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Abstract Nematodes serve as key indicators of soil health in ecological studies. Therefore, the current study examined the community structure and metabolic footprint of soil nematodes in alfalfa fields across varying levels of N supply in the semi-arid Loess Plateau. The findings offer theoretical guidance for the sustainable management of artificial alfalfa grasslands in this region. The research was based on alfalfa fields with different N application rates (0, 50, 100, 150 kg/ha2) as the research object, The shallow plate method was used to separate and extract soil nematodes, identify soil nematode groups, calculate ecological function index and metabolic footprint, and identify indicator species. A total of 6346 nematodes were isolated in this study, belonging to 27 genera and 19 families. Notably, the plant parasitic nematode Helicotylenchus was predominant. As N addition increased, the plant parasitic index (PPI) increased significantly. A N50 application significantly enhanced the soil nematode diversity index ( $$\text{H}$$ H ) and the free-living index (MI). The findings showcased a noticeable decrease in disturbance within the N50 soil nematode community. This resulted in a mature and stable community structure primarily attributed to the heightened abundance of omnivorous/predatory nematodes. Across various N levels, soil nematode communities underwent significant alterations in the soil food web structure through shifts in their metabolic footprint. Future strategies should focus on refining N management practices and integrating sustainable approaches like crop rotation and pest management. These efforts will contribute to guidelines ensuring artificial alfalfa grasslands lasting health and productivity.

Innovative superabsorbent hydrogels were synthesized from watermelon rind (WR), an abundant agricultural waste. The process involved free radical polymerization of acrylic acid (AA) and acrylamide (AAm) with WR particles activated by ammonium persulfate (APS), resulting in (AA-co-AAm)/WR hydrogels with high equilibrium swelling capacities of 749 ± 32 g/g. Notably, after eight cycles, the WR hydrogel maintained 94.88 % of its initial swelling capacity, significantly outperforming the (AA-co-AAm) hydrogel without WR (13.80 % retention). This durability, combined with excellent water retention across various soil textures and high adsorption capacity for methylene blue (MB), underscores the WR hydrogel as a superior soil moisture conservation agent. This study marks a significant advance in recycling organic waste and enhancing water management in agricultural soils, demonstrating the potential for sustainable hydrogel development.

Water stress is the most important factor limiting crop production in arid and semiarid regions. Cultivating crops using a plastic film mulch can significantly increase crop yields by optimizing soil hydrothermal conditions in semiarid agroecosystems. Therefore, clarifying root adaptability to plastic film mulch cultivation is crucial when attempting to produce stable and high maize yields. A two-year experiment was conducted to investigate the effects of two treatments, no mulching (NM) and plastic film mulching (FM), on the yield, water productivity (WP), and root morphology of spring maize on the Loess Plateau. The results showed that the FM yield (14.31–15.02 t ha–1) significantly increased by 18.6–29.7 % compared to NM (11.03–12.66 t ha–1). The FM treatment also significantly increased dry matter (51.0–61.6 %), leaf area (19.7–25.7 %), and WP (28.8–46.3 %), but decreased ET (8.6–12.8 %). In addition, soil water storage in the FM surface soil layer significantly increased compared to that of NM. Film mulching also produced more robust roots and promoted the convergence of roots towards the surface of the soil, whereas NM roots tended to grow downwards to obtain water from the lower soil layers. The regression analyses indicated that root length (R2 = 0.725, P < 0.01) and biomass (R2 = 0.736, P < 0.01) were positively correlated with grain yield. The results suggested that maize adapts to changes in root morphological behavior under FM. These changes contribute to soil water and nutrient capture and shoot development, which subsequently support the high yields produced under plastic film mulching. Therefore, film mulching is a promising strategy for improving yield and WP and for optimizing root morphology in dryland agriculture.

The Loess Plateau is one of the most vulnerable areas in the world. Numerous studies have been conducted to investigate alfalfa fields with different planting years. Soil microorganisms and nematodes are vital in ecosystem functionality and nutrient cycling. Therefore, comprehending their response to alfalfa fields with varying years of planting is essential for predicting the direction and trajectory of degradation. Alfalfa fields with different planting years (2 years, 9 years, and 18 years) were used as the research object, and farmland was used as the control (CK). High-throughput sequencing and morphological methods determined the community composition of microorganisms and nematodes. Carbon metabolic footprints, correlation networks, and structural equations were used to study soil microorganisms and nematode interactions. Principal component analysis (PCA) results showed that alfalfa fields with different planting years significantly impacted soil microorganisms and nematode community structures. Planting alfalfa significantly increased the nematode channel ratio (NCR) and Wasilewska index (WI), but significantly reduced the soil nematode PPI/MI and dominance (λ). The correlation network results indicated that, for the 2-year and 18-year treatments, the total number of links and positive links are higher than other treatments. Conversely, the 9-year treatment had fewer positive links and more negative links compared to other treatments. Additionally, the keystone species within each network varied based on the treatment years. Structural equation results show that alfalfa planting years directly impact soil fungal community structure and plant-parasitic nematodes’ carbon metabolism omnivorous-predatory nematodes. Furthermore, the carbon metabolism of omnivorous-predatory nematodes directly influences soil organic carbon fixation. Moreover, as the duration of alfalfa planting increases, the metabolic footprint of plant-parasitic nematodes decreases while that of omnivorous-predatory nematodes rises. Among treatments varying in alfalfa planting durations, the 9-year treatment exhibited the most incredible energy conversion and utilization efficiency within the soil food web, demonstrating the most stable structure. This study reveals optimal alfalfa planting duration for soil ecosystem stability in the Loess Plateau. Future research should explore sustainable crop rotations and alfalfa–soil–climate interactions for improved agricultural management.

Drought stress critically hinders agricultural productivity, especially in arid and semi-arid zones. The results of this study show that the application of watermelon rind-based hydrogels (WR hydrogels), synthesized from a watermelon rind, acrylic acid (AA), and acrylamide (AAm), significantly enhanced soil water retention by 77.46% at a 0.3% concentration, increasing the plant height by 28.98% and biomass by 35.28% under controlled greenhouse conditions (25 °C/20 °C day/night temperature cycle, with a 12 h photoperiod at 400–500 μmol·m−2·s−1 of illuminance and 30–40% relative humidity). The accumulation of proline and soluble sugars decreased, indicating reduced osmotic stress in barley subjected to mild and severe drought conditions (6–15% FC and 17–26% FC). The chlorophyll content rose by 16.36%, boosting photosynthetic activity. A correlation and principal component analysis further highlighted the positive effects of hydrogel addition on plant growth and drought resistance. These findings underscore the potential of WR hydrogels as an effective soil amendment for promoting sustainable agriculture in water-limited conditions.

Water scarcity poses a significant threat to the sustainable production of crops in Northern China. Despite this, the effect of water management practices, such as deficit irrigation, on the yield and WUE of potatoes has been rarely explored. Based on the meta-analysis of field experiment data, this study evaluated the influence of deficit irrigation on potato yield, evapotranspiration (ET), water use efficiency (WUE) and irrigation water use efficiency (IWUE) under variable soil types, water-saving ratio, irrigation methods, soil organic carbon (SOC) content, and fertilizer rate in Northern China. Here, we determined that potato WUE and IWUE were significantly increased by 10.0 and 31.6%, respectively, under deficit irrigation, while ET was significantly decreased by 26.3% compared to full irrigation. Conclusively, deficit irrigation significantly reduced potato yields by 16.4% compared to full irrigation. Furthermore, SOC content played a vital role in improving the WUE and alleviating potato yield losses under deficit irrigation. Our study suggested that maximum WUE with lower potato yield losses under deficit irrigation can be achieved in the Central Plains region of China or in yellow loam soil, brown soil, and meadow soil under alternate root-zone irrigation when the water-saving ratio was less than 45% and fertilizer application rates were 300 kg N ha−1, >240 kg P2O5 ha−1, and 181–300 kg K2O ha−1. Overall, these findings highlight the need for a comprehensive understanding of various agricultural management practices and local environmental conditions to optimize the benefits of deficit irrigation in potato-growing regions across Northern China.

The intricate decomposition pathways within soil micro-food webs are vital for cycling soil organic carbon and nutrients, influencing the quality, productivity, and sustainability of soil systems. However, the impact of diverse phosphorus addition on these organic decomposition pathways still needs to be explored. In an 8-year experiment, phosphorus (P) fertilizer was added at varying levels (0 kg ha−1, CK; 60 kg ha−1, P60; 120 kg ha−1, P120; and 180 kg ha−1, P180), to investigate the response of the soil micro-food web. The results revealed a significant effect of phosphorus addition on soil microorganisms and nematodes, with P60 exerting a greater influence than other treatments. At P60, the Shannon index of nematodes and fungi surpassed other treatments, indicating higher diversity, while the Shannon index of bacteria was lower. The Chao1 index of bacteria and fungi at P60 was higher, contrasting with the lower index for nematodes. Metabolic footprints of bacterivores and omnivores–predators (BFMF and OPMF) were higher at P60, while metabolic footprints of fungivores and plant parasites (FFMF and PPMF) were lower, signifying altered energy flow. Functional metabolic footprints and energy flow analysis unveiled a stable soil micro-food web structure at P60, with enhanced energy conversion efficiency. Network analysis illustrated positive correlations between fungi, fungivorous nematodes (FF), and omnivorous-predatory nematodes (OP) at P60, while P120 and P180 showed positive correlations among bacteria, bacterivorous nematodes (BF), and OP. Path analysis underscored the higher contribution rate of BF-C, FF-C, and OP-C to soil organic carbon at P60 compared with P120 and P180. These findings suggest that nutrient interactions between fungi and nematodes regulate soil micro-food web decomposition under low phosphorus concentrations. In contrast, interactions between bacteria and nematodes dominate at high phosphorus concentrations. The study indicates that adding phosphorus has nuanced bottom-up effects, intricately shaping the structure and activity of the pathways and underscoring the need for a comprehensive understanding of nutrient dynamics in soil ecosystems.

For potato production, continuous cropping (CC) could lead to autotoxicity buildup and microflora imbalance in the field soil, which may result in failure of crops and reduction in yield. In this study, non-targeted metabolomics (via liquid chromatography with tandem mass spectrometry (LC–MS/MS)) combined with metagenomic profiling (via high-throughput amplicon sequencing) were used to evaluate correlations between metabolomics of potato root exudates and communities of bacteria and fungi around potato plants to illustrate the impacts of CC. Potato plants were grown in soil collected from fields with various CC years (0, 1, 4, and 7 years). Metabolomic analysis showed that the contents and types of potential autotoxins in potato root exudates increased significantly in CC4 and CC7 plants (i.e., grown in soils with 4 and 7 years of CC). The differentially expressed metabolites were mainly produced via alpha-linolenic acid metabolism in plant groups CC0 and CC1 (i.e., no CC or 1 year CC). The metabolomics of the groups CC4 and CC7 became dominated by styrene degradation, biosynthesis of siderophore group non-ribosomal peptides, phenylpropanoid biosynthesis, and biosynthesis of various plant secondary metabolites. Continuous cropping beyond 4 years significantly changed the bacterial and fungal communities in the soil around the potato crops, with significant reduction of beneficial bacteria and accumulation of harmful fungi. Correlations between DEMs and microflora biomarkers were established with strong significances. These results suggested that continuous cropping of potato crops changed their metabolism as reflected in the plant root exudates and drove rhizosphere microflora to directions less favorable to plant growth, and it needs to be well managed to assure potato yield.

Abstract A growing body of literature have emphasized the effects of fertilization regimes on soil respiration and microbial community in the semiarid region, however, fertilization treatment effects on the soil CO2 emission, soil bacterial community, and their relationships from long-term experiments is lacking. In the present study, we investigated the effects of long-term fertilization regimes on soil bacterial community and thereafter on soil CO2 emission. A 9-year field experiment was conducted with five treatments, including no fertilizer (NA) and four fertilization treatments (inorganic fertilizer (CF), inorganic plus organic fertilizer (SC), organic fertilizer (SM), and maize straw (MS)) with equal N input as N 200 kg hm–2. The results indicated that CO2 emission was significantly increased under fertilization treatments compared to NA treatment. The bacterial abundance was higher under MS treatment than under NA treatment, while the Chao1 richness showed opposite trend. MS treatment significantly change soil bacterial community composition compared to NA treatment, the phyla (Alphaproteobacteria and Gammaproteobacteria) and potential keystone taxa (Nitrosomonadaceae and Beijerinckiaceae) were higher, while the Acidobacteriota was lower under MS treatment than under NA treatment. CO2 emission was positively correlated with the abundance of Alphaproteobacteria, Gammaproteobacteria, and keystone taxa, negatively correlated with these of Acidobacteriota. Random forest modeling and structural equation modeling determined soil organic carbon, total nitrogen, and the composition and network module III of the bacterial community are the main factors contribute to CO2 emission. In conclusion, our results suggest that the increased CO2 emission was affected by the varied of soil bacterial community composition derived from fertilization treatments, which was related to Alphaproteobacteria, Gammaproteobacteria, Acidobacteriota, and potential keystone taxa (Nitrosomonadaceae and Beijerinckiaceae), and highlight that the ecological importance of the bacterial community in mediating carbon cycling in the semiarid Loess Plateau.

A meta-analysis was conducted with the aim of exploring the influence of irrigation on potato yield, evapotranspiration (ET), and water-use efficiency (WUE) in northern China, considering factors such as irrigation methods, growing region, irrigation water-use efficiency (IWUE), irrigation frequency, soil types, and nitrogen (N) fertilizer rate. Overall, irrigation significantly increased potato yield and ET by an average of 45 and 54% compared to non-irrigation, respectively, but did not significantly increase the WUE. The increase in potato yield under irrigation is the most evident in aeolian sandy soil in northeast China and northwest China. Drip irrigation demonstrated the highest positive impact on both yield and WUE. Optimal yields were achieved with an irrigation amount ranging from 100 to 200 mm, while the highest WUE was observed with an irrigation amount of 30–50 mm. When the amount of irrigation exceeded 100 mm, the irrigation significantly resulted in decreased WUE compared to non-irrigation. The relative increase in yield per unit of irrigation amount and IWUE gradually decreased and eventually stabilized when the irrigation amount exceeded 100 mm. Therefore, the yield and WUE perform best when the irrigation amount is below 100 mm and the irrigation frequency is less than three times for sprinkling and flood irrigation methods. The greatest increases in yield and WUE under irrigation were found under a moderate N rate (150–250 kg N ha−1). Additionally, the relative increase in yield per unit of irrigation amount decreases gradually as the organic matter content increases. These findings suggest that the optimal benefits from irrigation might be realized when the irrigation amount is below 100 mm, with a moderate nitrogen fertilizer application and an irrigation frequency of three times. However, it is essential to consider local environmental factors such as the growing region, soil types, and organic carbon content.

Global climate change, dominated by climate warming, is seriously affecting the balance of global ecosystems, but the risk of species extinction is particularly high in low-altitude mountain areas. To clarify the response of the endemic and critically endangered species Ilex nanchuanensis to climate change, this study used the MaxEnt model to simulate and predict the potential habitat of I. nanchuanensis during the Last Interglacial, Last Glacial Maximum, the current period, and two future periods (the 2050 s and 2070 s). The results showed that the hottest monthly minimum temperature is the most important climatic factor affecting the geographical distribution of I. nanchuanensis. Furthermore, I. nanchuanensis will be at risk of population shrinkage and extinction in the future, with the center of mass moving further northwest as concentrations of greenhouse gases increase, especially in the 2070 s, when its geographical distribution shrinks the most under the RCP6 scenario. Therefore, to actively respond to the impacts of climate change, protected areas should be established around the geographical distribution centers of species, and core, buffer, and experimental areas should be scientifically and rationally delineated for the conservation and cultivation of germplasm resources.

Improving the water-use efficiency (WUE) of crops is the most effective way to increase yields in semi-arid regions. Field research was carried out based on a long-term experiment initiated in 2001, aimed to explore the mechanisms of different tillage practices effects on grain yield and WUE of spring wheat. Tillage practices in the research including conventional tillage (CT), no tillage with no straw mulching (NT), conventional tillage with straw incorporation (TS), and no tillage with straw mulching (NTS). The effects of tillage practices on soil’s physical and chemical properties, dry matter accumulation, grain yield, dynamics of stress-related substances, and WUE were observed. Soil and plant samples in this research were collected in 2020 (wet year), 2021 (dry year), and 2022 (dry year). The results indicated that NTS improved the soil’s physical and chemical properties. The NTS treatment had the lowest soil bulk and pH and the highest total N, NO3--N, and available P. Throughout the whole growth stage, soil water content in the NTS and TS treatments were significantly higher than that of CT by 8.77–20.40% and 2.19–18.83, respectively. Averaged catalase (CAT), peroxidase (POD), and soluble protein across the three years with NTS and TS were significantly increased by 1.26–25.52% compared to CT. Meanwhile, the NTS treatment had the lowest malondialdehyde (MDA) content among the different tillage practices. NTS maintained the highest dry matter accumulation throughout the whole growth stage among different treatments; it was increased by 10.47–73.33% compared with CT. The average grain yields and WUE of NTS across the three years were 6.09–30.70% and 6.79–40.55% higher than other tillage practices, respectively. It is concluded that NTS influences dry matter accumulation and water-use efficiency during the whole growth stage of spring wheat by improving the soil’s physicochemical properties and modulating spring wheat substances related to stress, which in turn promotes yield formation.

China's Loess Plateau regions have experienced severe soil erosion for many decades due to fragmented landscapes, steep slopes, and concentrated rainfall storm-events. Restoring sub-optimal or marginal farming fields, mostly on steep, hilly terrain, to plantation forests has been a long-standing strategic policy in China aimed at rehabilitating degraded environments and reducing soil and water erosion. While there are numerous studies that have focused on the effects of forests at controlling soil erosion at relatively short time scales, few have addressed longer-term effects of plantation forests on reducing runoff and the mechanisms that inhibit erosion. Chinese pine (Pinus tabulaeformis) has been widely planted in abandoned or reclaimed lands that were formerly farmed in Northwest China; however, there is limited knowledge about the effectiveness of the tree species at reducing soil and water erosion. In this study, we examined reduction rates of runoff and erosion by Chinese pine plantation in comparison with agricultural land as a control (i.e., wheat, a dominant agricultural commodity in the region), based on long-term monitoring of modified standard erosion plots with slopes of 10°, 15°, and 20°. Results showed that as the slope of the land increased, rates of erosion increased for both plantation and agricultural land use. However, the runoff and soil erosion rates under Chinese pine plantation forest were about 11% and 60% lower, respectively, than those under agricultural land use of the same slope. Scaling with the slope, the highest reduced runoff and erosion rates by Chinese pine forest were 17% and 72%, respectively, on 20° slope. Also, it was found that runoff rates from the forested land were positively related to erosive rainfall (i.e., rainfall when runoff generated), and varied with forest canopy coverage. The rates of runoff and erosion can be well model led with multiple regression models. Taken together, this study provides insight into the importance and potential of Chinese pine plantations in the conservation of soil and water in China's Loess Plateau.

Increasing water and nitrogen use efficiencies (i.e., WUE and NUE) in dryland agroecosystems to maintain high agricultural output with lower environmental costs, such as minimal soil water depletion and nitrate-N residue, are key responsibilities to assure food security for a growing global population. The impact of N rate on soil water balance, soil nitrate N residue, grain yield, WUE, crop N recovery efficiency (REN), agronomic use efficiency of N fertilizer (AE), and net economic return were examined on maize production on the rainfed Loess Plateau during 2011–2018. Field treatments included four N application rates (N0, no N fertilizer applied; N100, 100 kg N ha−1; N200, 200 kg N ha−1; N300, 300 kg N ha−1). Results showed that compared with N0, grain yield increased by 56, 110, and 115% under N100, N200, and N300, respectively, with corresponding improvements in net economic return of 5497, 10,878, and 11,088 RMB ha−1 yr−1, respectively; no significant difference was detected between N200 and N300. Compared to N0, N fertilization significantly increased WUE through improving photosynthetic WUE (i.e., transpiration efficiency), but there was no significant difference between N200 and N300. Compared to N100, the REN was gradually decreased as N rates increased, AE was not significantly changed under N200 and significantly decreased under N300 due to a decreased leaf photosynthetic NUE. Compared to original soil water storage at 0–300 cm soil depths, after seven years of continuous experiments, treatment of N0 enhanced soil water storage by 52 mm and treatment of N100 had no effect on soil water storage, but treatments of N200 and N300 depleted soil water storage by 73 and 109 mm, respectively. Our findings showed that 200 kg N ha−1 improves WUE and NUE with less environmental cost and should be regarded as the economically optimal N rate on the semiarid western Loess Plateau of China for sustainable maize production.

The roles of bacterial communities in the health of soil microenvironments can be more adequately defined through longer-term soil management options. Carbon dioxide (CO2) fixation by autotrophic bacteria is a principal factor in soil carbon cycles. However, the information is limited to how conservation tillage practices alter soil physiochemical properties, autotrophic bacterial communities, and microbial catabolic diversity. In this study, we determined the changes in autotrophic bacterial communities and carbon substrate utilization in response to different soil management practices. A replicated field study was established in 2001, with the following soil treatments arranged in a randomized complete block: conventional tillage with crop residue removed (T), conventional tillage with residue incorporated into the soil (TS), no tillage with crop residue removed (NT), and no tillage with residue remaining on the soil surface (NTS). Soils were sampled in 2019 and microbial DNA was analyzed using high-throughput sequencing. After the 19-year (2001–2019) treatments, the soils with conservation tillage (NTS and NT) increased the soil’s microbial biomass carbon by 13%, organic carbon by 5%, and total nitrogen by 16% compared to conventional tillage (T and TS). The NTS treatment increased the abundance of the cbbL gene by 53% in the soil compared with the other soil treatments. The cbbL-carrying bacterial community was mainly affiliated with the phylum Proteobacteria and Actinobacteria, accounting for 56–85% of the community. Retaining crop residue in the field (NTS and TS) enhanced community-level physiological profiles by 31% and carbon substrate utilization by 32% compared to those without residue retention (T and NT). The 19 years of soil management lead to the conclusion that minimal soil disturbance, coupled with crop residue retention, shaped autotrophic bacterial phylogenetics, modified soil physicochemical properties, and created a microenvironment that favored CO2-fixing activity and increased soil productivity.

Due to depleting water supplies and the cultivation of high water-demanding crops such as lucerne, the effect of water deficits in crop production has become a major concern, especially in semiarid regions of China. A six-year field experiment (2012–2018) was conducted to evaluate soil water recovery and soil fertility after lucerne-to-crop conversions on the western Loess Plateau of China. Six rotation treatments (lucerne initially grew from 2003 to 2012 followed by the rotation of other crops or fallow until assessments in 2018) were: (1) lucerne (Medicago sativa L.)–lucerne (L-L); (2) lucerne–fallow (L-F); (3) lucerne–wheat (Triticum aestivum L.) (L-W); (4) lucerne–corn (Zea mays L.) (L-C); (6) lucerne–potato (Solanum tuberosum L.) (L-P); and (6) lucerne–millet (Setaria italica) (L-M). The same crops were grown each year after cultivation during 2013–2018. According to the findings, all rotation types gradually increased the soil water content, with the 0–110 cm soil layer experiencing the maximum soil water replenishment rate, followed by the 110–200 and 200–300 cm soil layers. After converting lucerne to crops, the amount of organic carbon, total nitrogen, and mineral nitrogen in the soil decreased, whereas total phosphorus and accessible phosphorus increased. Soil bulk density was reduced under rotation treatments. Soil water absolute restoration index was the highest under L-F, followed by L-C, L-W, L-P, and L-M. The rate of soil water recovery was 39.5, 33.0, 33.7, 33.5, 29, and 8.2 mm yr−1 under L-F, L-W, L-C, L-P, L-M, and L-L, respectively. The net economic return was greatest under L-C, followed by L-L, L-W, L-P, and L-M. From the analysis of the long-term experimental results, this study shows that the effect of soil water restoration is greatest when continuous alfalfa is converted into wheat, corn, and potato or fallow after 9 years. When the economic benefits and soil moisture recovery are considered comprehensively, corn sown in a ridge–furrow system with fully plastic film annual mulching is the most suitable field management practice after lucerne-to-crop conversion on the western Loess Plateau of China.

Bacterial diversity and its functions are essential to soil health. N fertilization changes bacterial communities and interferes with the soil biogeochemical N cycle. In this study, bacterial community and soil physicochemical properties were studied in 2018 after applying N fertilizers (0, 52.5, 105, 157.5, and 210 kg N ha−1) for a long (2003–2018) and a short (2003–2004) duration in a wheat field on the Loess Plateau of China. Soil bacteria were determined using 16S rRNA Illumina-MiSeq®, and the prediction function was analyzed through PICRUSt. The study showed that N fertilizer significantly changed the diversity and abundance of bacterial communities. The phyla Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi were most abundant, accounting for 74–80% of the bacterial community abundance. The optimum rates of N fertilizer application (N105) maintain soil health by promoting soil microbial diversity and abundance. The bacterial population abundance was higher after short-term N application than after N application for a long duration and lowest with the high N-fertilizer treatment (N210). High N enrichment led to more heterotrophic N-fixing microorganisms (Alphaproteobacteria), in which metabolism and genetic information processing dominated, while cellular processes, genetic information processing, metabolism, and organismal systems were the main functional categories under low N. The phyla Gemmatimonadetes, Actinobacteria, Bacteroidetes, and Chloroflexi were the key bacteria in the co-occurrence network. The genus Saccharimonadales of the superphylum Patescibacteria has a more significant impact under low N treatment. Long-term N fertilization affected the soil pH, NO3-N, and other physicochemical properties, and soil NO3-N was the highest indicator, contributing 81% of the bacterial community function under different N fertilizer treatments.

This study evaluated the properties of soil water dynamics and desiccation to a depth of 500 cm and tested the idea that land use affects soil drying in deep profiles. Four land use types were chosen: farmland, artificial forest and grassland, and abandoned land. Soil water content was most outstanding under long-term wheat fields, but average soil water content under artificial vegetation of Caragana korshinskii Kom. and alfalfa dropped to 6–8% within the 160–500 cm soil profile, very near to the 7.0% wilting point. Long-term continuous maize cultivation in a fully mulched ridge–furrow system significantly depleted soil water and resulted in a dried soil layer with a thickness of 240 cm. Short-term or long-term land abandonment enhanced soil reservoir and reduced soil water storage deficit degree compared to long-term maize and artificial vegetation. Soil water storage in the 160–500 cm soil profile was depleted by 240 and 464 mm under long-term maize and Caragana korshinskii Kom., respectively, by 267, 319, 381, and 463 mm under 5-, 10-, 20-, and 30-year alfalfa, and by −58, 278, 234, and 93 mm under 5-, 10-, 20-, and 30-year abandonment land, respectively, compared to long-term wheat. Based on the analysis of long-term experimental results, this study shows that the phenomenon of soil drying caused by long-term intensive maize production cannot be ignored in semi-arid areas and that natural re-vegetation under long-term abandonment, rather than artificial vegetation, may be the best type of vegetation reconstruction for this region based on soil water balances.

Soil autotrophic bacteria play a crucial role in regulating CO2 fixation and crop productivity. However, the information is limited to how fertilization amendments alter soil autotrophic bacterial community, crop yield, and carbon emission efficiency (CEE). Here, we estimated the impact of the structure and co-occurrence network of soil autotrophic bacterial community on maize yield and CEE. A long-term field experiment was conducted with five fertilization treatments in semiarid Loess Plateau, including no amendment (NA), chemical fertilizer (CF), chemical fertilizer plus commercial organic fertilizer (SC), commercial organic fertilizer (SM), and maize straw (MS). The results showed that fertilization amendments impacted the structure and network of soil Calvin–Benson–Bassham (CBB) (cbbL) gene-carrying bacterial community via changing soil pH and NO3–N. Compared with no amendment, the cbbL-carrying bacterial diversity was increased under the SC, SM, and MS treatments but decreased under the CF treatment. Soil autotrophic bacterial network contained distinct microbial modules that consisted of closely associated microbial species. We detected the higher abundances of soil cbbL-carrying bacterial genus Xanthobacter, Bradyrhizobium, and Nitrosospira. Structural equation modeling further suggested that the diversity, composition, and network of autotrophic bacterial community had strongly positive relationships with CEE and maize yield. Taken together, our results suggest that soil autotrophic bacterial community may drive crop productivity and CEE, and mitigate the atmospheric greenhouse effect.

Increasing agricultural productivity without undermining further the integrity of the Earth’s environmental systems such as soil water balance are important tasks to ensure food security for an increasing global population in rainfed agriculture. The impact of intercropping maize (Zea mays L.) with potato (Solanum tuberosum L.) on yield, land equivalent ratios (LER), water equivalent ratio (WER), water use, energy output, and net economic return were examined under seven planting systems: potato grown solely or intercropped on the flat field without mulching, maize grown solely or intercropped with potato on ridges or flat field with or without plastic film mulched. The three intercropping systems had 3–13% less water use than the monocropping. Among the intercropped systems, flat field caused more depletion of soil water than ridged field for both years. Compared to monocultures, intercropping with plastic film mulching and ridging significantly increased LER and WER. Meanwhile, intercropping with mulching and ridging significantly increased net economic return and energy output by 8% and 24%, respectively, when compared to monocropping. These results suggest that maize under plastic film mulched ridge-furrow plot intercropped with potato under flat plot without mulching increased energy output, net economic return, and water use efficiency without increasing soil water depletion, which could be an optimal intercropping system for the semiarid farmland on the western Loess Plateau.

In semi-arid areas, increasing CO2 emissions are threatening agricultural sustainability. It is unclear whether different tillage practices without residue returned could help alleviate these issues while increasing crop productivity. This study aimed to quantify soil respiration under conventional tillage (CT); rotary tillage (RT); subsoiling (SS) and no-till (NT), all without residue returned in the Western Loess Plateau. The results showed that SS and NT significantly decreased soil respiration compared to CT, but the effects of SS was the greatest. As a result, SS decreased carbon emission by 22% in 2014 and 19% in 2015 versus CT. The trends of net ecosystem production under different tillage systems were as follows: CT > RT > NT > SS. No-till increased net ecosystem production by 33% in 2014 and 12% in 2015 relative to CT. The SS treatment increased average grain yield by 27% and 23% over CT and RT, and enhanced water use efficiency by an average of 43%. On average, SS increased carbon emission efficiency by 60% and 43% compared to CT and RT, respectively. Thus, subsoiling management strategy is a promising option for the development of sustainable agriculture in semi-arid areas.

Nitrogen (N) is the most limiting nutrient for maize, and appropriate N fertilization can promote maize growth and yield. The effect of N fertilizer rates and timings on morphology, antioxidant enzymes, and grain yield of maize (Zea mays L.) in the Loess Plateau of China was evaluated. The four N levels, i.e., 0 (N0), 100 (N1), 200 (N2), and 300 (N3) kg ha−1, were applied at two timings (T1, one-third N at sowing and two-thirds at the six-leaf stage of maize; T2, one-third applied at sowing, six-leaf stage, and eleven-leaf stage of maize). The results show that N2 and N3 significantly increased the plant height, stem and leaf dry weight, and leaf area index of maize compared with a non-N-fertilized control (N0). The net photosynthetic rate, transpiration rate, stomatal conductance, and leaf chlorophyll contents were lower, while the intercellular carbon dioxide concentration was higher for non-fertilized plants compared to fertilized plants. The activities of peroxidase (POD) and superoxide dismutase (SOD) increased with N rate, but the difference between 200 and 300 kg ha−1 was not significant; further, the isozyme bands of POD and SOD also changed with their activities. Compared with a non-N-fertilized control, N2 and N3 significantly increased grain yield by 2.76- and 3.11-fold in 2018, 2.74- and 2.80-fold in 2019, and 2.71- and 2.89-fold in 2020, and there was no significant difference between N2 and N3. N application timing only affected yield in 2018. In conclusion, 200 kg N ha−1 application increased yield through optimizing the antioxidant enzyme system, increasing photosynthetic capacity, and promoting dry matter accumulation. Further research is necessary to evaluate the response of more cultivars under more seasons to validate the results obtained.

Soil bacteria are key components of the soil microbial community contributing to soil health. Nitrogen (N) fertilization is an important factor that affects soil microbial community and cereal production. This study aims to explore the impact of long-term N fertilization on soil bacterial diversity, nitrogen use efficiency (NUE), and the grain yield of wheat in the semiarid region of Loess Plateau, China. The field experiment was conducted from 2003 to 2018 including five N treatments: 0 (N0), 52.5 (N52.5), 105 (N105), 157.5 (N157.5), and 210 (N210) kg N ha−1 yr−1. The soil pH was decreased by the N fertilization, while the soil ammonium, nitrate, and available phosphorus were increased. The N uptake and grain yield of wheat were significantly increased with N and the highest NUE (28%) and grain yield (44% higher than control) were observed at 105 kg N ha−1, but no significant increase in yield was observed by further increasing N rate. The bacterial diversity was significantly increased at N105. Soil bacteria community was strongly related to soil chemical properties and ammonium content was the most important contributor. The dominant soil bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, Bacteroidetes, Nitrospirae, Verrucomicrobia, and Planctomycetes. The higher grain yield of wheat was related to the higher class Gammaproteobacteria and Sphingobacteriia abundance, and lower class Acidobacteria and Chloroflexia abundance. In summary, 105 kg ha−1 yr−1 was the optimum rate of N for diversified soil bacterial community and wheat yield for sustainable wheat production in semiarid Loess Plateau of China, whose higher N use efficiency was attributed to the higher phyla Verrucomicrobia and Planctomycetes, and lower Proteobacteria abundance.

Cropping systems are structured to maximize crop yields and increase sustainability in agricultural production. A field study was conducted to investigate different long-term cropping systems on soil organic matter and microbial communities. The cropping systems studied were: (i) a 14-year continuous alfalfa (Medicago sativa L.) (CA), (ii) a 9-year alfalfa removed and rotated with 4–5 years continuous annual crops (spring wheat (Triticum aestivum L.), maize (Zea mays L.), potato (Solanum tuberosum L.), and millet (Panicum miliaceum L.)), and (iii) a 5-year field fallow after alfalfa. Results showed that continued annual crops decreased total organic C and labile organic C by 10 to 20% and 17 to 34% in the topsoil (0–30 cm), and by 15 to 35% and 20 to 46% in the subsoil (30–60 cm), respectively, compared with CA. Similar trends were found in soil total N concentration, which decreased by 7 to 20% in the topsoil. Highest microbial biomass C was found in CA. Shannon-Wiener diversity and substrate richness of soil microbes measured by Biolog EcoPlates was significantly affected by cropping system with CA exhibiting a higher degree of soil microbial functional diversity in the topsoil, while the lowest values were found in the alfalfa-potato system. The higher soil organic matter content and functional diversity of soil microbe in CA indicates that soil nutrition and microbial activity did not limit alfalfa development and growth in the dryland area. The lower microbial activity and functional diversity observed in the potato field indicates the importance of crop selection in cropping systems.

Soil physiochemical properties are regulated by cropping practices, but little is known about how tillage influences soil microbial community diversity and functions. Here, we assessed soil bacterial community assembly and functional profiles in relation to tillage. Soils, collected in 2018 from a 17-year field experiment in northwestern China, were analyzed using high-throughput sequencing and the PICRUSt approach. The taxonomic diversity of bacterial communities was dominated primarily by the phyla Proteobacteria (32–56%), Bacteroidetes (12–33%), and Actinobacteria (17–27%). Alpha diversity (Chao1, Shannon, Simpson, and operational taxonomic unit (OTU) richness) was highest under no-tillage with crop residue removed (NT). Crop residue retention on the soil surface (NTS) or incorporated into soil (TS) promoted the abundance of Proteobacteria by 16 to 74% as compared to conventional tillage (T). Tillage practices mainly affected the pathways of soil metabolism, genetic information processing, and environmental information processing. Soil organic C and NH4–N were the principal contributors to the diversity and composition of soil microbiota, whereas soil pH, total nitrogen, total P, and moisture had little effect. Our results suggest that long-term conservation practices with no-tillage and crop residue retention shape soil bacterial community composition through modifying soil physicochemical properties and promoting the metabolic function of soil microbiomes.

In dry environments, potato (Solanum tuberosum L.) is grown under mulching for water conservation and improving tuber yield and nitrogen use efficiency (NUE). A meta-analysis was conducted to determine how mulching improved tuber yield and NUE in potato and how yield and NUE is influenced by fertilization, tillage practices, and growing environment in China. A search of peer-reviewed publications was performed to collect data on the effects of mulching on yield and NUE in potato grown in China. The data included were from field studies with a mulching and a no mulching treatment and data on tuber yield and NUE. A total of 169 publications (17 in English and 152 in Chinese) containing 1802 observations from 105 sites were compiled into the dataset. Mulching significantly increased both tuber yield and NUE by an average of 24% compared to no mulching, respectively. Plastic film mulching was more effective in improving yield and NUE than straw mulching. The yield and NUE increase were highest under plastic film mulching on ridge-furrow plots and straw mulching on flat plots. Mulching was more effective at improving yield and NUE in the Northwest dryland region at a plant density between 55,000 and 70,000 plants ha−1 and with application of synthetic N and P2O5 at rates of 100−200 kg ha−1, K fertilization at 0−100 kg K2O ha−1, and without organic fertilization. Integrated use of organic fertilizer and mulching was found to reduce synthetic N and P fertilizer input by 50% and K fertilizer input by 100% for production without affecting yield and NUE. These results demonstrate that mulching increases yield and NUE in potato in China, but the benefits occur when the growing region, tillage, and fertilization practices are appropriately considered.

Water availability is a major constraint for crop production in semiarid environments. The impact of tillage practices on water potential gradient, water transfer resistance, yield, and water use efficiency (WUEg) of spring wheat was determined on the western Loess Plateau. Six tillage practices implemented in 2001 and their effects were determined in 2016 and 2017 including conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP), and no-till with plastic mulch (NTP). No-till with straw cover, TP, and NTP significantly improved soil water potential at the seedling stage by 42, 47, and 57%, respectively; root water potential at the seedling stage by 34, 35, and 51%, respectively; leaf water potential at the seedling stage by 37, 48, and 42%, respectively; tillering stage by 21, 24, and 30%, respectively; jointing stage by 28, 32, and 36%, respectively; and flowering stage by 10, 26, and 16%, respectively, compared to T. These treatments also significantly reduced the soil−leaf water potential gradient at the 0−10 cm soil depth at the seedling stage by 35, 48, and 35%, respectively, and at the 30−50 cm soil depth at flowering by 62, 46, and 65%, respectively, compared to T. Thus, NTS, TP, and NTP reduced soil−leaf water transfer resistance and enhanced transpiration. Compared to T, the NTS, TP, and NTP practices increased biomass yield by 18, 36, and 40%; grain yield by 28, 22, and 24%; and WUEg by 24, 26, and 24%, respectively. These results demonstrate that no-till with straw mulch and plastic mulching with either no-till or conventional tillage decrease the soil−leaf water potential gradient and soil−leaf water transfer resistance and enhance sustainable intensification of wheat production in semi-arid areas.