Reducing Fertilizer Application Research Articles

Study on the nitrogen content estimation model of cotton leaves based on "image-spectrum-fluorescence" data fusion.

Precise monitoring of cotton leaves' nitrogen content is important for increasing yield and reducing fertilizer application. Spectra and images are used to monitor crop nitrogen information. However, the information expressed using nitrogen monitoring based on a single data source is limited and cannot consider the expression of various phenotypic and physiological parameters simultaneously, which can affect the accuracy of inversion. Introducing a multi-source data-fusion mechanism can improve the accuracy and stability of cotton nitrogen content monitoring from the perspective of information complementarity. Five nitrogen treatments were applied to the test crop, Xinluzao No. 53 cotton, grown indoors. Cotton leaf hyperspectral, chlorophyll fluorescence, and digital image data were collected and screened. A multilevel data-fusion model combining multiple machine learning and stacking integration learning was built from three dimensions: feature-level fusion, decision-level fusion, and hybrid fusion. The determination coefficients (R2) of the feature-level fusion, decision-level fusion, and hybrid-fusion models were 0.752, 0.771, and 0.848, and the root-mean-square errors (RMSE) were 3.806, 3.558, and 2.898, respectively. Compared with the nitrogen estimation models of the three single data sources, R2 increased by 5.0%, 6.8%, and 14.6%, and the RMSE decreased by 3.2%, 9.5%, and 26.3%, respectively. The multilevel fusion model can improve accuracy to varying degrees, and the accuracy and stability were highest with the hybrid-fusion model; these results provide theoretical and technical support for optimizing an accurate method of monitoring cotton leaf nitrogen content.

Effect of the Different Fertilization Treatments Application on Paddy Soil Enzyme Activities and Bacterial Community Composition

The application amount of fertilizer is believed to dramatically influence soil bacteria in paddy fields, and soil bacteria critically affect soil enzyme activities and the growth of rice in paddy fields. Thus, providing a suitable amount of fertilization to ensure rice yields is an important issue in field management. In this study, four treatments were carried out in a paddy field, including control (fertilization methods commonly used by farmers in the past), IT + RF 10, IT + RF 20, and IT + RF 30 (integrated technology and 10%, 20%, and 30% reduction in nitrogen fertilizer, respectively). Soil samples were collected in two periods, the rice booting stage and the harvest period. High-throughput sequencing was used for analysis of soil bacterial diversity and community composition across different fertilizer treatments, and clarified the effects of different fertilizer treatments on soil enzyme activities and bacterial community composition. This study showed that a reduction in chemical fertilizer application has a certain impact on the soil pH, total nitrogen (TN), total phosphorus (TP), soil organic matter (SOM) value, and bacterial community of the rice planting system, and that the IT + RF 10 treatment was the best way to reduce fertilizer application, which can reduce nutrient loss in the paddy soil. The application of organic fertilizer partially replaces chemical fertilizer, which not only effectively stimulates soil enzyme activity, but also enriches bacterial groups that may participate in complex organic matter decomposition and soil nutrient mobilization.

Bumblebees sense rootstock-mediated nutrition and fertilization regime in tomato

AimsSince producing more with less is required for increasing agricultural sustainability and reducing its environmental impact, breeding varieties with increased yield stability under reduced fertilizer application is an important goal, particularly in high valued horticultural crops such as tomato (Solanum lycopersicum L.). However, because of the difficulties to conciliate yield and fertilizer use efficiency through breeding, the graft-compatible genetic biodiversity existing in horticultural species offers the possibility to directly approach this objective in high-yielding elite varieties through improving nutrient capture and promoting ecosystem services such as insect pollination. We hypothesized that rootstocks affect pollinator foraging decisions through the nutritional status that impacts yield.MethodsFifteen genetically diverse experimental rootstocks were grafted to a scion tomato variety and cultivated under optimal and reduced (25% of optimal) P and NPK fertilization in the presence of managed bumblebee pollinators (Bombus terrestris).ResultsUp to twofold yield variability between rootstocks was associated with leaf nutrition and photosynthesis of the scion. Interestingly, fertilization regime and the rootstock genotype influenced the pollinator foraging decisions since bumblebees showed feeding preference for plants cultivated under low P, and for the most yielding and nutritious graft combinations under reduced but not under optimal fertilization. Bumblebees can sense plant nutritional status through source-sink relations, as supported by the consistent relationship between pollinator preferences and leaf carbon concentration.ConclusionsThis study opens new perspectives for using pollinators as “phenotypers” to select the most resilient plants under suboptimal conditions and/or genotypes that synergistically increase crop productivity by promoting the ecosystem service provided by the insects.

Co-Inoculation of Trichoderma asperellum with Bacillus subtilis to Promote Growth and Nutrient Absorption in Marandu Grass

The authors have investigated the effects of different doses of mineral fertilizers combined with co-inoculation of Bacillus subtilis and Trichoderma asperellum to promote plant growth and use efficient nutrients in a plant Urochloa (Syn. Brachiaria) brizantha cv. Marandu. Individual experiments with doses of the nutrients nitrogen (N), phosphorus (P), and potassium (K) were carried out. The experiment was conducted in a completely randomized design, factorial 3 × 5. With the treatments: control noninoculation, inoculation with Bacillus subtilisUFRA-92, and coinoculation (MIX) with T. asperellum (UFRA-06, UFRA-09, UFRA-12, and UFRA-52) + B. subtilis x nutrient omissions (0%, 25%, 50%, 75%, and 100%). Each treatment had five replications. Biometric parameters, nutrient content, and nutrient use efficiency were evaluated. The results showed that the inoculants promoted growth in Marandu grass. The use of inoculants promoted growth and increased N, P, and K uptake by Marandu grass. Co-inoculation changed leaf area, shoot length, elongation rate, and leaf appearance for N and K and root dry mass for P. In addition, the co-inoculation combined with doses of 75% of N, 50% of P, and 50% of K increased the nutritional content of the leaves by 256% of N, 280% of P, and 29% of K and provided greater agronomic efficiency, with increments of 462% of N, 544% of P, and 177% of K, compared to the control treatment. We present the potential of co-inoculation of B. subtilis and T. asperellum to promote the growth of Urochloa under reduced fertilizer application. There was an improvement in plant growth and nutrient use efficiency.

Effects of Fertilizer Level and Intercropping Planting Pattern with Corn on the Yield-Related Traits and Insect Community of Soybean

Intercropping of corn and soybean is widely practiced in agricultural production. However, few studies have investigated the effect of intercropping and fertilizer reduction on soybean yield. In the present study, corn and soybean were interplanted in 2:2, 2:3 and 2:4 ratios. Two fertilizer levels (normal: 600 kg/ha VS. reduced: 375 kg/ha) were set. The effects of fertilizer levels and intercropping planting patterns on the growth and yield of intercropping soybeans were studied based on the changes in enzyme activities related to nitrogen metabolism and insect community in the field. The results show that fertilizer reduction significantly reduced the biomass, 100-seed weight and yield of soybean. Intercropping also reduced these yield-related traits; a decreasing trend was more obvious with a decrease in soybean ratio. Intercropping had greater effect on soybean plant biomass, 100-seed weight and yield than fertilizer reduction. Reduction in fertilizer reduced the activities of nitrogen-metabolism-related enzymes in soybean. In addition to increased NR (nitrate reductase) enzyme activity in R5, intercropping planting pattern also had negative effect on the activities of nitrogen-metabolism-related enzymes in soybean. Reduced fertilizer only significantly reduced the Pielou evenness index. Reduced fertilizer application was beneficial with respect to the outbreak of greenhouse whitefly. However, an intercropping planting pattern can significantly increase the number of species, as well as the Shannon–Wiener diversity index and the Pielou evenness index of the insect community, and significantly reduce the Simpson dominance index and the population of the important pest, green leafhopper. In conclusion, C2S4 (two corn rows with four rows of soybean) is a scientific intercropping planting pattern that can reduce the occurrence of pests through ecological regulation and does not significantly reduce the activity of enzymes-related to nitrogen metabolism in most cases, ensuring soybean yield.

Environmental effects of rural e-commerce: A case study of chemical fertilizer reduction in China

The economic effects of rural e-commerce have been fully discussed by scholars, but few studies focus on the environmental effects of rural e-commerce. This study takes the reduced application of chemical fertilizer in China as an example. On the basis of constructing the corresponding theoretical framework, we take the promotion of Rural E-Commerce Demonstration County (REDC) policy as a quasi-natural experiment, using the county panel data from 2000 to 2020 and the multi-period difference-in-difference method to excavate the influence of rural e-commerce on the fertilizer reduction. Our results show that REDC policy reduces the amount of chemical fertilizer applied in the county by 21%, which is unexpected. Our findings passed a series of robustness tests, including dealing with selective bias, eliminating other policy interference in the same period and placebo test. Based on the heterogeneity analysis of grain production and marketing regions and informatization level, it is found that the effect of fertilizer reduction by rural e-commerce is more impressive in the major grain production areas and counties with low informatization level. According to the theoretical framework, we use the mediating effect model to verify the transmission mechanism of marginal income improvement, mechanization and labor transfer. Therefore, we believe that policy designers can use e-commerce to promote farmers to adopt the production strategies of reducing fertilizer application. The findings and recommendations of this study may be relevant to other countries with free trading markets and e-commerce platforms.

Effect of agricultural subsidies on heterogeneous farmers’ fertilizer application intensity and its mediating mechanism: Based on China household finance survey database

Agricultural subsidies have an important effect on the farmer’s fertilizer application behavior, but the differences in the effect on different farmers and its mediating mechanism have not been sufficiently studied. Using relevant data from the CFHS database in 2015, this paper focused on the differences in the effect of agricultural subsidies on fertilizer application intensity among farmers with different operation scales and planting structures, as well as the mediating mechanism of the effect of agricultural subsidies on farmers’ fertilizer application intensity. It was found that agricultural subsidies in general helped farmers reduce fertilizer application. This finding still held after replacing the explanatory variables. However, the effect of agricultural subsidies on fertilizer application intensity varied significantly across farmers with different operation scales and planting structures. The fertilizer reduction effect of agricultural subsidies was weakened by the increase in the operation scale and the share of food crop cultivation, i.e., the fertilizer reduction effect of agricultural subsidies on smaller farmers and cash crop cultivation was greater relative to larger farmers and food crop cultivation. Farmers’ operation scale, planting structure and farm machinery inputs are important mediating variables of the effect of agricultural subsidies on farmers’ fertilizer application intensity. The agricultural subsidies played a role in reducing fertilizer application intensity by encouraging farmers to expand their operation scale and increase food crop cultivation, and increased fertilizer application intensity by incentivizing farmers to purchase farm machinery and adopt mechanical farming. Finally, some suggestions were put forward to play the fertilizer reduction effect of agricultural subsidies based on the findings of the study.

Spatial Pattern of Water Footprints for Crop Production in Northeast China

Water is an important resource for crop production; identifying the spatial pattern of the crop water footprint (WF) is of great significance for the optimization of water resource consumption and management in agricultural production. This study quantified the green, blue and grey water footprints (GWF, BWF and GRWF) and water consumption (GWC, BWC and GRWC) of rice, maize and soybean at the 1 km grid level and city level in Northeast China in 2019 based on the CROPWAT 8.0 model. The results showed that the average total water footprints of rice (TWFr), maize (TWFm) and soybean (TWFs) were 624.31 m3·ton−1, 527.26 m3·ton−1 and 1298.21 m3·ton−1, respectively. The spatial differences in the WF of each crop were obvious in Northeast China, with the highest values of TWFr mainly occurring in Baicheng, Dalian and Qitaihe; the highest TWFm values were mainly found in Baicheng, Yingkou and Hulundao, and the highest TWFs were mainly found in Baicheng, Chifeng and Tongliao. The total water consumption of all three crops (TWCc) in Northeast China was 94 billion m3·yr−1 (42% green, 26% blue and 32% grey), in which the total water consumption of maize production (TWCm) accounted for 60%. The production of rice, maize and soybean in Northeast China mainly depends on green water, grey water and blue water, respectively. Combining the results of the spatial patterns of crop TWF and TWC, the study revealed that the planting pattern of crops in Northeast China was relatively reasonable for sustainable water use. Meanwhile, cities that have the potential to enhance crop production and cities that should improve their water use efficiency and reduce fertilizer application were also identified.

Water Footprint Assessment of Green and Traditional Cultivation of Crops in the Huang-Huai-Hai Farming Region

With the increasing consumer awareness and knowledge about safe and healthy food, it is imperative to develop ‘green’ crops with reduced fertilizer application for quality food production, environmental protection and sustainable agricultural development. This study systematically evaluated and compared the water footprint (WF) including WFblue, WFgreen and WFgrey of eight crops including wheat, maize, rice, sweet potato, soybean, millet, mung bean and sorghum under green and traditional cultivation in the Huang-Huai-Hai farming region. The data came from 252 onsite questionnaires conducted in 2018 for land under green and traditional cultivation by 19 green planting companies and farming cooperatives with green food production certification authorized by the government of China. The results revealed that, compared to traditional cultivation, green cultivation under reduced N fertilizer application (1) decreased crop yields by 3–13%; (2) reduced the average WFtotal by 29% to 1168 m3 t−1 and average WFgrey by 57% to 419 m3 t−1 with no significant differences in WFblue and WFgreen; (3) decreased the WFtotal of maize by 55%, rice by 41%, wheat by 27%, mung bean by 31%, sorghum by 24%, sweet potato by 19%, millet by 17% and soybean by 17%. The WFgrey proportion of WFtotal under green cultivation ranged from 27–57% and contributed the most to the decline in WFtotal. This study offers insight into the impact of green cultivation on water requirements and pollution relative to traditional cultivation. Precision N fertilizer application and improved N use efficiencies on-farm are important pathways to sustainable agricultural development.

The responses of soil organic carbon and total nitrogen to chemical nitrogen fertilizers reduction base on a meta-analysis

Soil organic carbon (SOC), total nitrogen (TN), and their ratio (C:N) play important roles in preserving soil fertility, and their values are closely related to fertilizer use. However, the overall trend and magnitude of changes in SOC, TN and C:N in response to chemical nitrogen fertilizers reduction remain inconclusive. Here, the meta-analysis conducted comparisons at 48 sites covering various cropping system, soil type, and climatic regions of China to investigate the responses of SOC, TN and C:N to chemical nitrogen fertilizers reduction. The results showed that chemical nitrogen fertilizers reduction decreased SOC by 2.76 ± 0.3% and TN by 4.19 ± 0.8%, and increased the C:N by 6.11 ± 0.9% across all the database. Specifically, the reduction of chemical nitrogen without adding organic nitrogen fertilizers would reduce SOC and TN by 3.83% and 11.46% respectively, while they increased SOC and TN by 4.92% and 8.33% respectively with organic fertilizers supplement, suggesting that organic fertilizers could cover the loss of SOC, TN induced by chemical nitrogen fertilizers reduction. Medium magnitude (20–30%) of chemical nitrogen fertilizers reduction enhanced SOC by 6.9%, while high magnitude (≧30%) and total (100%) of chemical nitrogen fertilizers reduction significantly decreased SOC by 3.10% and 7.26% respectively. Moreover, SOC showed a negative response to nitrogen fertilizers reduction at short-term duration (1–2 years), while the results converted under medium-long-termThis system analysis fills the gap on the effects of fertilizer reduction on soil organic carbon and nitrogen at the national scale, and provides technical foundation for the action of reducing fertilizer application while increase efficiency.

Evaluating the anthropogenic nitrogen emissions to water using a hybrid approach in a city cluster: Insights into historical evolution, attribution, and mitigation potential

Anthropogenic reactive nitrogen (Nr) emissions from agricultural production and food consumption in city clusters have caused water quality degradation and scarcity. In this study, anthropogenic Nr emissions to the water environment were quantitatively evaluated in the Yangtze River Delta city cluster from 2011 to 2020 using coupling nitrogen (N) flow analysis and the grey water footprint (GWF) method. The spatiotemporal characteristics of the GWF and the relative contributions of natural and human factors to the water pollution level (WPL) were analyzed. The results showed that from 2011 to 2020, the total N-related GWF decreased by 12.1 %, mainly driven by reduced fertilizer application and livestock numbers. In 2020, the primary pollution source changed from livestock to humans; however, non-point sources still dominated the GWF. The spatial clustering trend of the GWF was significant: high and low GWF were mainly concentrated in the northeast and southwest regions, respectively. From 2011 to 2020, the mean center of the GWF moved west due to the decrease and increase in the eastern and western regions, respectively, supporting the pollution haven hypothesis. The WPL ranged from 2.67 to 5.03 and fluctuated due to variations in precipitation. The relative contributions of natural and human factors to the WPL evolution were 72.9 % and 27.1 %, respectively. According to the scenario analysis, increasing the N use efficiency to 50 %, manure recycling rate to 80 %, and sewage treatment rate in urban and rural regions to 98 % and 40 %, respectively, could decrease GWF by 39.6 %. The present study establishes an open framework to evaluate anthropogenic N emissions to water, and the outcomes provide valuable references for sustainable N management in city clusters.

Closing the irrigation water productivity gap to alleviate water shortage in an endorheic basin

Closing the irrigation water productivity (IWP) gap is an effective approach to alleviating water deficits and ensuring food security. However, few studies have attempted to quantify the IWP gap and the potential benefits of closing it. This study adopted the Heihe River Basin, the second-largest inland basin in China, as a typical study area. The aims of this study were to: (1) assess the positive achievements and potential risks triggered by the Heihe Ecological Water Diversion Project (EWDP) according to multi-source and multi-scale measured data; (2) analyze potential approaches to improve the IWP and quantify the potential benefits that can be achieved by closing its IWP gap. The results of this study indicated that the EWDP effectively reallocated surface water resources, replenished groundwater in the lower reaches, and facilitated the recovery of oases and economic development in the downstream regions. However, this project has indirectly led to an imbalance in the groundwater resource between the middle and lower reaches, resulting in decline in groundwater levels and degradation of local vegetation in the midstream regions. In addition, the expansion of cultivated land in the midstream and downstream oases has resulted in the deterioration of farmland environment. The water transfer resulted in a deceleration in the growth of IWP from 2.44 % to 1.15 %, and the existing IWP gap was 1.43 kg/m3 between 1984 and 2017. This study predicted a future increase in the IWP to 2.01 kg/m3 with a reduction in the gap to 0.45 kg/m3 while maintaining food production. The potential for conserving water in the Heihe agricultural region can reach 552 million m3 by reducing the planting area by 10 %, improving irrigation water use efficiency by 20 %, maintaining existing agricultural film inputs, and reducing fertilizer application by 10 %. Following the research recommendations can greatly alleviate the agricultural water shortage and over-extraction of groundwater in the middle reaches and ensure meeting ecological water demand in the lower reaches. This study can act as a reference for sustainable management of an endorheic basin.

Impact of reduced fertilizer application on the yield and non-point source pollution from Yongyou rice cultivation

<p>In the major grain production regions of China, agricultural non-point source pollution and the eutrophication of adjacent surface waters due to the excessive use of chemical fertilizers continue to be significant issues. To address the irrational traditional fertilization practices of farmers and to mitigate agricultural non-point source pollution, a fertilization reduction project was initiated in Jiangshan City. This project aimed to investigate the impact of reducing fertilizer application by 10% to 30% on the yield of Yongyou 15 rice variety and the loss of nutrients (total nitrogen, total phosphorus, and total potassium) in the surface runoff from paddy fields, relative to the farmers' standard fertilization practices. The findings indicated that reducing the conventional fertilizer dosage by 10% to 20% did not lead to a significant decrease in rice yield, with the yield being highest at a 10% reduction. Following fertilization, the nutrient concentration in the paddy field drainage rapidly reached a peak within one hour, after which nitrogen, phosphorus, and potassium concentrations decreased sharply by 25.9% to 66.0%, 70.1% to 88.3%, and 25.0% to 52.5%, respectively, within 24 hours. Subsequently, all nutrient levels continued to decline gradually until the end of the experiment. This suggests that the risk period for nutrient loss, which also corresponds to a high-risk period for non-point source pollution, occurs within a few days after fertilization, particularly if the paddy field is drained due to heavy rain or artificial means. The reduction in chemical fertilizer significantly influenced the nutrient content in the paddy field drainage. One hour after fertilization, reducing the conventional fertilization rate by 10% to 30% resulted in decreases in the concentrations of total nitrogen, total phosphorus, and total potassium in the drainage by 3.7% to 68.2%, 26.3% to 64.8%, and 5.8% to 57.5%, respectively. This approach holds significant potential for enhancing economic benefits and safeguarding the ecological environment in rice cultivation.</p>

Fertilization Practices: Optimization in Greenhouse Vegetable Cultivation with Different Planting Years

Cucumber plant growth and the fate of N in the plant-soil system are influenced by fertilization practices, the strengths of which may vary among soils. Three soils with different years of greenhouse vegetable cultivation (0, 2, and 18 years) were fertilized differently (CK, no N fertilizer applied; CF, chemical NPK fertilizers applied; RCF, reduced chemical NPK fertilizers applied, with N, P, and K reduced by 46.5%, 68.6%, and 54.7%; RCF+CM, 75% of the total N derived from chemical fertilizer and the rest from chicken manure in the case of reduced fertilization) in a pot experiment to study the changes in cucumber (Cucumis sativus L.) growth, N uptake, residue, and losses. The original N in soil was insufficient to maintain leaf growth and chlorophyll synthesis at later growth stages, even in soil with 18 years of greenhouse vegetable cultivation, where the original N content was the highest (total N 1.73 g kg−1). However, the CF treatment with excessive N fertilization inhibited leaf growth at the early growing stage and accelerated leaf senescence later, especially in soil with longer years of greenhouse vegetable cultivation. Therefore, reduced fertilizer application (RCF and RCF+CM) is appropriate to improve cucumber growth and productivity in greenhouse cultivation with different planting years. Although the same amount of N was applied, the RCF+CM treatment performed better than the RCF treatment in terms of increasing plant N uptake (by 30.5%) and soil N pool storage (by 25.0%) while decreasing N losses (by 16.6%) in soil with 0 years of greenhouse vegetable cultivation. In soil with 2 and 18 years of greenhouse vegetable cultivation, the soil itself functions much better in exogenous N retention and supply, with the N storage and losses not significantly different between the RCF and RCF+CM treatments. We conclude that reduced fertilization with the co-application of chicken manure is optimal for plant growth promotion, output-input ratio increase, soil N fertility improvement, and environmental risk mitigation.

Portable shifted excitation Raman difference spectroscopy for on‐site soil analysis

AbstractOn‐site soil analysis in the framework of precision agriculture is gaining significant importance to achieve improved crop productivity, increased soil health and reduced fertilizer application. In situ sensing techniques can provide the information required for decision support systems immediately on the field, for example, to control fertilization and liming. Shifted excitation Raman difference spectroscopy (SERDS) pilot investigations for on‐site soil analysis are presented using a portable SERDS sensor system specifically developed for in‐field studies. The SERDS sensor includes a dual‐wavelength diode laser at 785 nm integrated in an in‐house realized turnkey laser system and an optical power of 36 mW at the sample was chosen for our experiments. Outdoor pre‐investigations with the device and polystyrene as test sample show the capability of SERDS for qualitative and quantitative analysis under changing daylight conditions. On‐site soil analysis is carried out and SERDS extracts Raman signals from disturbing background interference with a 15‐fold improvement of the signal‐to‐background‐noise ratio. Beside others, closely neighboured Raman signals of calcite and dolomite are identified and even mixtures of both soil carbonates are discriminated using SERDS. The number of accumulations for generating an averaged SERDS spectrum of soil with a sufficient signal stability and signal‐to‐background‐noise ratio is evaluated to optimize the overall exposure time for such in situ experiments. The presented results demonstrate the large capability of the developed portable SERDS sensor system for on‐site soil investigations as promising tool for precision agriculture.

Energy, Economic, and Environmental Assessment of Sweet Potato Production on Plantations of Various Sizes in South China

Sweet potato (Ipomoea batatas L.) is an important starch-producing crop used worldwide. However, few studies have been conducted on the energy efficient, cost benefit, and greenhouse gas (GHG) emissions of sweet potato production. To address this issue, the data were collected using a questionnaire for face-to-face interviews of 78 sweet potato growers and 74 reference crop (i.e., rice, maize, and potato) growers in Guangdong province. Results revealed that sweet potato production exhibited the highest value of energy efficiency (0.83 kg MJ−1) and economic productivity (0.85 kg CNY−1) among four crops. The GHG emissions from sweet potato production (1165 kg CO2-eq ha−1) were significantly higher than GHG from rice and maize but lower than GHG from potatoes. Moreover, plantation size significantly (p < 0.05) affected inputs of labor, machinery, and diesel fuel and further affected the energy rate, energy efficiency, and GHG emissions of sweet potato production. Sweet potato production in small-size farms (<2.0 ha) exhibited the highest energy efficiency (0.97 kg MJ−1) and the lowest GHG emissions (1045 kg CO2-eq ha−1). Quartering assessments based on energy efficiency, economic productivity, and GHG emissions showed that fertilizers and labor were the major contributors to energy consumption, economic costs, and GHG emissions. Future efforts should be made to reduce fertilizer application and increase fertilizer use efficiency for sustainable sweet potato production.

Characteristics of endophytic bacterial community structure in roots of sugarcane under different fertilizer applications

<p id="C3">To explore the beneficial endophytic bacteria in sugarcanes and their functions, we analyzed the characteristics of endophytic bacterial community structure in roots of sugarcane under different fertilizer applications. At the phylum level, the proportion of Actinobacteria in roots of sugarcanes under different fertilization levels were lower than that in the control. However, the proportion of Chloroflexi in roots of sugarcanes under different fertilization levels applications were higher than that in CK. At the genus level, <italic>Haliangium</italic>, <italic>Acidicapsa</italic>, <italic>unclassified_f__Ktedonobacteraceae</italic>, and <italic>unclassified_f__Acidobacteriaceae_ Subgroup_</italic>1 were the specific dominant endophytic bacterial genera in root of sugarcanes under conventional fertilization level (3000 kg hm^-2, H treatment); while <italic>Sphingomonas</italic> was the specific dominant endophytic bacterial genus in roots of sugarcanes under fertilization level (1500 kg hm^-2, M treatment); <italic>Mesorhizobium</italic>, <italic>norank_f__BIrii</italic>41, <italic>Glycomyces</italic>, <italic>norank_f__</italic>67-14, <italic>Reyranella</italic>, <italic>unclassified_f__Steroidobacteraceae</italic>, <italic>unclassified_f__Xanthobacteraceae</italic>, <italic>norank_f__Roseiflexaceae</italic>, and <italic>Dongia</italic> were the specific dominant endophytic bacterial genus in roots of sugarcanes under the fertilization level (300 kg hm^-2, L treatment). On the contrary, <italic>Caulobacter</italic>, <italic>Pseudonocardia</italic>, <italic>Nocardia</italic>, <italic>Kitasatospora</italic>, <italic>norank_f__norank_o__norank_c__Actinobacteria</italic>, <italic>Oceanibaculum</italic>, and <italic>Amycolatopsis</italic> were the unique dominant endophytic bacterial genera in root of sugarcane without fertilization application (control). And <italic>Actinospica</italic>, <italic>Catenulispora</italic>, <italic>Acidothermus</italic>, <italic>Dyella</italic>, and <italic>norank_f__Xanthobacteraceae</italic> were lost in root of sugarcanes under low nitrogen applications. Gene function prediction also revealed that, compared to no-fertilization treatment, both the endophytic bacterial community structure and the metabolic functions of endophytic bacteria in roots of sugarcanes were affected by different fertilizer applications. However, the structures of endophytic bacterial community in roots of sugarcane were significant differences among different fertilization treatments depending on the amounts of fertilizer applications. Compared to conventional fertilization, the yields of sugarcanes, and the structure, metabolic function of endophytic bacteria in roots of sugarcanes were not significantly changed by fertilizer application under 1500 kg hm^-2 treatment. In conclusion, the conventional fertilization at the present stage can be substituted by reducing fertilizer application from 3000 kg hm^-2 to 1500 kg hm^-2 level in sugarcane.

Grain self-sufficiency versus environmental stress: An integration of system dynamics and life cycle assessment

Developing a sustainable grain supply is essential, especially in China. However, most previous research adopted a static approach to assess the environmental impacts of grain production, and such an approach focuses only on the product supply chain. An integrated system dynamics and life cycle assessment model was employed in this study to estimate and simulate the long-term performance of China's grain system from 2009 to 2030 from a holistic and dynamic perspective. Results showed that the fossil depletion of China's current 1 t of grain production per year was 1.11 × 104 MJ, which was mainly attributed to fertilizer production. For water footprint, the human health impact was 4.85 × 10−4 DALY/t, in which the water consumption contributed almost 77%, while the ecosystem quality impact was 7.86 × 10−6 species. yr/t, overwhelmingly derived from water pollution. Simulation results showed that the environmental impacts of China's grain production will increase by at least 19% in 2030 compared with the current situation if current development modes remain unchanged. Considerable benefits were observed in the integrated scenario, which would decrease the footprint results by up to 27% while increasing the self-sufficiency rate by 10%. Scenario analyses indicated that adopting measures from the production and consumption perspectives (e.g., simultaneously adjusting planting structure, increasing rural investment, reducing fertilizer application, and modifying diet structure) could effectively mitigate the environmental burdens while enhancing food security. Moreover, promoting the development of agricultural water conservancy measures and renewable energy with high utilization rates is recommended to ameliorate the water scarcity impact and ensure sustainable agricultural development.

Disentangling the Influence of Landscape Characteristics, Hydroclimatic Variability and Land Management on Surface Water NO3‐N Dynamics: Spatially Distributed Modeling Over 30 yr in a Lowland Mixed Land Use Catchment

AbstractNitrate (NO3‐N) mobilization is generally controlled by available sources, hydrological connectivity, and biogeochemical transformations along the dominant flow paths. However, their spatial heterogeneity and complex interactions often impede integrated understanding of NO3‐N dynamics at the catchment scale. To fully integrate spatiotemporal information for NO3‐N simulations, a grid‐based model, mHM‐Nitrate, was applied to a 68 km2 lowland, mixed land use catchment (Demnitzer Millcreek, DMC) near Berlin. The model successfully captured the spatiotemporal distribution of flow and NO3‐N between 2001 and 2019, but was less successful in 1992–2000 due to land management changes. Re‐optimization of relative parameters was subsequently conducted for this period to understand management effects. The simulated results revealed landscape characteristics and hydroclimatic variability as the main controlling factors on respective spatial and temporal patterns. The combined effects of vegetation cover and fertilizer inputs dictated the spatial distribution of water and NO3‐N fluxes, while wetness condition determined the temporal NO3‐N dynamics by regulating hydrological connectivity and NO3‐N mobilization. Denitrification was also closely coupled with hydroclimatic conditions, which accounted for ∼20% of NO3‐N inputs. In contrast, restoration of riparian wetlands had a modest impact on NO3‐N export (∼10% reduction during 2001–2019), suggesting further interventions (e.g., reducing fertilizer application or increased wetland areas) are needed. Our modeling application demonstrated that mHM‐Nitrate could provide robust spatially distributed simulations of hydrological and NO3‐N fluxes over a long‐term period and could successfully differentiate the key controlling factors. This underlines the model's value in contributing to an evidence base to guide future management practices under climate change.

Effects of long-term different fertilization patterns on soil nutrients and microbial community structure of tomato in a solar greenhouse.

The phospholipid fatty acid (PLFA) technique was used to investigate the effects of fertilization on soil characteristics and microbial community of tomato in a solar greenhouse in Shouguang, Shandong Province, China, based on a long-term (12-year) fertilization experiment. The experiment involved a control (CK) and five fertilization treatments, namely, traditional nitrogen application (CN), traditional nitrogen application+straw return (CNS), optimized nitrogen application (SN), optimized nitrogen application+straw return (SNS), and organic manure nitrogen application+straw return (MNS). Results showed that the contents of soil organic matter and avai-lable P and K under all fertilization treatments were significantly higher than that of CK, but no significant difference among fertilization treatments. The traditional nitrogen application (i.e., CN and CNS) significantly decreased soil pH. The reduction of nitrogen fertilizer (i.e., SN, SNS and MNS) did not affect soil pH. Compared with CK, no straw treatment (i.e., CN and SN) and MNS did not affect the content of soil available N, but nitrogen combined with straw returned (i.e., CNS and SNS) significantly increased soil available N content. The optimized N with straw return (i.e., SNS) treatment resulted in the highest soil available N. Compared with CK and treatments without straw (i.e., CN, SN), treatments with straw (i.e., MNS, CNS and SNS) substantially changed soil microbial community structure and increased the biomass of soil bacteria, fungi, actinomycetes, mycorrhizal fungi, and the total amount of PLFA. SNS treatment had the highest soil microbial diversity, the highest biomass of soil bacteria, fungi, and actinomycetes, the highest total amount of PLFA, the highest ratios of fungi/bacteria and monounsaturated fatty acids/saturated fatty acids (MONO/SAT), the two indicators for soil ecosystem stability. Further, it had the lowest ratios of iso/anteiso fatty acids (i/a) and gram-positive/gram-negative bacteria (G+/G-), the indicators for nutritional stress. Redundancy and correlation analysis revealed that soil organic matter was the main factor affecting soil microbial community structure, with a significant positive correlation with actinomycetes and gram-positive bacteria. In conclusion, straw returning combined with optimized nitrogen application (i.e., SNS, 8 t·hm-2 of wheat straw with N fertilizer reduced by 58.3%) could improve soil nutrient status, soil microbial biomass, soil microbial community structure, and soil ecological environment. It would be an effective measure for reducing fertilizer application and improving efficiency.