Winter Wheat-summer Maize Research Articles

Eight years of variations in ecosystem respiration over a residue-incorporated rotation cropland and its controlling factors

The carbon dioxide emissions from cropland play important roles in the regional carbon budget. In this study, continuous measurements of the ecosystem respiration (RE) were obtained using the eddy covariance technique in a winter wheat–summer maize double cropping agroecosystem mainly between 2004 and 2012 in order to identify the among-year variations in RE and the related factors responsible. The annual RE, estimated by Lloyd and Taylor model, which was the most accurate, was 1866.4 ± 105.75 g C m−2 year−1 and it ranged from 1650.68 g C m−2 year−1 to 1945.57 g C m−2 year−1 during the eight years. The seasonal RE values were 867.98 ± 125.24 g C m−2 year−1 and 890.55 ± 131.34 g C m−2 year−1 for wheat and maize, respectively. Additionally, crop residue carbon ranged from 322.73 g C m−2 year−1 in 2012 and 453.49 g C m−2 year−1 in 2007. Correlation analysis indicated that the interannual variations in wheat and maize RE were correlated with the seasonal mean soil water content (W-Ws) and maximum leaf area index (W-LAImax) of wheat, and seasonal mean air temperature of maize (S-Ta), respectively. A rest method was attempted to investigate whether these relationships were occasional or inevitable. The rests of RE, i.e. the difference between simulated and observed RE values, were significantly influenced by LAI of wheat and hourly Ta of maize season but not by hourly Ws of maize season, indicating that the influence of W-LAImax and S-Ta on RE were inevitable outcomes and that of W-Ws on wheat RE was occasional. So we suggested that one should not confirm the controlling factors of interannual variations in carbon fluxes just from simple relationships, which may be statistical coincidences and do not correlated with biotical processes.

Crop yield and N2O emission affected by long-term organic manure substitution fertilizer under winter wheat-summer maize cropping system

Application of organic manure combined with synthetic fertilizer can maintain crop yield and improve soil fertility, but the long-term effects of substituting different proportions of synthetic fertilizers with organic manure on N2O emission remain unclear. In this study, field experiments and DNDC model simulations were used to study the long-term effects of substituting synthetic fertilizers with organic manure on crop yield and N2O emission. The field experiment was conducted at Guanzhong Plain, northern China, under a wheat-maize cropping system. Six treatments were included: no fertilization (CK); synthetic nitrogen (N), phosphorus (P) and potassium (K) fertilizers (NPK); and 25%, 50%, 75% and 100% of the synthetic N substituted by dairy manure (25%M, 50%M, 75%M, and 100%M), respectively. The DNDC model was calibrated using the field data from the NPK treatment from 2014 to 2017 and was validated for the other treatments. The results showed that the DNDC model can successfully simulate the crop yield (e.g. nRMSE < 5%) and annual N2O emission (nRMSE < 20%). In addition, a 30-year simulation found that organic manure substitution treatments could maintain wheat yield well, and the yield variation between different years was small. However, relative to the NPK treatment, the maize yields for the first 6 and 7 years were lower under 50%M and 75%M, and under 100%M maize yields were reduced for the first 15 years. The long-term simulation showed that N2O emission of fertilized treatment had an increasing trend over time, especially the 75%M treatment where the N2O emission was higher than that of NPK treatment after 25 years of fertilization. The annual mean N2O emission under different treatments was, in decreasing order, NPK > 25%M > 50%M > 75%M > 100%M > CK. The yield-scale N2O emission and emission factor were highest for the NPK treatment. Considering crop yield, yield stability and N2O emission, substitution of 25% synthetic fertilizer by organic manure can simultaneously ensure crop productivity and environmental protection under the tested environment.

Global sensitivity and uncertainty analysis of the dynamic simulation of crop N uptake by using various N dilution curve approaches

Abstract Crop nitrogen (N) uptake is a key process in soil-crop models. This process affects crop growth and soil N cycling and determines crop quality. However, crop N uptake modeling remains uncertain because of the various N dilution curve approaches adopted in soil-crop models. In this study, four different representative N dilution curve approaches (i.e., DAISY, M1; CERES and RZWQM, M2; EPIC, M3; and CROPSYST or STICS, M4) were incorporated into a soil-crop model platform (WHCNS), and their effects on crop N uptake and crop growth simulation under different water and N stresses were evaluated via global sensitivity analysis methods. The three-year field experiment data of winter wheat-summer maize rotation under different water and N management practices were used to test the model. Results showed that the WHCNS model performed well in modeling the supplies of soil water and mineral N. The values of statistical indices for crop N uptake, LAI, dry matter and yield simulation by the four methods were within the acceptable ranges, and had the relative mean square error (RRMSE) 0.81 and Nash and Sutcliffe index (NSE) > 0.37. However, the M2 method performed well using the minimum input parameters, and hence recommended to simulate crop N uptake in soil-crop models. In this study, the dataset of high water and N input treatment was more suitable for model parameter estimation to reduce uncertainty, and the datasets of middle and low water and N input treatments was appropriate to validate the model. These information were useful to guide selecting the modeling method and the model calibration dataset.

Optimal Nitrogen Practice in Winter Wheat-Summer Maize Rotation Affecting the Fates of 15N-Labeled Fertilizer

Lower nitrogen recovery efficiency (NRE) and negative environmental impacts caused by excessive nitrogen (N) fertilization threaten the sustainability of agriculture. Efficient and appropriate fertilization practices are extremely important to achieve higher crop yield with minimum N loss. A field microplot experiment was conducted in a wheat-maize rotation system in Shaanxi province, at North China Plain, using the 15N isotope tracer technique to qualify the different annual N managements in terms of crop yield, NRE, N distribution in plant-soil, and N losses to optimize the N management. The experiment included four N treatments: conventional practice with 510 kg ha−1 annually in four applications (N1), and three optimized N treatments, reducing N rate to 420 kg ha−1, adjusting topdressing fertilizer times and using slow-release fertilizer (SRF) (N2, N3, N4). The results showed that the grain yield and N uptake did not differ significantly among treatments. N from fertilizer taken up (Ndff) by wheat was not affected by N management; however, in maize, Ndff performed differently. Optimized treatments significantly decreased the Ndff as compared to N1 treatment. Furthermore, NRE of wheat and annual nitrogen recovery efficiency (annual NRE) did not differ among treatments in 2016 but significantly increased in 2017 compared to N1. Annual NRE in 2017 was similar to that obtained for wheat. For maize, optimized N managements decreased the NRE in N3 and N4 treatments of two years. Potential losses in wheat were also similar amongst treatments, but in maize, N3 and N4 had lower residual N in the soil’s top 60 cm but resulted in higher potential losses than N1 and N2. Overall, our results demonstrate that applying 420 kg N ha−1 annually in three applications and combining SRF and urea are effective to sustain crop yield, improve the efficiency of N usage by maize, and reduce N losses in this region.

Carbon Sequestration in Irrigated and Rain-Fed Cropping Systems Under Long-Term Fertilization Regimes

It is important to understand soil organic carbon (SOC) sequestration and its relationship with crop productivity. Based on two long-term experiments under irrigated vs rain-fed conditions conducted in the China Loess Plateau, we evaluated SOC sequestration efficiency under diverse fertilization regimes and quantified the relationship between crop yield and SOC. The experiments consisted of a winter wheat-summer maize system under irrigated conditions with nine treatments—nitrogen (N), N and phosphorus (P), N and potassium (K), P and K (PK), combined NPK, crop straw (S) in combination with NPK (SNPK) and dairy manure (M) integrated with NPK (M1NPK and M2NPK)—and a winter wheat-summer fallow system under rain-fed conditions with seven treatments—CK, N, NK, PK, NP, NPK, and MNPK. After 25 years, the SOC storage was generally higher in the irrigated plots than in the rain-fed plots by 6% on average. The carbon sequestration efficiency was higher under the rain-fed (28%) than under the irrigated (19%) condition. The relationship between relative yield and SOC content suggested that the threshold SOC contents for obtaining the highest crop yield were 10.0 and 8.8 g kg−1 for the winter wheat-summer maize and winter wheat-summer fallow cropping systems, respectively. This difference suggests that a higher SOC level is required to support high crop productivity in the irrigated system than in the rain-fed system.

Spatiotemporal variations in soil CO2 fluxes under a winter wheat-summer maize cropping system in the North China Plain

Most studies on soil CO2 fluxes focus on the upper soil layers (i.e., 0–200 mm); however, there is a lack of investigation into soil layers below 200 mm, even though about half of soil organic carbon (SOC) is stored at these depths. In order to investigate the responses of CO2 fluxes in subsurface soils to crop residue incorporation in the topsoil, a field experiment comprising two treatments (i.e., conventional tillage with and without crop residue incorporation) was carried out under a winter wheat-summer maize cropping system from 2014 to 2016 in the Yucheng Agricultural Station, Shandong Province, China. The results showed that soil CO2 fluxes had large spatiotemporal variabilities and were significantly affected by crop residue applications (P < 0.05). Soil CO2 fluxes increased with soil depth. The CO2 fluxes from 100 to 400 mm soil depths were 1.1–5.1 times higher than those from 0 to 100 mm soil depths. Incorporation of crop residues into the soil significantly increased soil CO2 fluxes in all sampled layers (P < 0.05), and the magnitude increased with increasing soil depth. Soil moisture and the ratio of soil dissolved organic carbon to nitrogen (DOC/DON) were the dominant factors regulating soil CO2 fluxes in the wheat growing season, whereas soil DON concentrations dominated in the maize growing season. Our study indicated that deep soil C was more vulnerable to the incorporation of crop residues than the C present in surface soil. Incorporation of crop residues into surface soil might not increase SOC sequestration in the subsurface soil.

Calibration and validation of the DNDC model to estimate nitrous oxide emissions and crop productivity for a summer maize-winter wheat double cropping system in Hebei, China

The main aim of this paper was to calibrate and evaluate the DeNitrification-DeComposition (DNDC) model for estimating N2O emissions and crop productivity for a summer maize-winter wheat double cropping system with different N fertilizer rates in Hebei, China. The model’s performance was assessed before and after calibration and model sensitivity was investigated. The calibrated and validated DNDC performed effectively in estimating cumulative N2O emissions (coefficient of determination (1:1 relationship; r2) = 0.91; relative deviation (RD) = −13 to 16%) and grain yields for both crops (r2 = 0.91; RD = −21 to 7%) from all fertilized treatments, but poorly estimated daily N2O patterns. Observed and simulated results showed that optimal N fertilizer treatment decreased cumulative N2O flux, compared to conventional N fertilizer, without a significant impact on grain yields of the summer maize-winter wheat double cropping system. The high sensitivity of the DNDC model to rainfall, soil organic carbon and temperature resulted in significant overestimation of N2O peaks during the warm wet season. The model also satisfactorily estimated daily patterns/average soil temperature (o C; 0–5 cm depth) (r2 = 0.88 to 0.89; root mean square error (RMSE) = 4 °C; normalized RMSE (nRMSE) = 25% and index of agreement (d) = 0.89–0.97) but under-predicted water filled pore space (WFPS; %; 0–20 cm depth) (r2 = 0.3 to 0.4) and soil ammonium and nitrate (exchangeable NH4+ & NO3−; kg N ha−1; r2 = 0.97). With reference to the control treatment (no N fertilizer), DNDC was weak in simulating both N2O emissions and crop productivity. To be further improved for use under pedo-climatic conditions of the summer maize-winter wheat double cropping system we suggest future studies to identify and resolve the existing problems with the DNDC, especially with the control treatment.

Zinc fractions in soils and uptake in winter wheat as affected by repeated applications of zinc fertilizer

This field study was conducted to determine the effect of repeated zinc (Zn) applications at different rates on the concentrations and availability of different forms of Zn in the calcareous soil, in relationship to their contributions to Zn uptake by wheat. Plot-based field experiment was established in 2009 in a winter wheat-summer maize rotation. In each growing season of wheat and maize, six levels of Zn (0, 2.3, 5.7, 11.4, 22.7 and 34.1 kg Zn ha−1) as ZnSO4·7H2O were applied at planting. Following the harvest of the winter wheat in 2010, 2012, 2014 and 2016, soil samples (0−30 cm) from 5 selected Zn levels except 2.3 kg Zn ha-1 were collected and subjected to a sequential extraction to examine the concentrations of Zn fractions including water soluble plus exchangeable Zn (Ex-Zn) and Zn as bounded to carbonate (Car-Zn), manganese oxide (MnO-Zn), iron oxide (FeO-Zn), or organic matter (OM-Zn), and residual (Res-Zn). Stepwise multiple regression was used to identify the contributions of each soil Zn fraction to variation in crop Zn uptake. The results showed that repeated Zn fertilization over the multiple years increased concentrations of all soil Zn fractions. However, the percentage of each Zn fraction to total Zn varied with Zn inputs. Increasing Zn input increased the percentages of Ex-, Carb-, MnO- and FeO-Zn to soil total Zn, whereas reduced that of OM- and Res-Zn. The FeO-, Ex-, and Res-Zn were selected by the stepwise regression procedure as the significant variables explaining the variation in wheat Zn uptake, with partial adjusted coefficient (R2) of 0.81, 0.03 and 0.04, respectively. Crop Zn uptake also increased linearly with soil DTPA-extractable Zn and reached a maximum at DTPA-extractable Zn concentration of 12 mg kg−1. In conclusion, repeated Zn fertilization increased the concentrations of Zn in exchangeable and adsorption forms, which in turn resulted in higher uptake of Zn by winter wheat. DTPA-extractable Zn is a good indicator of Zn availability for wheat. Fraction of FeO-Zn is an important Zn retention pool for determining crop uptake on the calcareous soil. These results emphasize the importance of Zn retention capacity in response to repeated application of Zn fertilizer.

Sowing Methods Influence Soil Bacterial Diversity and Community Composition in a Winter Wheat-Summer Maize Rotation System on the Loess Plateau.

Soil bacterial diversity and community composition are crucial for soil health and plant growth, and their dynamics in response to agronomic practices are poorly understood. The aim of this study was to investigate the response of soil bacterial community structure to the changes of sowing methods, soil depth and distance to roots in a winter wheat-summer maize crop rotation system on the Loess Plateau in china (35°17′38′′N, 111°40′24′′E). The experiment was laid out as completely randomized block design with three replications. Sowing methods trialed were: traditional sowing (TS), film-mulched ridge and furrow sowing (FMR&F), wide ridge and narrow furrow sowing (WR&NF) and unplanted control (CK). The result showed that the WR&NF sowing method treatment significantly decreased soil bacterial diversity (Chao 1 and Shannon indices) compared to the TS and FMR&F treatment, but increased abundance of beneficial bacteria such as genera Bacillus and Pseudomonas compared to the TS treatment. These genera showed a stronger correlation with soil properties and contributed to the soil nutrient cycling and crop productivity. Bacillus, Pseudomonas, Nevskia, and Lactococcus were the keystone genera in this winter wheat-summer maize rotation system on the Loess Plateau. Strong correlations between changes in soil properties and soil bacterial diversity and abundance were identified. In summary, we suggest that the WR&NF treatment, as a no-mulching film and no-deep tillage sowing method, would be the most suitable sowing technique in the winter wheat-summer maize rotation on Loess soil.

Regional simulation of nitrate leaching potential from winter wheat-summer maize rotation croplands on the North China Plain using the NLEAP-GIS model

Identifying the regional characteristics of nitrate leaching from croplands is of great importance when attempting to assess the groundwater contamination risk due to nitrate leaching from croplands. The regional scale model in the Nitrogen Loss and Environmental Assessment Package with GIS Capabilities (NLEAP-GIS), which takes spatial variations in soil profile properties, meteorological data, and farm practices into account, was adopted in this study to simulate the occurrence dynamics and spatial pattern of nitrate leaching downwards through the crop root zone (0–100 cm) in winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) rotation croplands during 2011 and 2012 across the Jing-Jin-Ji region on the North China Plain (NCP). The results showed that the monthly nitrate leaching occurrences were driven by rainfall, irrigation, and fertilizer application. The simulated large spatial variation in cumulative nitrate leaching was positively correlated with both rainfall and fertilizer N application rates, whereas it was negatively correlated with N use efficiency. The cumulative nitrate leaching was mostly lower than 10 kg N ha–1 during the winter wheat growing season, whereas nitrate leaching during the summer maize growing season was much higher and mostly ranged from 20 to 100 kg N ha–1. The average cumulative nitrate leaching in the winter wheat-summer maize rotation system was 55.7 ± 33.5 kg N ha–1, accounting for 17.2 ± 10.2 % of the fertilizer N applied (average 176.3 ± 86.2 kg N ha–1 during each crop season). Fertilizer N application rates of 100–200 kg N ha–1 are recommended during each winter wheat and summer maize season to simultaneously achieve higher grain yields, greater N use efficiency, and a lower groundwater nitrate pollution risk on the NCP. The simulated spatial variation in nitrate leaching implied that there was a potential nitrate groundwater contaminant source and the results contributed to the spatial distribution assessment of groundwater nitrate contamination risk caused by fertilizer N inputs.

An Ammoniated Straw Incorporation Increased Biomass Production and Water Use Efficiency in an Annual Wheat-Maize Rotation System in Semi-Arid China

Water shortage and excessive chemical fertilizers application result in low soil water and nutrient availability and limit crop production in the Loess Plateau of Northwest China. Ammoniated straw incorporation with N fertilization may be an efficient strategy to maintain agricultural sustainability. However, the interactive effects of straw incorporation and N fertilizer on the biomass water use efficiency (WUE) in the winter wheat–summer maize rotation system remain unclear. A 3-year field experiment was conducted to evaluate the effects of combining ammoniated straw incorporation and N fertilizer on soil water, biomass yield and biomass water use efficiency (WUE) in an annual summer maize (Zea mays L.)—Winter wheat (Triticum aestivum L.) rotation system. There were three treatments: (i) long straw (5 cm) mulching with N fertilizer (CK), (ii) long straw with N fertilizer plowed into the soil (LP), and (iii) ammoniated long straw with N fertilizer plowed into the soil (ALP). Compared with the CK treatment, LP and ALP led to a similar soil water storage capacity. ALP improved summer maize biomass yield and winter wheat biomass yield at the jointing-maturity stage. ALP improved summer maize WUE at the ten-leaf collar-tasseling stage and winter wheat WUE from the tillering stage to the maturity stage. Also, the ALP treatment increased the total water use efficiency (TWUE) of winter wheat by 4.1–22.0%. Overall, ammoniated straw incorporation produced the most favorable biomass yield and WUE in the summer maize—Winter wheat rotation system in the Loess Plateau of China.

Effects of Seven Diversified Crop Rotations on Selected Soil Health Indicators and Wheat Productivity

Diversified cropping systems can enhance soil condition and increase system productivity worldwide. To reduce the negative effects that accompany the continuous winter wheat–summer maize (WM) double-cropping in the North China Plain (NCP), diversified crop rotation (DCR) needs to be considered. The objective of this study is to evaluate the effect of DCR on soil health and wheat productivity as compared to a continuous WM double-cropping. A field experiment (37°41′ N, 116°37′ E) was established in the NCP including a traditional WM double-cropping as a baseline. During 2016/2017–2017/2018, the control is winter wheat–summer maize→winter wheat–summer maize (WM→WM) and seven DCRs as follow: fallow→winter wheat–summer maize (F→WM); spring maize→winter wheat–summer maize (Ms→WM); winter wheat→winter wheat–summer maize (W→WM); sweet potato→winter wheat–summer maize (Psw→WM); spring peanut→winter wheat–summer maize (Pns→WM); winter wheat–summer peanut→winter wheat–summer maize (WPn→WM) and potato–silage maize→winter wheat–summer maize (PMl→WM). Our results indicated that DCRs significantly changed certain soil health indicators in 2016/2017 compared with the control, where F→WM rotation significantly decreased soil pH by 2.7%. The DCRs, especial Psw→WM and Pns→WM rotations showed a potential positive effect on soil health indicators at the end of the second year (2017/2018) compared with the control, where sweet potato increased soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP), urease activity (UA) and alkaline phosphatase activity (APA) in 2017/2018 by 5.1%, 5.3%, 13.8%, 9.4%, and 13.5%, respectively. With the spring peanut, TN, AP, and soil APA were increased by 2.1%, 13.2%, and 7.7%, respectively. Although fertilizer and irrigation input of DCRs were lower than the control, no significant decrease was observed on actual wheat yield as compared to the control (7.79 Mg/ha). The finding of this study highlights the value of DCRs, especially, Psw→WM and Pns→WM rotations over WM double-cropping in the NCP.

Effect of N fertilizer types on N2O and NO emissions under drip fertigation from an agricultural field in the North China Plain.

N2O and NO emissions from a winter wheat-summer maize rotation field in the North China Plain were comparably investigated under three different treatments: 1) flood irrigation (A-Flood treatment) plus fertilization of NH4Cl, 2) drip fertigation (A-Drip treatment) plus fertilization of NH4Cl and 3) drip fertigation (AN-Drip treatment) plus fertilization of a mixture of Ca(NO3)2 and NH4Cl. The annual N2O cumulative emissions from the A-Drip treatment and the A-Flood treatment were almost identical, whereas it from the AN-Drip treatment was significantly lower (33%) than that from the A-Flood treatment. Compared with the A-Flood treatment, the annual NO cumulative emission from the A-Drip treatment was significantly increased by 140% but it from the AN-Drip treatment was only slightly increased by 14%. Compared with drip fertigation with NH4Cl, drip fertigation with the mixture of Ca(NO3)2 and NH4Cl significantly reduced the cumulative emissions of N2O (31%) and NO (52%) from the nitrification dominated fields by decreasing the supplement of NH4+ substrate. Among the three fertilization treatments, the yields of the maize from the A-Drip and AN-Drip treatments were significantly increased, while the yields of the wheat were almost the same. Considering the benefit of increasing yields and reducing N fertilizer and water input, the application of nitrate-based fertilizer instead of partial ammonium-based fertilizer through drip fertigation could be a promising method for keeping agronomic productivity and environmental sustainability.

The utility of a boundary line approach for simulating denitrification and nitrous oxide emissions from a Regosol under summer maize-winter wheat crop rotation in Southwest China

Despite the ever-increasing measurements of denitrification and nitrous oxide (N2O) emissions globally, boundary line analyses of these important processes have only been applied to a limited number of agroecosystems. The primary aims of this study were to determine the responses of denitrification and N2O emissions from a subtropical cropland to several soil parameters through boundary line analyses, and to evaluate the ability of site-specific boundary line models for simulating gaseous nitrogen (N) losses using available soil parameters. We performed 403 measurements of denitrification and N2O emissions from two fields cropped with a winter wheat-summer maize rotation in the Sichuan Basin, Southwest China, from October 2004 to September 2005. Boundary lines were fitted for denitrification and N2O emission data against soil temperature, water content, ammonium and/or nitrate substrates, and heterotrophic respiration rates. The boundary lines were largely in agreement with existing theoretical concepts. By incorporating the regulatory effects of soil temperature, water content, N substrates, and an unknown factor that could be related to ammonium content, the boundary line models reasonably simulated the seasonal variations in denitrification and N2O emissions that were collected from a field trial in the same region during the maize season in 2012. The models overestimated the denitrification and N2O emissions on the sampling dates by 8% and 22% on average, respectively. We conclude that boundary line models are useful tools for estimating gaseous N losses from a given cropland. However, the application of the models is limited by the availability of input data.

Characteristics of annual climate resource distribution and utilization for different cropping systems in the south of Yellow-Huaihe-Haihe Rivers plain

Clarifying the characteristics of annual yield, distribution and utilization of climatic resources, and establishing rational quantitative indexes of annual climatic resources distribution for different cropping systems are helpful to provide theoretical basis for further improving annual yield and resource use efficiency in the Yellow-Huaihe-Haihe Rivers plain. In this study, the experiment was conducted from 2011 to 2015 at Xinxiang, Henan province to analyze the grain yield, biomass, dry matter production energy, and distribution and utilization efficiency of climatic resources under four cropping systems, namely winter wheat–summer maize, winter wheat–summer soybean, double maize and one–season spring maize. There were no differences in the annual grain yield, total biomass, and dry matter production energy between the winter wheat–summer maize and double maize cropping systems, but they were significantly higher than those of the winter wheat–summer soybean and one-season spring maize cropping systems, with an average increase of 45.4%–61.5%, 37.3%–71.3%, and 35.77%–70.7%, respectively. The annual radiation production efficiency, radiation use efficiency of grain and total biomass for double maize and one-season spring maize cropping systems were significantly higher than those of the winter wheat–summer maize and winter wheat–summer soybean cropping systems, with an average increase of 11.8%–66.7% in the annual radiation production efficiency, and 0.13–0.42 and 0.18–0.69 percentage points increase in the radiation use efficiency of grain and total biomass, respectively. The accumulative temperature distribution rate for two seasons of winter wheat–summer maize was 45.6% and 54.4%, respectively, while those of double maize was 51.4% and 48.6%, respectively. The accumulative temperature ratio between two seasons was of winter wheat–summer maize 0.8, while that of double maize was 1.1. Considering both yield and resource use efficiency, winter wheat–summer maize and double maize cropping systems can be used to optimize the layout of planting patterns and support the sustainable development of agricultural production in the Yellow-Huaihe-Haihe Rivers plain. Furthermore, clarifying the accumulated temperature distribution rate and the accumulated temperature ratio between two seasons is helpful to optimize climate resource distribution, and further improve the yield potential and the resources use efficiency of double cropping system in the Yellow- Huaihe-Haihe Rivers plain.

Developing climate-smart agricultural systems in the North China Plain

Developing climate-smart agricultural systems is essential for climate change adaptation and mitigation. In the past decades, the typical winter wheat- summer maize rotation system in the North China Plain (NCP) has produced high yield, but the overuse of nitrogen fertilizer and over-pumping of groundwater for irrigation have caused severe environmental problems. It is necessary to develop climate-smart agricultural systems through a comprehensive multiple-objective assessment and optimization of alternative cropping systems and agronomic managements. Here, with the agricultural system model of APSIM, eight alternative cropping systems at four typical sites across the NCP under two climate change scenarios and two tillage managements were comprehensively evaluated in terms of crop yield, water use efficiency (WUE), nitrogen use efficiency (NUE), evapotranspiration (ET), groundwater recharge (GWR), N2O emission, N leaching, surface soil organic carbon (SOC), and carbon footprint (CF). The results showed that under both baseline and future climate scenarios, the currently dominant winter wheat- summer maize rotation system had the largest ET, N leaching and N2O emission, a medium crop yield, WUE, and SOC, however a low NUE, and GWR. The rotation/intercropping systems could have higher grain yields, while the monoculture cropping systems could have advantage on water conservation. Maize had relatively higher yield, WUE, NUE, GWR, and SOC, and lower N loss and CF than wheat and soybean because it could have a high yield without irrigation. The optimized winter wheat-summer maize rotation system, with the optimal irrigation, fertilizer and cultivar, had the greatest advantage over other seven systems with the highest yields, WUE, NUE, high ET, GWR, and SOC, and the lowest N losses and CF. Compared with conventional tillage, each cropping system would have a little bit less negative response to future climate change with conservation tillage. The study demonstrated a useful framework to develop climate-smart agricultural systems and sustainable agricultural strategies to meet the challenges of global climate change, which can be widely applied to other cropping systems and regions.

Wheat‐derived soil organic carbon accumulates more than its maize counterpart in a wheat–maize cropping system after 21 years

AbstractFertilization is the most common way to supply nutrients to the soil and to maintain crop productivity in agricultural ecosystems, which may also influence soil organic carbon (SOC) accumulation rates. In 1996, we set up a long‐term field experiment to explore the effect of fertilization on soil properties in a winter wheat–summer maize cropping system in the North China Plain. Eight treatments included: no fertilization (Ct), nitrogen (N), phosphorus (P) and N combined with P (NP) fertilizer application with or without potassium (K). After 21 years of fertilization, N application did not increase soil total N content, but P application significantly increased soil total P contents by 33.9%. The single application of N or P did not significantly affect SOC content, whereas the NP combination significantly increased SOC contents by 22.1 and 29.6% compared to Ct in the no K and K treatments, respectively. The natural 13C abundance approach and the SOC contents suggested that the NP combination increased C3 wheat‐derived SOC by 37.5 and 49.8% in the no K and K treatments, respectively. However, fertilization had no impact on C4 maize‐derived SOC content. Wheat‐derived SOC was positively correlated with the wheat yield, whereas maize‐derived SOC was not correlated with the maize yield, which indicated that wheat‐derived SOC accumulated more than maize‐derived SOC in the wheat–maize cropping system. In addition, soil inorganic carbon (SIC) and its compositions were not affected by the long‐term fertilization. Our results indicate that N combined with P application is more beneficial than N or P alone to enlarge SOC sequestration in the North China Plain, especially for wheat‐derived SOC. Thus, in soil with nutrient limitations, nutrient resources should be supplied with priority to the wheat growing season in wheat–maize cropping systems, to maintain or enlarge SOC storage.Highlights Long‐term N combined with P application increased wheat‐derived SOC Wheat‐derived SOC accumulated more than maize‐derived SOC in the cropping system Wheat yield was lower than maize in the wheat–maize cropping system Long‐term N, P or NP fertilization did not influence soil inorganic carbon

Area extraction and spatiotemporal characteristics of winter wheat-summer maize in Shandong Province using NDVI time series.

The use of remote sensing to rapidly and accurately obtain information on the spatiotemporal distribution of large-scale wheat and maize acreage is of great significance for improving the level of food production management and ensuring food security. We constructed a MODIS-NDVI time series dataset, combined linear interpolation and the Harmonic Analysis of Time Series algorithm to smooth the time series data curve, and classified the data with random forest algorithms. The results show that winter wheat-summer maize planting areas were mainly distributed in the western plains, southern region, and north-eastern part of the middle mountainous regions while the eastern hilly regions were less distributed and scattered. The winter wheat-summer maize planting areas in the study area continued to grow from 2004-2016, with the most significant growth in the northern part of the western plains and Yellow River Delta. The spatial planting probability reflected the planting core area and showed an intensive planting pattern. During the study period, the peak value and time for the NDVI of the winter wheat were significantly different and showed an increasing trend, while these parameters for the summer maize were relatively stable with little change. Therefore, we mapped a spatial distribution of the winter wheat and summer maize, using the time series data pre-processing synthesis and phenology curve random forest classification methods. Through precision analysis, we obtained satisfactory results, which provided a straightforward and efficient method to monitor the winter wheat and summer maize.

Improved straw management practices promote in situ straw decomposition and nutrient release, and increase crop production

The annual double-cropping system of winter wheat-summer maize on the North China Plain has caused severe land degradation, particularly soil infertility due to the biannual tillage and straw removal. Two field experiments were conducted from 2012 to 2014. The in situ incubation of wheat and maize straw was measured under four management practices: (i) straw incorporated with application of chemical fertilizer (SF); (ii) straw incorporated with chemical fertilizer and manure (SFM); (iii) straw incorporated with chemical fertilizer and straw-decomposition inoculants (SFD); and (iv) only straw incorporated (CK). Our results showed that SFM and SFD significantly increased the decomposable fraction of straw mass from 64% to 66% in wheat, and 64%–65% in maize straw, as compared to 60% and 53% in wheat and maize respectively, in CKs. SFM and SFD released 77%–78% N and 84%–85% P in wheat straw, while 65%–71% N and 76%–77% P in maize straw in the following crop growing season. A significant increase in straw decomposition and nutrient release induced higher soil urease, phosphatase and invertase activities in SFM and SFD than SF and CK, which resulted higher available N and P in SFM and SFD. Thus, crop yield in the SFM and SFD treatments increased significantly up-to 18–53%. Application of straw incorporated with chemical fertilizer and manure, and their decomposition inoculant is recommended with the advantages of maintaining soil fertility and improving crop production.

Exploring optimal irrigation and nitrogen fertilization in a winter wheat-summer maize rotation system for improving crop yield and reducing water and nitrogen leaching

Irrigation and nitrogen (N) fertilization play important roles in grain yield. However, amounts supplied in excess of crop demand are responsible for water and N leaching during intensive agricultural production. A three-year winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) rotation experiment involving varied irrigation and N fertilization treatments was conducted in the Jinghui Canal irrigation area of Guanzhong Plain in China. To develop a more sustainable agroecosystem taking into account crop yields, deep percolation and N leaching, the RZWQM2 model was used to simulate crop production. Various irrigation and N fertilization strategies were simulated to obtain high crop yields and to reduce water and N leaching in different precipitation years, using long-term historical weather data spanning 57 years (1961–2017). The simulated soil water and NO3-N content, grain yield, water and nitrogen use efficiencies (with nRMSE values ranging from 5.3–25.1 %), and the simulated crop biomass and N uptake (with RE values ranging from -16.4–18.3 %) were in good agreement with observed data. Simulated LAI values were acceptable (with RMSE ranging from 0.31 to 1.68 and index of agreement, d, ranging from 0.28 to 0.94), with the poorer simulations occurring with water and N stress. Maize seedling stage and wheat jointing stage were the phases most sensitive to water deficit, and optimal irrigation schedules could be adjusted according to variable precipitation and other climate changes. The best irrigation strategies for maize in the Guanzhong Plain were irrigation applied at the seedling stage in wet and normal years, and two irrigations applied at the seedling and jointing stages in dry years. The best irrigation strategies for wheat were two, three, and four irrigations applied in wet, normal, and dry years, respectively. Irrigation at different crop growth stages significantly influenced N leaching and nitrogen use efficiency. Increasing N input led to greater water use efficiency and less deep percolation water. Considering the interactive effects of water and N input on yield, deep percolation, and N leaching, the most appropriate N application rates in all precipitation years were 140 kg N ha-1 for maize and 240 kg N ha-1 for wheat, coupled with the recommended irrigation strategies. Improving water and N management can significantly reduce deep percolation of water and N leaching while maintaining agricultural productivity and environmental sustainability.