Wheat-maize Rotation Research Articles

After-effects of straw and straw-derived biochar application on crop growth, yield, and soil properties in wheat (Triticum aestivum L.) -maize (Zea mays L.) rotations: A four-year field experiment.

Research on the after-effects of straw and straw-derived biochar applications on crop growth, yield, and retention of carbon (C) and nitrogen (N) in soil in wheat-maize rotation systems is limited, and has presented inconsistent conclusions. The purpose of this research was to compare the after-effects of straw and straw-derived biochar on wheat (Triticum aestivum L.) and maize (Zea mays L.) growth and yield, and on soil properties. A field experiment was conducted in four consecutive wheat-maize rotation cycles in the Loess Plateau of China under five treatments: CK (control without nitrogen and phosphate fertilizer, straw, or biochar); NP (conventional single application of nitrogen and phosphate chemical fertilizers); SNP (8tha-1 wheat straw returned to the field plus fertilizer); B1NP (8tha-1 straw-derived biochar plus fertilizer); B2NP (16tha-1 straw-derived biochar plus fertilizer). The highest plant height and aboveground biomass for both wheat and maize always occurred with the B2NP treatment for the four study years. Grains per spike/ear and 1000-grain weight for both wheat and maize in B2NP and B1NP were significantly higher than observed for the other treatments. The four-year average wheat yields for NP, SNP, B1NP, and B2NP were 50.5%, 63.1%, 66.3%, and 81.7% greater than for CK, respectively, and the four-year average maize yields were 45.0%, 49.8%, 65.4%, and 72.1% greater than for CK, respectively. The application of straw-derived biochar significantly increased soil organic carbon, total nitrogen, microbial biomass carbon, and nitrogen in the soil surface layer compared with returning straw to the field. Both straw and straw-derived biochar reduced nitrate N leaching. Therefore, using straw-derived biochar to amend soil could be an appropriate practice for sustaining soil fertility and crop yield in wheat-maize rotation systems in the Loess Plateau of China.

δ15N–N2O signatures in response to N fertilization in a wheat–maize rotation

The responses of δ15N–N2O isotopic signatures to nitrogen (N) fertilization in in situ soils are not yet clear in agricultural field settings. We therefore conducted a 1-year field experiment to assess how N fertilization (0 and 400 kg N ha−1 year−1, N0 and N400) affects the δ15N–N2O isotopic signatures both at soil surface and in soil profile (0–3 m) in a wheat–maize rotation in North China. N fertilization increased N2O concentrations by 18–79% in the soil profile. It increased N2O fluxes by 9 times and 1–7 times at the soil surface and 0–0.9 m soil depth, respectively. In comparison, N fertilization reduced δ15N–N2O values by 10–74% in the soil profile. It reduced δ15N–N2O isotopic signatures at the soil surface and in the soil profile by 18% and 33%, respectively. The δ15N–N2O isotopic signature was dominated by substrate δ15N signature and N isotope fractionation during cold and warm seasons, respectively. Our results indicate that denitrification steps of NO3− → N2O dominated N2O production (over 99%) in the N0 treatment and the N400 treatment during N-fertilizer-free period. Following N fertilization, the NO3− → N2O dominated N2O production (over 99%) in the soil profile, N2O flux from the soil surface was mostly derived from NO3− → N2O and less from NH4+ → N2O. Overall, denitrification was found to dominate soil N2O transformation metabolism in the wheat–maize rotation cropland in North China.

Biogas slurry application could potentially reduce N2O emissions and increase crop yield.

The huge excrement quantity from the increasing large-scale livestock stressed the ecological, environmental deterioration. As a major benefit for handling livestock manure, the slurry of biogas (BS) is developed during the production of biogas that might increase plant productivity. However, nitrous oxide (N2O) emissions from BS are considered a significant danger to the environment due to global warming potential. Furthermore, applying different proportions of BS combined with chemical fertilizer (CF) on N2O productions in the North China Plain (NCP) remains unclear. Herein, two sequential field trials were performed by maize-wheat rotations to substitute the CF by BS and reduce N2O emissions while keeping the crop yield stable. Four treatments were conducted, including T1, T3, T6, and CK. A total of 226.5kgNha-1 used in the maize-wheat rotation system. Additionally, different ratios of BS (100%, 80%, and 50%) combined with CF were used in wheat season in the tillering stage. Results showed integrated applications of BS with CF have potential for reducing N2O emission. Our findings showed that the maximum grain yield of CF was 6250kgha-1, which might be achieved by applying 38% BS and 62% of CF. This ratio yielded 1.03kgha-1 N2O emissions, which was 15% lesser than the N2O emission of CK, 1.21kgha-1. Considering whole growing period of wheat biogas treatments significantly reduced the cumulative N2O emissions from 17% to 26% compared to CF. To achieve maximum yield and minimum N2O emissions, an optimum 38% BS ratio has been suggested. The integrated use of BS and CF provided the greatest grain yield because of necessary nutrients provided by both slurry and CF. Consequently, N2O emissions reduced based on frequency and type of fertilizer. In conclusion, 38% ratio of BS combined with 62% CF would be a suitable approach to mitigate N2O emission and simultaneously increase crop yield in NCP.

Effects of Biochar and Straw on Soil N2O Emission from a Wheat Maize Rotation System

The effects of biochar and straw return on soil N2O emissions were studied in the winter wheat-summer maize rotation system of intensively farmed land in North China to provide a theoretical basis for N2O emission reduction and the efficient straw utilization. The experiment included the following four treatments:① Control (CK); ② Biochar application at a rate of 9.0 t·(hm2·a)-1 (C); ③ Straw return (SR); and ④ Straw return plus biochar application at a rate of 9.0 t·(hm2·a)-1 (C+SR). The results showed that in the wheat season, the CK treatment showed a slight decrease in soil N2O emission while the SR and C+SR treatments promoted soil N2O emission by 47.4% and 71.8%, respectively. In the maize-growing season, the CK treatment reduced soil N2O emission by 29.8% while the SR and C+SR treatments increased soil N2O emission by 13.4% and 35.8%, respectively. During the wheat-growing season, the soil water, NH4+-N, and MBN content were the main environmental factors affecting N2O emissions; during the maize-growing season, NO3--N, NH4+-N, and MBC content were the main environmental factors affecting emissions. Based on our results, the application of biochar to cropland is an effective option for mitigating greenhouse gas emissions, whereas direct straw return to fields might not be an effective strategy. More research is now needed to examine the effect of the return of straw of different maturity on N2O emissions.

Soil profile rather than reclamation time drives the mudflat soil microbial community in the wheat-maize rotation system of Nantong, China

Conversion of coastal mudflats to agricultural soil is one of the most important land use practices in Eastern China. However, effects of soil profile and reclamation time on soil microbial community, which play an important role in soil nutrient cycling, are still poorly documented. Soil profile (0–15 cm, 15–30 cm, 30–45 cm) samples were collected from four sites with different reclamation ages (R12: 12 years, R38: 38 years, R68: 68 years, R100: 100 years) in Rudong County, Nantong, Jiangsu, China. Soil bacterial communities were determined via Illumina 16S rRNA gene high-throughput sequencing. Soil electrical conductivity (EC) responded more rapidly to reclamation time than soil pH. Soil total carbon and nitrogen increased with increasing reclamation age. Soil available nutrients (ammonium, nitrate, dissolved organic carbon, and available phosphorus) were affected by the agricultural practice and did not show a unanimous tendency between different reclaimed sites. Proteobacteria, Acidobacteriota, and Bacteroidota dominated the bacterial community across different sites and soil profiles. However, Methylomirabilota- and Nitrospirota-associated species, which are involved in nitrogen cycling, increased with increasing soil depth. Canonical correspondence analysis (CCA) showed that bacterial community was grouped by soil depth and also significantly affected by soil pH, EC, and reclaimed time. Moreover, co-occurrence network analysis showed a potential role of low abundant phyla besides dominant phyla in stabilizing the bacterial community, and the connection between soil properties and bacterial amplicon sequence variant (ASV) numbers would shift along soil profiles. Reclamation time of the coastal mudflats is not the only reason for the shift of bacterial community. Here, we found soil profile had a strong influence on soil bacterial composition in the coastal reclaimed wheat-maize rotation soils.

Evaluating soil physical quality indicators of a Vertisol as affected by different tillage practices under wheat-maize system in the North China Plain

Soil physical quality (SPQ) is an important parameter for crop growth. Tillage management is widely recognized to affect SPQ remarkably, but such an effect is complicated in Vertisols by shrinking and swelling soil structure. The objectives of this study were to (i) investigate how tillage practices affected SPQ as indicated by the S index, least limiting water range (LLWR) and water stress percentage (WSP); and (ii) determine the relationship between these SPQ indicators and crop yield. A 4-year field experiment, which was conducted in a Vertisol under wheat-maize rotation system in the North China Plain, consisted of four tillage treatments: no tillage (NT), rotary tillage (RT), subsoiling (SS), and deep ploughing (DP). Soil water retention curve (SWRC), soil shrinkage curve (SSC), penetration resistance (PR), and bulk density (BD) of the 0−10 and 10−20 cm layer were measured during wheat and maize seasons, and soil water content was continuously monitored in situ. The S index, LLWR and WSP were determined. Our results showed that SSCs were parallel to each other among four tillage treatments, indicating that tillage did not impact shrinkage capacity (P > 0.05). Relative to NT and RT treatments, the SS and DP treatments improved soil physical quality (higher S index and larger LLWR), particularly in the 10−20 cm layer. The S index presented a poor relation with wheat (P > 0.05) and maize yields (P > 0.05), while LLWR had a significant correlation with wheat yield (P < 0.05) but not with maize yield (P > 0.05). A new proposed SPQ indicator, WSP, is defined as the percentage of the period when the soil water content is above the field water capacity (waterlogging stress percentage, WLP) or below the wilting point (drought stress percentage, DSP) to the entire crop season period. The WLP presented a significantly negative relation with maize yield (P < 0.01) but not with wheat yield (P > 0.05), whereas the DSP had no relation with wheat and maize yield (P > 0.05). Moreover, the WSP was observed to be independent of the volume change in the Vertisol. Our results demonstrate that LLWR and WLP can be regarded as suitable indicators for evaluating SPQ in wheat and maize seasons, respectively, but the latter is more conveniently applied in a Vertisol.

Long-term straw mulching with nitrogen fertilization increases nutrient and microbial determinants of soil quality in a maize–wheat rotation on China's Loess Plateau

Mulching and nitrogen (N) fertilization are essential to increase crop yields in semiarid drylands. However, their long-term effects on soil physicochemical properties, extracellular enzyme activities, microbial community structure, and therefore soil quality via developing a soil quality index (SQI) remain largely unexplored. Hence, we analyzed soils after 14 years of mulching (CT, no mulch; RF, plastic film-mulched ridges and straw mulched-furrows; SM, straw mulching) and N fertilization (0, 120 and 240 kg ha−1) treatments in a maize–wheat rotation on China's Loess Plateau. Compared with CT, RF and SM significantly increased soil moisture content (SMC), organic carbon (SOC), phosphatase, and total phospholipid fatty acids (PLFAs). Compared with RF, SM increased SOC, total N, available phosphorus (AP), available potassium (AK), β-glucosidase, N-acetyl-glucosaminidase (NAG), peroxidase, and cellobiohydrolase, gram-negative bacteria (G−), and fungi. Consequently, the SQI was highest in SM (0.698), followed by RF (0.642) and CT (0.620). Nitrogen fertilization significantly increased total N, NO3−, microbial biomass N, α-glucosidase, NAG, total PLFAs, and G−, but caused a significant decline in pH, AP, AK, and the G+:G− ratio. Averaged across N-fertilizations, the SQI was ranked N240 (0.680) > N120 (0.650) > N0 (0.630). Redundancy analysis showed that SOC was closely associated with enzyme activities, whereas NO3−, SOC, and SMC were the key variables regulating microbial community composition. Structural equation model indicated that mulching and N fertilization strongly and positively affected SQI by regulating soil available N, P, and K, enzyme activities, and microbial communities, and the total effect of mulching (0.62) on SQI was greater than that of N addition (0.34). Collectively, the highest SQI observed in the SM + N240 treatment suggested that straw mulch, rather than plastic-film mulch, combined with high N addition could be a sustainable land management practice that improves soil quality in semiarid dryland farming systems.

Stoichiometric analysis of an arable crop–soil–microbe system after repeated fertilizer and compost application for 10 years

Little is known about the impact application of fertilizer and manure nutrients on the nutrient stoichiometry of crop–soil–microbe systems. We ask the question to what extent the nutrient availability in the microbe–soil–plant system may be affected by the application of fertilizers or manures. The influence of application of inorganic fertilizers or composted manure on the concentrations of carbon (C), nitrogen (N), and phosphorus (P) and their stoichiometric ratios in soil, microbial biomass, enzymes, and plant tissues within the rhizosphere of maize was investigated in a maize–wheat rotation established for 10 years in China. The higher rate of composted manure was most effective in increasing soil C, N, and P contents and the microbial biomass. Microbes changed biomass stoichiometry instead of regulating related enzyme secretion under different nutrient supplies. Although plants and microbes showed tight but different relationships with the two nutrient sources, competition for N consistently occurred. Pearson’s inter-correlation demonstrates stable Redfield-like C:N:P fractions existed in soil properties and related enzyme activity, but was not always found in crop and microbial biomass after fertilizer and manure application. The results indicate that soil microbial functioning and coupled feedback with the plants are important in maintaining the stability of fertilized/manured agricultural ecosystems.

Dynamics of Soil Organic Carbon and Labile Carbon Fractions in Soil Aggregates Affected by Different Tillage Managements

Our study aimed to provide a scientific basis for an appropriate tillage management of wheat-maize rotation system, which is beneficial to the sustainable development of agriculture in the fluvo-aquic soil areas in China. Four tillage treatments were investigated after maize harvest, including rotary tillage with straw returning (RT), deep ploughing with straw returning (DP), subsoiling with straw returning (SS), and no tillage with straw mulching (NT). We evaluated soil organic carbon (SOC), dissolved organic carbon (DOC), permanganate oxidizable carbon (POXC), microbial biomass carbon (MBC), and particulate organic carbon (POC) in bulk soil and soil aggregates with five particle sizes (&gt;5 mm, 5–2 mm, 2–1 mm, 1–0.25 mm, and &lt;0.25 mm) under different tillage managements. Results showed that compared with RT treatment, NT treatment not only increased soil aggregate stability, but also enhanced SOC, DOC, and POC contents, especially those in large size macroaggregates. DP treatment also showed positive effects on soil aggregate stability and labile carbon fractions (DOC and POXC). Consequently, we suggest that no tillage or deep ploughing, rather than rotary tillage, could be better tillage management considering carbon storage. Meanwhile, we implied that mass fractal dimension (Dm) and POXC could be effective indicators of soil quality, as affected by tillage managements.

Optimal Blends of Controlled-Release Urea and Conventional Urea Improved Nitrogen Use Efficiency in Wheat and Maize with Reduced Nitrogen Application

Blending controlled-release urea (CRU) with conventional urea has the potential to be an effective option for improving nitrogen (N) use efficiency (NUE), although determination of optimal blends in combination with a reduced N application rate has not been well studied. A field experiment was conducted to compare the effects of CRU (a mixture of polymer-coated urea and urea with N ratios of 100:00, 75:25, and 50:50 at 144 kg N ha−1, hereafter denoted as CRU1, CRU2, and CRU3, respectively), urea at 180 (U1) and 144 kg N ha−1 (U2) and a control (no N fertilizer applied, CK) on grain yield, NUE, and economic benefits in a wheat–maize rotation system. The CRU treatments were one-time applied, while for the U treatments, fertilizer N was applied in a split application. The results suggest that a one-time application of CRU prior to sowing of both crops fulfilled the demand of crop plants for N across the entire growth period. Relative to U1, the CRU treatments achieved approximately the same grain yield and 4.7–26.6% greater NUE at 20% reduced N application. Moreover, under CRU2, the yield, NUE, and economic benefits were increased by 12.2%, 9.7%, and 19.1%, respectively, for wheat, and under CRU3, they were increased by 10.9%, 20.6%, and 17.3%, respectively, for maize, compared with the U2 treatment. These results demonstrate that a mixture of CRU and urea at a ratio of 75:25 for wheat and 50:50 for maize with a 20% reduction in N application rate can maintain productivity, while enhancing NUE in the North China Plain.

Peat-vermiculite alters microbiota composition towards increased soil fertility and crop productivity

Harnessing soil microbiomes is a major demand for development of sustainable and productive agriculture. Here we aimed to assess the impact of two different types of organic material amendments in combination with chemical fertilizer on the plant-soil microbiota in maize farming and its link to soil fertility and crop productivity. Soils and roots were collected from a long-term wheat-maize rotation system involving three experimental treatments: chemical fertilizer (CF); chemical fertilizer plus seasonal application of manure (OM); and chemical fertilizer plus one-time application of peat and vermiculite (PV). Crop residues were returned in all three treatments each season. Bacterial 16S rRNA gene and fungal ITS sequencing were conducted to elucidate the treatment-specific response of the microbiota in bulk soil, rhizosphere soil, and root compartment. Relative to CF and OM treatments, PV amendment led to significant increases in soil organic carbon (SOC) content, aboveground plant biomass, and grain yield over the five-year field study. The PV-induced changes in microbial composition involved the greatest treatment-specific “effect size” on indicator ASVs (amplicon sequence variants) in bulk and rhizosphere soils. The number of interactions was more than doubled in the PV co-occurrence network relative to those in the CF and OM co-occurrence networks. Potential beneficial microbes, such as Glomeromycota (arbuscular mycorrhiza), Basidiomycota, and various members of the Actinobacteria and Burkholderiales, were most enriched in the root compartment of the PV treatment. Peat-vermiculite enhanced microbiota-driven soil fertility and crop productivity, thereby providing new insights into plant-soil-microbiota interactions that can be harnessed for smart farming.

Soil carbon and nitrogen of wheat–maize rotation system under continuous straw and plastic mulch

Straw and plastic mulching have been widely used in northwest China because of their ability to improve water use efficiency and increase grain yields. However, the dynamic changes of soil carbon (C) and nitrogen (N) under continuous straw and plastic mulching is rarely mentioned. A field experiment was conducted over four consecutive wheat (Triticum aestivum L.)-maize (Zea mays L.) rotation cycles in Northwest China to determine dynamic changes in soil C and N under three treatments: CK (traditional non-mulched), PM (transparent plastic mulching), and SM (straw mulching). Over the four wheat–maize cycles, soil organic carbon (SOC) in SM increased by 18% in the 0–0.2 m soil layer, while in PM SOC decreased by 15%, and in CK SOC changed little. Total N under CK and SM remained basically unchanged over time, but declined over time under PM. The overall microbial biomass carbon (MBC) and nitrogen (MBN) under SM increased by 32% and 17%, respectively, after four rotation cycles compared with significant decreases of 29% and 22% under PM and little change under CK. SM reduced soil temperature and increased soil water content, while PM increased both ST and water relation to the CK. Both SM and PM treatments increased grain yield and reduced nitrate N leaching. In the long run, straw mulching can improve SOC, MBC, MBN, and wheat–maize yield, and should be the recommended mulching practice for sustainable wheat–maize production in dryland areas in response to the potential challenges of climate change to dryland agriculture.

Effects of Long-Term Straw-Return Modes on Soil Organic Carbon Content and Carbon Footprint in Wheat–Maize Rotation System

Straw return is widely applied in China to achieve sustainable grain production. However, inappropriate farm practices can increase greenhouse gas (GHG) emissions and reduce soil organic carbon (SOC) sequestration, thereby increasing the carbon footprint (CFP) and affecting soil fertility and climate change. A 10-year experiment was conducted to evaluate and quantify the effects of straw management on SOC, crop yield, and CFP under a winter wheat–summer maize rotation in the Guanzhong Plain. The experiment involved seven straw-return modes, namely high wheat stubble retention and chopped maize straw return (WH-MC), high wheat stubble retention and chopped maize straw return with sub-soiling every two years (WH-MM), high wheat stubble retention and no maize straw return (WH-MN), both chopped wheat and maize straw return (WC-MC), chopped wheat and maize straw return with sub-soiling every two years (WC-MM), chopped wheat straw return and no maize straw return (WC-MN), and a control with no return of either wheat or maize straw (WN-MN). The results indicate that SOC change, crop yield, and CFP were significantly influenced by the straw-return mode in the annual wheat–maize season. SOC sequestration rate was positively correlated with cumulative plant-derived C input, which ranged from 29.4 Mg C ha −1 in WN-MN to 100.7 Mg C ha −1 in WH-MC. Of all the studied treatments, WH-MC produced the highest grain yield and lowest CFP, which were 26% higher and 20.5% lower than those of the control, respectively. However, crop yield and CFP in the individual wheat or maize seasons were only slightly affected by straw-return mode; only WC-MN in the wheat season and WH-MC, WH-MM, and WC-MN in the maize season produced a significantly higher grain yield and lower CFP compared to the no straw return treatment. Annual GHG emissions were highest in the WC-MM treatment and lowest in WH-MN. Therefore, WH-MC found to be the most suitable straw-return for lowering CFP and enhancing crop yield and SOC sequestration. However, to achieve the coordinated development of agriculture and the livestock industry it is necessary to remove some straw for animal feed and fuel, so WH-MN produced optimum yield and maintained SOC stock with low GHG emissions.

At the farm level, reducing agricultural water footprints

Beijing is one of the world's most water-stressed cities. Reducing agricultural water consumption has long been the cornerstone of municipal water strategy. The potential to decrease the life cycle (cradle to gate) water footprints of wheat and maize, which account for 94 percent of local grain output, was evaluated in this paper. The wheat-maize rotation system's consumptive and derivative water consumption was modeled using ISO 14046 under various irrigation and nitrogen (N) application choices. Although there was no significant production reduction when irrigation water volume was reduced by 33.3 percent compared to current practice, the water scarcity footprint and the water eutrophication footprint were reduced by 27.5 percent and 23.9 percent, respectively. Similarly, decreasing the nitrogen application rate by 33.3 percent from present practice did not result in a substantial yield decrease, but it did result in a 52.3 percent reduction in water eutrophication while keeping a comparable water scarcity footprint. These findings show that better water and fertilizer management has a lot of promise for lowering crop water footprints at the farm level. This scenario in Beijing is likely to be indicative of the difficulty that many of China's water-stressed areas face in finding a long-term agricultural solution.

Effects of Sheep Manure Combined with Chemical Fertilizers on Maize Yield and Quality and Spatial and Temporal Distribution of Soil Inorganic Nitrogen

In order to explore the influences of sheep manure mixed with chemical fertilizers upon the yield and quality of maize and the spatial and temporal distribution of soil inorganic nitrogen under the wheat‐maize rotation system, achieve increased yield and efficiency with rational fertilization of maize in this area, and at the same time provide a reasonable scientific basis for green production, an experiment was performed at Wanbei Comprehensive Experimental Station of Anhui Agricultural University in 2020 accordingly. The soil for the experiment is sand ginger black soil, and the subject is Zhengdan 958. The experiment adopts a randomized block design with 6 treatments: no fertilizer (T1), single application of the chemical fertilizer (T2), 15% sheep manure mixed with the chemical fertilizer (T3), 30% sheep manure combined with the chemical fertilizer (T4), 45% sheep manure added with the chemical fertilizer (T5), and only sheep manure (T6). The amount of nitrogen, phosphorus, and potassium applied in each treatment remains the same. The result of the experiment shows that T1 treatment has the lowest yield, followed by T6 treatment. The yield of sheep manure combined with the chemical fertilizer is much higher than that of pure sheep manure and no fertilizer. Among them, the yield of T3 is the highest and T4 is the lowest. There is no obvious variation between the combined treatments. Compared with single usage of the chemical fertilizer, the fat content of maize kernels treated with T3 and T4 is 8.9% and 5.6% higher than that of T2 treatment. The protein content of maize kernels treated with T3, T4, and T5 is 2.3%, 2.5%, and 2% higher than that of T2. It shows that the mixture of sheep manure and chemical fertilizer can improve the quality of maize kernels in some degree. The partial productivity of the nitrogen fertilizer in T3 and T5 treatments is 3.7% and 0.8% higher than that of T2 treatment, and the agronomic utilization rate of the nitrogen fertilizer is 10.9% and 1.6% higher than that of T2 treatment. T6 is much lower than that of T2 treatment. It certifies that the combined application of chemical fertilizers with sheep manure can increase the partial productivity and the agronomic utilization rate of the nitrogen fertilizer and increase crop yields and farmers’ income. The nitrate nitrogen of 40–60 cm soil layer is increased by 30.4%, 60–80 cm soil layer is increased by 56.5%, and 80–100 cm soil layer is increased by 11.6%. It shows that the mixed usage of organic and inorganic fertilizers can prevent nitrate nitrogen from moving to deep soil and reduce groundwater pollution.

Successive biochar amendment affected crop yield by regulating soil nitrogen functional microbes in wheat-maize rotation farmland

Biochar has attracted increased attention because of its potential benefits for carbon sequestration, soil fertility, and contaminant immobilization. However, mechanism of long-term successive biochar amendment affected crop yield by regulating soil properties and nitrogen (N) functional microbes is still unclear by now. A field fixed experiment was carried out from 2011 to 2018 that aimed to study the effects of successive biochar on soil properties, soil nitrogen functional microbial genes, and grain yield in wheat and maize rotation farmland in Northern China. Four straw biochar treatments were tested in this study: 0 (BC0, CK), 2.25 (BC2.25), 6.75 (BC6.75), and 11.25 (BC11.25) Mg ha−1. The results showed that, after seven wheat-maize rotations, the total organic carbon (TOC), total N (TN), NO3−, available potassium (AK), and the C/N ratio in 0–20 cm topsoil were increased significantly following biochar application; however, there were no obvious differences in available phosphorus (AP) and NH4+ among biochar treatments. Biochar also resulted in a significant increase in crop yield and NO3− accumulation in 0–200 cm soil layer, with the highest yield in BC6.75. Furthermore, a marked increase was found in the amoA gene abundance in topsoil; however, it decreased significantly with excessive biochar application (BC11.25). At wheat maturity, the nirS gene abundance consistently decreased following biochar application, whereas the nosZ gene abundance initially increased and then decreased (peaking in BC6.75); however, no obvious changes in the nirK gene were observed. At maize maturity, biochar significantly increased the nirS and nosZ gene abundance in topsoil, especially in BC6.75. In addition, redundancy analysis indicated that the soil moisture content, AP, AK, TN, TOC, NO3−, NH4+, pH, and C/N ratio had markedly effects on the abundance of the amoA, nirK, nirS, and nosZ genes. In general, biochar-induced alterations of soil properties resulted in changes of gene abundance of soil nitrifying and denitrifying bacteria, and eventually affecting crop yields.

Flower strips as a bridge habitat facilitate the movement of predatory beetles from wheat to maize crops.

Generalist predators play a key role in the biocontrol of insect pests in agricultural systems. However, predators are subject to frequent mortality events due to periodic disturbance regimes such as crop planting and harvest, which inevitably affect the population development of predators. Conservation of predators in this critical period is important for double-cropping systems such as winter wheat and summer maize, the most widely used cropping system in North China. Planting Cnidium monnieri flower strips at field borders could not only serve as a bridge habitat to conserve the dominant predator Propylaea japonica in wheat fields during harvest but also help the predator immigrate to adjacent maize fields. The predator abundance was 7-fold higher on flower strips than that on natural vegetation strips during the wheat postharvest period and before the maize plant emergence for about a month, and its abundance in maize fields planted with flower strips was nearly 2-fold higher than that in maize fields planted with natural vegetation strips. Moreover, 77.56% of predators that entered maize fields were proven to originate from flower strips. Our findings provided evidence that manipulating flower strips as a bridge habitat in wheat-maize rotation fields could conserve P. japonica during crop phenophase changes, and we quantitatively testified that the proportion of this predator in maize fields derived from flower strips. In practice, such a strategy may also be applied in other double-cropping and triple-cropping systems. © 2020 Society of Chemical Industry.

The salt-tolerant phenazine-1-carboxamide-producing bacterium Pseudomonas aeruginosa NF011 isolated from wheat rhizosphere soil in dry farmland with antagonism against Fusarium graminearum

Fusarium head blight (FHB) disease caused by Fusarium graminearum (Fg) seriously affects the yield and quality of wheat. In this study, after bacterial community analysis of two wheat rhizosphere soils, the genus Pseudomonas was shown to be enriched in normal dry farmland (maize-wheat rotation) compared to that observed nearby paddy farmland (rice-wheat rotation) with serious FHB disease. Subsequently, a P. aeruginosa strain, NF011 with the highest antagonistic activity against Fg and excellent tolerance to 8.0 % of NaCl was isolated from the wheat rhizosphere soil in the normal dry farmland. Dual culture assay results showed that NF011 is a broad-spectrum fungicide for controlling six wheat pathogenic fungi. The major antifungal compound produced by NF011 was identified as phenazine-1-carboxamide (PCN) by LC–MS and nuclear magnetic resonance. 1.0 × 108 CFU/mL of NF011 or 32 mg/L of PCN could completely inhibit Fg spore germination and resulted in the destruction of Fg hypha vacuoles. Mannitol, peanut meal, beef extract, metal ions (Mn2+, Ca2+, Fe2+, and Mg2+), and amino acids (Arg and Lys) could promote the production of PCN by NF011, moreover, the optimal pH and temperature was 6.0 and 20 °C. The PCN produced by NF011 under the optimized culture conditions reached 436.55 ± 11.06 mg/L, 4.90-fold higher than that observed under the basic culture conditions. Finally, infection experiment results showed that NF011 can effectively prevent Fg spores from infecting wheat spikes and wheat grains and suppress the production of deoxynivalenol (DON). Therefore, the salt-tolerant PCN-producing NF011 has the potential to control wheat fungal disease.

No tillage with previous plastic covering increases water harvesting and decreases soil CO2 emissions of wheat in dry regions

In arid and highly populated areas, water shortage and soil CO2 emission (CE) are seriously threatening the sustainability of agriculture. Optimization of tillage, irrigation, and nitrogen (N) application within cropping systems are keys to reducing CE. We hypothesized that an integrated system could increase crop yields and improve water harvesting, while reducing CE and enhancing C sequestration potential from crop production. In 2016–2018, this hypothesis was tested under spring wheat of maize-wheat rotation in field experiments in the arid inland irrigation of China. This research evaluated how no tillage, reduced the supply levels of irrigation and N affect crop yield, water harvesting, and CE, C sequestration potential of following spring wheat after plastic-mulched maize. Across the three study years, tillage practice, irrigation level, and N level individually had a significant effect on grain yield, water harvesting, and CE characteristics of wheat in each year, but the interaction among the three factors was hardly significant. No tillage with previous residual plastic covering (NTP), reduced irrigation, and reduced N application increased grain yield, improved water harvesting of wheat, but decreased CE. On average, NTP practice combined with a reduction of 20 % in irrigation and N supply levels (i.e., the optimized system, NTPI2N2), increased grain yield, soil water storage between pre-sowing and post-harvesting (wheat harvesting), and the ratio of transpiration to evaporation (T/E) by 13.6, 150.0, and 79.7 % (P < 0.05), respectively, compared to conventional tillage with local conventional high supply level in irrigation and N (i.e., the control, CTI2N3). The optimized system reduced CE and carbon emission intensity (CEI) by 31.3 % and 39.0 % (P < 0.05) compared to the control treatment, respectively. However, the optimized system had 7.5, 12.6, 7.5, and 57.4 % (P < 0.05) greater net primary production (NPP), net ecosystem production (NEP), carbon in harvested wheat (harvest-C), and the ratio of NPP/CE than the control. It indicates that the optimized system had greater potential for enhancing soil C sequestration. Therefore, no tillage with previous residual plastic covering from the previous maize combined with a 20 % reduction in both irrigation and N levels is a promising strategy to improve water harvesting, reduce CE, and enhance soil C sequestration potential of wheat production in dry regions.

Quantifying the compensatory effect of increased soil temperature under plastic film mulching on crop growing degree days in a wheat–maize rotation system

• The compensatory effect (CE) under plastic mulching (PM) had a time window. • Crop apical meristem emergence can be the reference terminal time for the CE. • CE disappeared due to no soil temperature increases around wheat regreening stage. • For summer maize, CE did not last by the unfavorable delayed senescence under PM. • Compensatory coefficient can be calculated by inflection points of logistic equation. Plastic film mulching (PM) has a compensatory effect on crop growing degree days by increasing soil temperature. However, only few studies addressed the question whether a terminal time for the compensatory effect window exists and if it exists how it can be quantified. The objective of this study was to use the logistic equation to describe the cumulative crop plant height and to quantify the compensatory effect. Crop apical meristem emergence was used as the reference for the terminal time of the compensatory effect window. A three-year field experiment (2013–2016), conducted under continuous PM in a typical winter wheat ( Triticum aestivum L.) and summer maize ( Zea mays L.) rotation on the Loess Plateau, Northwest China, indicated that the logistic equation performed well in representing and quantifying the compensatory effect of PM. The compensatory effect of PM reached a plateau during winter wheat growing seasons due to the lack of increased soil temperature during regreening stage, and during summer maize growing seasons due to unfavorably delayed senescence. The terminal time can be estimated during winter wheat and summer maize growing seasons from thermal time nodes at the maximum slope (t 2 ) and second inflection point (t 3 ), respectively. The compensatory coefficients could be estimated by thermal time intervals of (0, t 1 ) and (t 1 , t 2 )in winter wheat growing seasons and thermal time internals (0, t 1 ), (t 1 , t 2 ), and (t 2 , t 3 ) in summer maize growing seasons, respectively. Compensatory coefficients tended to increase with maize plant development. The minimum data requirement using a logistic equation to calculate compensatory coefficients includes data for staged plant height and mean daily air temperature.