Wheat-soybean Rotation Research Articles

Liming and phosphate fertilization influence soil fertility, physical properties, and carbon stock in a subtropical Ferralsol in Brazil

Understanding the effects of liming plus phosphate fertilization on soil physical and chemical properties, as well as carbon stock, is critical for improving soil fertility management under conventional till (CT) and no-till (NT) systems. This study aimed to quantify changes in these soil properties resulting from incorporation (CT) or not (NT) of limestone and phosphorus (P) in a subtropical Ferralsol in southern Brazil. The experiment was conducted in Campo Mourão, Paraná State, Brazil, according to a randomized complete block design with a 6 × 4 factorial arrangement and four replications. The treatments comprised six strategies for limestone and P management and four soil depth layers (0–0.05, 0.05–0.10, 0.10–0.20 and 0.20–0.40 m), as follows: NLNT - no liming under no-till; NLCT - no liming under conventional till; LPNT - liming and P fertilization under no-till; LPCT - liming and P fertilization under conventional till; LNT - liming under no-till; and LCT - liming under conventional till. In 2012, 5.0 Mg ha−1 dolomitic limestone and 53.3 kg ha−1 P were applied. In 2016, dolomitic limestone was reapplied to a soybean–wheat rotation. Liming and liming plus P treatments influenced soil properties up to a depth of 0.10 m, increasing pH and decreasing Al3+, without significant differences between CT and NT. Higher levels of Ca2+ and Mg2+ were observed at 0–0.05 m, except in unlimed treatments. Liming and liming plus P fertilization treatments resulted in mean increments of 1.83 and 1.37 cmolc dm−3 in Ca2+ and Mg2+ levels, respectively, regardless of the tillage system. Base saturation did not differ between treatments in the 0.10 m layer. However, LPCT resulted in higher base saturation in the 0.10–0.20 m (55 %) and 0.20–0.40 m (53 %) layers. P contents were affected up to 0.10 m depth, being 30 % higher in LPNT than in LPCT at 0–0.05 m. In the 0–0.05 m layer, soil bulk density was highest in NLCT and LPCT, and macroporosity was lowest in LPCT. Carbon stock was not affected by tillage practices, liming, or P fertilization. There was a positive correlation between P content and carbon stock at 0.20–0.40 m, suggesting that increased P availability at depth contributes to carbon sequestration. At 0–0.05 m, soil physical properties were negatively influenced by the combined application of liming and P fertilization under CT, indicating possible simultaneous effects on clay dispersion and pore obstruction.

Linking main ecological clusters of soil bacterial–fungal networks and nitrogen cycling genes to crop yields under diverse cropping systems in the North China Plain

BackgroundCrop rotation changes crop species and the associated management strategies, significantly influencing soil fertility and soil microbial communities. Interactions among the species in microbial communities are important for soil nutrient cycling. Yet, the contribution of soil microbial interactions to crop yield and soil nitrogen-cycle function under wheat–maize and wheat–soybean rotation conversion remains unclear. An 8-year field experiment was conducted to investigate the impact of simple [8-year wheat–maize rotation (8WM) and 8-year wheat–soybean rotation (8WS)] and diverse cropping systems [4-year wheat–soybean followed by 4-year wheat–maize rotation (4WS4WM) and 4-year wheat–maize followed by 4-year wheat–soybean rotation (4WM4WS)] on crop yield, soil properties, bacterial–fungal co-occurrence networks and nitrogen functional potentials. The abundances of genes with nitrogen fixation (nifH), nitrification (AOB and nxrA) and denitrification (narG, nirK, norB and nosZ) potentials were quantified and bacterial and fungal communities were characterized.Results4WS4WM led to higher succeeding maize yields and lower bacterial–fungal network complexity, nitrogen fixation potentials and denitrifying potentials than 8WM. Meanwhile, 4WM4WS exhibited higher succeeding wheat and soybean yields, network complexity and lower nitrifying potentials than 8WS. The ecological cluster with the most nitrifying and denitrifying bacterial species (Module#5) and that with the least species (Module#3) dominated the potentials of nitrogen fixation, nitrification and denitrification and succeeding maize yields in 4WS4WM and 8WM. Module#4 with the highest abundances of nitrifying bacteria (Nitrosomonadaceae) and Module#2 with the most species dominated the nitrifying potentials and succeeding wheat and soybean yields in 4WM4WS and 8WS. Soil water content, organic carbon, dissolved organic carbon, NO3− and pH were key drivers influencing Module#3 and Module#5, while only NH4+ significantly affected Module#2 and Module#4.ConclusionsThese findings demonstrate the importance of ecological clusters within soil microbial network in regulating crop yield and soil nitrogen cycling, and identify specific ecological clusters dominating nitrogen functional potentials in wheat–maize and wheat–soybean rotations, offering science-based recommendations for sustainable crop rotation practices.Graphical

Metagenomic insights into microbial variation and carbon cycling function in crop rotation systems

The decomposition and utilization of plant-derived carbon by microorganisms and carbon fixation are crucial pathways for enhancing soil organic carbon (SOC) storage. However, a gap remains in our understanding of the impact of microorganisms on the decomposition of plant-derived carbon and their capacity for carbon fixation in crop rotation systems. Based on a 12-year experiment with wheat–maize (WM), wheat–cotton (WC), and wheat–soybean (WS) rotations, the microbial communities and carbon cycle function were investigated. The results indicated that WS rotation significantly increased SOC content compared to WM and WC. In addition, a significant increase was observed in microbially available carbon and microbial biomass carbon in the WS soil compared with those in the others. Further analysis of the microbial community factors that influenced SOC content revealed that WS rotation, in contrast to WM rotation, enhanced the diversity and richness of bacteria and fungi. Analysis of microbial carbon decomposition functions revealed an increase in starch, lignin, and hemicellulose decomposition genes in the WS soil compared to the others. The changes in carbon decomposition genes were primarily attributed to six bacterial genera, namely Nocardioides, Agromyces, Microvirga, Skermanella, Anaeromyxobacter, and Arthrobacter, as well as four fungal genera, namely Dendryphion, Staphylotrichum, Apiotrichum, and Abortiporus, which were significantly influenced by the crop rotation systems. In addition, microbial carbon fixation-related genes such as ACAT, IDH1, GAPDH, rpiA, and rbcS were significantly enriched in WS. Species annotation of differential carbon fixation genes identified 18 genera that play a role in soil carbon fixation variation within the crop rotation systems. This study highlights the impact of crop rotation systems on SOC content and alterations in specific microbial communities on carbon cycle function.

Straw Retention with Reduced Fertilization Enhances Soil Properties, Crop Yields, and Emergy Sustainability of Wheat-Soybean Rotation.

Cereal + legume rotation is an integrated system that facilitates soil fertility and sustainable agricultural production. However, research on the management compatibility affecting soil physico-chemical properties yields overall agro-ecosystem sustainability, but profitability is lacking, especially under straw retention and potential reductions in fertilizer application. An 11-year field experiment investigated three treatments: no straw retention + traditional mineral fertilization (TNS), straw retention + traditional mineral fertilization (TS), and straw retention + reduced mineral fertilization (DS). Compared with TNS, TS significantly improved soil physico-chemical properties, including macro-aggregates (R > 0.25 mm), porosity, field water capacity (FWC), soil organic carbon (SOC) storage, total nitrogen storage, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) by 17.3%, 3.2%, 13.0%, 5.5%, 3.2%, 15.5%, and 13.8%, respectively. TS also significantly increased total (wheat + soybean) yields (TYs), economic profits, and emergy sustainability index (ESI) by 15.8%, 25.0%, 3.7 times that of TNS, respectively. Surprisingly, compared with TS, DS further significantly improved R > 0.25 mm, porosity, FWC, SOC storage, MBC, MBN, TY, economic profits, and ESI by 11.4%, 1.5%, 6.1%, 3.0%, 10.6%, 7.2%, 5.7%, 11.1%, and 36.5%, respectively. Overall, retaining straw with reduced fertilization enhances soil properties, yields, and emergy sustainability in wheat-soybean rotation systems.

Metagenomes reveal the effect of crop rotation systems on phosphorus cycling functional genes and soil phosphorus avail–ability

The use of different cropping systems affects soil phosphorus (P) availability. Microbes play a main role in regulating soil P cycling. Currently, there is a knowledge gap on the effects of the long-term use of different crop rotation systems on microbial functional genes involved in P cycling on soil P availability. In this study, metagenomics was used to determine microbial functional genes involved in P cycling in a 12-year experiment that included three crop rotation systems: wheat–maize rotation (WM), wheat–cotton rotation (WC), and wheat–soybean rotation (WS). WS had a significantly higher AP content than WC (37.3%) and WM (41.5%). Further analysis of the soil microbial population showed that WS mainly enriched the abundance of Proteobacteria, Actinobacteria, and Firmicutes from the phylum to genus levels. For the P-cycling genes, WS significantly increased the P-cycling gene abundance of organic P mineralization (phoD, phnA, and phnP) compared with WC and WM. WC enhanced the microbial function of the Inorganic P solubilization genes gcd and gppa. WM enhanced the function of polyphosphate degradation, and the abundance of genes spoT and ppnK was significantly increased in WM soil compared with WC and WS soil. In addition, our structural equation model and network analysis showed that the organic P mineralization gene abundance had a significant effect on the available P content; the effect coefficients were 0.73, and the organic P mineralization genes phoD, phnA, and phnP, which were enriched in WS soil, were keystone genes in the process of increasing the soil-available P. Our results highlight the relationship between P cycle functions and cropping systems, which also has implications for enhancing P availability through the use of different crop systems in agricultural production.

Water Requirements and Comprehensive Benefit Evaluation of Diversified Crop Rotations in the Huang-Huai Plain

An intensified farming system can significantly increase crop productivity but can also cause major groundwater overdraft for irrigation and the loss of crop diversity. It is imperative to develop alternative crop rotations beyond the simplified conventional winter wheat–summer maize (W–M) rotation for alleviating the groundwater over-extraction in China’s Huang-Huai Plain. This study systematically quantified crop water requirement (ETc) and irrigation water requirement (ETaw) of eight crops from 2013 to 2018 based on the SIMETAW model applied to the Shangqiu area in the Huang-Huai Plain. Fourteen crop rotations (CI (i.e., crop harvests per rotation cycle year) 1.5 or 2) were constructed based on the ROTAT model. Results showed that compared to W–M rotation, the alternative rotations (CI = 1.5) significantly reduced the annual ETc in wet, normal, and dry years by 9–21%. Replacing winter wheat in the double cropping system did not significantly decrease annual ETc. Wheat–soybean rotation had similar annual ETc and ETaw accompanied by higher economic output and equivalent yield about 1.2 times, with 9% more protein output than the W–M rotation. There were eight crop rotations having greater comprehensive evaluation index (CEI) than W–M rotation by Entropy-TOPSIS when considering 10 indicators including water requirements, yield, economic benefits, water use efficiency, energy, and nutritional values. Spring potato–summer soybean had the highest CEI of 0.627. Sweet potato and potato showed advantages when included in rotations by increasing yield. “Wheat–soybean”-based rotations (CI = 1.5) also performed well in profitability and protein output. Replacing summer maize with soybean is promising for profitability and nutrition output without increasing irrigation requirements. Therefore, decreasing the cropping index, or involving soybean or sweet potato in rotations can be a useful way to improve sustainable land use, save water, and ensure food products in this water stressed region.

Irrigation Optimization via Crop Water Use in Saline Coastal Areas-A Field Data Analysis in China's Yellow River Delta.

Freshwater resources are becoming increasingly scarce in coastal areas, limiting crop productivity in coastal farmlands. Although the characteristic of crop water use is an important factor for water conservation in coastal farmlands, it has not been studied extensively. This study aimed to depict the water use process of soil-plant systems under saline stress in coastal ecosystems and optimize water management. An intensive observation experiment was performed within China's Yellow River Delta to identify the water use processes and crop coefficients (KC) and also quantify the impacts of salt stress on crop water use. The results show that shallow groundwater did not contribute to soil water in the whole rotation; KC values for wheat-maize, wheat-sorghum, and wheat-soybean rotation systems were 45.0, 58.4, and 57% less, respectively, than the FAO values. The water use efficiency of the maize (8.70) and sorghum (9.00) in coastal farmlands was higher than that of the soybean (4.37). By identifying the critical periods of water and salt stress, this paper provides suggestions for water-saving and salinity control in coastal farmlands. Our findings can inform the sustainable development of coastal farmlands and provide new insights to cope with aspects of the global food crisis.

The shift of soil microbial community induced by cropping sequence affect soil properties and crop yield.

Rational cropping maintains high soil fertility and a healthy ecosystem. Soil microorganism is the controller of soil fertility. Meanwhile, soil microbial communities also respond to different cropping patterns. The mechanisms by which biotic and abiotic factors were affected by different cropping sequences remain unclear in the major grain-producing regions of northeastern China. To evaluate the effects of different cropping sequences under conventional fertilization practices on soil properties, microbial communities, and crop yield, six types of plant cropping systems were performed, including soybean monoculture, wheat-soybean rotation, wheat-maize-soybean rotation, soybean-maize-maize rotation, maize-soybean-soybean rotation and maize monoculture. Our results showed that compared with the single cropping system, soybean and maize crop rotation in different combinations or sequences can increase soil total organic carbon and nutrients, and promote soybean and maize yield, especially using soybean-maize-maize and maize-soybean-soybean planting system. The 16S rRNA and internal transcribed spacer (ITS) amplicon sequencing showed that different cropping systems had different effects on bacterial and fungal communities. The bacterial and fungal communities of soybean monoculture were less diverse when compared to the other crop rotation planting system. Among the different cropping sequences, the number of observed bacterial species was greater in soybean-maize-maize planting setup and fungal species in maize-soybean-soybean planting setup. Some dominant and functional bacterial and fungal taxa in the rotation soils were observed. Network-based analysis suggests that bacterial phyla Acidobacteria and Actinobacteria while fungal phylum Ascomycota showed a positive correlation with other microbial communities. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) result showed the presence of various metabolic pathways. Besides, the soybean-maize-maize significantly increased the proportion of some beneficial microorganisms in the soil and reduced the soil-borne animal and plant pathogens. These results warrant further investigation into the mechanisms driving responses of beneficial microbial communities and their capacity on improving soil fertility during legume cropping. The present study extends our understanding of how different crop rotations effect soil parameters, microbial diversity, and metabolic functions, and reveals the importance of crop rotation sequences. These findings could be used to guide decision-making from the microbial perspective for annual crop planting and soil management approaches.

Effect of soybean–wheat rotation on soil aggregation, organic nitrogen and net nitrogen mineralization characteristics: a four-year field study

ABSTRACT Long-term, excessive application of synthetic N fertilizers will reduce soil aggregate stability and N supply capacity in corn–wheat (Zea mays L. – Triticum aestivum L.) rotation. This study aimed to determine the effects of soybean (Glycine max L.) on soil aggregation, soil organic N (SON) and net amount of N mineralization (NANM) in wheat season compared with corn. Three rotation systems, corn–wheat (C-W), soybean–wheat (S-W) and soybean inoculated with Rhizobium-wheat (SR-W) were established in 2017. In wet screening, compared with C-W rotation, the mass proportions of large macro-aggregates (LM%) + small macro-aggregates (SM%) at 0–20 cm was increased by 51.9% and 16.6% under S-W and SR-W rotations, respectively, and was increased by 50.6% and 59.8%, respectively, in the 20–40 cm. The proportions of LM + SM-associated N (LMN% + SMN%), ammonium N (AN) and amino acid N (AAN) were higher under the S-W and SR-W rotations. Furthermore, the NANM of S-W and SR-W rotations increased by 34.1% and 28.6% compared with C-W rotation, respectively, and the non-N benefits of soybean played an important role. In conclusion, the improvement degree of soil aggregation by soybean is an important factor affecting soil N mineralization in wheat season.

Long-Term Wheat-Soybean Rotation and the Effect of Straw Retention on the Soil Nutrition Content and Bacterial Community

Straw retention and wheat-soybean rotation play critical role in maintaining soil quality. However, the correlation between bacterial diversity and community structure, and soil nutrients is unknown, and a systematic understanding of their responses to straw retention is lacking. In the field experiment, the straw retention treatments included no straw (NS), half straw (HS), and total straw (TS) retention during long-term wheat-soybean rotation. The mean contents of soil total nitrogen (TN), nitrate-N (NO3−-N), and microbial biomass nitrogen (MBN) increased by 15.06%, 21.10%, and 38.23%, respectively, with straw retention relative to NS, while that of ammonium-N (NH4+-N) reduced by 3.68%. The concentration of carbon components increased as straw retention increased. The levels of soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), and soil organic carbon (SOC) increased by 4.34%, 7.63%, and 9.34%, respectively, with straw retention relative to NS. Soil bacterial alpha diversity was reduced with straw retention. Soil pH and nutrient content were identified as the main factors affecting the soil microbial diversity and structure at the phylum level. Accordingly, straw retention and soybean-wheat rotation enable sustainable agriculture in the dryland of northern China.

Farm-scale practical strategies to increase nitrogen use efficiency and reduce nitrogen footprint in crop production across the North China Plain

Achieving a pathway for green development is a critically important challenge for agriculture in China and beyond. The current study evaluates the effects of a range of management interventions including planting, fertilizer nitrogen (N) rate optimization and increasing farm size to promote agricultural green development across the North China Plain (NCP) based on large-scale farm surveys. Our results showed that the mean annual N fertilizer rate for wheat-soybean rotation was much lower than that of wheat-maize and wheat-peanut. Interestingly, our study indicated strong pre-crop effects of summer soybean ( Glycine max (Linn.) Merr.) on the following winter wheat ( Triticum aestivum Linn.) in N saving compared to summer maize ( Zea mays Linn.) and summer peanuts ( Arachis hypogaea Linn.), the low N rate for summer soybean and its ‘legume’ carryover effects led to the low N rate, N surplus and N footprint, and high N use efficiency (NUE) in wheat-soybean. The survey results showed that the optimal N rates for achieving maximum yield of summer maize, summer peanuts and winter wheat were 229, 249 and 236–260 kg ha −1 across the NCP, respectively. Moreover, better N management is beneficial for reducing the N surplus and leads to higher NUE and lower N footprint. Generally, large farms applied less N fertilizer than small farms, thus leading to a lower N surplus and higher N partial factor productivity with the same yield level. Here we show for the first time that the combinations of crop rotation design, optimizing N rate application and increasing farm size are very efficient in reducing N fertilizer applications and the N footprint with stable crop yields. N management should play a more important role in agricultural green development across the NCP and similar regions around the world. • The mean annual N rate, N surplus and N footprint of wheat-soybean was lowest among the three major crop rotations. • Pre-crop effects of soybean on winter wheat increased PFP and reduced N footprint without affecting wheat yield. • The optimal N rate for the maximum crop yield of maize, peanut, wheat were 229, 249, 236–260 kg N ha −1 , respectively. • The NUE was higher and N footprint was lower in large farms compared with small farms.

Farm-scale practical strategies to reduce carbon footprint and emergy while increasing economic benefits in crop production in the North China plain

How to achieve China's “Carbon Peak” and “Carbon Neutrality” targets in the agriculture sector is crucial but still remains challenging. This study thus aims to assess the effects of crop rotations and farm size with optimized nitrogen (N) rate on carbon footprint (CF), emergy and economic benefits to promote agricultural transformation in the North China Plain (NCP) based on 792 on-farm questionnaires. Our results showed that the CF and emergy of wheat ( Triticum aestivum Linn.)-soybean ( Glycine max (Linn.) Merr.) was 32–45% and 20–21% lower than that of wheat-maize ( Zea mays Linn.) and wheat-peanut ( Arachis hypogaea Linn.) mainly due to reduced N application by the biological nitrogen fixation (BNF) and pre-crop effects of soybean, while the farming net income (FNI) was lowest in the wheat-soybean mainly because of the low soybean yield. Furthermore, the sustainability performance index (SPI) was highest for wheat-soybean while lowest for wheat-maize. Large-size farms (LF, larger than 3.3 ha) efficiently reduced N rate without negatively influencing crop yield, thus decreasing CF and emergy compared to smallholders (SF, smaller than 3.3 ha), and the total farming profit was much higher in the LF due to the scale effect. Our results indicated that the joint application of increased soybean planting area in concert with larger farm size using optimized N rate was beneficial for reducing CF and emergy, but also increasing crop production in the NCP. However, low soybean yield was the critical factor that constrained soybean planting area in the NCP. We suggest that practical, cost-effective strategies to increase soybean yield with concurrent financial subsidies are urgently required to maximize the eco-benefits of wheat-soybean rotation in promoting agricultural green development in the NCP. • The carbon footprint (CF) and emergy was lowest in wheat-soybean. • The sustainability performance index (SPI) was highest in wheat-soybean. • Large-size farms induced lower CF and emergy compared to smallholders. • Optimizing crop rotations with larger farm size and better N managements should be beneficial for SDGs.

Organic amendment regulates soil microbial biomass and activity in wheat-maize and wheat-soybean rotation systems

Long-term heavy application of inorganic fertilizers is associated with a decrease in soil quality and biodiversity. Organic amendments have been reported to positively affect soil quality; however, relatively little is known regarding soil carbon (C) cycle enzyme kinetic parameters (Vmax and Km), community-level physiological profiles (CLPP), and the interactions between these factors and soil microbes and physicochemical properties under sustained organic amendment. Therefore, this study aimed to evaluate the effect of organic amendments on crop yield, soil chemical properties, microbial activity, enzyme kinetic parameters of five extracellular C cycle-related hydrolase enzymes, and soil microbial functional diversity in wheat-maize (WM) and wheat-soybean (WS) rotation crop systems. The results of the study showed that combined application of organic and inorganic fertilizers increased crop yield (6.81–17.47%), soil total organic C (TOC, 29.44–39.54%), total nitrogen (TN, 24.22–50.79%), available potassium (AK, 39.47–59.62%), total dissolved nitrogen (TDN, 19.68–33.75%), dissolved organic C (DOC, 14.54–55.10%), available phosphorus (AP, 34.81–243.90%), and microbial biomass C and nitrogen (MBC, 17.65–40.86% and MBN, 18.63–50.76%) concentration. The combined application also enhanced microbial growth when compared with an inorganic amendments regime. Additionally, the combined application of organic and inorganic fertilizers increased soil microbial activity and catabolic diversity and maintained a high substrate-induced respiration (SIR) value. Furthermore, the conversion from a WM rotation to a WS rotation increased both soil pH and microbial biomass, and the resultant soil exhibited lower potential activity and higher enzyme-substrate affinity. Overall, the findings of this study showed that an increase in soil microbial biomass is a key determinant of microbial catabolic activity and functional diversity.

Wheat Straw Return Influences Soybean Root-Associated Bacterial and Fungal Microbiota in a Wheat-Soybean Rotation System.

Roots hold complex microbial communities at the soil–root interface, which can affect plant nutrition, growth, and health. Although the composition of plant microbiomes has been extensively described for various plant species and environments, little is known about the effect of wheat straw return (WSR) on the soybean root microbiota. We used Illumina-based 16S rRNA and ITS amplicon sequencing to track changes in bacterial and fungal microbiota in bulk soil and soybean rhizosphere, rhizoplane, s1and endosphere during the third and fourth years after implementing WSR in a wheat–soybean rotation system. The results revealed that WSR had a greater impact on fungal communities than bacterial communities, particularly in bulk soil, rhizosphere, and rhizoplane. WSR enriched the relative abundance of cellulose-degrading fungi (e.g., Acremonium, Trichoderma, and Myrmecridium, among which Trichoderma also had antimicrobial activity), saprotroph (e.g., Exophiala), and nitrogen cycling bacteria (e.g., Chryseolinea). Furthermore, WSR depleted the relative abundance of pathogenic fungi (e.g., Fusarium and Alternaria). These data revealed for the first time that WSR had diverse effects on soybean root-associated microbial community composition, not only in soil but also in the rhizosphere, rhizoplane, and endosphere.

Vertical and temporal variations of soil bacterial and archaeal communities in wheat-soybean rotation agroecosystem.

Soil microbes are an essential component of terrestrial ecosystems and drive many biogeochemical processes throughout the soil profile. Prior field studies mainly focused on the vertical patterns of soil microbial communities, meaning their temporal dynamics have been largely neglected. In the present study, we investigated the vertical and temporal patterns of soil bacterial and archaeal communities in a wheat-soybean rotation agroecosystem at a depth of millions of sequences per sample. Our results revealed different vertical bacterial and archaeal richness patterns: bacterial richness was lowest in the deep soil layer and peaked in the surface or middle soil layer. In contrast, archaeal richness did not differ among soil layers. PERMANOVA analysis indicated that both bacterial and archaeal community compositions were significantly impacted by soil depth but unaffected by sampling time. Notably, the proportion of rare bacteria gradually decreased along with the soil profile. The rare bacterial community composition was the most important indicator for soil nutrient fertility index, as determined by random forest analysis. The soil prokaryotic co-occurrence networks of the surface and middle soil layers are more connected and harbored fewer negative links than that of the deep soil layer. Overall, our results highlighted soil depth as a more important determinant than temporal variation in shaping the soil prokaryotic community and interspecific interactions and revealed a potential role of rare taxa in soil biogeochemical function.

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.

Agronomic system for stabilizing wheat yields and enhancing the sustainable utilization of soil: A 12-year in-situ rotation study in a semi-arid agro-ecosystem

Continuous wheat (Triticum aestivum L.) cropping in the Loess Plateau of China has led to soil degradation and yield reductions. In the present study, we conducted a long-term wheat rotation experiment in Zhenyuan County, Gansu Province, China, between 2005 and 2017, where three cropping systems were tested: (1) continuous winter wheat cropping (W), (2) wheat–wheat–wheat–soybean, i.e., 3 years of wheat and 1 year of soybean (Glycine max L.) rotation (W3–S), and (3) wheat–wheat–wheat–maize, i.e., 3 years of wheat and 1 year of maize (Zea mays L.) rotation (W3-M). Equal amounts of fertilizer were applied to all treatments. All treatments were conducted for four years and repeated three times, with a total of 12 years. Continuous wheat cropping increased the soil bulk density and decreased the soil porosity compared with 2005. However, W3–S and W3-M significantly reduced the soil bulk density and increased the soil nutrients and enzyme activities in 2017 compared with continuous wheat cropping. The average increases in the soil water storage under W3–S and W3-M were 12.7% and 5.9%, respectively. During the wheat growing season, the water use efficiencies under W3–S and W3-M were 22.9% and 12.9% higher, respectively, than that under continuous wheat cropping. The average wheat yields under W3–S and W3-M increased by 25.1% and 14.1%, respectively. Furthermore, according to principal component analysis and correlation analysis, the yield increases were due to the enhanced soil quality, enzyme activities, and water use efficiency. These results suggest that rotation can enhance the soil properties, soil enzyme activity, crop yield, and soil water use efficiency. In addition, wheat–soybean rotation had more positive effects than wheat–maize rotation on the soil quality and crop productivity in the study area. However, wheat was not produced in the fourth year of rotation so the replacement crop would need to be economically viable to facilitate widespread adoption. Further investigation is also required to determine whether the lower biomass production associated with legumes was offset by the increased soil organic carbon during the wheat phase of the rotation. The best rotation method identified in this study may provide a cleaner agronomic production strategy.

Long‐term reduced tillage and no‐till cropping systems affect crop yields and economics

AbstractThere has been increased implementation of conservation practices on highly erodible Missouri soils. The objectives were to evaluate the effects of long‐term no‐till and reduced tillage cropping systems on yields and economics of production systems. Research was initiated in 1994 near Novelty, MO. Treatments included a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–wheat (Triticum aestivum L.) rotation with three tillage/cropping systems: (1) no‐till corn–soybean–wheat with double‐crop soybean (NT DCS), (2) no‐till corn–soybean–wheat with frost‐seeded red clover (Trifolium pratense L.) cover crop (NT FSC), and (3) reduced‐till corn–soybean–wheat (RT). Each crop and cropping system was represented each year in large plots (9.1 by 90 m). Significant differences in corn yields occurred in 1995–1996, 2000, 2009–2010, and 2015–2016 with the highest‐yielding treatments being five RT, one NT DCS, and one RT = NT DCS. Significant differences in soybean yield occurred in 3 yr with the highest‐yielding cropping system being NT DCS twice and RT once. Significant differences in wheat yield occurred in 4 yr with RT yielding the highest each time. Input costs were greatest in RT and NT DCS, while net income was greatest in NT DCS, which produces four cash crops in 3 yr. Highest net returns occurred in NT DCS, which was US$135 and 145 ha–1 greater than NT FSC and RT, respectively. The productivity and economics of systems need to be balanced with ecosystem benefits of NT. In this corn–soybean–wheat rotation, hybrid cropping systems including RT corn and wheat, followed by NT DCS, and NT soybean is recommended.

Eukaryotes in soil aggregates across conservation managements: Major roles of protists, fungi and taxa linkages in soil structuring and C stock

The stabilization of soil organic carbon (SOC) promoted by conservation agriculture (CA) depends on soil aggregation. Aggregation protects SOC and creates heterogeneous microhabitats hosting diverse soil biota which in turn promote aggregation. A long-term experiment, studying the interaction of tillage with nitrogen (N) fertilization on a soybean-wheat rotation, was used to investigate eukaryotic community diversity, composition, and structure within small macroaggregates (sM) and occluded microaggregates (mM). Using high-throughput Illumina sequencing, we found (i) a different eukaryote diversity response to management intensification across soil aggregates and soil depths; (ii) a conserved core community composition of eukaryotes across CA treatments and aggregates at surface and subsurface layers; (iii) a different effect of tillage on eukaryotic community structure in sM and mM along the soil profile according to N availability; (iv) a positive association of protists, and fungi with the amount of sM and mM, and their SOC content; (v) a stronger complexity of within- and cross-domain networks (eukaryotes and eukaryotes-prokaryotes) in mM than in sM at surface layer. Overall, our findings demonstrate for the first time that protists together with fungi play major roles in soil structuring and C cycling, and that Cercozoa represent hubs in soil biota aggregate networks.

Effects of Rotations With Legume on Soil Functional Microbial Communities Involved in Phosphorus Transformation.

Including legumes in the cereal cropping could improve the crop yield and the uptake of nitrogen (N) and phosphorus (P) of subsequent cereals. The effects of legume-cereal crop rotations on the soil microbial community have been studied in recent years, the impact on soil functional genes especially involved in P cycling is raising great concerns. The metagenomic approach was used to investigate the impacts of crop rotation managements of soybean-wheat (SW) and maize-wheat (MW) lasting 2 and 7years on soil microbial communities and genes involved in P transformation in a field experiment. Results indicated that SW rotation increased the relative abundances of Firmicutes and Bacteroidetes, reduced Actinobacteria, Verrucomicrobia, and Chloroflexi compared to MW rotation. gcd, phoR, phoD, and ppx predominated in genes involved in P transformation in both rotations. Genes of gcd, ppa, and ugpABCE showed higher abundances in SW rotation than in MW rotation, whereas gadAC and pstS showed less abundances. Proteobacteria, Acidobacteria, and Gemmatimonadetes played predominant roles in microbial P cycling. Our study provides a novel insight into crop P, which requires strategy and help to understand the mechanism of improving crop nutrient uptake and productivity in different rotations.