani are the main soybean root rot pathogens in northern China. We investigated the distribution and driving factors of Fusarium under different cropping systems to evaluate and regulate soil health. The factors affecting Fusarium in soybean cropping systems were assessed using high-throughput sequencing of ITS1 to identify soil microbial population diversity, and then the soil physicochemical properties were assessed to determine the levels of various elements present in the environment. According to the results, the abundance of Fusarium was obviously reduced in the corn–soybean rotation and uncultivated soil systems. The relative abundance of Fusarium in the soil and the abundance and diversity of fungal communities were significantly positively associated with the abundance of Ascomycota. Additionally, the relative abundance of Fusarium was significantly positively correlated with the zinc (Zn) content. When the Zn content was high, the abundance of Fusarium increased, and the correlations with Chaetomium, Cryptococcus, Penicillium and Trichoderma significantly decreased. Soybean yield was significantly negatively correlated with fungal community abundance and diversity. Based on our results, the uncultivated soil and corn–soybean rotation cropping systems improved the organizational structure of the soil fungal community and were conducive to the health and production of soybean.

Evaluation of Agrobiodiversity and Cover Crop Adoption in Southern Ontario Field Crops

Incorporating cover crops into corn and soybean operations across Southern Ontario is essential for maintaining yields under environmental stressors. Unfortunately, amongst the literature, there is a concern about the low adoption rate of cover crops in the northern Corn Belt due to a shift toward low agrobiodiversity and dominance of more profitable corn and soybean cropping systems, encouraged by extensive use of fertilizers, herbicides, and pesticides. This study examines whether Southern Ontario is following suit in decreasing agrobiodiversity trends, at the county level, and examines the adoption of cover crops within corn and soybean operations across Southern Ontario using digital imagery from 2013 to 2018. Results reveal that Southern Ontario is indeed shifting from systems characterized by higher agrobiodiversity to systems dominated with corn, soybean, and hay. Despite the benefits of cover crops, this study reveals that most of the current corn and soybean operations are not incorporating cover crops into the rotation. More significantly, the low adoption of cover crops is most apparent in southwestern Ontario, and increases in adoption occur toward the north.

EFFECT OF FOUR BIOCHAR TYPES AND INORGANIC PHOSPHATE FERTILIZER ON GROWTH AND NODULATION OF SOYBEAN (GLYCINE MAX (L.) MOENCH)

There is a compelling need to explore the use of biochar as a sustainable alternative to the use of chemical or mineral fertilizer amendment in the contexts of soybean cropping system in Sub-Sahara Africa. A pot experiment was conducted to evaluate the effects of poultry manure biochar (PB), swine dung biochar (DB), maize cob biochar (MB), saw dust biochar (SB) and inorganic phosphate fertilizer (single supper phosphate) applied singly on the growth and nodulation of soybean in Minna, southern Guinea savanna zone of Nigeria. The biochars were applied at four levels of 0, 5, 10, and 15 t ha-1 while single supper phosphate (SSP) was applied at 30 kg P ha-1. The experimental design was a completely randomized design (CRD) with three replications. The results showed that soybean plant parameters of height, number of leaves, number and dry weight of nodules, shoot, root and total dry biomass increased in all treatments that received animal waste biochars (PB & DB) over the non-treated control (0 t ha-1) except the plant root length and shoot/root ratio. However, the difference was statistically significant (p<0.05) only at the higher application level of 10 t ha-1. Plant-based biochars (MB & SB) were less beneficial to soybean plant, and their influence on soybean parameters did not differ significantly from non-treated control. Soybean plant also responded positively to the application of SSP but was significantly better than the control only for plant height. The results showed that animal waste-derived biochars were more beneficial to soybean plant in terms of nodulation and growth than the plant-based biochars and SSP fertilizer. Evidence that soyabean growth, biomass accumulation and nodulation benefit more from amending soil medium planted to soyabean with manure based biochars applied at 10 tons ha-1 compared to the plant-based biochar showed that, manure base biochars are more suitable as soil amendments for legumes like soyabean that require more P and less amount of N in their nutrition.

Enlist volunteer corn affects the crop development and seed quality of Enlist soybean

EnlistTM technology is a new trait on soybean and corn conferring tolerance to auxinic-type (2,4-D choline) and graminicides (aryloxyphenoxypropionates – FOPs) herbicides. However, the occurrence of volunteer corn tolerant to 2,4-D and FOPs can become a significant weed on soybean cropping systems, affecting the crop yield and reducing seed quality. This research aimed to evaluate herbicides to EnlistTM volunteer corn control and their effects on plant development, crop yield, and physiological seed quality of EnlistTM soybean. Field experiment was performed in a complete randomized block experimental design with four replicates, using a density of 10 plants·m-2 of EnlistTM volunteer corn. Treatments consisted of herbicides applied at 3-4-leaves stage of volunteer corn with haloxyfop-P-methyl, clethodim, pinoxaden, cloransulam-methyl and imazethapyr regarding to a control with and without volunteer corn. The development and yield components of EnlistTM soybean were evaluated and physiological seed testing performed on soybean’s seeds. Clethodim controlled EnlistTM volunteer corn, whereas haloxyfop-P-methyl, pinoxaden, and cloransulam-methyl showed insufficient control levels (30-35%) at 30 days after spray. Imazethapyr exhibited 84% of control of EnlistTM volunteer corn and injured the EnlistTM soybean, affecting its seed viability. EnlistTM volunteer corn interferences negatively the soybean crop yield, yield components, and affects the plant development pattern.

Comparing the Nutrient Management Pattern in Soybean and Rice based Cropping Systems by Soil Health Card holders and Non-holders

The paper discusses about the importance of Soil Health Card (SHC) based nutrient management based on a study carried out during 2017-18 on 100 SHC beneficiary farmers and 50 SHC non-beneficiary farmers of Madhya Pradesh. Significant differences between the beneficiary and non-beneficiary farmers of soil health card in the nutrient use pattern in soybean and rice-based cropping systems were found. Majority of the SHC beneficiaries failed to adopt the fertilizer nutrients as per recommendation. Major reasons identified behind this negative trend were difficulty in understanding the SHC information without the help of an agricultural/ extension officer and lack of knowledge about the importance of SHC &benefits associated with adopting soil test based nutrient management. Further, the positive correlation of micro and secondary nutrients application with the yield and income from the adopters’ farm fields reaffirms the key role scientific nutrient management plays in improving agriculture based rural economies. More efforts from the promoting agencies required to convince farmers to adopt SHC based nutrient recommendation.

Control of common weeds in Wisconsin soybean cropping systems with pre‐emergence herbicides

AbstractThe integration of pre‐emergence (PRE) herbicides is an important component of sustainable long‐term weed management programs in soybean [Glycine max (L.) Merr.]. The objective of this study was to evaluate the efficacy of 11 PRE herbicides on residual weed control in soybean. Field experiments were conducted in 2018 and 2019 at Arlington and Lancaster, WI. Herbicide treatments consisted of imazethapyr, chlorimuron‐ethyl, and cloransulam‐methyl (acetolactate synthase [ALS] inhibitors), metribuzin (photosystem II [PSII] inhibitor), sulfentrazone, flumioxazin, and saflufenacil (protoporphyrinogen oxidase [PPO] inhibitors), acetochlor, S‐metolachlor, dimethenamid‐P, and pyroxasulfone (very long‐chain fatty acid [VLCFA] inhibitors), and a nontreated control. Predominant weed species included common lambsquarters, [Chenopodium album (L.)], common purslane [Portulaca oleracea (L.)], common ragweed [Ambrosia artemisiifolia (L.)], giant foxtail (Setaria faberi Herrm.), waterhemp [Amaranthus tuberculatus (Moq.) J.D. Sauer], and yellow foxtail [Setaria pumila (Poir.) Roem. & Schult.]. Visual weed control was assessed by species and weed biomass across species 65 days after treatment (DAT). The PRE herbicide efficacy varied across site‐years due to the different weed species present at each site. The ALS inhibitors controlled common purslane and common lambsquarters ≥95% 65 DAT at Arlington and Lancaster in 2018 but controlled waterhemp <50% at Lancaster in 2018 and 2019. The PPO inhibitors controlled waterhemp >90% 65 DAT at Lancaster in 2018 and 2019. The VLCFA inhibitors controlled common purslane, common lambsquarters, foxtail species, and waterhemp ≥70% 65 DAT across site‐years but ≤30% common ragweed control at Arlington in 2019. Results showcase the importance of knowing the weed species composition in the seedbank within each field; this can assist growers and crop advisers with selection of the appropriate effective PRE herbicide(s) that matches the weed species composition in each individual field.

Simulating no-tillage effects on crop yield and greenhouse gas emissions in Kentucky corn and soybean cropping systems: 1980–2018

CONTEXTNo-tillage (NT) is a conservation practice that aims to minimize soil disturbance and improve crop production. However, NT effects on crop production remain controversial due to the spatial heterogeneity of climate and soil conditions. Some studies argued that NT might offset its greenhouse gas (GHG) mitigation potential in agriculture by promoting soil N2O emissions. OBJECTIVEThis study used a process-based agroecosystem model (DLEM-Ag) along with spatially explicit environmental datasets to quantify the long-term effects of NT on crop yield and GHG emissions in corn and soybean cropping systems in the state of Kentucky (USA) from 1980 to 2018. METHODSThe DLEM-Ag was used to quantify the long-term effects of NT on crop yield and GHG emissions in corn and soybean cropping systems in the state of Kentucky. Three spatiotemporal tillage scenarios, i.e., historical varying tillage, consistent conventional tillage (CT), and consistent NT, were adopted to simulate changes in crop yield and GHG emissions. RESULTS AND CONCLUSIONSOverall, our results showed that NT could reduce soil CO2 (−1.6% for corn and −4.53% for soybean) and N2O emissions (−10.5% for corn and −19.6% for soybean) in Kentucky, as compared to CT, although corn and soybean yields with NT were not significantly different from those with CT. Our further analysis suggested that air temperature and soil clay content were the two main factors influencing NT advantages in reducing GHG emissions. The increased temperature decreased the benefits of mitigating GHG emissions, while high clay content soils had less N2O emission under NT. SIGNIFICANCEThis study represents one of few attempts to quantify the effects of NT on crop yield and soil GHG emissions at the regional scale using an agroecosystem modeling approach. The findings from this study provide insights into how NT can enhance agroecosystem production stability and support climate change mitigation. This information may be used by the scientific community and policymakers working on practical technologies to mitigate climate change from agriculture.

Performance of a wheat–soybean cropping system as affected by applying phosphogypsum in combination with urea

High-intensity crop-production seeking for higher grain yields increases nutrient demand by plants. A field experiment was performed in Parana State, Brazil, on a clayey Haplic Cambisol to evaluate the effects of phosphogypsum and nitrogen (N) amendments on a wheat–soybean rotation. Phosphogypsum was surface-applied to plots at 0, 2, 4, and 6 Mg ha−1 before wheat sowing and two rates of urea at 40 and 80 kg N ha−1 were applied to subplots in top dressing at tillering of wheat. Phosphogypsum improved the yield performance of wheat–soybean rotation. Wheat grain yield increased by 20% due to phosphogypsum application only when a higher rate of urea at 80 kg N ha−1 was applied in top dressing, indicating an influence of the interaction between N and sulfur (S). Soybean grain yield increased by 16% with phosphogypsum application, regardless of the urea-N rates to the previous wheat crop. Higher grain yields of wheat and soybean were related to higher levels of Ca2+ and S in the soil profile (0–0.40 m). Although there was a slight involvement of phosphogypsum in reducing aluminum Al3+ toxicity in the subsoil due to a reduction in Al3+ saturation caused by increased Ca2+ concentration, the improvements imparted by the use of phosphogypsum resulted mainly from increased S concentration. The results showed that the critical levels of SO4–S by 0.01 mol L−1 Ca(H2PO4)2 were 14 and 27 mg dm−3 at 0–0.20 m and 0–0.40 m depths, respectively, for the wheat–soybean cropping system.

Season-specific management strategies for rainfed soybean in the South American Pampas based on a seasonal precipitation forecast

CONTEXTGlobal climate change is resulting in more frequent and more damaging extreme events affecting the performance of production systems. It is imperative to develop good season-specific crop management recommendations to help farmers to improve their adaptive capacity to a changing climate one season at a time. OBJECTIVEWe aimed to evaluate the skill of the International Research Institute for Climate and Society (IRI) seasonal precipitation forecasts and the interaction between the forecasted seasonal precipitation scenarios and management practices for rainfed soybean cropping systems using a crop simulation model. METHODSWe used a crop simulation model (CROPGRO-Soybean) coupled with weather data to assess the potential use of the IRI seasonal precipitation forecasts as a tool to optimize season-specific management strategies for rainfed soybean in Uruguay. We used a total of 620–668 IRI seasonal precipitation forecasts released from 2003 to 2016 for each of the five weather stations located in the main soybean producing area. The analysis was performed for two soybean cropping systems (i.e., sown as a single crop or as double-cropped soybean), for which we considered combinations of sowing dates and maturity groups (11 sowing dates × 3 maturity groups combinations for each soybean cropping system). RESULTS AND CONCLUSIONSThe IRI seasonal precipitation forecasts were able to successfully forecast below-normal precipitation scenarios in 77% of the total predictions developed for this scenario considering all weather stations during the study period (2003–2016), while it was less accurate in forecasting above-normal precipitation scenarios (60% of success). We found that earlier sowing dates were a better strategy for years when an above-normal precipitation forecast was released for the December–January-February period (4.7 Mg ha−1 average seed yield). In contrast, delayed sowing dates were more appropriate for below-normal precipitation forecasts (3.7 Mg ha−1 average seed yield). Applying season-specific management practices farmers could potentially increase their soybean yields by up to 0.6 and 1.6 Mg ha−1, in years with below- or above-normal forecasted precipitations, respectively. The benefit of season-specific management will depend on the interaction among all management practices, the effective capacity of farmers to implement it, and the risk profile the farmer adopts and it is exposed to. SIGNIFICANCEHere we built a novel approach to assess the impact of considering seasonal precipitation forecasts for optimizing crop production. This assessment provided insights on how farmers can use seasonal precipitation forecasts to optimize rainfed soybean yield for a specific cropping season.

Agro-economic prospects for expanding soybean production beyond its current northerly limit in Europe

Soybean is one of the five crops that dominate global agriculture, along with maize, wheat, cotton and rice. In Europe, soybean still plays a minor role and is cultivated mainly in the South and East. Very little is known about the potential for soybean in higher latitudes with relatively cool conditions. To investigate the agronomic potential and limitations of soybean for feed (high grain yield) and food (high protein content, e.g., for tofu production) in higher latitudes, an organic soybean cropping system experiment was carried out from 2015 to 2017 in northeastern Germany. The objectives were: (1) to identify food- and feed-grade soybean cultivars that are adapted to a central European climate in terms of protein, grain yield, and yield stability, (2) to explore the effect of irrigation on soybean protein and grain yield under relatively dry growing conditions, and (3) to determine the agro-economic potential of soybean cultivation for both feed and food markets. Three soybean cultivars were tested with and without irrigation. The soybean feed-grade cultivars ‘Sultana’ and ‘Merlin’ were better adapted to the growing cycle and temperature, providing higher and more stable yields (average 2700 kg ha−1) than the food-grade cultivar ‘Protibus’ (average 1300 kg ha−1). Irrigation increased soybean grain yields by 41% on average. In the year with sufficient precipitation, no additional irrigation was necessary. Gross margins of organic soybean ranged between 750 € ha−1 for the rainfed food-grade soybean and 2000 € ha−1 for the irrigated feed-grade soybean and were higher than other crops. We demonstrated a large agro-economic potential for soybean as a novel grain legume crop to diversify cropping systems and increase the production of protein crops in central Europe.

Low carryover risk of corn and soybean herbicides across soil management practices and environments

AbstractHerbicides with soil-residual activity have the potential for carryover into subsequent crops, resulting in injury to sensitive crops and limiting productivity if severe. The increased use of soil-residual herbicides in the United States for management of troublesome weeds in corn- and soybean-cropping systems has potential to result in more cases of carryover. Soil management practices have different effects on the soil environment, potentially influencing herbicide degradation and likelihood of carryover. Field experiments were conducted at three sites in 2019 and 2020 to determine the effects of corn (clopyralid and mesotrione) and soybean (fomesafen and imazethapyr) herbicides applied in the fall at reduced rates (25% and 50% of labeled rates) and three soil management practices (tillage, no-tillage, and a fall-established cereal rye cover crop) on subsequent growth and productivity of the cereal rye cover crop and the soybean and corn crops, respectively. Most response variables (cereal rye biomass and crop canopy cover at cover crop termination in the spring, early-season crop stand and herbicide injury ratings, and crop yield) were not affected by herbicide carryover. Corn yield was lower when soil was managed with a cereal rye cover crop compared with tillage at all three sites, while yield was lower for no-till compared with tillage at two sites. Soybean yield was lower when managed with a cereal rye cover crop compared with tillage and no-till at one site. Findings from this research indicate a low carryover risk for these herbicides across site-years when label rotational restrictions are followed and environmental conditions favorable for herbicide degradation exist, regardless of soil management practice on silt loam or silty clay loam soil types in the U.S. Midwest region.

Dynamics and composition of soil organic carbon in response to 15 years of straw return in a Mollisol

Crop straw return is being widely applied as a sustainable soil management practice to improve soil organic carbon (SOC) storage in intensive agricultural ecosystems. However, the dynamics and chemical composition of SOC under long-term straw return are not fully understood. Based on a 15-year field experiment with soybean (Glycine max (L.) Merrill.)–maize (Zea mays L.) cropping system, we studied SOC temporal dynamics under no fertilization (NF), mineral fertilizers (NPK) and mineral fertilizers with straw return (NPKS). Meanwhile, we determined five labile carbon (C) pools, i.e., microbial biomass C (MBC), water-soluble organic C (WSOC), light fraction C (LFC), readily oxidizable organic C (ROC), and particulate organic C (POC), as well as δ13C values and organic functional groups of soil organic matter (SOM). After 15-year application of continuous straw return with mineral fertilizer application, SOC content increased by 14.2%. The δ13C values of SOC increased with time under all treatments, and its positive relationship with cumulative maize C input indicated a larger C contribution to SOC from maize than soybean residues. The NPKS treatment significantly increased the contents of MBC, WSOC, LFC, ROC, and POC and their proportion in SOC, compared with the NF treatment. The aliphatic and aromatic relative peak areas were significantly affected by straw return, with an increasing relative peak area at 2930 cm−1 and decreasing at 1620 cm−1, respectively. Our results demonstrate that straw return could continuously increase SOC in an inter-annual rotation of soybean and maize cropping system in Mollisol. Meanwhile, long-term fertilization can alter SOM chemical composition, with lower humification degree under the combined application of straw and mineral NPK fertilizers.

Management of Nano-black Carbon, Phosphorous and Bio Fertilizer Improve Soil Organic Carbon and Ensilage Biomass of Soybean and Maize

ABSTRACT Field experiments were conducted for two-consecutive summer seasons of 2016–17 and 2017–18 at Agriculture Research Institute Mingora Swat, Pakistan, on soybean and maize under soybean-wheat (S-W) and maize-wheat (M-W) cropping systems. Three peach sources were used as a residues, its compost and its Nano-black carbon, three phosphorus-rates (50, 75 and 100 kg-ha−1) and two beneficial microbes (PSB and Trichoderma) were tested for improvement of ensilage biomass of maize and soybean, and soil organic-carbon (SOC) under both cropping systems. The results revealed that all the treated plots produced highest SOC compared to the control plots under soybean and maize cropping system. Improved SOC was noted with the OS amendment of Nano-black carbon in both cropping systems. Whereas minimum SOC was noted in soybean experimentation with compost while in maize plot reduced SOC was noted with peach residues incorporation. Beneficial microbes had a significant effect on SOC and improved SOC was recorded with soil application Trichoderma as compared to seed inoculation with PSB in soybean and maize plots. Phosphorus levels had also significant effect on SOC and highest SOC was recorded at 100 kg P ha−1 followed by 75 kg P ha−1 whereas the smallest SOC was recorded with 50 kg P ha−1. Ensilage highest biomass of the both crops was noted with peach Nano-black carbon, followed by compost and reduced biomass were noted with peach residues application. Among the P-rate, increased ensilage biomass was recorded with 100 kg P ha−1application while in case of beneficial microbes application, soil application of Trichoderma produced highest biomass as compared to seed inoculation with PSB.

Detecting Recent Crop Phenology Dynamics in Corn and Soybean Cropping Systems of Kentucky

Accurate phenological information is essential for monitoring crop development, predicting crop yield, and enhancing resilience to cope with climate change. This study employed a curve-change-based dynamic threshold approach on NDVI (Normalized Differential Vegetation Index) time series to detect the planting and harvesting dates for corn and soybean in Kentucky, a typical climatic transition zone, from 2000 to 2018. We compared satellite-based estimates with ground observations and performed trend analyses of crop phenological stages over the study period to analyze their relationships with climate change and crop yields. Our results showed that corn and soybean planting dates were delayed by 0.01 and 0.07 days/year, respectively. Corn harvesting dates were also delayed at a rate of 0.67 days/year, while advanced soybean harvesting occurred at a rate of 0.05 days/year. The growing season length has increased considerably at a rate of 0.66 days/year for corn and was shortened by 0.12 days/year for soybean. Sensitivity analysis showed that planting dates were more sensitive to the early season temperature, while harvesting dates were significantly correlated with temperature over the entire growing season. In terms of the changing climatic factors, only the increased summer precipitation was statistically related to the delayed corn harvesting dates in Kentucky. Further analysis showed that the increased corn yield was significantly correlated with the delayed harvesting dates (1.37 Bu/acre per day) and extended growing season length (1.67 Bu/acre per day). Our results suggested that seasonal climate change (e.g., summer precipitation) was the main factor influencing crop phenological trends, particularly corn harvesting in Kentucky over the study period. We also highlighted the critical role of changing crop phenology in constraining crop production, which needs further efforts for optimizing crop management practices.

Changes in Soil Microbial Activity, Bacterial Community Composition and Function in a Long-Term Continuous Soybean Cropping System After Corn Insertion and Fertilization.

Corn-soybean rotation and fertilization are common practices improving soil fertility and crop yield. Their effects on bacterial community have been extensively studied, yet, few comprehensive studies about the microbial activity, bacterial community and functional groups in a long-term continuous soybean cropping system after corn insertion and fertilization. The effects of corn insertions (Sm: no corn insertion, CS: 3 cycles of corn-soybean rotations and CCS: 2 cycles of corn-corn-soybean rotations) with two fertilization regimes (No fertilization and NPK) on bacterial community and microbial activity were investigated in a long-term field experiment. The bacterial communities among treatments were evaluated using high-throughput sequencing then bacterial functions were predicted based on the FaProTax database. Soil respiration and extracellular enzyme activities were used to assess soil microbial activity. Soil bacterial community structure was significantly altered by corn insertions (p < 0.01) and fertilization (p < 0.01), whereas bacterial functional structure was only affected by corn insertion (p < 0.01). The activities of four enzymes (invertase, β-glucosidase, β-xylosidase, and β-D-1,4-cellobiohydrolase) involved in soil C cycling were enhanced by NPK fertilizer, and were also enhanced by corn insertions except for the invertase and β-xylosidase under NPK fertilization. NPK fertilizer significantly improved soil microbial activity except for soil metabolic quotient (qCO2) and the microbial quotient under corn insertions. Corn insertions also significantly improved soil microbial activity except for the ratio of soil induced respiration (SIR) to basal respiration (BR) under fertilization and the qCO2 was decreased by corn insertions. These activity parameters were highly correlated with the soil functional capability of aromatic compound degradation, which was the main predictors of bacterial functional structure. In general, the combination of soil microbial activity, bacterial community and corresponding functional analysis provided comprehensive insights into compositional and functional adaptations to corn insertions and fertilization.

Paddy-upland rotation with Chinese milk vetch incorporation reduced the global warming potential and greenhouse gas emissions intensity of double rice cropping system.

It is a common practice to maintain soil fertility based on the paddy-upland rotation with green manure in the subtropical region of China. However, rare studies are known about greenhouse gas (GHG) emissions from the paddy-upland rotation with green manure incorporation. Therefore, we conducted a field experiment of two years to compared with the effect of two kinds of green manure (CV: Chinese milk vetch and OR: Oilseed rape), and two kinds of cropping system (DR: double rice system and PR: paddy-upland rotation) on greenhouse gases emissions. We have found that the annual accumulation of CH4 of Chinese milk vetch-rice-sweet potato || soybean was significantly reduced by 32.95%∼63.22% compared with other treatments, mainly because Chinese milk vetch reduced the abundance of methanogens by reducing soil C/N ratio. Meanwhile increasing soil permeability resulting from paddy-upland rotation also reduced soil CH4 emission. However, The annual accumulation of N2O of Chinese milk vetch-rice-sweet potato || soybean was increased by 17.39%∼870.11% compared with other treatments, mainly attributed to paddy-upland rotation decreased soil pH and nosZ abundance and increased nirK and nirS, thus enhancing N2O emission, meanwhile the Chinese milk vetch incorporation and its interaction with the paddy-upland rotation has greatly enhanced the contents of NO3--N and abundance of ammonia-oxidizing archaea (AOA). The area-scaled global warming potential (GWP) and the biomass-scaled greenhouse gas emissions intensity (GHGI) of Chinese milk vetch-rice-sweet potato || soybean was reduced by 19.01%∼50.69% and 5.38%∼35.77% respectively. Thereby, the Chinese milk vetch-rice-sweet potato || soybean cropping system was suitable for agricultural sustainable development.

The Environmental Impact of Ecological Intensification in Soybean Cropping Systems in the U.S. Upper Midwest

Introducing cover crops is a form of ecological intensification that can potentially reduce local, regional and global environmental impacts of soybean cropping systems. An assessment of multiple environmental impacts (global warming potential, eutrophication, soil erosion and soil organic carbon variation) was performed on a continuous soybean system in the U.S. upper Midwest. Four sequences were assessed and compared: a soybean cropping system with winter camelina, field pennycress, or winter rye as cover crop, plus a control (sole soybean). Cover crops were interseeded into standing soybean in Year 1, while in Year 2 soybean was relay-cropped into standing camelina or pennycress. Rye was terminated before sowing soybean. When compared with the control, sequences with cover crops showed lower eutrophication potential (4–9% reduction) and soil erosion (5–32% reduction) per ha year−1, in addition to a lower global warming potential (3–8% reduction) when the cover crop was not fertilized. However, when the economic component was included in the assessment, and the results expressed per USD net margin, the sequences with cover crops significantly reduced their performance in all categories of impact considered. A further optimization of field management for camelina and pennycress is recommended to make the cropping system more sustainable.

Long-term tillage effect on with-in season variations in soil conditions and respiration from dryland winter wheat and soybean cropping systems

Soil respiration from agricultural soils is a major anthropogenic source of CO2 to the atmosphere. With-in season emission of soil CO2 from croplands are affected by changes in weather, tillage, plant row spacing, and plant growth stage. Tillage involves physical turning of soils which accelerate residue decomposition and CO2 emission. No-tillage lacks soil disturbance and residues undergo slower decomposition at the surface. In this study, we compared with-in season soil conditions (temperature and moisture) and soil respiration from two major crops (soybean and winter wheat) by making high temporal frequency measurements using automated chambers at half-hourly intervals. The experiment lasted for 179 days. Total number of measurements made from conventional and no-tillage soybean and winter wheat plots were 6480 and 4456, respectively. Average flux after the winter-dormancy period of wheat was 37% higher in tilled soil compared to no-till soil. However, average flux during the soybean growing season was 8% lower in conventional till compared to no-till soil. This differential response of soil respiration in wheat and soybean was primarily due to tillage-induced changes in surface characteristics (residue cover) and soil environmental conditions (soil temperature and soil moisture). Results from this study can help elucidate relationships for modeling and assessment of field-scale soil CO2 emissions from dryland wheat and soybean crops grown in sub-tropics.

Environment quality, sowing date, and genotype determine soybean yields in the Argentinean Gran Chaco

The Argentinean Gran Chaco is one of the global regions with the highest recent rates of agricultural expansion due to soybean production. The area has been heavily deforested during the last 30 years. Despite the economic relevance of soybean for this region, studies that provide options for sustainable management of these production systems are scarce. The objectives of this study were (i) to identify and to quantify key management and environmental soybean yield predictors, and (ii) to explore interactions with maturity group (MG) selection, since farmers are sowing genotypes ranging from MGs V to VIII. We evaluated commercial genotypes in 112 multi-environment on-farm trials (METs) consisting of 14–19 genotypes each during 11 consecutive years (from 2008 to 2019).We first analyzed a single genotype sown in 106 METs to identify environmental and management yield predictors with good explanatory power for yield, which ranged from 435 to 5117 kg ha−1. Relevant environmental variables were, in order of importance, rainfall from 30 days before sowing to physiological maturity (R7), years after land conversion to agriculture, reference evapotranspiration from sowing to R7, and the number of 2-day periods with maximum temperatures above 35 °C from beginning of flowering (R1) to R7. Based on variable relative importance (RI) sowing date was the most important management variable (RI = 0.99), followed by phosphorous availability (RI = 0.59). Genotype selection also had a strong significant effect. There was an interaction between MG and sowing date, yield reductions with delayed sowings ranked as MG VIII > VII > VI = V. The largest yield differences between MGs were observed under environments with high soil organic matter (explored range from 1.64 to 4.05 %). These results illustrate specific management variables to guide farmers and advisors to optimize regional soybean cropping systems. The negative yield effect promoted by years after land conversion and reductions in soil organic matter suggest a decline in the environmental quality of the region and the need for new production alternatives to halt these trends.