Long-term residue returning increased subsoil carbon quality in a rice-wheat cropping system.

Residue returning (RR) was widely implemented to increase soil organic carbon (SOC) in farmland. Extensive studies concentrated on the effects of RR on SOC quantity instead of SOC fractions at aggregate scales. This study investigated the effects of 20-year RR on the distribution of labile (e.g., dissolved, microbial biomass, and permanganate oxidizable organic) and stable (e.g., microbial necromass) carbon fractions at aggregate scales, as well as their contribution to SOC accumulation and mineralization. The findings indicated a synchronized variation in the carbon content of bacterial and fungal necromass. Residue retention (RR) notably elevated the concentration of bacterial and fungal necromass carbon, while it did not amplify the microbial necromass carbon (MNC) contribution to SOC when compared to residue removal (R0) in the topsoil (0-5 cm). In the subsoil (5-15 cm), RR increased the MNC contribution to SOC concentration by 21.2%-33.4% and mitigated SOC mineralization by 12.6% in micro-aggregates (P < 0.05). Besides, RR increased soil ß-glucosidase and peroxidase activities but decreased soil phenol oxidase activity in micro-aggregates (P < 0.05). These indicated that RR might accelerate cellulose degradation and conversion to stable microbial necromass C, and thus RR improved SOC stability because SOC occluded in micro-aggregates were more stable. Interestingly, SOC concentration was mainly regulated by MNC, while SOC mineralization was by dissolved organic carbon under RR, both of which were affected by soil carbon, nitrogen, and phosphorus associated nutrients and enzyme activities. The findings of this study emphasize that the paths of RR-induced SOC accumulation and mineralization were different, and depended on stable and labile C, respectively. Overall, long-term RR increased topsoil carbon quantity and subsoil carbon quality.

Reduced Root Cortical Tissue with an Increased Root Xylem Investment Is Associated with High Wheat Yields in Central China.

Trait-based approaches are increasingly used to understand crop yield improvement, although they have not been widely applied to anatomical traits. Little is known about the relationships between root and leaf anatomy and yield in wheat. We selected 20 genotypes that have been widely planted in Luoyang, in the major wheat-producing area of China, to explore these relationships. A field study was performed to measure the yields and yield components of the genotypes. Root and leaf samples were collected at anthesis to measure the anatomical traits relevant to carbon allocation and water transport. Yield was negatively correlated with cross-sectional root cortex area, indicating that reduced root cortical tissue and therefore reduced carbon investment have contributed to yield improvement in this region. Yield was positively correlated with root xylem area, suggesting that a higher water transport capacity has also contributed to increased yields in this study. The area of the leaf veins did not significantly correlate with yield, showing that the high-yield genotypes did not have larger veins, but they may have had a conservative water use strategy, with tight regulation of water loss from the leaves. This study demonstrates that breeding for higher yields in this region has changed wheat's anatomical traits, reducing the roots' cortical tissue and increasing the roots' xylem investment.

Identifying synergistic solutions for the food-energy-water nexus via plastic film mulching cultivation.

Food security, water scarcity, and excessive fossil energy use pose considerable challenges to sustainable agriculture. To understand how rain-fed farming systems on the Loess Plateau, China, reconcile yield increases with ecological conservation, we conducted an integrated evaluation based on the denitrification-decomposition (DNDC) model, agricultural statistics data using the Food-Energy-Water (FEW) nexus indicator. The results showed that maize yields with ridge-furrow plastic film mulching (PFM) were 3479, 8942, and 11,124 kg ha-1 under low (50 kg N ha-1), medium (200 kg N ha-1), and high (350 kg N ha-1) nitrogen (N) fertilizer rates, respectively, and that PFM increased yield and water use efficiency (WUE) by 110-253 % and 166-205 % compared to using no mulching (control, CK), respectively. Plastic film mulching also increased net energy (126-436 %), energy use efficiency (81-578 %), energy productivity (100-670 %), and energy profitability (126-994 %), and nitrogen fertilizer, compound fertilizer, and diesel fuel consumption by agricultural machinery were the main energy inputs. The PFM system reduced water consumption during the maize growing season and the green water footprint and gray water footprint decreased by 66-74 % and 44-68 %, respectively. The FEW nexus indicator, based on a high production at low environmental cost scenario, was greater under the PFM system and had the widest spatial distribution area at the medium-N application rate. Among the environmental factors, the nexus indicator was negatively correlated with precipitation (-0.37), air temperature (-0.36), and the aridity index (-0.36), but positively correlated with elevation (0.17). Our results suggest that the PFM system promotes resource-saving while increasing yields and moves dryland agriculture in an environmentally friendly direction, thus promoting the sustainable development of agroecosystems.

Fungal community composition changes and reduced bacterial diversity drive improvements in the soil quality index during arable land restoration.

Arable land is facing the growing challenge of land degradation due to intensive use and this is beginning to affect global food security. However, active and passive restoration can improve soil characteristics and reshape microbial communities. Despite the increasing focus on changes in microbial communities during restoration, the mechanisms underlying how microbes drive the soil quality index (SQI) in arable land restoration remain unclear. In this study, we selected conventional farmland (CF, heavily intensified) and two restoration strategies (AR, artificial restoration; NR, natural restoration), with the same context (including soil texture, climate, etc.), and measured the microbial indicators over 2 years to investigate the mechanisms driving SQI improvement on restored arable land. The AR and NR treatments resulted in a 50% and 58% increase in SQI, respectively, compared to CF as soil nutrient levels increased, resulting in higher microbial biomasses and enzyme activities. Microbial abundance on the AR land was approximately two times greater than on the NR land due to the introduction of legumes. Bacterial diversity declined, while fungi developed in a more diverse direction under the restoration strategies. The AR and NR areas were mainly enriched with rhizobium (Microvirga, Bradyrhizobium), which contribute to healthy plant growth. The pathogenic fungi (Gibberella, Fusarium, Volutella) were more abundant in the CF area and the plant pathogen guild was about five times higher in the restored areas. Following arable land restoration, microbial life history strategies shifted from r-to K-strategists due to the higher proportion of recalcitrant SOC (DOC/SOC decreased by 18%-30%). The altered microbial community in the restored areas created new levels of functionality, with a 2.6%-4.3% decrease in bacterial energy metabolism (oxidative phosphorylation, C fixation, and N metabolism decreased by 7%, 4%, and 6%, respectively). Structural equation modelling suggested that restoration strategy affected SQI either directly by increasing total soil nutrient levels or indirectly by altering the microbial community and that fungal community composition and bacterial diversity made the largest contributions to SQI. These results provided new insights into soil quality improvement from a microbial perspective and can help guide future arable land restoration.

The prolonged effect of film mulch and P application on lucerne forage yield in a semiarid environment.

Introduction: Limited water and soil phosphorus (P) availability often hampers lucerne productivity in semiarid regions. Plastic film mulch and P application typically enhance young lucerne (2-3 years) productivity by increasing soil water use and P availability. However, the prolonged impact of film mulch and P application on lucerne productivity as the stand ages remains unclear. Methods: This study conducted a 9-year field experiment on the semiarid Loess Plateau to investigate how film mulch and P application affect lucerne forage yield, soil water content, and soil fertility. The field experiment used a split-plot design with randomized blocks, in which the whole plots were with (M1) and without plastic film mulch (M0), and the split plots were four P rates (0 (P0), 9.7 (P1), 19.2 (P2), and 28.8 (P3) kg P ha-1). Results and discussion: The M1 treatment produced significantly higher lucerne forage yields than the M0 treatment during the first five years, but the yield-increasing effect of film mulch gradually diminished over time, with no effect in Years 6-8, and lower yields than the M0 treatment in Year 9. Phosphorus fertilization significantly increased forage yield after Year 3 in the M0 treatment, but only in Years 3-5 in the M1 treatment. In Years 2-5, film mulch significantly increased soil organic carbon, total nitrogen (N), inorganic N, and microbial biomass carbon in P0, P1, and P2 but not in P3. However, in Years 7-9, film mulch significantly decreased soil available potassium (K), organic carbon mineralization, lucerne density, and shoot K concentration, but did not reduce soil N and P availability at any level P of application. Moreover, plastic film mulch significantly increased the soil water content at 0-300 cm deep from Year 7 onwards. In conclusion, film mulch ceased to enhance lucerne production beyond year 6, which could not be attributed to soil water content, N or P availability but was partially associated with reduced soil K availability. Consequently, future research should focus on soil K availability, and K addition should be considered after five years in lucerne pastures mulched with plastic film in semiarid areas.

[Photodegradation of Plastic Blends in Seawater and Its Risk to the Marine Environment].

The production and use of plastic blends have been gradually increasing owing to their versatility and low cost. However, the photodegradation of plastic blends in seawater and the potential risk to the marine environment are still not well understood. In this study, plastic blends including polypropylene/thermoplastic starch blends(PP/TPS) and polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch blends(PLA/PBAT/TPS) were investigated. The corresponding neat polymers, namely polypropylene(PP) and polylactic acid(PLA), were set as control groups. We investigated the formation of MPs and the changes in the physicochemical properties of plastic blends after photodegradation in seawater. The size distribution of MPs indicated that PP/TPS and PLA/PBAT/TPS were more likely to produce small-sized particles after photodegradation than PP and PLA owing to their poorer mechanical properties and lower resistance to UV irradiation. Noticeable surface morphology alterations, including cracks and wrinkles, were observed for plastic blends following photodegradation, whereas PP and PLA were relatively resistant. After photodegradation, the ATR-FTIR spectrum of PP/TPS and PLA/PBAT/TPS showed a significant decrease in the characteristic bands of thermoplastic starch(TPS), indicating the degradation of their starch fractions. The C 1s spectra demonstrated that aged plastic blends contained fewer -OH groups than the pristine MPs did, further confirming the photodegradation of TPS. These results indicate that PP/TPS and PLA/PBAT/TPS had a higher degree of photodegradation than PP and PLA and thereby generated more small-sized MPs. In summary, plastic blends may pose a higher risk to the marine environment than neat polymers, and caution should be taken in the production and use of plastic blends.

Seasonal resource selection of free-ranging Zhongwei goats in the semi-arid grassland.

Goats rarely move and forage randomly. They tend to move in ways generally influenced by biotic and abiotic factors, respectively. However, few studies have explored the foraging behaviour of goats in the absence of predation and human disturbance. Based on step selection function modelling framework, Normalised Difference Vegetation Index, vegetation surveys, and Global Positioning System tracking of 124 free-ranging domestic adult male Zhongwei goats over one year (2016-2017) were used to assess how biotic and abiotic environmental factors affected their spatiotemporal distribution, and developed a conceptual model to represent the goats' trade-off between forage quantity and preference at different seasons, in the semi-arid grassland of Loess Plateau of 1 178 hectare. The results showed that spatial distributions of goats responded to spatiotemporal variation of biotic factors rather than abiotic factors of elevation, slope and solar radiation, which indicated that biotic factors were of priority to abiotic factors in the foraging process for the goats. According to the season changing, the goats positively used areas with higher forage quantity in the spring and winter, areas of higher forage quantity and preferred species in summer, and areas of abundance of preferred species in autumn. We developed a model to describe the phenomenon that the goats selected areas with higher preferred species only when the forage quantity was plentiful, otherwise they selected areas with higher forage quantity. Better understanding of the patterns and drivers of spatiotemporal distribution of the goats can improve our ability to predict foraging behaviour of livestock in heterogeneous environment and lead to better management practices and policies for the sustainability of these semi-arid landscapes and associated ecosystem services.

Plant biomass mediates the decomposition of polythene film-sourced pollutants in soil through plastisphere bacteria island effect.

The polyethylene (PE) film mulching as a water conservation technology has been widely used in dryland agriculture, yet the long-term mulching has led to increasing accumulation of secondary pollutants in soils. The decomposition of PE film-sourced pollutants is directly associated with the enrichment of specific bacterial communities. We therefore hypothesized that plant biomass may act as an organic media to mediate the pollutant decomposition via reshaping bacterial communities. To validate this hypothesis, plant biomass (dried maize straw and living clover) was embedded at the underlying surface of PE film, to track the changes in the composition and function of bacterial communities in maize field across two years. The results indicated that both dry crop straw and alive clover massively promoted the α-diversity and abundance of dominant bacteria at plastisphere, relative to bulk soil. Bacterial communities tended to be clustered at plastisphere, forming the bacteria islands to enrich pollutant-degrading bacteria, such as Sphingobacterium, Arthrobacter and Paracoccus. As such, plastisphere bacteria islands substantially enhanced the degradation potential of chloroalkene and benzoate (p < 0.05). Simultaneously, bacterial network became stabilized and congregated at plastisphere, and markedly improved the abundance of plastisphere module hubs and connectors bacteria via stochastic process. Particularly, bacterial community composition and plastic film-sourced pollutants metabolism were evidently affected by soil pH, carbon and nitrogen sources that were mainly derived from the embedded biomass. To sum up, plant biomass embedding as a nature-based strategy (NbS) can positively mediate the decomposition of plastic-sourced pollutants through plastisphere bacteria island effects.

The impact of crop residue return on the food-carbon-water-energy nexus in a rice-wheat rotation system under climate warming.

Rice-wheat rotation (RWR) is one of the major cropping systems in China and plays a crucial role in the country's food security. With the promotion of "burn ban" and "straw return" policies, the "straw return + rice-wheat crop rotation system" has been developed in China's RWR area. However, the effect of promotion of straw return on production and ecological benefits of RWR areas is unclear. In this study, the main planting zones of RWR were examined, and ecological footprints and scenario simulation were applied to explore the effect of straw return on the food-carbon-water-energy nexus under conditions of a warming world. The results indicate that with rising temperatures and the promotion of straw return policies, the study area was in a "carbon sink" state during 2000-2019. The study area's total yield climbed by 48 % and the carbon (CF), water (WF) and energy (EF) footprints decreased by 163 %, 20 % and 11 %, respectively. Compared to 2000-2009, the temperature increase for 2010-2019 was negatively correlated with the increase in CF and WF and positively correlated with the increase of yield and EF. A 16 % reduction in chemical fertilizers, increasing the straw return rate to 80 % and utilizing tillage techniques such as furrow-buried straw return would contribute to sustainable agriculture in the RWR area under a projection of 1.5 °C increase in air temperature. The promotion of straw return has contributed to improved production and the maintenance and reduction of CF, WF, and EF in the RWR, but further optimization measures are required to reduce the footprint of agriculture in a warmer world.

Research review on the pollution of antibiotic resistance genes in livestock and poultry farming environments.

Increasingly serious pollution of antibiotic resistance genes (ARGs) caused by the abuse of antibiotics in livestock and poultry industry has raised worldwide concerns. ARGs could spread among various farming environmental media through adsorption, desorption, migration, and also could transfer into human gut microbiome by hori-zontal gene transfer (HGT), posing potential threats to public health. However, the comprehensive review on the pollution patterns, environmental behaviors, and control techniques of ARGs in livestock and poultry environments in view of One Health is still inadequate, resulting in the difficulties in effectively assessing ARGs transmission risk and developing the efficient control strategies. Here, we analyzed the pollution characteristics of typical ARGs in various countries, regions, livestock species, and environmental media, reviewed the critical environmental fate and influencing factors, control strategies, and the shortcomings of current researches about ARGs in the livestock and poultry farming industry combined with One Health philosophy. In particular, we addressed the importance and urgency of identifying the distribution characteristics and environmental process mechanisms of ARGs, and developing green and efficient ARG control means in livestock farming environments. We further proposed gaps and prospects for the future research. It would provide theoretical basis for the research on health risk assessment and technology exploitation of alleviating ARG pollution in livestock farming environment.

Soil organic carbon regulates CH4 production through methanogenic evenness and available phosphorus under different straw managements.

Methane (CH4) is the main greenhouse gas emitted from rice paddy fields driven by methanogens, for which methanogenic abundance on CH4 production has been intensively investigated. However, information is limited about the relationship between methanogenic diversity (e.g., richness and evenness) and CH4 production. Three independent field experiments with different straw managements including returning method, burial depth, and burial amount were used to identify the effects of methanogenic diversity on CH4 production, and its regulating factors from soil properties in a rice-wheat cropping system. The results showed that methanogenic evenness (dominance) can explain 23% of variations in CH4 production potential. CH4 production potential was positively related to methanogenic evenness (R2 = 0.310, p < 0.001), which is driven by soil organic carbon (SOC), available phosphorus (AP), and nitrate (NO3-) through structure equation model (SEM). These findings indicate that methanogenic evenness has a critical role in evaluating the responses of CH4 production to agricultural practices following changes in soil properties. The SEM also revealed that SOC concentration influenced CH4 production potential indirectly via complementarity of methanogenic evenness (dominance) and available phosphorus (AP). Increasing SOC accumulation improved AP release and stimulated CH4 production when SOC was at a low level, whereas decreased evenness and suppressed CH4 production when SOC was at a high level. A nonlinear relationship was detected between SOC and CH4 production potential, and CH4 production potential decreased when SOC was ≥14.16 g kg-1. Our results indicated that the higher SOC sequestration can not only mitigate CO2 emissions directly but CH4 emissions indirectly, highlighting the importance to enhance SOC sequestration using optimum agricultural practices in a rice-wheat cropping system.

Reducing plant pathogens could increase crop yields after plastic film mulching.

Soil fungi are closely associated with crop growth in agricultural ecosystems through processes such as nutrient uptake and pathogenesis. Plastic film mulching (PM) plays a dominant role in increasing crop yields in dryland agriculture worldwide. The functional guilds of soil fungi under PM and their effects on crops remain unclear. In this study, we explored the absolute abundance, diversity, community composition, and functional guilds of soil fungi after short-term (2 years) and long-term (10 years) mulching experiments. Short-term mulching caused a 37 %-51 % decrease in absolute fungal abundance owing to abrupt changes in the microenvironment. The response of the fungal community to PM varied with sites, with the effect being more pronounced under poor hydrothermal conditions (314 mm). The abundance of potential fungal pathogens decreased under PM; for example, Gibberella (maize ear rot) abundance was 45 % and 72 % lower under short- and long-term mulching, respectively, when compared with that in control. In contrast, the abundance of plant biocontrol fungi increased under PM; for instance, Glomeromycota abundance increased twofold under long-term mulching. Although PM did not alter the complexity and stability of fungal co-occurrence network, competition among fungi increased in the absence of sufficient carbon (C) sources. Long-term mulching reduced phytopathogen guilds by 12 %-77 % and increased arbuscular mycorrhizal fungi (AMF) guilds by 89 %-94 %. Structural equation modeling suggested that PM altered fungal functional guilds mainly by shaping the structure of the fungal community, and fungal pathogens decreased with increased AMF functional guilds, inducing higher maize yields. These results showed for the first time, from a microbial perspective, that pathogens reduction owing to PM could explain 4.4 % of maize yield variation, providing theoretical guidance to accomplish sustainability of continuous maize mulching.

Straw incorporation interacting with earthworms mitigates N2O emissions from upland soil in a rice-wheat rotation system.

Intensive attentions have been paid to the positive effects on nitrous oxide (N2O) production under straw return or the presence of earthworms. Straw return as a sustainable practice can promote earthworm growth, how the interactions between straw and earthworms affect N2O production is still not well known. A split-plot field experiment (straw return as main plot and earthworm addition as subplot) was performed to quantify the interactive effects of straw and earthworm on N2O emissions from a wheat field and to determine the underlying mechanisms from nitrification and denitrification processes. The results showed that straw return significantly increased N2O emissions by 41.0 % under no earthworm addition but decreased it by 19.0 % under earthworm addition compared with straw removal (P < 0.05). The significant interaction between straw and earthworm benefits the mitigation of N2O emissions. Random forest model showed that denitrification and nitrification were dominant processes to affect N2O emissions at the jointing and booting growth stages of wheat, respectively. The interaction between straw and earthworm significantly decreased the abundances of N2O-producing bacterial genes such as nirS and nirK at the jointing stages, and AOB at the booting stages. The contrasting mechanisms in regulating N2O emissions at different growth stages should be considered in nitrogen recycling models to accurately predict available N and N2O dynamics. Our findings suggest that N2O emissions under straw return can be weakened with the increasing earthworm populations under the scenario of widely used conservation practices (e.g., straw return and no-till) due to significant interaction between straw and earthworms.

Long-term alfalfa (Medicago sativa L.) establishment could alleviate phosphorus limitation induced by nitrogen deposition in the carbonate soil.

Phosphorus (P) limitation is a widespread problem of primary production in dryland submitted to persistent nitrogen (N) deposition. The legume alfalfa (Medicago sativa L.), which can fix N2, might potentially strengthen P limitation in dryland ecosystems and is widely distributed as forage. However, there is still unclear how alfalfa grassland mobilizes the soil P to meet its demand. In this experiment, alfalfa introduction was used for long-term revegetation to evaluate the P uptake of plants from deep soil and assess the P limitation induced by N deposition compared with fallow. Our results showed that alfalfa introduction increased the soil P storage significantly at 0-2.4 m soil depth (+0.74 Mg ha-1), whereas it decreased at 2.4-4.8 m soil depth (-0.21 Mg ha-1) after 15-year establishment. Alfalfa establishment increased soil organic P concentration (180.9 mg kg-1 vs. 67.2 mg kg-1) and its relative contribution to total P (19.64% vs. 8.08%) at 0-4.8 m. Alfalfa establishment also increased the concentration and proportion of labile and intermediate P fractions at 0-4.8 m (9.12 mg kg-1 vs. 6.87 mg kg-1, 1.12% vs. 0.98%; 16.06 mg kg-1 vs. 8.39 mg kg-1, 1.69% vs. 1.17%). Alfalfa introduction decreased the concentrated HCl-Pi (250.66 mg kg-1 vs. 229.32 mg kg-1, 36.81% vs. 28.91%) in 2.4-4.8 m soil depth. These results indicated that the deep root system of alfalfa grassland could promote the P mobilization from deep to shallow soil. The concentrated HCl-Pi may be the main potential P source of alfalfa from 2.4-4.8 m to 0-2.4 m of soil depth, and long-term establishment of alfalfa can alleviate P limitation caused by N deposition in carbonate soil. Our results suggested that species with deep roots (such as alfalfa) could be selected as an economical way to mitigate nitrogen deposition in drylands.

Effects on Photosynthetic Response and Biomass Productivity of Acacia longifolia ssp. longifolia Under Elevated CO2 and Water-Limited Regimes.

It is known that the impact of elevated CO2 (eCO2) will cause differential photosynthetic responses in plants, resulting in varying magnitudes of growth and productivity of competing species. Because of the aggressive invasive nature of Acacia longifolia ssp. longifolia, this study is designed to investigate the effect of eCO2 on gas exchange parameters, water use efficiency, photosystem II (PSII) activities, and growth of this species. Plants of A. longifolia ssp. longifolia were grown at 400 ppm (ambient) and 700 ppm (elevated) CO2 under 100 and 60% field capacity. Leaf gas exchange parameters, water use efficiency, intrinsic water use efficiency, instantaneous carboxylation efficiency, and PSII activity were measured for 10 days at 2-day intervals. eCO2 mitigated the adverse effects of drought conditions on the aforementioned parameters compared to that grown under ambient CO2 (aCO2) conditions. A. longifolia, grown under drought conditions and re-watered at day 8, indicated a partial recovery in most of the parameters measured, suggesting that the recovery of this species under eCO2 will be higher than that with aCO2 concentration. This gave an increase in water use efficiency, which is one of the reasons for the observed enhanced growth of A. longifolia under drought stress. Thus, eCO2 will allow to adopt this species in the new environment, even under severe climatic conditions, and foreshadow its likelihood of invasion into new areas.

Biomass Allocation Responses to Root Interactions in Wheat Cultivars Support Predictions of Crop Evolutionary Ecology Theory.

The goal of agriculture is to optimize the population yield, but natural selection has produced active competition among plants, which decreases population performance. Therefore, cultivar breeding should be based on group selection, increasing yield by weakening individual competitive responses. We hypothesize that this has occurred inadvertently to some degree, so modern cultivars have weakened competitive traits and responses, such as reduced root proliferation in response to neighboring roots. We conducted a field experiment with eight cultivars of spring wheat that have been released over the last hundred years, which we grew at two densities. Two contrasting wheat cultivars, a landrace and a modern cultivar, were used in a second field experiment on competition within and between the two cultivars to quantify their competitiveness. Finally, a greenhouse experiment was conducted with these two cultivars gown (a) in mixture and monoculture, (b) at four densities, (c) two watering levels, and (d) with permeable vs. non-permeable soil dividers, to study root proliferation responses to competition. Results of field experiment 1 showed that the population aboveground biomass (AGB) had increased, while belowground biomass had decreased over the course of breeding, so that the root to shoot ratio (R/S) was negatively correlated with the release year of the cultivar. The landrace had stronger competitiveness than the modern cultivar in the field experiment 2. There was clear evidence of root proliferation and a resultant reduction in AGB in response to neighboring roots in the greenhouse experiment, and the modern variety showed less root proliferation in response to neighbors. We conclude that the newer cultivar was a weaker competitor but higher-yielding in two ways: (1) it had higher reproductive effort and therefore less allocation to structures that increase competitive ability, and (2) it had reduced root proliferation in response to the roots of neighboring plants. Our results show that wheat plants change their biomass allocation in response to resource levels and the presence of neighboring roots. The presence of root proliferation in the modern cultivar, albeit less than in the landrace, suggests that further increases in yield via group selection are possible.

Conservation tillage or plastic film mulching? A comprehensive global meta-analysis based on maize yield and nitrogen use efficiency.

Rain-fed agriculture is an important part of the global agriculture system and plays a vital role in ensuring food security. Conservation tillage (CT) is widely used in USA maize cultivation in the Mid-west Corn Belt. Meanwhile, Chinese farmers' adoption of CT is limited and plastic film mulching (PM) is widely developed to increase maize yield in northern China. This paper compared the yield and nitrogen use efficiency (NUE) between CT and PM, and analyzed the reasons for the differences in the choice of maize cultivation practice. We collected 767 observations for CT and 217 observations for PM and analyzed how these two tillage practices affected yield. For NUE, there were 66 and 56 observations, respectively. The meta-analysis showed that PM significantly increased maize yield by 36% and NUE by 34% compared with the control, and CT significantly decreased maize yield by 5% and NUE by 15%. The effects of PM on maize yield were mainly determined by growing season precipitation (GSP) and temperature (GST). The yield response ratio was also influenced by the type of plastic film, mulching cycle, pH, soil saturated hydraulic conductivity, and soil bulk density. The negative effects of CT on yield could be alleviated under good hydrothermal conditions and with straw mulching. The yield response ratio was also affected by soil texture and N application rate. In conclusion, PM should be applied under limited hydrothermal conditions (GSP < 650 mm or GST < 23 °C), and CT was conducive to higher maize yield under good hydrothermal conditions (GSP > 650 mm or GST > 23 °C) . Besides, the average farm size was positively correlated with the CT total areas.

The effects of plastic film mulching and straw mulching on licorice root yield and soil organic carbon content in a dryland farming.

The increasing worldwide demand for traditional herbs has been met by growing cultivated herbs. It is undoubtedly very important to seek a reasonable cultivation mode for the yield, quality and long-term production stability of traditional herbs. In this study, licorice (Glycyrrhiza uralensis Fisch.) was investigated using a field experiment and a process-based model (Denitrification-Decomposition (DNDC) model) to study the effects of mulching methods on root yield and soil organic carbon (SOC) long-term changes. The field experiment contained four treatments: plat planting without mulching (CK), ridge-furrow maize straw mulching (SM), ridge-furrow plastic film mulching (RP), and plat planting with plastic film mulching (FP). Licorice root yield was significantly higher in the SM, RP, and FP than in the CK. SM, RP and FP treatments increased the accumulation of liquiritin and glycyrrhizin in licorice roots. The SM significantly increased SOC content, SOC stocks, SOC sequestration rate, dissolved organic carbon (DOC) content and microbial biomass carbon (MBC) compared to CK, but there was no significant difference in SOC and DOC among CK, RP and FP. The DNDC model was calibrated based on the field test data and showed that under the four CMIP6 SSPs scenarios, the predicted root yield of each treatment was increasing obviously. The production and stability of RP and FP were greater than CK and SM. The SOC under SM showed an increasing trend, whereas it continuously decreased under CK, RP, and FP in the future. The SOC of simulated RS treatment of straw incorporation plus a plastic film mulch was always at the highest value in all the treatments, and its root yield was slightly lower than that of RP and FP, the latter both were very close. Therefore, it is suggested that RS should be adopted to achieve sustained high yield while maintaining a high SOC level.

Optimum fertilizer application rate to ensure yield and decrease greenhouse gas emissions in rain-fed agriculture system of the Loess Plateau.

Application of nitrogen (N) can increase the supply of N in soil and, in turn, can lead to higher yield-but also to large increase in emissions of greenhouse gases (GHGs) if applied in excess. To determine the optimum dose of N for maize planting system, we analysed the relationship between yield and emissions of GHGs at seven levels of N, namely 50, 100, 150, 200, 250, 300, and 350 kg ha-1, using the DNDC (denitrification decomposition) model and maize grown with and without mulching. The model simulated the following variables: maize production; emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4); global warming potential (GWP); and GHG intensity (GHGI). We used data from 1980 to 2013 for a rain-fed region of the Loess Plateau in north-western China and validated the DNDC model against data from field experiments. The model performed well in simulating yield and GHG emissions (Adj.R2 > 0.61). Under mulching, the average yield of maize was 3.6-12.2 t ha-1 and the partial factor productivity was 73.1-35.0 kg kg-1; and both of these were significantly higher 78%-236% than those in the crop without mulching. The emissions of CO2, N2O, and the GWP increased with the increase in the dose of N whereas CH4 emissions remained unaffected by the dose. Mulching increased yields significantly in the north-western region, and the GWP and GHGI were higher mainly in the central and north-western regions. The optimum dose of N for maize grown with mulching ranged between 150 kg ha-1 and 200 kg ha-1 and offers the best balance between higher yield and lower emissions. The optimum dose may promote the development of mulched maize and provide a reference standard for dryland agriculture in zones with similar climates elsewhere in the world.

Optimum plastic mulching application to reduce greenhouse gas emissions without compromising on crop yield and farmers' income.

With the rapid socio-economic development in China, poverty alleviation and the reduction of the environmental footprint in the plastic film mulching (PM) planting system have become key to sustainable agricultural production. Although many studies have evaluated the maize yield, agricultural economic benefits, and greenhouse gas (GHG) emissions associated with PM through small-scale field experiments, identifying suitable PM regions in combination with their demographic characteristics and the future development of such systems has received little attention. This study combines a Denitrification-Decomposition (DNDC) model and demographic characteristics to determine the optimum PM region in rainfed areas of the Loess Plateau in northwest China. The results demonstrated that PM produced a higher maize yield, agricultural net profit (ANP), and cost-benefit ratio compared to a control treatment (CK) without PM. An agricultural income far above the poverty level would assist in meeting the goals of alleviating poverty and building a prosperous society. In addition, the PM system produced more GHG emissions, but had a lower greenhouse gas intensity (GHGI) than CK under both low (200 kg N ha-1) and high (300 kg N ha-1) nitrogen (N) fertilizer rates. This study developed a framework to evaluate maize yield alongside economic and environmental indicators. We concluded that PM should be adopted in areas with precipitation less than 500 mm, and concentrated in the region with rainfall of 200-400 mm. The results provide a theoretical basis for the sustainable development of the PM maize planting system, and will contribute to the desired goal of environmentally sustainable agricultural production.