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The research on terahertz wave manipulation based on metasurfaces has gradually deepened, and the number of functions or electromagnetic control dimensions in a single device is constantly increasing. For the spatial dimension of terahertz field regulation, its design degrees of freedom have been expanded from a single transverse plane to the propagation path. In this paper, we propose a novel circularly polarization multiplexed metasurface for dual channel terahertz wave transmission control. Based on the spatial integration of two heterogeneous meta-atoms, which are spin-decoupled and isotropic, respectively, there are four phase channels that can be used at the same time, thus achieving different switching between vector and scalar beams in different circularly polarization channels along the optical path. For linearly polarized wave incidence, the device exhibits conversion between different vector beams longitudinally. To control more electric field components, we combine focused wavefront design with vector or scalar fields and utilize the focusing induced spin–orbit coupling effect, then complex amplitude switching of longitudinal electric field components is obtained. This article extends the manipulation of terahertz waves along the propagation trajectory based on metasurface from single to dual channel for the first time, providing a reference for the design of multifunctional meta-device in terahertz band.

In a Magnetically Coupled Resonant Wireless Power Transfer (MCR-WPT) system, the magnetic coupling coil is one of the key factors that determines the system’s output power, transmission efficiency, anti-offset capability, and so on. This article proposes a coil parameter optimization method for a wireless power transfer system based on crowding distance division and adaptive genetic operators. Through optimizing the design of decision variables, such as the numbers of transmitting and receiving coil turns, the spacings between transmitting and receiving coil turns, the inner radii of the transmitting and receiving coils, and the vertical distance of the coil, the best transmission performance can be achieved. This study improves the NSGA-II algorithm through proposing a genetic operator algorithm for average crowding and high crowding populations based on adaptive operators, as well as a genetic operator algorithm for low crowding populations based on information entropy. These improved algorithms avoid problems inherent to traditional genetic operators such as fixed genetic proportions, do not easily cause the algorithm to fall into a local optimal solution, and show better convergence in the ZDT1–ZDT3 test functions. The optimization design method in this article is not only independent of commercial software such as ANSYS Maxwell 2021 R1, but can also significantly improve the calculation speed compared with traditional simulation software.

IntroductionOrganic agriculture is highly regarded by people for its commitment to health, ecology, care, and fairness. The soil microbial community responds quickly to environmental changes and is a good indicator for evaluating soil microecology. Therefore, from the perspective of soil microbial communities, elucidating the impact of organic management on soil microecology in tea plantations has great significance for improving local tea plantation systems.MethodsThe study collected bulk soil from organic management (OM) and conventional management (CM) tea plantations in Pu'er City, a major tea-producing area in China, and analyzed their species diversity, structural composition, and co-occurrence networks using metagenomics technology.ResultsCompared with CM, the diversity index (Shannon) and evenness index (Heip) of soil fungi increased by 7.38% and 84.2% in OM tea plantations, respectively. The relative abundance of microorganisms related to the nitrogen cycle increased. Specifically, there was a significant increase in Rhodobiales, a 2-fold increase in Nitrospirae, and approximately 1.95 and 2.03 times increases in unclassified genera within Betaproteobacteria and Deltaproteobacteria, respectively. The relative abundance of plant residue degradation species, Gemmatimonadetes, Ascomycota, and Basidiomycota, increased by 2.8, 1, and 1.4 times, respectively. The OM was conducive to the establishment of collaborative relationships among bacterial species and increased the diversity and complexity of species relationships in fungal communities. The network stability of soil ecosystems was promoted. The organic tea plantations' keystone taxa contained mycorrhizal fungi (Pezoloma_ericae, Rhizophagus_irregularis, Rhizophagus_clarus), as well as species involved in soil nitrogen metabolism (Acidobacteria_bacterium, Acidobacteriia_bacterium_AA117, Sphingomonas_sp._URHD0007, Enhydrobacter_aerosaccus), pathogen (Erysiphe_pulchra), and parasites (Paramycosporidium saccamoeba). The partial least squares method (PLS-SEM) indicated that OM affected N-NH4+ negatively, increasing the abundance of fungi, and thereby positively affecting the Shannon index.ConclusionIn brief, reasonable organic management can improve the diversity of soil microorganisms, increase the relative abundance of beneficial bacteria in tea plantation soil, and promote the stability of the soil microbial ecological network.

Maize (Zea mays L.) can exhibit yield penalties as a result of unfavorable changes to growing conditions. The main threat to current and future global maize production is heat stress. Maize may suffer from heat stress in all of the growth stages, either continuously or separately. In order to manage the impact of climate driven heat stress on the different growth stages of maize, there is an urgent need to understand the similarities and differences in how heat stress affects maize growth and yield in the different growth stages. For the purposes of this review, the maize growth cycle was divided into seven growth stages, namely the germination and seedling stage, early ear expansion stage, late vegetative growth stage before flowering, flowering stage, lag phase, effective grain-filling stage, and late grain-filling stage. The main focus of this review is on the yield penalty and the potential physiological changes caused by heat stress in these seven different stages. The commonalities and differences in heat stress related impacts on various physiological processes in the different growth stages are also compared and discussed. Finally, a framework is proposed to describe the main influences on yield components in different stages, which can serve as a useful guide for identifying management interventions to mitigate heat stress related declines in maize yield.

Sustainable agricultural development is a topic of global concern aiming at satisfying food demand of the growing population while reducing impact on environment. Circular agriculture has become a promising development pattern with the advantages of complementing environmental resources, replacing feedback from outside system, and processing waste of bottom of system, etc. This study combined economic analysis, life cycle assessment and emergy accounting to evaluate sustainability of an integrated maize-pig system (IS) driven by indigenous microbes in Northeast China, compared with separated maize and pig system (SS). IS reduced input of concentrate feed, coal, vaccines, disinfectants, fertilizer and labor by 14.35%, 100%, 46.11%, 100%, 60.1% and 60.8% driven by indigenous microbes. Economic analysis results showed that IS has 82.88% higher profit than that of SS. The sum of potential environmental impacts of IS was lower than SS for 80.65% according to lifecycle assessment. The emergy results revealed that IS performed better sustainability. Internal feedback emergy for fertilizer and local resources for maize straw increasing of IS significantly improved emergy efficiency. The reduction resulted in nonrenewable resources decreased 33.01% than that of SS, and increased renewable resources by 67.81%, which reduced environmental load ratio of IS by 60.08% of IS. Meanwhile, these factors were the primary factors generating higher sustainability of IS. Overall, the integrated maize-pig system driven by indigenous microbes in this study can effectively alleviate the problems caused by agricultural waste and promote sustainable agricultural development.

Intercropping often substantially increases phosphorus (P) availability to plants compared with monocropping, which could be an effective strategy for soil legacy P recovery and agricultural production. However, the biogeochemical interactions among plants, microbes, and soil that mobilize P remain largely unknown in intercropping systems. Pot experiments with maize-soybean intercropping in a calcareous soil were conducted to investigate the potential chemical and biological transformation mechanisms of inorganic P (Pi) and organic P (Po) using sequential extraction and Illumina MiSeq sequencing. Compared to monocropping of each crop, maize-soybean intercropping significantly enhanced total P uptake of the two crops by mobilizing Ca2-Pi [extracted by bicarbonate (NaHCO3)], Al-Pi/Po [extracted by ammonium fluoride (NH4F)] and Fe-Pi [extracted by sodium hydroxide and sodium carbonate (NaOH-Na2CO3)] fractions. Furthermore, there were significant increases in the organic carbon content and alkaline phosphomonoesterase (ALP) and phosphodiesterase (PDE) activities as well as the abundances of Microvirga, Lysobacter, Microlunatus and Sphingomonas under maize-soybean intercropping relative to monocropping. In contrast, compared to monocroppping, no significant change in the soil pH was observed under maize-soybean intercropping. Therefore, the enhanced P uptake of the maize-soybean intercropping probably resulted from a synergistic effect of rhizosphere organic carbon deposit, increased activities of ALP and PDE, together with the bacteria (Microvirga, Lysobacter, Microlunatus and Sphingomonas) which showed correlation with soil P forms, while the generally recognized rhizosphere acidification was excluded in this investigated calcareous soil. Moreover, the selected bacterial genera exhibited a closer network in the rhizosphere of soybean compared to maize, suggesting enhanced interactions among bacteria in the soybean rhizosphere. These results provide theoretical bases for the recovery of soil legacy P by maize-soybean intercropping.

Improving phosphorus (P) fertilization strategies benefits mitigating future global P shortage and reducing legacy P loss risk in agricultural lands. In this study, the molecular transformation mechanisms of P in Entisol soils under multiple long-term fertilization regimes including PK; NK; NPK; NPK with pig manure (NPKM); and NPK with rice straw return (NPKS) were investigated by sequential fractionation (SF), synchrotron-based P K-edge X-ray absorption near-edge structure (P-XANES) and solution 31P nuclear magnetic resonance (P-NMR) spectroscopy. Compared with conventional NPK fertilization, a higher accumulation of total P occurred in soils under the PK, NPKM and NPKS treatments. By SF, there were relatively higher contents of NaHCO3-extracted inorganic P (Pi) fractions for the soils under PK (52.5 mg/kg) and NPKM (35.5 mg/kg) fertilization relative to the NPK (23.3 mg/kg) treatment. Consistently, P-XANES analysis revealed that there was a higher proportion of brushite, as a bioavailable P form, in soil under the PK and NPKM treatments compared with the NPK treatment, indicating higher P availability in the Entisol soils under PK and NPKM fertilizations. By P-NMR, long-term PK fertilization resulted in relatively a higher ratio of orthophosphate diesters to orthophosphate monoesters after correction compared with the NPK fertilization, which strongly suggested that N deficiency enhanced the biodegradability of soil organic P (Po) pools, thus providing new molecular-level insights into soil Po transformation. Collectively, these results, obtained from a long-term experimental study, facilitates the comprehensive understanding of P availability and transformation mechanisms in Entisol soils under multiple fertilization regimes, and thus benefits the improvement of fertilization strategies in agricultural soils.

Extreme climate change, rapid population growth and economic development drive a growing demand for resources, which lead to energy, food, water and their intertwined nexus becoming increasingly important. Agricultural decisions considering the interconnections among water, energy, and food are critical. The consumption of large amounts groundwater and non-renewable energy by the predominant traditional wheat-maize cropping system has caused a serious water shortage in the North China Plain (NCP), which is a large food production region in China. This situation has strained the relationship between water/energy consumption and food production. It is important to seek synergy in the water-energy-food nexus. This paper proposed a relative index of water-energy-food (WEFRI) based on different values of resource consumption and use efficiency between treatment systems and control system to analyze the synergy between water utilization, energy consumption and food supply in different cropping systems at the field scale. The goal is to seek a sustainable cropping system to balance crop production while reducing energy consumption and water depletion. In this case, different systems including monocropped maize (Zea mays) (MM), intercropped maize and soybean (Glycine max) (MS), relay cropped of maize with pea (Pisum sativum) (MP) and potato (Solanum tuberosum) (MO), rotation of maize with spinach (Spinacia oleracea) (MI) and ryegrass (Secale cereale) (MR), and using traditional wheat-maize (Triticum aestivum) (MW) as a control. MM, MS, MP and MO were the best systems within a particular range of food supply reduction. The WEFRI of the MM/MS system was the highest (2.96/2.78). Compared to the MW system, the groundwater consumption of MM/MS was reduced by 73.84%/73.84%, and non-renewable energy inputs were reduced by 48.01%/48.30%; however, the food supply decreased by 48.05%/51.70%. The WEFRI of the MP system was 1.98. In comparison with the MW system, the groundwater consumption of the MP system was reduced by 28.46%, and the non-renewable energy inputs were reduced by 42.68%. However, the food supply decreased by 37.13%. The WEFRI of MO system was 1.92. Compared to the MW system, the groundwater consumption of MO was reduced by 11.47%, non-renewable energy inputs were reduced by 32.14%, and the food supply only decreased by 26.27%. In conclusion, we theoretically proposed the following references for cropping systems in the NCP: MM and MS are implemented when the areas has extreme water shortages, MO is implemented when a less than 30% reduction in the food supply capacity is acceptable, and MP is recommended if a 30%–40% reduction in the food supply is acceptable.

Abscisic acid (ABA) plays a physiological role in regulating the heat tolerance of plants and maintaining crop productivity under high-temperature stress. Appropriate cultivation techniques can regulate endogenous ABA and help farmers improve food production under high-temperature stress. Here, the physiological basis for ABA-induced heat tolerance in crops is reviewed. High-temperature stress stimulates ABA, which reduces stomatal opening and promotes root growth. The root system absorbs water to maintain the water status, thus allowing the plant to maintain physiological activities under high-temperature stress. ABA plays a synergistic role with nicotinamide adenine dinucleotide biosynthesis to improve the thermal stability of the cell membrane, maintain a dynamic balance between material and energy, and reduce the negative effects of high-temperature stress on kernel number and kernel weight. Cultivation and tillage techniques adapted to high-temperature stress, such as adjustment of sowing time, application of plant growth regulators and fertilizers, and the use of irrigation, subsoiling and heat acclimation, and the mechanisms by which they improve crop heat tolerance, are also reviewed. The results of the studies reviewed here will help researchers develop techniques for cultivating food crops under heat stress and apply them to food-production fields to improve crop productivity.

For the sustainable development of human beings and society, it is important to conserve the ecosystems and alleviate poverty in the areas that have low agricultural productivity and are ecologically vulnerable. To avoid the decrease in ecosystem services (ES) under the effects associated with reducing poverty, we need to carefully consider the relationship between land use changes and the economic development in economically poor areas. We selected the Lingqiu County as our study area, which is a national impoverished county in China, and analyzed the impact of poverty alleviation efforts on the ecological and economic sustainability in the region through ES evaluation. The results showed that land use change in the Lingqiu County has not changed the ES significantly during 2007–2016. The gross domestic product (GDP) growth rate (15.81 %) during 2001–2016, indicates the effectiveness of the poverty alleviation efforts implemented. The rise in the index of ecological and economic relationship during 2001–2016 (from 0.2389–0.3629) maintaining in a harmonious coordination situation indicates that the land use change had positive consequences for the local residents, Presently, the value of ES has not been converted to market–based benefits, and therefore, it is indispensable to find a marketplace for ES (in an innovative way) to promote the high–quality sustainable development of a local economy.

Nitrogen-based pollution from agriculture has global environmental consequences. Excessive use of chemical nitrogen fertilizer, incorrect manure management and rural waste treatment are key contributors. Circular agriculture combining cropland and livestock is an efficient channel to reduce the use of chemical nitrogen fertilizers, promote the recycling of livestock manure, and reduce the global N surplus. The internal circulation of organic nitrogen resources in the cropland-livestock system can not only reduce the dependence on external synthetic nitrogen, but also reduce the environmental impacts of organic waste disposal. Therefore, this study tried to clarify the reactive nitrogen emissions of the crop-swine integrated system compared to the separated system from a life cycle perspective, and analyze the reasons for the differences in nitrogen footprints of the two systems. The results showed that the integrated crop production and swine production increased the grain yield by 14.38% than that of the separated system. The nitrogen footprints of crop production and swine production from the integrated system were 12.02% (per unit area) and 19.78% lower than that from the separated system, respectively. The total nitrogen footprint of the integrated system showed a reduction of 17.06%. The reduction was from simpler waste manure management and less agricultural inputs for both chemical fertilizer and raw material for forage processing. In conclusion, as a link between crop planting and pig breeding, the integrated system not only reduces the input of chemical fertilizers, but also promotes the utilization of manure, increases crop yield, and decreases environmental pollution. Integrated cropland and livestock is a promising model for agriculture green and sustainable development in China.

Further enhancement of maize (Zea mays L.) productivity will benefit from a thorough understanding of thermotolerance. The effects of nitrogen fertilization regimes (ratio of nitrogen (N) doses prior to planting: V7:V15:R3) on reducing yield penalty imposed by high temperature stress are discussed in this study. Field experiments were conducted in 2013 and 2014 using three nitrogen fertilization regimes (N1 - 120:180:0:0; N2 - 60:90:150:0; N3 - 60:90:60:90) and CK (control) treatment (1:0:0:0) to discuss the effect of nitrogen fertilization regimes on alleviating high temperature stress of spring maize. Total N rates for 2013 and 2014 were 280 and 300 kg/ha, respectively. Yield in 2013 and 2014 was averaged as 9.37 and 12.35 t/ha for N3, respectively, which was 13.47% higher than CK. During the grain-filling stage, leaf area index and the SPAD (soil plant analysis development) value in N3 were the highest, but electrical conductivity and malondialdehyde content of ear leaf in N3 were the lowest. Moreover, photosynthetic rate of ear leaf in N3 increased by 9.95% compared to CK. These results indicate that nitrogen fertilization regimes, especially with N3 treatment, can help maintain relatively higher photosynthetic supply capacity during the grain-filling stage under high temperature stress, thereby resulting in improved grain yield.

A number of new rural management models have emerged to solve the problems of economic backwardness, insufficient resource utilization, and technical shortages in rural areas in the context of poverty alleviation to the rural revitalization strategy in China. However, the influence of new rural management model under all countermeasures for rural sustainable development with a comprehensive perspective is lacking. Therefore, exploring whether the new rural management model meets the requirements of sustainable development is an urgent issue. From the theory of system metabolism and emergy accounting method, this study classified the government funds for poverty alleviation measures as import resources, and analyzed the metabolic structure, efficiency, and the rural development factors of Chehe Village before and after poverty alleviation measures are carried out (the year of 2012 and 2019) to verify whether the new model was sustainable. According to the results of this study, the new management model of Chehe Village declined the rural system sustainability with the emergy sustainability index decreasing from 1.96 in 2012 to 0.32 in 2019. With the development of economy, the system metabolic efficiency of Chehe Village promoted and the metabolic structure became more reasonable manifesting in the decline of emergy use per unit GDP and the increase of emergy exchange rate. Moreover, production and livelihood had been highly valued in Chehe Village. In conclusion, it is feasible to add countermeasures of poverty alleviation and rural revitalization into the village system metabolism. The new management model of Chehe Village needs to change exogenous force into endogenous force to meet the requirements of rural sustainable development.

High-temperature stress (HTS) at the grain-filling stage in spring maize (Zea mays L.) is the main obstacle to increasing productivity in the North China Plain (NCP). To solve this problem, the physiological mechanisms of HTS, and its causes and impacts, must be understood. The HTS threshold of the duration and rate in grain filling, photosynthetic characteristics (e.g., the thermal stability of thylakoid membrane, chlorophyll and electron transfer, photosynthetic carbon assimilation), water status (e.g., leaf water potential, turgor and leaf relative water content) and signal transduction in maize are reviewed. The HTS threshold for spring maize is highly desirable to be appraised to prevent damages by unfavorable temperatures during grain filling in this region. HTS has negative impacts on maize photosynthesis by damaging the stability of the thylakoid membrane structure and degrading chlorophyll, which reduces light energy absorption, transfer and photosynthetic carbon assimilation. In addition, photosynthesis can be deleteriously affected due to inhibited root growth under HTS in which plants decrease their water-absorbing capacity, leaf water potential, turgor, leaf relative water content, and stomatal conductance. Inhibited photosynthesis decrease the supply of photosynthates to the grain, leading to falling of kernel weight and even grain yield. However, maize does not respond passively to HTS. The plant transduces the abscisic acid (ABA) signal to express heat shock proteins (HSPs), which are molecular chaperones that participate in protein refolding and degradation caused by HTS. HSPs stabilize target protein configurations and indirectly improve thylakoid membrane structure stability, light energy absorption and passing, electron transport, and fixed carbon assimilation, leading to improved photosynthesis. ABA also induces stomatal closure to maintain a good water status for photosynthesis. Based on understanding of such mechanisms, strategies for alleviating HTS at the grain-filling stage in spring maize are summarized. Eight strategies have the potential to improve the ability of spring maize to avoid or tolerate HTS in this study, e.g., adjusting sowing date to avoid HTS, breeding heat-tolerance varieties, and tillage methods, optimizing irrigation, heat acclimation, regulating chemicals, nutritional management, and planting geometric design to tolerate HTS. Based on the single technology breakthrough, a comprehensive integrated technical system is needed to improve heat tolerance and increase the spring maize yield in the NCP.

To address the low productivity of sandy farmlands, our study aimed to conduct a comparative study on the effects of different organic amendment (OA) inputs for the potential improvement of crop yield and soil quality in sandy alkaline farmlands through the selection of a suitable OA. This study set up straw (ST) returning as control and chemical fertilizer (CF) treatment as a side control, and chose three OAs returning as treatments, including pig manure (PM), biogas residue (BR), and straw biochar (BC), for improving soil fertility, with all amendments having matched doses of nitrogen (N). The experiment was conducted at the Wuqiao Experimental Station (37°41 N, 116°37 E) of China Agricultural University in Hebei Province, China, from October 2012 to September 2016. The cropping rotation was the winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) rotation system. Through a consecutive four-year field experiment, the principal results showed that three types of OA application significantly increased soil organic carbon from 1.46 g kg−1 to 8.24 g kg−1, soil total N from 0.21 g kg−1 to 0.64 g kg−1, soil available potassium from 55.85 mg kg−1 to 288.76 mg kg−1, and soil available phosphate from 4.86 mg kg−1 to 65.00 mg kg−1 in the 0–20 cm soil layer. The BR was the most effective in improving soil nutrients as compared with the ST. The PM and BR treatments were more conducive to promoting crop yield by 6–20% than ST, and the BC treatment significantly reduced the yield of winter wheat by 19% and summer maize by 8%. As the BR and PM treatments improved the soil nutrient content and significantly increased crop yield, these were the top choices for transforming the low-yield sandy farmlands.

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.

Biomass yields and concentrations of crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude fiber (CF) were analyzed for five cultivars of summer-sown maize (Zea mays L.) stover grown in field trials at three rates of N fertilization, and sampled immediately after grain harvest. The results revealed differences in yields and concentrations of nutrients according to stalk height and hence harvest portion among the cultivars. N application greatly increased biomass yield and CP, especially in upper stalks and to a lesser extent, EE. Concentrations of NDF and ADF decreased as N rate increased. The results show that stovers from all local popular maize cultivars are suitable as animal fodder and that moderate N application improves feed quality of stover.

To make recycling utilization of organic materials produced in various agricultural systems, five kinds of organic materials were applied in a field test, including crop straw (CS), biogas residue (BR), mushroom residue (MR), wine residue (WR), pig manure (PM), with a mineral fertilizer (CF) and a no-fertilizer (CK) treatment as a control. Our objectives were: i) to quantify the effects of organic materials on soil C and N accumulation; ii) to evaluate the effects of organic materials on soil aggregate stability, along with the total organic carbon (TOC), and N in different aggregate fractions; and iii) to assess the relationships among the organic material components, soil C and N, and C, N in aggregate fractions. The trial was conducted in Wuqiao County, Hebei Province, China. The organic materials were incorporated at an equal rate of C, and combined with a mineral fertilizer in amounts of 150 kg N ha−1, 26 kg P ha−1 and 124 kg K ha−1 respectively during each crop season of a wheat-maize rotation system. The inputted C quantity of each organic material treatment was equivalent to the total amount of C contained in the crop straw harvested in CS treatement in the previous season. TOC, N, water-stable aggregates, and aggregate-associated TOC and N were investigated. The results showed that organic material incorporation increased soil aggregation and stabilization. On average, the soil macroaggregate proportion increased by 14%, the microaggregate proportion increased by 3%, and mean-weight diameter (MWD) increased by 20%. TOC content followed the order of PM>WR>MR>BR>CS>CK>CF; N content followed the order WR>PM>MR>BR>CS>CF>CK. No significant correlation was found between TOC, N, and the quality of organic material. Soil silt and clay particles contained the largest part of TOC, whereas the small macroaggregate fraction was the most sensitive to organic materials. Our results indicate that PM and WR exerted better effects on soil C and N accumulation, followed by MR and BR, suggesting that organic materials from ex situ farmland could promote soil quality more as compared to straw returned in situ.

In the North China Plain, groundwater tables have been dropping at unsustainable rates of 1 m per year due to irrigation of a double cropping system of winter wheat and summer maize. To reverse the trend, we examined whether alternative crop rotations could save water. Moisture contents were measured weekly at 20 cm intervals in the top 180 cm of soil as part of a 12-year field experiment with four crop rotations: sweet potato→ cotton→ sweet potato→ winter wheat-summer maize (SpCSpWS, 4-year cycle); peanuts → winter wheat-summer maize (PWS, 2-year cycle); ryegrass–cotton→ peanuts→ winter wheat-summer maize (RCPWS, 3-year cycle); and winter wheat-summer maize (WS, each year). We found that, compared to WS, the SpCSpWS annual evapotranspiration was 28% lower, PWS was 19% lower and RCPWS was 14% lower. The yield per unit of water evaporated improved for wheat within any alternative rotation compared to WS, increasing up to 19%. Average soil moisture contents at the sowing date of wheat in the SpCSpWS, PWS, and RCPWS rotations were 7, 4, and 10% higher than WS, respectively. The advantage of alternative rotations was that a deep rooted crop of winter wheat reaching down to 180 cm followed shallow rooted crops (sweet potato and peanut drawing soil moisture from 0 to 120 cm). They benefited from the sequencing and vertical complementarity of soil moisture extraction. Thus, replacing the traditional crop rotation with cropping system that involves rotating with annual shallow rooted crops is promising for reducing groundwater depletion in the North China Plain.

Many studies have focused on various agricultural management measures to reduce agricultural nitrous oxide (N2O) emission. However, few studies have investigated soil N2O emissions in intercropping systems in the North China Plain. Thus, we conducted a field experiment to compare N2O emissions under monoculture and maize-legume intercropping systems. In 2010, five treatments, including monocultured maize (M), maize-peanut (MP), maize-alfalfa (MA), maize-soybean (MS), and maize-sweet clover (MSC) intercropping were designed to investigate this issue using the static chamber technique. In 2011, M, MP, and MS remained, and monocultured peanuts (P) and soybean (S) were added to the trial. The results showed that total production of N2O from different treatments ranged from (0.87±0.12) to (1.17±0.11) kg ha−1 in 2010, while those ranged from (3.35±0.30) to (9.10±2.09) kg ha−1 in 2011. MA and MSC had no significant effect on soil N2O production compared to that of M (P

The maize sole cropping system solves problems related to ground water resource shortages and guarantees food security in the North China Plain. Using optimal sowing dates is an effective management practice for increasing maize yield. The goal of this study was to explore an optimum sowing date for high-yield maize. Six sowing dates (SDs) from early April to late June with intervals of 10 to 20 days between SD—SD1 (early April), SD2 (mid to late April), SD3 (early May), SD4 (mid to late May), SD5 (early June), SD6 (late June)—were applied from 2012 to 2017. The results showed that yield was correlated with the sowing date based on the thermal time before sowing (r = 0.62**), which was defined as the pre-thermal time (PTt), and that the yield was steadily maintained at a high level (>10,500 kg ha−1) when PTt was greater than 479 °C. To satisfy the growing degree-days required for maturity, maize needs to be sown before a PTt of 750 °C. Data analysis of the results from 2014, 2015, and 2017 revealed the following: i) Most of the grain-filling parameters of late-sown dates (SD4, SD5 and SD6) were better than those in early-sown dates (SD1, SD2, and SD3) in all years, because of the high daily maximum temperature (Tmax) and wide diurnal temperature (Td) from silking to blister (R1–R2) of early-sown dates. The weight of maximum grain-filling rate (Wmax) of SD3 decreased compare with SD4 by the narrow Td from blister to physiological maturity (R2–R6) in all years (−5, −12, and −33 mg kernel−1 in 2014, 2015, and 2017, respectively). ii) In 2017, the pollination failure rates of early-sown dates were 8.4~14.5%, which was caused by the high Tmax and Td of R1–R2. The apical kernel abortion rates were 28.6 (SD2) and 38.7% (SD3), which were affected by Tmax and Td during R2–R6. iii) Compared with late-sown dates, the wide Td of early-sown dates in R1–R2 was caused by higher Tmax, but the narrow Td in R2-R6 was caused by higher Tmin. Our results indicate that high-yielding maize can be obtained by postponing the sowing date with a PTt of 480~750 °C, which can prevent the negative effects of the high Tmax of R1–R2 and high Tmin of R2–R6 on kernel number and weight formation. Moreover, these above-mentioned traits should be considered for heat tolerance breeding to further increase the maize yield.

High temperature stress (HTS) on spring maize (Zea mays L.) during the filling stage is the key factor that limits the yield increase in the North China Plain (NCP). Subsoiling (SS) and ridge tillage (R) were introduced to enhance the ability of spring maize to resist HTS during the filling stage. The field experiments were conducted during the 2011 and 2012 maize growing seasons at Wuqiao County, Hebei Province, China. Compared with rotary tillage (RT), the net photosynthetic rate, stomatal conductance, transpiration rate, and chlorophyll relative content (SPAD) of maize leaves was increased by 40.0, 42.6, 12.8, and 29.7% under SS, and increased by 20.4, 20.0, 5.4, and 14.2% under R, repectively. However, the treatments reduce the intercellular CO2 concentration under HTS. The SS and R treatments increased the relative water content (RWC) by 11.9 and 6.2%, and the water use efficiency (WUE) by 24.3 and 14.3%, respectively, compared with RT. The SS treatment increased the root length density and soil moisture in the 0-80 cm soil profile, whereas the R treatment increased the root length density and soil moisture in the 0-40 cm soil profile compared with the RT treatment. Compared with 2011, the number of days with temperatures ⩾33°C was more 2 d and the mean day temperature was higher 0.9°C than that in 2012, whereas the plant yield decreased by 2.5, 8.5 and 10.9%, the net photosynthetic rate reduced by 7.5, 10.5 and 18.0%, the RWC reduced by 3.9, 5.6 and 6.2%, and the WUE at leaf level reduced by 1.8, 5.2 and 13.1% in the SS, R and RT treatments, respectively. Both the root length density and the soil moisture also decreased at different levels. The yield, photosynthetic rate, plant water status, root length density, and soil moisture under the SS and R treatments declined less than that under the RT treatment. The results indicated that SS and R can enhance the HTS resistance of spring maize during the filling stage, and led to higher yield by directly improving soil moisture and root growth and indirectly improving plant water status, photosynthesis and grain filling. The study can provide a theoretical basis for improving yield of maize by adjusting soil tillage in the NCP.

A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station (116.3°E, 39.9°N) in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize (Zea mays L.): sole maize (CK), maize + soybean (CST), maize + groundnut (CGT), maize + ryegrass (CHM), and maize + alfalfa (CMX). Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK>CST>CMX>CHM>CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9-174.8 (CGT), 35.2-130.8 (CHM), 60.4-122.0 (CMX), and 30.6-82.4 kg ha−1 (CST). The results also suggested that intercropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.

Weed control is one of the major constraint factors in crop production around the world. Field experiments were conducted during 2008-2009 under intercropping systems involving alfalfa (Medicago sativa L.), sweet potato (Ipomoea batatas [L.] Lam.), peanut (Arachis hypogaea L.), and sunflower (Helianthus annuus L.) in maize (Zea mays L.) without any weeds control methods taken. The results demonstrate that maize||sunflower is most effective on weed suppression and that it also has a more competitively inhibitory effect on Xanthium compared with the other patterns by evaluating the Xanthium density and dry weight under different intercropping systems with maize. Maize||peanut, maize||alfalfa and maize||sweet potato intercrops have no apparent inhibitory effect on weeds. To further investigate the effect of maize||sunflower on weed control, indoor pot experiments were conducted by determining the effect of extractions on germination rate (GR), root vigor, MDA (malondialdehyde), SOD (superoxide dismutase) and POD (peroxidase) content of Xanthium. The results better prove that maize||sunflower extractions have more significant inhibitory effect on GR and young root vigor of Xanthium than maize monocrop extractions.

Monocropping systems, which currently dominate China’s major grain production regions, contribute to resource scarcity and environmental pollution. Intercropping has the potential to improve resource use efficiency. However, prior studies of intercropping systems have generally focused on ecological, economic, and social consequences. Here, we make a comparative ecological sustainability analysis on energy capture and efficiency of maize monocropping and maize⁻soybean intercropping systems through emergy evaluation based on field experiments performed from 2012 to 2014. We find that maize monocropping shows higher sustainability than maize⁻soybean intercropping in the North China Plain at present. Quantitative results indicate that for maize monocropping, the emergy yield ratio (EYR) and emergy sustainability index (ESI) are 13.7% and 21.1% higher than that of intercropping systems, and the environmental loading ratio (ELR) is 7.3% lower than that of intercropping systems. To further test, we applied three levels of nitrogen fertilizer in intercropping systems (120 kg ha−1, 180 kg ha−1, 240 kg ha−1), and find that a reduced rate of N fertilizer for intercropped system leads to higher sustainability (ESI 5.3% higher) but still lower sustainability than maize monocropping. Key drivers of the different sustainability outcomes are decreased energy output and a larger proportion of labor input associated with intercropping systems.

The root bark essential oil of Periploca sepium Bunge (Asclepiadaceae/ Apocynaceae) obtained by hydrodistillation was investigated by GC and GC-MS. 2-Hydroxy-4-methoxybenzaldehyde was found to be the main component (78.8% of the total) among 17 identified compounds. 2-Hydroxy-4-methoxybenzaldehyde was separated and purified by preparative thin layer chromatography, and was further identified by means of physicochemical and spectrometric analysis. Both the essential oil and 2-hydroxy-4-methoxybenzaldehyde exhibited antimicrobial activities on all test bacteria and fungi, with MBC/MFC values ranging from 125 μg/mL to 300 μg/mL, MIC values from 80 μg/mL to 300 μg/mL, and IC50 values from 63.29 μg/mL to 167.30 μg/mL. They also showed moderate antioxidant activity in the DPPH free radical scavenging, β-carotene bleaching and ferrozine-ferrous ions assays. The results indicated that the major portion of these antimicrobial and antioxidant activities was due to the presence of 2-hydroxy-4-methoxy-benzaldehyde in the oil, which could potentially be developed as an antimicrobial and antioxidant agent in the future.

Water tables are dropping by approximately one meter annually throughout the North China Plain mainly due to water withdrawals for irrigating winter wheat year after year. In order to examine whether the drawdown can be reduced we calculate the net water use for an 11 year field experiment from 2003 to 2013 where six irrigated crops (winter wheat, summer maize, cotton, peanuts, sweet potato, ryegrass) were grown in different crop rotations in the North China Plain. As part of this experiment moisture contents were measured each at 20 cm intervals in the top 1.8 m. Recharge and net water use were calculated based on these moisture measurement. Results showed that winter wheat and ryegrass had the least recharge with an average of 27 mm/year and 39 mm/year, respectively; cotton had the most recharge with an average of 211 mm/year) followed by peanuts with 118 mm/year, sweet potato with 76 mm/year, and summer maize with 44 mm/year. Recharge depended on the amount of irrigation water pumped from the aquifer and was therefore a poor indicator of future groundwater decline. Instead net water use (recharge minus irrigation) was found to be a good indicator for the decline of the water table. The smallest amount of net (ground water) used was cotton with an average of 14 mm/year, followed by peanut with 32 mm/year, summer maize with 71 mm/year, sweet potato with 74 mm/year. Winter wheat and ryegrass had the greatest net water use with the average of 198 mm/year and 111 mm/year, respectively. Our calculations showed that any single crop would use less water than the prevalent winter wheat summer maize rotation. This growing one crop instead of two will reduce the decline of groundwater and in some rain rich years increase the ground water level, but will result in less income for the farmers.

Abstract Background Epidemiological studies suggest considerable overlap between functional dyspepsia (FD) and irritable bowel syndrome (IBS). To date, no surveys have been performed to investigate the clinical overlap between these two disorders using Rome III criteria. Our aim was to investigate the prevalence and risk factors for the overlap of FD and IBS based on Rome III criteria in a large clinical sample. Methods Consecutive patients at the general gastroenterology outpatient clinic were requested to complete a self-report questionnaire. FD and IBS were defined by Rome III criteria. Results Questionnaires were returned by 3014 patients (52.8% female, 89% response rate). FD-IBS overlap was observed in 5.0% of the patients, while 15.2% and 10.9% of the patients were classified as FD alone and IBS alone, respectively. Compared with non-IBS patients, the odds ratio of having FD among IBS patients was 2.09 (95% CI: 1.68–2.59). Patients with FD-IBS overlap had higher severity scores for the postprandial fullness symptom (2.35 ± 1.49 vs. 1.72 ± 1.59, P < 0.001) and overall FD symptom (6.65 ± 2.88 vs. 5.82 ± 2.76, P = 0.002) than those with FD alone. The only independent risk factor for FD-IBS overlap vs. FD alone was the presence of postprandial fullness symptom (OR 2.67, 95% CI: 1.34–5.31). Conclusion Clinical overlap of FD and IBS according to Rome III criteria is very common. One risk factor for FD-IBS overlap is the presence of postprandial fullness symptom. This study provides clues for future pathophysiological studies of FD and IBS.