Winter Wheat-summer Maize Rotation System Research Articles

Phosphorus fertilizer management for high yields in intensive winter wheat-summer maize rotation system: Integrating phosphorus budget and soil available phosphorus

Overuse of phosphorus (P) fertilizer in crop cultivation accelerates the consistent increase in soil P accumulation and increases the risk of P leaching from the agricultural system. The long-term implications of balanced P management on soil P availability and crop P uptake are still unknown. A three-year field experiment with six different P rates was conducted to determine the effect of a balanced P application strategy on crop yield, P uptake, soil P accumulation, and P transformation in a winter wheat-summer maize rotation system. The results found that the yield and P uptake of summer maize and wheat increased linearly with P fertilization up to 12.5 kg P ha–1, after which they stabilized, and the critical threshold is 50 kg P ha–1 for winter wheat. The soil P budget under agronomic thresholds from 2017 to 2020 was observed as –2.99 to –11.04 kg P ha−1 for maize but 15.1–24.5 kg P ha–1 for wheat. Excessive P fertilization accelerated the downward movement of soil P and stocked it in the deep soil in the form of soil labile P and moderately labile P, increasing the risk of soil P leaching. The annual application of 600 kg ha–1 P fertilizer substantially increased the total P concentration by 30%–99% from deep soil to topsoil compared to the no P treatment, while the 75 kg ha–1 and 150 kg ha–1 P fertilizer treatments did not affect soil P accumulation along the soil profile. Soil Olsen-P concentration to meet crop yield requirements is still far from meeting the critical environmental threshold of 47.6 mg kg–1 and increased slightly by an annual 2.39 mg kg–1 under the balanced P fertilization strategy. An annual negative soil P budget of 3–11 kg ha–1 for summer maize could sustain optimal yields and P use efficiency. Winter wheat cultivation required additional P application to reach the agronomic threshold, set at 15–25 kg ha–1 annually. In conclusion, balanced P fertilization can reduce soil P surplus and subsoil P stock while maintaining crop yields.

Evaluating the adoption of irrigation technology in a well-irrigated winter wheat－summer maize cropping system

Determining suitable irrigation technology is of paramount for promoting water-saving agriculture, particularly for winter wheat-summer maize rotation system in well-irrigated regions. To optimize and assess the efficacy of various irrigation technologies (specifically, semi-fixed sprinkler irrigation, walking sprinkler, semi-automatic buried telescopic sprinkler irrigation, thin-soft spray tape irrigation, drip irrigation, self-driven winch sprinkler and manually moving spray gun irrigation, marked as A, B, C, D, E, F and G) applied in south central North China Plain, we first conducted an economic analysis for the winter wheat-summer maize rotation. Subsequently, employing a comprehensive set of 20 indicators spanning economic, societal, technological, ecological, and resource aspects, we employed a TOPSIS model with integrative weighting approach using “AHP + Entropy”. We also employed principal component analysis and the Sankey diagram method to explore characteristics of different irrigation techniques and indexes. Irrigation mode E, conserving energy by 63.19% compared to mode B and offering labor savings five times greater than the mode D. The highest economic benefit for the rotation system was observed with the mode C, resulting in a 25.26% increase compared to the mode G. The top three irrigation modes based on scores were D, G, and E, with scores of 0.532, 0.490, and 0.474, respectively. The Sankey diagram revealed distinct preferences among different agricultural entities for specific irrigation modes. For specific stakeholders, we recommend irrigation modes D, G, F, and B for small farmers, large and specialized family businesses, family farms, and farmer cooperatives, respectively. In conclusion, our findings provide valuable scientific support and recommendations for the practical application of irrigation technology in agricultural production.

Ammoniated straw returning: A win-win strategy for increasing crop production and soil carbon sequestration

Increasing crop production and soil carbon sequestration is critical for sustainable agricultural development. Straw returning, a common agricultural practice, positively affects grain yield and soil organic carbon. Nevertheless, the slow decomposition rate and high carbon-to-nitrogen ratio of straw are significant obstacles to its effectiveness. Ammonifying straw using urea and calcium hydroxide may be a promising solution, whereas limited information is available on the impacts of ammoniated straw returning on crop production and soil carbon sequestration. Therefore, in a winter wheat-summer maize rotation system, we conducted an experiment with three straw returning treatments (T1, straw removal; T2, traditional straw returning; T3, ammoniated straw returning) to investigate their impacts on crop growth, grain yield and yield components, carbon inputs and outputs, and net ecosystem carbon budget (NECB). The results showed that T3 outperformed T2 regarding increasing leaf area index and aboveground biomass. Ear density and thousand kernel weight of winter wheat and hundred kernel weight of summer maize were ranked T1 < T2 < T3, with no significant differences between treatments for other grain yield components. Consequently, winter wheat, summer maize, and annual grain yields were the highest under T3, followed by T2 and T1. In comparison with T1, T2 and T3 increased annual total carbon inputs by 5463 and 7271 kg C ha–1, respectively, due to the increased carbon inputs from returned straw and net primary productivity. Annual carbon total outputs, primarily from aboveground biomass removal at harvest and carbon respiration, increased by 3305 kg C ha–1 under T2 and 4264 kg C ha–1 under T3, compared with T1. Balancing annual total carbon inputs and outputs, T1, T2, and T3 had annual NECB values of –1215, 944, and 1793 kg C ha–1, respectively. Therefore, the T1 agroecosystem acted as a carbon source, whereas the T2 and T3 agroecosystems, particularly T3, acted as a carbon sink on an annual scale. These results suggest that ammoniated straw returning may be a superior straw application practice for increasing crop production and soil carbon sequestration simultaneously.

Response of net water productivity to climate and edaphic moisture in wheat-maize rotation system

Comprehending the mechanisms underlying the response of water productivity to changing climate is essential for developing effective strategies that can maintain sustainable agricultural productivity and ecological stability amidst water scarcity and climate change. This study aimed to clarify the effects of climate and associated biologic and abiotic factors on the net water productivity (NWP) in the winter wheat—summer maize rotation system within the North China Plain (NCP), through integrating spatial-temporal pattern analysis, the Optimal Parameter-based Geographical Detector model, Random Forest, and Structural Equation Modeling. Despite climate warming and water scarcity, the NWP in the vast majority of rotation systems within the NCP exhibited an increasing trend between 2000 and 2019, which was anticipated to persist in the future. From 2000–2019, the impact of climate on the NWP exerted a fluctuating diminishment, besides the influence of WS. It is essential to add adaptive strategies that can cope with WS fluctuation in future management, to better tackle climate variability. Apart from direct effects, meteorological factors indirectly induced NWP variation primarily by influencing edaphic moisture dynamic and crop growth factors. In the paths underlying the effect of climate change on NWP, positive and negative effects coexisted. Edaphic moisture within the 40–100 cm layer played an important role in affecting NWP throughout rotation systems. To sustainably improve NWP, it was advisable to adopt deeper-rooting crop varieties in conjunction with moderate deficit irrigation and improving topsoil water retention capability. Overall, we incorporated soil and crop factors into the framework of climate impact research, providing a systematic elucidation for the mechanisms through which climate change affects NWP. Additionally, the conclusions were based on a continuous spatiotemporal framework that accounted for the geospatial heterogeneity of variables, thereby giving conclusions ample regional universality.

Managing nitrogen for sustainable crop production with reduced hydrological nitrogen losses under a winter wheat-summer maize rotation system: an eight-season field study.

Excessive nitrogen (N) application in wheat-maize cropping systems was adjusted towards more sustainable practices to reduce hydrological N losses while maintaining crop yield. In comprehensive quantification of N management effects on crop yield, N use efficiency (NUE), hydrological N losses, and soil nitrate residual across eight seasons, we have added to growing evidence of strategies beneficial for sustainable crop production with lower hydrological N losses. The results show that adjusted N practices enhanced crop yield and NUE, as compared to farmer's practices, but benefits varied with N rates and types. Optimized N treatment (OPT, 180 kg N ha-1 in both maize and wheat seasons) with or without straw returning produced the most crop yield. They increased maize yield by 5.5% and 7.3% and wheat yield by 6.2% and 3.2% on average, as compared to farmer's practice with huge N application (FP, 345 kg N ha-1 and 240 kg N ha-1 in maize and wheat). Regulation of N release through amendment with controlled release urea at a rate of 144 kg N ha-1 crop-1 (CRU treatment) obtained 4.4% greater maize yield than FP, and sustained a similar wheat yield with less N input, resulting in the highest crop NUE. Additionally, CRU was most effective in mitigating hydrological N loss, with 39.5% and 45.5% less leachate N and 31.9% and 35.9% less runoff N loss than FP in maize and wheat seasons. Synthetic N input correlated significantly and positively with runoff and leachate N losses, indicating it was one of the dominant factors driving hydrological N losses. Moreover, compared to OPT, additional straw returning (STR) or substituting 20% of the nutrients by duck manure (DMS) further reduced runoff N discharges due to the fact that organic matter incorporation increased resilience to rainfall. N over-application in FP caused considerable nitrate accumulation in the 0-90-cm soil profile, while the adjusted N practices, i.e., OPT, STR, CRU, and DMS treatments effectively controlled it to a range of 79.6-92.9 kg N ha-1. This study suggests that efforts using optimized N treatment integrated with CRU or straw returning should be encouraged for sustainable crop production in this region.

Optimizing irrigation strategies for sustainable crop productivity and reduced groundwater consumption in a winter wheat-maize rotation system

Inefficient irrigation practices have hindered crop yields, wasted irrigation water resources, and posed threats to groundwater levels and agricultural sustainability. This study evaluated different irrigation strategies for a winter wheat-summer maize rotation system to identify sustainable practices for maintaining yields while reducing groundwater depletion. A two-year field experiment was conducted, implementing three optimized irrigation strategies during the winter wheat season: I-4 (irrigated until the soil water content (SWC) of the 40 cm soil layer reaches 60% of field capacity (FC), I-6 (irrigated until the SWC of the 60 cm soil layer reaches 80% FC), and a rainfed (R) as control. Irrigation was repeated when the SWC dropped to the specified level. No irrigation level was used during the summer maize season, except for irrigation after sowing that ensuring the normal emergence of maize. WHCNS (Water Heat Carbon Nitrogen Simulator) model was developed to simulate soil water dynamics, field water consumption, and yield of both crops. The result indicated WHCNS model accurately simulated water dynamics, consumption, and grain yield. Compared to R treatment, the I-4 treatment significantly increased annual crop yield by 19.83%–28.65% (p < 0.05), while maintaining similar crop water productivity. Furthermore, the I-4 treatment achieved comparable yields to the I-6 treatment, but with a 33.91% reduction in irrigation water use, resulting in a 33.46% increase in crop water productivity and a 90.53% increase in irrigation water productivity. From a sustainable perspective, the I-4 treatment effectively reduced field water losses and maintained relatively high soil water storage, particularly in the topsoil, which was beneficial for the early growth of subsequent crops. The R treatment greatly contributed to groundwater recharge when precipitation was sufficient, while it led to severe yield losses. Overall, under the condition of annual rotation planting systems, the I-4 treatment sustainably maintained yields with less irrigation, decreasing groundwater consumption. This approach could conserve regional water resources and groundwater table while upholding agricultural productivity and achieving system sustainable water use.

A dataset of carbon and water fluxes in farmland ecosystems at Gucheng Station (2020–2022)

Hebei Gucheng Agricultural Meteorology National Observation and Research Station (Gucheng Station) is one of the national field scientific observation and research stations approved by the Ministry of Science and Technology (MOST). Located in the irrigated high-yield agricultural area in the northern part of the North China Plain, it is a typical North China winter wheat-summer maize rotation system. Based on the eddy covariance technique, the observation of cropland ecosystem carbon and water fluxes has been carried out at Gucheng Station for a long time. Following the ChinaFLUX data processing protocols, we collected the carbon and water fluxes and auxiliary meteorological environment observations of the winter wheat and summer maize rotation ecosystem at Gucheng Station from 2020 to 2022, and produced a standardized dataset after data quality control and processing. This dataset has important scientific significance and practical application value in the assessment of farmland ecosystem carbon budget, water resources utilization, and the mitigation of the impact of adverse meteorological conditions on farmland ecosystems and agricultural production.

Spatial-temporal coupling pattern between irrigation demand and soil moisture dynamics throughout wheat-maize rotation system in the North China Plain

Irrigation water requirement (Iwr) and soil moisture (SM) are two essential metrics that guide scientific irrigation and agricultural water-saving practices. Although they have been extensively studied in the North China Plain (NCP), an exploration into their spatial-temporal coupling pattern remains absent. Here, the spatial-temporal coupling pattern underlying the variations of Iwr and SM across the winter wheat–summer maize rotation system within the NCP was elucidated from a geographic perspective, by developing a geo-statistic framework that integrated the global spatial autocorrelation, spatial hot-spot technique, geographically weighted regression, and the optimal parameters-based geographic detector. From 2000–2019, the Iwr and SM exerted a distinct geospatial heterogeneity. Winter wheat demonstrated a spatially descending gradient in Iwr from north to south, while the pattern in summer maize Iwr varied greatly across periods. Generally, winter wheat had a higher Iwr, while the geospatial pattern of summer maize Iwr displayed a greater variability. Spatial pattern of SM in 0–100 cm soil horizon exhibited an approximately inverse trajectory to that of Iwr, while SM in 100–200 cm horizon demonstrated a spatial staggered pattern. In most cases, there existed a notable negative coupling between Iwr and SM at 0–100 cm depth, but not universal at 100–200 cm. Nonetheless, a pronounced reciprocal enhancement mechanism between SM of two layers was confirmed. Between 2000 and 2019, a geospatial decoupling trend was detected between Iwr and SM throughout the NCP. Despite remaining universality, the pattern of high irrigation demand induced by soil moisture deficit was being weakened. Given these, climate-adaptive water-saving strategies were updated, which provide a new implication for regional agricultural water-saving practice and sustainable production.

A distributed agroecosystem model (RegWHCNS) for water and N management at the regional scale: A case study in the North China Plain

Process-based agroecosystem model is difficult to apply at the regional scale due to the complexity of model parameterization and execution efficiency. Thus, developing a regional agroecosystem model is challenging. In this study, a parallel computing framework is introduced to upscale an agroecosystem model (WHCNS model) from field to regional scale by integrating parallel computing, inversing modeling, and spatial calculation. The newly developed model was tested in the North China Plain (NCP) for modeling water consumption, N fate, and crop growth for winter wheat–summer maize rotation system under different water and N management practices. The optimum irrigation water and fertilizer N demands of winter wheat–summer maize system was estimated based on the auto-irrigation and auto-fertilization component in the model. Multisite testing showed that the model well reproduced soil water and N dynamics, crop biomass, LAI, yield, and crop N uptake, with R2 exceeding 0.886. The estimated annual average irrigation water and fertilizer N demands of winter wheat–summer maize rotation system was 395.8 mm and 529.5 kg N ha−1, respectively. Winter wheat was the major consumer of irrigation water and fertilizer N, accounting for 79.2 % and 54.4 % of annual irrigation water and chemical N fertilizer use, respectively. These results suggested that winter wheat was a crop with high water and fertilizer N demand in the NCP. The RegWHCNS model has potential value to assess and optimize regional water and N management for intensive agricultural-production systems. This study can provide as a scientific reference to upscale agroecosystem models from field to region for other agroecosystem models.

Comprehensive Effects of N Reduction Combined with Biostimulants on N Use Efficiency and Yield of the Winter Wheat–Summer Maize Rotation System

Biostimulants sprayed exogenously boost crop yield and quality. However, the effects of the co-application of biostimulants and fertilizers as base fertilizers in soil are still uncertain. The objective of this study was to investigate the overall effects of reducing N levels in conjunction with the application of biostimulants on the yield formation and N utilization of wheat and maize. Therefore, based on the winter wheat–summer maize rotation system in the modern R&amp;D base of Sichuan Agricultural University, soil enzyme activities, soil inorganic nitrogen dynamic content, crop nitrogen accumulation and transportation, crop yields, and composition were determined. To achieve this, a total of nine treatments were established based on the winter wheat–summer maize rotation system. The experiment included the following treatments: no fertilization (CK0); one-time application of common compound fertilizer (CK1, applied at a rate of 225 kg ha−1); common compound fertilizer as base fertilizer + urea as topdressing fertilizer (CK2, applied at a rate of 225 kg ha−1, base/topdressing, 6/4); biostimulant + common compound fertilizer with 20% or 30% N reduction (jf-20%, jf-30%); biostimulant chelated urea-formaldehyde fertilizer reducing N by 20%, 30%, or 40% (jn-20%, jn-30%, or jn-40%); and biostimulant chelated urea-formaldehyde fertilizer reducing N by 40% and combined with organic fertilizer, thereby totally reducing N by 27% (jny-27%). The results demonstrated that the application of a biostimulant increased the activities of urease, nitrate reductase, and nitrite reductase in the soil of wheat and maize during the flowering stage. At the same time, the amount of residual nitrate and ammonium N in the soil at maturity was reduced. Furthermore, when N application was appropriately reduced, wheat and maize plants treated with jf, jn, and jny showed a significant increase in N assimilation after the flowering stage, resulting in higher N accumulation in the grains at maturity and ultimately improving the yield compared to CK1 and CK2. The combined use of biostimulants also had a significant positive impact on N use efficiency (NUE). During the two-year period, the NUE in the wheat season showed an increase ranging from 6.70% to 24.00% compared to CK1 and from 5.30% to 22.60% compared to CK2. Similarly, in the maize season, the NUE increased by a range of 11.60% to 22.57% compared to CK1 and from 11.78% to 22.75% compared to CK2. Overall, biostimulants enhanced N absorption and transportation by matching crop N requirements in the mid-to-late stages and improved NUE and yield under appropriate N reduction. This study contributes to the design of improved measures for N reduction and yield stabilization in order to promote sustainable agricultural development.

The potential for soil C sequestration and N fixation under different planting patterns depends on the carbon and nitrogen content and stability of soil aggregates

The winter wheat-summer maize rotation system is common in the Huang-Huai-Hai Plain due to its consistent yield, however, it may cause soil quality degradation and increased risk of greenhouse gas emissions. To evaluate the effects of different planting patterns on soil organic carbon (SOC) and total nitrogen (TN) sequestration, as well as aggregate and C-N distribution, a three-year field experiment that included three annual double-cropping rotation patterns: winter wheat-maize (W-M), winter wheat-soybean (W-S), and winter wheat-sweet potato (W-SP) was conducted from 2020 to 2022, with W-M as the control. Our research revealed significant differences in soil carbon sequestration rates among the various planting systems. Specifically, the SOC stock in the W-S system was 12.21 % to 24.51 % higher than that of the W-M system and 10.28 % to 35.73 % higher than that of the W-SP system. While TN stock demonstrated an increase of 9.85 % to 37.39 % compared to the W-M system and 8.14 % to 67.43 % compared to the W-SP system. Moreover, SOC and TN sequestration were largely related to soil aggregates, with macroaggregates being the primary component in both W-S and W-M planting patterns, while microaggregates were more common in W-SP patterns. The accumulation of SOC and TN occurred mainly in macroaggregates, leading to a significant increase in C and N content in soil macroaggregates under the W-S planting pattern. The structural equation model suggested that the TN stock had both direct and indirect effects on SOC sequestration, with a total impact coefficient of 0.872. Our three-year field results indicate that the W-S model is advantageous in enhancing soil C and N sequestration capacity and had great potential in reducing greenhouse gas emissions in farmland.

Novel water-saving cultivation system maintains crop yield while reducing environmental costs in North China Plain

Poor irrigation practices are accelerating groundwater depletion, together with negative effects on climate change and had therefore threatened agricultural sustainability in North China Pain (NCP). Integrated optimization of cropping systems and water-saving cultivation techniques is critical. We developed a novel water-saving cultivation system that incorporates application of disposable pre-sowing irrigation in wheat to 85−90% of field capacity and irrigation only while sowing maize under winter wheat-summer maize rotation system (T1W0) and winter wheat/summer maize-single maize rotation system (three harvests in two years, T2W0). The T1W0 significantly reduced irrigation amount by 42.1% and mitigated carbon footprint by 35.5%, and achieved 92.2% of grain yield compared with conventional farming practice (three irrigation for wheat). Crop modeling showed that T2W0 had the potential of sustainable irrigation with groundwater decline at 0.12 m year−1. The T1W0 is recommended for most areas in NCP while T2W0 is for severe ground funnel areas.

Optimizing nitrogen input and nitrogen use efficiency through soil nitrogen balance in a long-term winter wheat-summer maize rotation system in North China

Nitrogen (N) fertilizer application has revolutionized agricultural productivity, but excessive N fertilizer application has resulted in low N use efficiency (NUE) and high N accumulation, increasing the risk of N losses. Here, we hypothesize that the apparent N balance can be used as an indicator to identify the N input for obtaining high yield with a high NUE. Thus, a 12-year field experiment involving seven N treatments (0, 120, 240, 360, 480, 600, and 720 kg N ha–1 per year) in a typical winter wheat-summer maize rotation system in North China was conducted to investigate the response of crop yield and NUE to the N balance under different N application rates and to identify the N input–output framework. The annual yield increased in a linear-platform and NUE decreased with increasing N fertilizer application. The N balance and yield are strongly correlated to predict changes in yield, and a critical N balance of 44.4–64.9 kg N ha–1 per year was recommended for optimal yield with minimal risk of N loss. The N balance and NUE can be presented in the framework of N input–output, and the critical N input estimated from the N balance of 217–252 kg N ha–1 could obtain high productivity with high NUE (74.3–79.6 %). Overall, the apparent N balance could be used as a key indicator for optimizing N input, providing a strong reference for limiting N excess in intensive production areas and evaluating agronomic and environmental performance in N management. Data AvailabilityThe datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request.

Identifying the critical phosphorus balance for optimizing phosphorus input and regulating soil phosphorus effectiveness in a typical winter wheat–summer maize rotation system in North China

Phosphorus (P) is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield. Excessive P fertilizer application is widespread in agricultural production, which not only wastes phosphate resources but also causes P accumulation and groundwater pollution. Here, we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency (PUE). A 12-year field experiment with P fertilization rates of 0, 45, 90, 135, 180, and 225 kg P2O5 ha−1 was conducted to determine the crop yield, PUE, and soil Olsen-P value response to P balance, and to optimize the P input. Annual yield stagnation occurred when the P fertilizer application exceeded a certain level, and high yield and PUE levels were achieved with annual P fertilizer application rates of 90–135 kg P2O5 ha−1. A critical P balance range of 2.15–4.45 kg P ha−1 was recommended to achieve optimum yield with minimal environmental risk. The critical P input range estimated from the P balance was 95.7–101 kg P2O5 ha−1, which improved relative yield (>90%) and PUE (90.0–94.9%). In addition, the P input–output balance helps in assessing future changes in Olsen-P values, which increased by 4.07 mg kg−1 of P for every 100 kg of P surplus. Overall, the P balance can be used as a critical indicator for P management in agriculture, providing a robust reference for limiting P excess and developing a more productive, efficient and environmentally friendly P fertilizer management strategy.

Responses of soil CO2 emissions to tillage practices in a wheat maize cropping system: A 4-year field study

Soil CO2 emissions respond differently to different tillage practices. However, limited information is available regarding the impact of conventional tillage (CT) and no-tillage (NT) on soil CO2 emissions and the primary controlling factors or processes. The goal of this study is to derive the relationship of soil CO2 emissions with soil physicochemical properties from differently tilled soils in a typical winter wheatsummer maize rotation system. We hypothesized that soil tillage practices would impact the soil carbon cycle by modifying soil physical and chemical properties, which would in turn affect the soil CO2 emissions. The study was conducted from 2018 to 2022 with two tillage practices using a randomized complete block design with three replicates. A leading international real-time monitoring system in situ was used to collect soil CO2 emission data. Cumulative soil CO2 emissions were reduced by 28.7% in maize and increased by 9.0% in wheat under NT as compared to CT. On an annual scale, the cumulative CO2 emissions were decreased by 20.5% in NT as compared to CT. Maize season accounted for 70%78% of soil CO2 emissions. NT improved the aboveground biomass by 7.74% and 6.44%, and grain yields by 10.2% and 4.49% for maize and wheat, respectively. The soil CO2 emission intensity of maize was reduced by 35.9% under NT as compared to CT. No significant differences were discovered under the two tillage practices for soil CO2 emission intensity of wheat. For maize, NT increased the bulk density, subsequently decreasing soil temperature and increasing soil moisture. NT also led to higher soil organic carbon and total nitrogen content, ultimately resulting in a significant reduction in soil CO2 emissions. For wheat, NT increased soil bulk density, further increasing soil moisture and lowering soil pH. NT thus resulted in lower soil organic carbon and total nitrogen content, ultimately leading to enhanced soil CO2 emissions. Some of these observations might not be consistent with theoretical predictions, which indicated that the unconsidered factors of actual field conditions might have much significant effects. Overall, NT can be extensively used as an eco-friendly cropland tillage practice based on its positive effects of reducing CO2 emissions and increasing crop yields.

Soil Compaction and Maize Root Distribution under Subsoiling Tillage in a Wheat–Maize Double Cropping System

Huang-Huai-Hai Plain is the most important region for grain production in China. In this area, long-term rotary tillage in winter wheat and no tillage in summer maize have significantly increased soil bulk density, which impede maize root growth and reduce the grain yield. Subsoiling tillage is an effective practice to improve soil properties and crop growth. The objective of this study was to investigate the integrated effects of subsoiling tillage in both winter wheat and summer maize seasons on soil bulk density, maize root growth and spatial distribution. A two-year field experiment was conducted in winter wheat–summer maize rotation system. Tillage treatments included rotary tillage (RT) and subsoiling tillage (ST) in wheat season, and no tillage (NT), inter–row subsoiling tillage (STIR), and on–row subsoiling tillage (STOR) in maize season. It was found that in the second year, i.e., in 2018, ST decreased soil bulk density by 3.87% and increased porosity by 5.86% at 30–40 cm soil depth at maize maturity. Meanwhile, maize root length density at 40–50 cm depth increased by 30.00% and grain yield increased by 4.70% under ST. In maize season tillage treatments, STOR decreased soil bulk density by 4.52% and increased soil porosity by 6.96% at 20–30 cm soil depth. Compared with NT, the STOR significantly increased maize root length density at 20–30 cm soil depth by 78.45%, and increased root length density in a horizontal area 0–10 cm for both years, with a significant increase of 58.89% in 2018. Therefore, this study demonstrated that in the Huang-Huai-Hai Plain, which has a tidal soil type, subsoiling tillage in winter wheat season and on–row subsoiling tillage in maize season can loosen the soil and improve vertical extension of maize root system in the soil.

Maize straw mulching with no-tillage increases fertile spike and grain yield of dryland wheat by regulating root-soil interaction and nitrogen nutrition

Straw mulching increases soil water availability, but the influence of tillage practices with straw mulching on soil water, soil nitrogen, root distribution, and the physiological response of wheat plants is poorly understood. Field experiments (2013–2017) were conducted to determine the combined effects of straw mulching (0 and 8,000 kg ha−1) and tillage methods (no-tillage, rotary tillage, and plow tillage) on soil water, N, root distribution, plant N nutrition, tiller capability, and grain yield of dryland wheat. Straw mulching with no-tillage showed higher soil moisture, mineral N, and Olsen-P content than no-mulch with rotary tillage or plow tillage. These changes increased the total root length and surface area in the 0–20 cm soil layer but not in the 20–40 cm soil layer. Topsoil foraging strategies of root increased total N uptake, wheat return N from straw, and N balance while reducing N surplus, indicating that maize straw harvesting by mulching with no-tillage leads to a more efficient N recycling in the winter wheat–summer maize rotation system. Straw mulching with no-tillage showed greater aboveground plant dry mass and shoot N%, leading to increased plant N nutrition, tillering capability, and grain yield. Our results indicated that maize straw mulch with no-tillage increased fertile spike and grain yield by increasing soil water and N availability and maximizing root-soil interactions among the different combinations studied. Maize straw mulching with no-tillage could hence be recommended to dryland farming communities to transition from rotary tillage to a no-tillage conservation system and to increase soil and crop productivity in the maize-wheat rotation system.

Climate and management impacts on the spatiotemporal dynamics of water-carbon fluxes in the North China Plain

Evapotranspiration (ET) and gross primary production (GPP) over agroecosystems could be noticeably altered by climate change and human activities. A better understanding of the impacts on water-carbon interactions and the underlying mechanisms, are crucial to improve water use efficiency (WUE). Comparing to 23 site-years of observations, regional ET dataset and statistical yields, the Remote Sensing-based cropland Ecohydrological Model (ReSEM) was validated to estimate the spatiotemporal dynamics of ET, GPP and WUE for dryland agroecosystems in the North China Plain (NCP) from 2001 to 2018. Spatially, the distributions of mean annual ET, GPP and WUE were comparable which changed obviously in different climatic conditions while varied slightly between various irrigation areas. The significantly increased WUE occurred in 38.6 % cropland, mainly located in the humid south regions with less irrigation requirement and the central sub-humid areas along the Yellow River with access to surface irrigation. The averaged increasing trend of WUE in the heavily irrigated semi-arid areas was relatively low. The temporal dynamic of regional mean WUE indicated a significantly increased rate of 0.026 gC kg−1H2O per year during 2001–2018. The spatiotemporal trends of WUE were mainly resulted from the significantly increased GPP rather than ET. The experimental simulations demonstrated that agricultural management dominated the interannual trend of WUE, whose relative contribution (79.5 %) was obviously larger than that of air CO2 concentration (40.2 %) and climate variable change (−19.7 %). Besides, the effects of agricultural management on WUE were further divided based on the classified six cropping systems, 82.4 % of which was attributed to the management of winter wheat-summer maize rotation system. This study sheds light on the improvement of WUE for dryland agroecosystem under changing environments and highlights the dominant impact of agricultural management.

Optimized tillage improves yield and energy efficiency while reducing carbon footprint in winter wheat-summer maize rotation systems

Conventional tillage consumes a lot of energy and produces a lot of greenhouse gases (GHGs), with quite limited contribution to food production. Optimizing tillage practices is an important measure to save energy, protect the environment and increase productivity. Based on this concept, a field experiment of two years duration (2019–2021) was performed to assess the impacts of various tillage techniques on grain yield, energy balance, carbon footprint (CF), and economic benefits of a winter wheat-summer maize rotation system in the Loess Plateau of China. The treatments included conventional tillage (CT), no-tillage (NT), ridge cultivation with no-tillage (RNT), and occasional tillage (OT). This study is the first to evaluates the economic and environmental benefits of OT and RNT in dry farming. The total annual average greenhouse gas emissions calculated through the life cycle assessment are 2869.2–3407.6 kg CO2-eq·ha−1, and the energy consumption and output are 28.2–37.7 GJ ha−1 and 575.2–659.0 GJ ha−1, respectively. The net ecosystem economic benefit is 26,206.6–34,787.4 CNY ha−1. Compared with CT, annual crop yields of RNT, OT and NT have increased by 13.5%, 15.4% and 4.0%, respectively, energy utilization efficiency has increased by 47.8%, 31.2% and 35.3%, and carbon footprint has been reduced by 79.3%, 46.2% and 73.2%, economic efficiency has increased by 32.7%, 29.8% and 19.6%, respectively. Despite reducing energy consumption and carbon footprint, NT has no significant impact on annual crop yields. Optimizing tillage practices (RNT and OT) can achieve higher economic and environmental benefits. The Z-score shows that RNT in dryland agroecosystems can be used as a promising tillage practice to boost crop productivity, energy efficiency and economic efficiency, reduce CF, and achieve sustainability. RNT can be selected as the recommended agricultural management measure suitable for areas with similar climatic patterns in the Loess Plateau.

Contrasting effects of biochar- and organic fertilizer-amendment on community compositions of nitrifiers and denitrifiers in a wheat-maize rotation system

This research investigated the N2O fluxes and community compositions of nitrifiers and denitrifiers in a winter wheat-summer maize rotation system on the North China Plain. The experiment included three treatments: 1) a control treatment (CK); 2) biochar at 10.0 t ha–1 yr−1 (C); and 3) organic fertilizer at 7.5 t ha−1 yr−1 (M). The application of biochar reduced the cumulative N2O emissions by 47.7% and 62.2% in the maize and wheat seasons, respectively, compared with those of the CK treatment. Organic fertilizer increased the cumulative N2O emissions by 311.1% in the maize season and had no significant effects on them in the wheat season. Organic fertilizer reduced the cumulative N2O emissions by 39.8% in the nonfertilizer period of the maize season. The cumulative N2O emissions in the maize season accounted for 75.2–90.0% of the annual emissions among all the treatments. Biochar and organic fertilizer affected soil N2O emissions mainly by changing soil denitrifiers. In the maize season, the lower abundances of Candidatus Nitrosoarchaeum (AOA-amoA), Nitrosomonas (AOB-amoA), Mesorhizobium (nirK), Magnetospirillum (nirS) and Halomonas (nirS) may result in lower N2O emissions in the biochar treatment, and organic fertilizer had a similar influencing mechanism on N2O emissions during the nonbasic fertilizer and nontopdressing periods of the maize season. In the wheat season, the dominant genus Alicycliphilus (nosZ) was the major contributor to decreasing N2O emissions in the biochar treatment, while there was no biomarker related to N2O emissions in the M treatment. The soil pH, NO3−-N content and water-filled pore space (WFPS) were the key factors shifting the community compositions of nitrifiers and denitrifiers in this study. The application of biochar could be a better practice to improve saline-alkali soil with lower N2O emissions. These findings will improve our understanding of the nitrifiers and denitrifiers response to biochar and organic fertilizer.