Winter Wheat-summer Maize Research Articles

Effect of plough pan thickness on crop growth parameters, nitrogen uptake and greenhouse gas (CO2 and N2O) emissions in a wheat-maize double-crop rotation in the Northern China Plain: A one-year study

Plough pan can affect crop growth, nutrient uptake and the fates of substances in the environment. To determine the effects of plough pan thickness on crop and environment, a field survey and a field experiment were conducted on a typical calcareous fluvo-aquic soil in a winter wheat-summer maize rotation system in Northern China Plain from 2014 to 2016. Specifically, the thickness of plough pans was surveyed in 108 field plots in 2014, and then based on the survey results a field experiment was established to study the effects of different plough pan thicknesses (PP15: 15 cm of plough pan; PP10: 10 cm of plough pan; PP5: 5 cm of plough pan; PP0: 0 cm of plough pan) on crop growth, nitrogen (N) utilization and the environment. The survey showed that the thickness of topsoil averaged at 14.7 cm, and the plough pan was approximately 15 cm deep. The plough pan was found at 76% of the survey locations, and it was distributed commonly from 15 to 30 cm beneath the soil surface. Breaking the original plough pan partially or completely could promote the net photosynthesis rate, leaf water use efficiency, crop yield, and N use efficiency, decrease N2O emission, but increase CO2 emission. Among all treatments, breaking plough pans completely (PP0) and by 2/3 (PP5) resulted in best crop performance, whose photosynthetic parameters (especially net photosynthetic rate and leaf water use efficiency) were significantly higher than PP10 and PP15. For both wheat and maize, PP5 resulted in greater yield (7 130 kg ha−1 for wheat and 8 240 kg ha−1 for maize) than other treatments. Although it did not differ with PP0 significantly, PP5 had significantly higher N uptake (410 kg ha−1) and N use efficiency (40.1%) than PP10 and PP15. The magnitude of N2O emission peak decreased with an increasing degree of plough pan breakage. The cumulative N2O emission and intensity in PP5 was obviously lower than that in PP10 and PP15. Annual cumulative CO2 emission did not differ significantly among PP5, PP10 and PP15. Net ecosystem productivity (NEP) of the rotation system increased as the thickness of plough pan decreased, so PP5 had relative higher NEP (9 740 kg C ha−1) than PP10 and PP15. Thus, considering better crop growth, higher yield, optimized N utilization, lower N2O and CO2 emissions, as well as higher NEP and less mechanical costs, breaking the original plough pan partially is a good choice to ameliorating the plough pan restrictions in the Northern China Plain.

Optimizing genotype-environment-management interactions to enhance productivity and eco-efficiency for wheat-maize rotation in the North China Plain

Agricultural production is facing unprecedented challenges to ensure food security by increasing productivity and in the meantime lowering environmental risk, especially in China. To enhance productivity and eco-efficiency of the typical winter wheat-summer maize rotation simultaneously in the North China Plain (NCP), we optimized the Genotype (G) × Environment (E) × Management (M) interactions to propose the optimal agronomic management practices and cultivars for four representative sites, with the Agricultural Production Systems sIMulator (APSIM) model and detailed field trial data. The results showed that an appropriate delay in sowing date could mitigate climatic negative effects and a proper increase in sowing density could increase yield. The optimal nitrogen application rate could be 180 kg N ha−1 year−1 for maize. For the cropping system, 240 mm of irrigation for wheat and 330–390 kg N ha−1 year−1 of nitrogen application rate (150–210 kg N ha−1 year−1 for wheat and 180 kg N ha−1 year−1 for maize) were suitable to sustain high yield, resource use efficiency, and lower N2O emissions. These recommended levels were, respectively, 40% less than the current irrigation and N application rate commonly used by local farmers. The recommended management practices could increase groundwater recharge while reducing nitrogen leaching and N2O emissions without reducing yield. The maize cultivars with a long growth duration, large grain number and grain-filling rate are desirable. The desirable wheat cultivars are characterized with a medium vernalization sensitivity and high grain filling rate. The present study demonstrated an effective approach to develop sustainable intensification options for producing more with less environmental costs through optimizing G × E × M interactions.

Soil nitrate nitrogen buffer capacity and environmentally safe nitrogen rate for winter wheat-summer maize cropping in Northern China

Maintaining high crop yield and meanwhile reducing the risk of environmental pollution are of paramount importance for food security and sustainability. The aims of this study were (i) quantify soil NO3− -N buffer capacity under wheat-maize cropping system in Northern China, and (ii) establish agronomic optimum and environmentally safe N rates to guide N recommendation for the region. We compiled data of 76 sets of wheat and 73 sets of maize experiments spanning about 20 years, where N rate experiments conducted and soil NO3− -N content were measured immediately after crop harvest under conventional practice. By applying linear-plateau and plateau-linear models, we computed the soil NO3− -N buffer capacity, agronomic optimum N rate and environmentally safe N rates. Soil NO3− -N buffer capacity ranged from 10 to 221 kg ha−1 for wheat season and from 14 to 212 kg ha−1 for maize season, which were mostly less than 100 kg ha−1 in the region. The agronomic optimum N rates for wheat and maize were 46–221 and 44–250 kg N ha−1 with means of 110 and 127 kg N ha−1, respectively. The environmentally safe N rates were 19–248 kg N ha−1 with mean of 107 kg N ha−1 for wheat, and 36–209 kg N ha−1 with mean of 99 kg N ha−1 for maize. It was found that agronomic optimum N rates from 61% of wheat and 52% of maize were higher than the environmentally safe N rates, implying that current N recommendation had the high potential risk of nitrate leaching. Hence, it is suggested that N recommendation should consider not only the agronomic optimum N but also environmentally safe N rate, especially in areas where are vulnerable to nitrate leaching the latter should be placed at the top priority.

A multi-indicator assessment of peri-urban agricultural production in Beijing, China

Urbanization has proceeded rapidly in China, bringing large-scale social, economic and environmental change to the strategically important peri-urban regions that surround expanding cities. In the Beijing Metropolitan Region, with an area of 16,411 km2, government policies have sought the development of multi-functional peri-urban agriculture, favoring the production of cash crops, and the area of vegetable, fruit and organically grown cereal production has increased, whereas the area under conventional cereal production has declined. In this study, six characteristic agricultural practices in the peri-urban zone were compared in terms of energy use efficiency, economic and environmental performance. A multi-dimensional index was also constructed to compare overall performance. Conventional cereal cropping of spring maize (AP1) and winter wheat-summer maize (AP2) had the lowest energy inputs, highest energy use efficiency, and a positive net energy balance. However, cash crops (greenhouse watermelon-tomato, open-field peach; AP3 and AP4) and organically produced crops (Chinese chestnut, millet; AP5 and AP6) achieved substantially higher economic returns per ha cultivated. Fruit and vegetable crops also achieved much higher yields than conventionally grown cereals. Organically produced crops, although higher in value, achieved lower yields. Product carbon footprints ranged from 0.53 to 6.1 kg CO2eq kg−1 and were lowest for fruit and vegetables. Water consumption ranged from <0.1 L kg−1 for Chinese chestnut to 435 L kg−1 for the outputs of the winter wheat-summer maize rotation. When the various indicator results were combined using a multi-dimensional index, the ranking of the different peri-urban agricultural practices was AP6 > AP5 > AP3 > AP1 > AP4 > AP2. These results demonstrate that the multiple functions of per-urban agriculture are not always complementary. However, the adjustment of peri-urban agricultural practices in the Beijing Metropolitan Region appears to be increasing overall benefits. Nevertheless, benchmarking against practices in other parts of China and the world, suggests that there is substantial scope for improvement of peri-urban agriculture in the Beijing Metropolitan Region, with excessive N fertilization identified as a major contributing factor for the performance gap. The development of peri-urban agriculture in Beijing, as elsewhere, has emphasized multi-functionality, providing local food supply, economic returns for local farmers, ecological functioning, along with amenity. Different agricultural practices provide these benefits in different ways. Assessments that address only a single aspect risk informing decisions that have adverse unintended consequences. Studies employing a variety of indicators across the social, economic and environmental dimensions are required if the potential benefits of peri-urban agriculture are to be realized.

Long-Term Nitrogen Fertilization Elevates the Activity and Abundance of Nitrifying and Denitrifying Microbial Communities in an Upland Soil: Implications for Nitrogen Loss From Intensive Agricultural Systems.

The continuous use of nitrogen (N) fertilizers to increase soil fertility and crop productivity often results in unexpected environmental effects and N losses through biological processes, such as nitrification and denitrification. In this study, multidisciplinary approaches were employed to assess the effects of N fertilization in a long-term (~20 years) field experiment in which a fertilizer gradient (0, 200, 400, and 600 kg N ha−1 yr−1) was applied in a winter wheat-summer maize rotation cropping system in the North China Plain, one of the most intensive agricultural regions in China. The potential nitrification/denitrification rates, bacterial community structure, and abundances of functional microbial communities involved in key processes of the N cycle were assessed during both the summer maize (SM) and winter wheat (WW) seasons. Long-term N fertilization resulted in a decrease in soil pH and an increase in soil organic matter (OM), total N and total carbon concentrations. Potential nitrification/denitrification and the abundances of corresponding functional N cycling genes were positively correlated with the fertilization intensity. High-throughput sequencing of the 16S rRNA gene revealed that the increased fertilization intensity caused a significant decrease of bacterial diversity in SM season, while changed the microbial community composition such as increasing the Bacteroidetes abundance and decreasing Acidobacteria abundance in both SM and WW seasons. The alteration of soil properties markedly correlated with the variation in microbial structure, as soil pH and OM were the most predominant factors affecting the microbial structure in the SM and WW seasons, respectively. Furthermore, consistently with the results of functional gene quantification, functional prediction of microbial communities based on 16S rRNA sequence data also revealed that the abundances of the key nitrificaiton/denitrification groups were elevated by long-term N inputs. Taken together, our results suggested that soil microbial community shifted consistently in both SM and WW seasons toward a higher proportion of N-cycle microbes and exhibited higher N turnover activities in response to long-term elevated N fertilizer. These findings provided new insights into the molecular mechanisms responsible for N loss in intensively N fertilized agricultural ecosystems.

Agricultural subsidies assessment of cropping system from environmental and economic perspectives in North China based on LCA

In China, government subsidies in the agricultural sector have played an important role in increasing grain production and supporting farming incomes. However, agricultural intensification has also led to concerns about environmental harm, especially on the North China Plain. In this study, life cycle assessment (LCA) was used to assess environmental impacts relating to the winter wheat-summer maize rotation system in the high-yielding and intensively cultivated Huantai County. Over the period 1996–2012, energy depletion potential, global warming potential, acidification potential and eutrophication potential all decreased both per t grain produced and per ha production area. However, water resource consumption, human toxicity potential, aquatic ecotoxicity potential and terrestrial ecotoxicity potential increased. The weighted environmental index, integrating all eight indicators into a single score, suggested that overall environmental impact had decreased by 15.2% per t of grain produced and 11% per ha cropped, largely as a result of improved management of N fertilizers as EP was identified as the most important environmental impact category. When human health impacts of emissions (assessed in DALYs) were monetarized, the life cycle environmental costs of both winter wheat and summer maize were also found to have decreased over time. Taking both the increased grain production and the reduction in life cycle impacts, the total life cycle environmental costs of grain production in Huantai County were found to have fallen from 16.6 million RMB.yr−1 to 12.8 million RMB.yr−1, a decrease of 23.2%. These results suggest that production and welfare-oriented subsidies in the agricultural sector in China have generally brought about environmental co-benefits. Nevertheless, there is scope for ongoing environmental improvement, particularly in relation to pesticide use. With agricultural subsidies increasingly viewed as a means of achieving environmental goals, there is an ongoing role for LCA to evaluate the different types of environmental impacts. The coupling of LCA with monetarization tools also has potential for use in informing the design of environmental policy instruments in the agricultural sector.

Peanut-Shell Biochar and Biogas Slurry Improve Soil Properties in the North China Plain: A Four-Year Field Study

Biochar and biogas slurry have been proved to improve the quality of some soil types, but the long-term effects on fluvo-aquic soil are not fully understood. This study aimed to compare the continuity effects of peanut-shell biochar and biogas slurry on the physicochemical properties, microbial population size, and enzyme activities of fluvo-aquic soil. We conducted a four-year field experiment of winter wheat-summer maize rotation in the North China Plain. Along with equal nitrogen inputs, three treatments were applied—conventional fertilizers, peanut-shell biochar, and hoggery biogas slurry—after which various soil quality indicators were compared. Compared with those of control, both biochar and biogas slurry increased the soil total nitrogen and organic matter content, and improved soil aggregation, microbial biomass, and actinomycetes. Biogas slurry decreased soil pH and improved urease and protease activities. With biochar and biogas slurry treatments, wheat yield increased by 8.46% and 23.47%, and maize yield by 18% and 15.46%, respectively. Biogas slurry increased the content of crude protein and starch in the grains. Both biogas slurry and peanut-shell biochar improved fluvo-aquic soil nutrient content, water-stable macroaggregates, and microbial population, which might be related to their high nutrient content, large specific surface area, adsorption capacity, and functional groups. Biogas slurry generally exhibited stronger effects than biochar probably because of its richness in nutrients and bioactive substances.

Conservation tillage increases carbon sequestration of winter wheat-summer maize farmland on Loess Plateau in China.

The idea of mitigating anthropogenic CO2 emissions by increasing soil organic carbon (SOC) is notable. However, the estimation of the net ecosystem carbon balance after conversion from conventional tillage to conservational tillage has been poorly quantified for the Loess Plateau in China. A 2-year field experiment was conducted to estimate the agroecosystem carbon balance of a winter wheat–summer maize rotation system using a full carbon cycle analysis. The results showed that a positive net ecosystem carbon balance value in the cases of rotary tillage with straw incorporation, chisel plow tillage with straw incorporation, and no tillage with straw mulching treatments. Note that a negative value was detected for the conventional moldboard plowing tillage without crop straw treatment. The conversion from conventional tillage to conservational tillage substantially enhanced the carbon sink potential from 0.84 t C ha−1 yr−1 to 2.69 t C ha−1 yr−1 in both years. Our findings suggest that the expansion of conservational tillage could enhance the potential carbon sink of the rain-fed land in China.

Crop rotation and N application rate affecting the performance of winter wheat under deficit irrigation

Deficit irrigation to winter wheat is gradually adopted in the North China Plain (NCP) for conservation of groundwater resources. N application to winter wheat should be decided based on the irrigation water availability. Under deficit irrigation, yield of winter wheat was also related to the water use characters of its previous crops. Field studies were conducted from 2013 to 2016 at Luancheng station in the NCP to evaluate the addition of soybean to the conventional annual double cropping system (winter wheat-summer maize) and reducing N input on the performance of winter wheat under deficit irrigation. Summer maize was either replaced by soybean or inter-planted with soybean. The subsequent winter wheat was applied with six nitrogen rates (0, 135, 216, 270, 324 and 405 kg/ha) with one irrigation or two irrigation applications. The results showed that the average seasonal water use of single soybean (SS), intercropping of maize and soybean (IMS) and single maize (SM) was 359.1 mm, 336.3 mm and 309.6 mm from 2013 to 2016, respectively. The inclusion of soybean as single or inter-planted crop increased the water use during the summer rainy season, which was related to the increase in leaf area index. As compared with the SM, the soil water stored in the 2 m soil profile at the summer crops harvesting was reduced by 24.7 mm and 94.7 mm in 2014, 15.9 mm and 95.6 mm in 2015, respectively, for the IMS and SS, respectively. Due to the dependent of winter wheat on the stored soil water before sowing, the reduction in pre-season soil water content significantly decreased the yield by 1005.4–1878.0 kg/ha. Yield of winter wheat didn’t respond to the increase in N application when N rate was over 135 kg/ha. The local N application rate at 270 kg/ha could be reduced up to 50% without apparent effects on crop productivity under deficit irrigation scheduling. The results indicated that for diminishing the reduction in yield of winter wheat under limited water supply, its previous crop with less water use in summer season should be selected. Yield of winter wheat could be maintained with half of its normal N application under limited water supply.

Sensitivity of simulated crop yield and nitrate leaching of the wheat-maize cropping system in the North China Plain to model parameters

Process-based crop simulation models are often over-parameterised and are therefore difficult to calibrate properly. Following this rationale, the Morris screening sensitivity method was carried out on the DAISY model to identify the most influential input parameters operating on selected model outputs, i.e. crop yield, grain nitrogen (N), evapotranspiration and N leaching. The results obtained refer to the winter wheat-summer maize cropping system in the North China Plain. In this study, four different N fertiliser treatments over six years were considered based on a randomised field experiment at Luancheng Experimental Station to elucidate the impact of weather and nitrogen inputs on model sensitivity. A total of 128 parameters were considered for the sensitivity analysis. The ratios [output changes/parameter increments] demonstrated high standard deviations for the most relevant parameters, indicating high parameter non-linearity/interactions. In general, about 34 parameters influenced the outputs of the DAISY model for both crops. The most influential parameters depended on the output considered with sensitivity patterns consistent with the expected dominant processes. Interestingly, some parameters related to the previous crop were found to affect output variables of the following crop, illustrating the importance of considering crop sequences for model calibration. The developed RDAISY toolbox used in this study can serve as a basis for following sensitivity analysis of the DAISY model, thus enabling the selection of the most influential parameters to be considered with model calibration.

Effects of straw management and nitrogen application rate on soil organic matter fractions and microbial properties in North China Plain

A 2-year field experiment was conducted on the North China Plain to assess the effects of two straw management practices and different nitrogen fertilizer addition levels on soil organic matter (SOM) fractions and microbial properties under a winter wheat-summer maize cropping system. Eight treatments (two straw management practices and four nitrogen fertilizer input levels) were established using a randomized complete block design. The straw management practices were no straw return and straw return. Each straw management practice received nitrogen fertilizer rates at 0 (N0), 270 (N270), 360 (N360), or 450 (N450) kg N ha−1 year−1. The soil properties measured included SOM fractionation, enzyme activities, community level physiology profile (CLPP), and microbial community abundance and composition, which were represented by phospholipid fatty acid (PLFA). Compared to no straw return, the addition of straw significantly increased soil total organic carbon and nitrogen, particulate organic carbon and nitrogen, and occluded particulate organic carbon and hot water extractable organic carbon by 7–29%. Invertase, protease, urease, and dehydrogenase activities increased by 22–40%. The biomasses of Gram-positive bacteria and fungi also increased. The increase in SOM fractions may be attributed to the decomposition of the added straw by more active enzymes, which may result from the shift of microbial community composition. In addition, hot-water extractable organic carbon, NO3-N, urease activity, and fungal biomass in the N270, N360, and N450 treatments significantly increased, independent of the nitrogen application rate, which indicated that N input level had a non-linear effect on soil properties in this area. Short-term straw return combined with a modest nitrogen fertilizer input (270 kg N ha−1 year−1) can increase SOM contents and microbial activity, which may help improve soil fertility in this region.

Change Characteristics of Soil Moisture Content Under Different Planting Patterns

In order to clarify the changes in the soil moisture content in different soil layers under different planting patterns, by using the field experiment, the change characteristics of soil moisture content under the treatment of 3 kinds of planting patterns of winter wheat-summer maize (T0), season spring maize (T1) and herbage- spring maize (T2) are analyzed from 2010 to 2011. The results show that the change range of the soil moisture content varies in different soil layers under different planting patterns and the moisture contents of T0, T1 and T2 treatment are the highest in 90-105cm, which are 0.28 m3·m-3, 0.44 m3·m-3 and 0.44 m3·m-3 respectively. Before sowing the spring maize for different planting patterns, T0 and T2 planting patterns decreased with the increase of time and the T1 planting pattern changed little with the increase of time. However, while in the growing season of maize, the soil moisture content of T0, T1 and T2 planting patterns has the consistent trend with the change of time.

Change characteristics of soil moisture content under different planting patterns and evaluation on crop economic benefits

In order to clarify the changes in the soil moisture content in different soil layers under different planting patterns, this paper uses the field experiment. This paper also analyzes the soil moisture content and crop yield and other related results under the treatment of three kinds of planting patterns of winter wheat-summer maize (T0), season spring maize (T1) and herbage-spring maize (T2) from 2010 to 2011 and evaluates the economic benefits. The results show that the annual yields under T0, T1 and T2 planting patterns are 12.2, 9.9 and 10.4t/hm2 respectively, and the total yield of T0 crops is 20.2% higher than that of T1 and T2. According to the analysis of economic benefits of wheat and maize purchase price and planting cost in 2011, the net incomes of T0, T1 and T2 planting patterns are 5679, 8690 and 12517 Yuan / hm2 respectively and the economic benefit of T0 planting pattern is 46.4% lower than that of T1 and T2. The soil water content of T1 and T2 planting patterns gradually increases with the soil depth, and the water change range of the two planting patterns is the same. The soil moisture content of the T0 planting pattern increases first and then decreases with the depth, and the water change range is lower than that of the T1 and T2 planting patterns. The test results show that the economic benefit of T0 planting pattern is 46.4% lower than the average value of T1 and T2. In the North China Plain, the possible choice to ensure food safety and minimize irrigation water is to plant the season spring maize, but it is necessary to increase the yield of spring maize by more than 20% based on the existing foundation through other measures.

Research on Characteristics of Groundwater Recharge in the Weishan Irrigated District Based on a Bromide Tracer

Bromide was used as tracer in the Weishan Irrigated District to determine the groundwater recharge as well as to evaluate the impacts of different irrigation basin locations, irrigation regimes, and crop types on the recharge. The comprehensive recharge coefficient and the Kriging Spatial Interpolation methods were used to distinguish the effects of precipitation and surface water irrigation on the groundwater recharge rate. The results show that the recharge rates ranged from 85.8 to 243 mm/a, with an average of 168 mm/a. The average recharge rate in the upstream district is greater in the downstream and the average recharge rate of irrigated land (193 mm/a) is greater than non-irrigated land (110 mm/a). The recharge rates in fields of winter wheat-summer maize and cotton with irrigation are 210 mm/a and 140 mm/a, respectively, while they are 115 mm/a and 94.1 mm/a under no irrigation conditions. The comprehensive recharge coefficient of groundwater in the upstream irrigation area is larger than that in the downstream. By comparing the spatial distribution of the groundwater level and the comprehensive recharge coefficient, it is found that there is a positive relationship between the groundwater level and the comprehensive recharge coefficient. The results of this study can provide reference and guidance to a water resources analysis of the Weishan Irrigated District.

Effect of Long-term Organic Amendments on Nitric Oxide Emissions from the Summer Maize-Winter Wheat Cropping System in Guanzhong Plain

Agricultural soil is a significant source of nitric oxide (NO). The primary aim of this study was to quantify the effect of long-term organic amendments on NO emissions from the summer maize-winter wheat cropping system in Guanzhong Plain. NO fluxes were regularly measured by the static chamber method for one year (June 2016 to June 2017). Field experiments included four fertilizer treatments that commenced in 1990. The control (CK, 0 kg·hm-2) treatment was unfertilized throughout the years. The fertilized treatments were synthetic fertilizer (NPK, 165 kg·hm-2), synthetic fertilizer plus maize stalk (NPKS, (165+40) kg·hm-2), and synthetic fertilizer plus dairy manure (NPKM, (50+115) kg·hm-2) during the winter wheat season. They were fertilized with synthetic fertilizer (188 kg·hm-2) during the summer maize season. The results showed small NO emission [<12.2 g·(hm2·d)-1] from the CK treatment within the experimental period. Large NO fluxes [up to 112.0 g·(hm2·d)-1 in NPK treatment] were captured following sowing and fertilization during the summer maize season and following fertilization during the winter wheat season for all fertilized treatments. Annual NO emissions and direct emission factors ranged from 0.13 to 0.57 kg·hm-2 and from 0.04% to 0.12%, respectively. Annual NO emissions from the NPKS and NPKM treatments were 17.6% lower and 68.0% (P<0.05) larger than those from the NPK treatment, respectively. Seasonal NO emissions from the NPKS and NPKM treatments were 41.1%-60.0% (P<0.05) lower than those from the NPK treatment during the winter wheat season, indicating that organic amendments reduced NO emissions. Seasonal NO emissions from the NPKS and NPKM treatments were 25.2%-292.1% (P<0.05) larger than that from the NPK treatment during the summer maize season, mostly due to the positive effect of soil organic matter content on NO emissions.

Carbon footprints of grain-, forage-, and energy-based cropping systems in the North China plain

Low carbon footprint agriculture has received increasing attention in the effect of reducing greenhouse gas emissions and mitigating climate change. However, little is known about how crop diversification may affect the system productivity and the carbon footprint. In this study, we analyzed the carbon footprints of four cropping systems: winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) (WM, grain crop pattern, 1-year cycle); ryegrass (Lolium perenne L.)–sweet sorghum (Sorghum bicolor (L.) Moench) (RS, forage crop pattern, 1-year cycle); ryegrass–sweet sorghum → winter wheat–summer maize (RSWM, grain plus forage crop pattern, 2-year cycle); and switchgrass (Panicum virgatum L.) perennial cropping (SG, energy crop pattern) that have been evaluated in a long-term (2009–2015) field experiment in the North China Plain (NCP). Carbon footprints were expressed using three metrics: CFa (per unit area), CFb (per kg of biomass), and CFe (per unit of economic output). The results showed that switchgrass as a perennial herbaceous crop with one cut per year had the lowest annual carbon footprint at three metrics. The WM cropping system had the highest annual CFa, CFb, and CFe values which were 1.73, 2.23, and 1.78 times higher, respectively, than those of the RSWM cropping system. The RS cropping system had the lower annual CFa, CFb, and CFe values, which accounted for 20.9, 3.4, and 2.9%, respectively, of the WM cropping system. The four cropping systems had annual carbon footprints at per unit area, per kilogram of biomass and per unit of economic output ranked from lowest to highest of SG < RS < RSWM < WM. We conclude that appropriately designed, diversified cropping systems that include grain, forage, and bioenergy crops can effectively reduce the carbon footprint while maintaining or even increasing the systems productivity in the North China Plain.

Soil nitrate accumulation and leaching in conventional, optimized and organic cropping systems

Excessive nitrogen (N) and water input, which are threatening the sustainability of conventional agriculture in the North China Plain (NCP), can lead to serious leaching of nitrate-N (NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N). This study evaluates grain yield, N and water consumption, NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N accumulation and leaching in conventional and two optimized winter wheat-summer maize double-cropping systems and an organic alfalfa-winter wheat cropping system. The results showed that compared to the conventional cropping system, the optimized systems could reduce N, water consumption and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N leaching by 33, 35 and 67–74%, respectively, while producing nearly identical grain yields. In optimized systems, soil NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N accumulation within the root zone was about 80 kg N/ha most of the time. In the organic system, N input, water consumption and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N leaching was reduced even more (by 71, 43 and 92%, respectively, compared to the conventional system). However, grain yield also declined by 46%. In the organic system, NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N accumulation within the root zone was generally less than 30 kg N/ha. The optimized systems showed a considerable potential to reduce N and water consumption and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;-N leaching while maintaining high grain yields, and thus should be considered for sustainable agricultural development in the NCP.

Abundance and depth stratification of soil arthropods as influenced by tillage regimes in a sandy loam soil

AbstractDifferent tillage regimes can change soil micro‐environmental characteristics, which may influence the distribution and abundance of soil arthropods. In this study, soil arthropods and soil properties under a winter wheat–summer maize cropping system were investigated in different tillage regimes over four seasons at two depths. The tillage treatments included conventional tillage (CT), tillage once a year (T1), tillage every two years (T2) and no‐tillage (NT). The results showed that the primary taxa of soil arthropod were Acarina (65.8%), Collembola (28.5%), Diplura (1.4%) and Coleoptera (1%) over the whole sampling period. The total arthropod density was influenced by tillage treatments and season of sampling. Values for CT plots were significantly greater than those for the NT plots in autumn and spring. In contrast, the Shannon–Wiener diversity index (H’) and the evenness index (J) were relatively higher in CT treatment. The Acarina/Collembola (A/C) ratio was significantly smaller in NT treatment for some sampling seasons as mites were more sensitive to tillage practices. The QBS‐ar index did not show a clear pattern among treatments in this study. Soil arthropods notably showed seasonal variation in depth stratification. Relative to CT, the total soil arthropods in the NT plots tended to concentrate in the upper layer due to soil compaction in the lower layer. The climate conditions and soil physical properties were the main factors affecting the soil arthropod distribution and composition, as the soil chemical and microbial properties did not differ significantly among all tillage treatments.

Tillage and residue management for long-term wheat-maize cropping in the North China Plain: I. Crop yield and integrated soil fertility index

Conservation tillage has been gaining increasing recognition for its role in improving soil quality and maintaining agricultural sustainability. This is the first in a series of papers describing the impacts of reduced/no-tillage with and without residue based on the field experiment in the North China Plain. The experiment was established in 2006 on a sandy loam soil and involved a winter wheat-summer maize rotation system per year. The objective of this study was to investigate the impacts of different conservation tillage systems on crop yield and soil fertility that was quantified by a minimum data set and integrated index. Soil samples were collected since 2011, and the stocks of soil organic matter (SOM), total nitrogen (TN), alkali-hydrolyzale nitrogen (AN), total phosphorus (TP), available phosphorus (AP), total potassium (TK) and available potassium (AK) were measured for each year as well as soil aggregates were fractionated for 2016. Compared to continuous tillage, the reduced/no-tillage, regardless of residue, significantly increased the macroaggregate mass and soil nutrient stocks at the 0–10 cm depth, while further improvements in these soil attributes apart from TK were observed at the 0–10 and 10–20 cm depths for residue returning relative to residue removing. The accumulations of soil nutrients were closely related to soil macroaggregation. The path analysis revealed that TN was the most important soil attribute to directly determine wheat and maize yields while other soil attributes apart for TK primarily made indirect contributions to the yields. The first two factors extracted using 8 soil attributes through factor analysis were selected as the integrated indicators for the minimum data set, and their integrated score was calculated to quantify soil fertility. It was found that reduced/no-tillage did not improved soil fertility at the 0–20 cm depth. Consequently, an average 6.9% decrease in wheat yield across all years was observed under no-tillage while reduced tillage only increased the yield in the first two years in a periodic reduced tillage event. No significant difference was observed for the mean maize yield among the three tillage regimes averaged across all years and residue managements. Wheat and maize yields were significantly correlated with the integrated score for soil fertility, and thus significant increases in grain yields of wheat and maize were observed for residue returning. It can be concluded that grain yields of wheat and maize within a given residue management practice were not significantly higher for reduced/no-tillage than continuous tillage, regardless of the effects of tillage on aggregates and soil nutrients.

Integrated agronomic practices management improve yield and nitrogen balance in double cropping of winter wheat-summer maize

Crop production alters nitrogen balance in double cropping of winter wheat-summer maize in grain nitrogen content, soil nitrogen pool and nitrogen loss, ultimately affecting nitrogen use efficiency and environmental health. In comparison to the information on crop responses only limited knowledge exists on the response of nitrogen balance to integrated agronomic practices management (IAPM, defined as a comprehensive management framework consisted of tillage method, plant density, seeding and harvest dates, and fertilizer application) under field. Planting pattern will affect crop production and environmental costs. And how the nitrogen balance change under IAPM? In order to answer this question, four treatments (T1, T2, T3 and T4) were conducted on double cropping of winter wheat-summer maize for 4 years in North China Plain. Annual grain yield of T2, T3, and T4 was 22.0%, 51.2%, and 33.3%, respectively, higher than T1. And single grain yield of winter wheat or summer maize had the same trend as the annual grain yield. Dry matter accumulation of T2, T3, and T4 in summer maize season were 8.3%, 42.0%, and 23.0%, and those in winter wheat season were 3.9%, 25.7%, and 12.1%, respectively, higher than T1 at harvest. The grain yield of T4 was lower than that of T3 but higher than that of T1 and T2, and net profit and nitrogen use efficiency of T4 were higher than that of T3. Meanwhile the highest current and residual nitrogen recovery efficiency (CREN and REREN) were obtained by T4 treatment during the study period. The soil nitrogen content in 0–90 depth (SN), grain nitrogen content (GN), nitrogen apparent recovery efficiency (AREN) and fertilizer nitrogen loss (FNL) were measured for nitrogen balance. T4 treatment promoted nitrogen balance as higher GN, higher AREN and lower FNL. The GN kept stable and FNL was increasing slowly in all treatments, which mean the contribution to soil nitrogen pool was decreasing with experimental years. The grain yield for T4 treatment of winter wheat, summer maize and annual increased by 36.4%, 31.3% and 33.3% averagely in the past 4 years, compared with T1 treatment. While maintaining crop production, T4 treatment made an important contribution to promoting nitrogen use efficiency, improving the situation of nitrogen balance, and reducing nitrogen loss about 39.1–54.4%, compared with other treatments.