Excessive Fertilizer Application Research Articles

Carbohydrate utilization by belowground organs defines the capacity of faba bean to exploit organic phosphorus sources

AbstractBackgroundLimited phosphate (Pi) reserves and the economic and adverse environmental impacts of excessive application of mineral fertilizers in soils are alarming. Therefore, the use of organic phosphorus (Porg) is suggested to reduce reliance on chemical fertilizers.AimsThere is currently little information regarding the accessibility of Porg to N2 fixation plants. Therefore, the present study aims to address the question of to what extent Porg substrates can serve as reliable sources of phosphorus (P) for faba bean in its nodulated phase. Specifically, we intended to explore whether N2‐fixing plants employ intrinsic mechanisms to facilitate Porg availability.MethodsA pot experiment was conducted to assess the inherent capacity of two faba bean varieties (Tiffany vs. Mallory) to utilize Porg supplied as phytic acid and Ca‐glycerophosphate. Plants were inoculated with Rhizobium leguminosarum bv. viciae 3841 strain and cultivated on sterilized loamy sand under greenhouse conditions.ResultsPhytic acid was relatively less efficient than Ca‐glycerophosphate in sustaining plant growth. Compared to Mallory, the variety Tiffany displayed a higher capability to use Porg, as evidenced by the relatively higher biomass production, nodulation, phosphorus use efficiency, and P‐ and N‐accumulations in plant tissues. Porg exploitation was intimately linked to the efficient utilization of the host's carbohydrate budget into nutrient‐acquiring structures (roots and nodules). In addition, the preferential allocation of Pi to prolific nodules is essential for plants to thrive best under these circumstances.ConclusionsTogether with N profitability, these findings suggested that N2‐fixing plants (e.g., faba bean) can promote the sustainable exploitation of Porg, thereby diminishing the sizeable environmental footprint.

Conversion from farmland to orchards has minor effects on nitrogen biological processes in deep loess deposits

High nitrate (NO3--N) accumulation has been observed globally in vadose zones due to the overuse of synthetic fertilizer, but its impacts on nitrogen (N) biological processes remain poorly understood, especially after land use conversion from farmlands to deep-rooted apple orchards. In this study, we collected paired soil samples to determine available N contents, NO3--N isotopes, and abundances of N functional genes (NFGs) in 10-m loess profiles under cultivated farmlands and adjacent apple orchards (n = 300). The average NO3--N accumulation under orchards was 4773 kg N ha−1 (10 times higher than farmlands), with the NO3--N profiles resembling a parabolic curve within 0 – 4 m below the surface. Regardless of excessive fertilizer application and well-developed root systems, the deep-rooted orchards had minor effects on N sources and biological processes in deep loess deposits, as indicated by our estimates of isotopes and NFGs abundances. We hypothesized that the limited and inactive microorganisms in the subsoil are more resistant to environmental disturbances, and that carbon source and ammonium substrate dominated the gene expression and occurrence of NFGs-indicated biological processes. The limited root biomass per unit depth and the inhibition effects of a dry soil horizon on root turnover and exudate release likely contributed to the less perturbed N biological processes under orchards. As the first study to explore N transformation processes in 10-m loess deposits, this study provided insights for complicated N biogeochemical cycles in arid regions with deep unsaturated soils and intensive agricultural land use.

Sensitivity analysis of greenhouse gas emissions at farm level: case study of grain and cash crops.

Sensitivity analysis is useful to downgrade/upgrade the number of inputs to limit greenhouse emissions and enhance crop yield. The primary data from the 300 rice (grain crop) and 300 cotton (cash crop) farmers were gathered in face-to-face interviews by applying a multistage random sampling technique using a well-structured pretested questionnaire. Energy use efficiency was estimated with data envelopment analysis (DEA) model, and a second-stage regression analysis was conducted by applying Cobb-Douglas production function to evaluate the influencing factors affecting. The results exhibit that chemical fertilizers, diesel fuel and water for irrigation are the major energy inputs that are accounted to be 15,721.55, 10,787.50 and 6411.08MJha-1 for rice production, while for cotton diesel fuel, chemical fertilizer and water for irrigation were calculated to be 13,860.94, 12,691.10 and 4456.34MJha-1, respectively. Total GHGs emissions were found to be 920.69 and 954.71kg CO2eq ha-1 from rice and cotton productions, respectively. Energy use efficiency (1.33 and 1.53), specific energy (11.03 and 7.69MJha-1), energy productivity (0.09 and 0.13kgMJ-1) and energy gained (14,497.85 and 20,047.56MJha-1) for rice and cotton crop, respectively. Moreover, the results obtained through the second-stage regression analysis revealed that excessive application of fertilizer had a negative impact on the yield of rice and cotton, while farm machinery, diesel fuel and biocides had a positive effect. We hope that these findings could help in the management of the energy budget that we believe will reduce the high emissions of GHGs to address the growing environmental hazards.

Estimation of Cotton Nutrient Uptake Based on the QUEFTS Model in Xinjiang

The Xinjiang cotton-producing region is the main cotton-growing region in China; however, the combination of excessive application but low utilization of fertilizers has restricted its agricultural development. Estimating the balanced nutrient requirements for cotton is essential to increase its yield and nutrient use efficiency. The results from 372 field experiments performed between 1996 and 2019 were used to build a QUEFTS (quantitative evaluation of the fertility of tropical soils) model to investigate relationships between cotton seed yield and nutrient accumulation, with the data from 2017 to 2020 used to validate the model. The results demonstrated that the QUEFTS model predicted a linear relationship between target yield and nutrient uptake until the target yield reached about 60–70% of the potential yield. To produce 1000 kg of seed cotton, 28.3 kg N, 6.1 kg P, and 29.6 kg K were required for cotton, and the corresponding ratio of N, P, and K was 4.64:1:4.85. The corresponding internal efficiencies (IEs) for N, P, and K were 35.4, 163.2, and 33.7 kg/kg, respectively. Field validation indicated that the QUEFTS model could be used to estimate nutrient uptake at a targeted yield and contribute to developing a fertilizer recommendation strategy for Xinjiang cotton production.

Link Between Aeration in the Rhizosphere and P-Acquisition Strategies: Constructing Efficient Vegetable Root Morphology

Excessive application of phosphate fertilizer is common in vegetable fields and causes deterioration of the rhizosphere environment, that is, the soil oxygen (O2) environment, which further constrains root morphology construction and limits vegetable yield. Nevertheless, the interaction between root morphology and the response of the rhizosphere O2 environment to vegetable P utilization has rarely been reported. Therefore, we carried out an experiment applying different concentrations of O2 generator, 10%, 30%, 50%, and 80% urea hydrogen peroxide (as pure nitrogen) instead of urea as a top dressing in the rhizosphere, to study the effect on root morphology and P adsorption, and its mechanism. We found that there were O2-deficient and P-deficient zones in the rhizosphere, and oxygenation could alleviate the rhizosphere O2 and P consumption in roots. The rhizosphere O2 concentration was maintained at approximately 250.6 μmol L−1, which significantly promoted total root length, root volume, average diameter, and root activity by 29.0%, 30.9%, 3.9%, and 111.2%, respectively. Oxygenation promoted organic P mineralization and increased the Olsen-P content in the rhizosphere. The characteristics of root morphology and increased available P in the rhizosphere jointly contributed to high P absorption and utilization, and the P use efficiency was improved by 9.3% and the shoot P accumulation by 10.9% in the 30% urea hydrogen peroxide treatment compared with CK. Moreover, this treatment also improved yield and quality, including vitamin C and the soluble sugar content. However, at a still higher O2 concentration (260.8 μmol L−1), vegetable growth exhibited O2 damage, resulting in reduced yield and quality. Our study provided new insights into constructing efficient root morphology by regulating the rhizosphere O2 environment to improve vegetable yield and quality, as well as to increase P use efficiency in vegetable fields.

Genome-wide identification and expression analysis of MYB gene family under nitrogen stress in Panax notoginseng.

The myeloblastosis (MYB) gene family, involved in regulating many important physiological and biochemical processes, is one of the largest transcript factor superfamilies in plants. Since the identification of genome sequencing of Panax notoginseng has been completed, there was little known about the whole genome of its specific MYB gene family and the response to abiotic stresses, in consideration of the excessive application of nitrogen fertilizers in P. notoginseng. In this study, 123 PnMYB genes (MYB genes of P. notoginseng) have been identified and divided into 3 subfamilies by the phylogenetic analysis. These PnMYB genes were unevenly located on 12 chromosomes. Meanwhile, the gene structure and protein conserved domain were established by MEME Suite. The analysis of collinear relationships reflected that there were 121 homologous genes between P. notoginseng and Arabidopsis and 30 between P. notoginseng and rice. Moreover, cis-acting elements of PnMYB gene promoters were predicted which indicated that PnMYBs are involved in biotic, abiotic stress, and hormone induction. The expressions of PnMYB transcription factors in its roots, flowers, and leaves were detected by qRT-PCR and they had tissue-specific expressions and related to the growth of different tissues. Under nitrogen stress, MYB transcription factors had great feedback. Ten R2R3-MYB subfamily genes were significantly induced and indicated the possible function of protecting P. notoginseng from excess nitrogen. With further knowledge on identification of PnMYB gene related to tissue selectivity and abiotic stresses, this study laid the foundation for the functional development of PnMYB gene family and improved the cultivation of P. notoginseng.

Potential to Reduce Chemical Fertilizer Application in Tea Plantations at Various Spatial Scales.

Tea is the main commercial crop grown in China, and excessive application of chemical fertilizers in tea plantations is common. However, the potential to reduce chemical fertilizer use in tea plantations is unclear. In this study, Zhejiang Province was selected as the research object to systematically analyze the potential for tea plantation chemical-fertilizer reduction at different spatial scales. The geographic information system-based analytic hierarchy process method and Soil and Water Assessment Tool model were used to determine the chemical fertilizer reduction potential at the province scale and watershed scale, respectively. At the field scale, two consecutive years of field experiments were conducted on a tea plantation. Province-level analysis showed that 51.7% of the area had an average total fertilization intensity greater than 350 kg/hm2 and a high reduction potential. Watershed analysis revealed that chemical fertilizer reduction had better potential in reducing total nitrogen and total phosphorus inputs to runoff in the short term, whereas 50% organic fertilizer substitution was the best strategy to achieve long-term effects. The field experiments further proved that organic fertilizer substitution balanced tea growth and environmental protection. This study provides a useful method to investigate strategies to reduce chemical fertilizer use in tea-growing areas.

Risk Assessment of Nitrate Pollution in the Shallow Groundwater of the Mihe Alluvial–Diluvial Fan Based on a DEA Model

Affected by excessive fertilizer application and livestock breeding, the problem of nitrate pollution in the groundwater in the Mihe alluvial–diluvial fan area is becoming increasingly prominent, which poses a great threat to human production and life. Given this, the risk of nitrate pollution in the shallow groundwater of the Mihe alluvial–diluvial fan is evaluated by introducing a data envelopment analysis (DEA) method. Using this model, 28 groundwater sampling points are selected as the decision-making unit (DMU); the nitrogen and pesticide application rate, livestock and poultry stock, groundwater burial depth, aquifer water abundance, and vegetable planting area are taken as the model input; and the nitrate content is taken as the model output to quantitatively calculate the pollution risk index to form a spatial distribution map of pollution risk. The calculation using the model shows that the average pollution risk index of the study area is 0.382, the spatial variation is 1.12, the pollution risk index gradually decreases from south to north, and agricultural planting and livestock and poultry breeding are the main pollution sources. The calculation of nitrate pollution risk using this model not only enriches the nitrate pollution evaluation model but also provides a basis for further implementing the action of reducing fertilizer use by increasing its efficiency and strengthening the prevention of agricultural diffused pollution.

Assaying the efficiency of sulfate, chelate and zinc nanoparticle fertilizers in green bean grown in alkaline soil

The excessive fertilizer application is a recurring problem in agriculture as it not only harms the soil texture but also diminishes the micronutrient availability i.e., zinc (Zn). Zn is an essential element for crop production and quality, and is also indispensable for human diet. Zn deficiency is a common problem in alkaline soils. This study aims to assess the efficiency of three different Zn fertilizers in Phaseolus vulgaris plants, grown in an alkaline soil. P. vulgaris plants were grown in an experimental greenhouse under four different treatments: control (no Zn fertilization), ZnSO4, the chelate diethylenetriaminepentaacetic acid (DTPA-Zn), and Zn nanoparticles (NfsZnO). Each Zn source was applied at three different doses (0, 25, 50, 100 mg kg−1). Parameters related to biomass, photosynthetic pigments, and Zn accumulation were analyzed. Zn sources enhanced bean pod growth and yield. Furthermore, the three Zn sources increased Zn accumulation in all plant organs, except in leaves. Whereas, plants supplied with 100 mg kg−1 of DTPA-Zn and 25 mg kg−1 of NfsZnO accumulated the highest bean Zn concentration. Generally, plants supplied with DTPA-Zn and NfsZnO showed the highest Zn content values. Besides, Zn sources enhanced the values of Zn efficiency parameters in a dose-dependent manner. According to the results, the three Zn fertilizers were effective to increase the parameters analyzed in P. vulgaris. However, DTPA-Zn and NfsZnO were more effective to enhance yield and bean Zn content, and thus can be useful for bean cultivation in alkaline soils.

Effects of different nitrogen fertilizer types and application rates on maize yield and nitrogen use efficiency in Loess Plateau of China

After excessive application of chemical fertilizer in farmland can cause serious impact on the environment. Therefore, it is urgent to explore the optimal application rate of maize yield and nitrogen use efficiency (NUE) in order to maintain the sustainable use of cultivated land. The objective of this study was to quantify the interaction effect of fertilizer type and N fertilizer application rate on maize grain yield, N uptake, N translocation, and N translocation efficiency. The experiment was arranged in a randomized complete block design with two factors (2 N fertilizer types × 5 N fertilizer application rates) in 2018, 2019, and 2020. The two N fertilizer types were urea and slow-release N fertilizer. The five N fertilizer application rates were 90 (N1), 120 (N2), 180 (N3), 240 (N4), and 300 (N5) kg N ha–1. The mean grain yield in slow-release N fertilizer was 21.3%, 25%, and 16.2% higher than that with urea fertilizer in 2018, 2019, and 2020, respectively. Total plant N uptake in slow-release N fertilizer was 2.3%, 5.5%, and 3.3% higher than that with urea fertilizer at silking stage in 2018, 2019, and 2020, respectively. Total N translocation under slow-release N fertilizer averaged over N fertilizer application rates and years was 9.3%, 22.9%, and 17.8% lower than observed under urea fertilizer in 2018, 2019 and 2020, respectively. Fertilizer type and N fertilizer application rate had significant effects on maize grain yield, N uptake, N translocation, and N translocation efficiency. The combination of slow-release N fertilizer and moderate N fertilizer application rate (180 kg N ha–1) was the optimal strategy for increasing maize grain yield.

Effect of Graded Levels of Nutrients and Organic Amendments on Growth and Flower Yield of African marigold (Tagetes erecta L.)

Production of marigold can be improved to a large extent by the judicious cultural operations i.e., application of optimum fertilizer at required time and appropriate crop management practices. Excessive application of chemical fertilizers produces adverse effects on the atmosphere and groundwater quality, causing several health hazards. In India, effective nutrient management has played a major role in accomplishing the enormous increase in food production. However, it is not possible to supply all the nutrient requirements of crops through inorganic fertilizers. Integrated Nutrient Management provides an excellent opportunity to sustain soil health and enhance the crop production. To improve the physical, chemical and biological properties of the soil, and increase the efficiency of applied fertilizers, apply the required quantity of organic manures and bio-fertilizers along with balanced use of chemical fertilizers [1].
 In this experiment, the organic amendments viz., Vermicompost, Humic acid and Arka microbial consortium applied as basal and the recommended full dose of phosphorus through single super phosphate and pottasium through Muriate of potash were applied just before transplanting of seedlings. Nitrogen through urea was applied in two split doses, i.e., first ½ dose of total nitrogen was applied at the time of transplanting of seedlings and remaining dose of nitrogen was applied at 45 DAT according to the treatment combinations. The experiment was carried out in Randomized Block Design with three replications and thirteen treatment combinations viz. Control (RDF 100% - 90:90:75 kg N, P2O5 and K2O kg ha-1) (T1), RDF 75% + Vermicompost (T2), RDF 100% + Vermicompost (T3), RDF 75% + Humic acid (T4), RDF 100% + Humic acid (T5), RDF 75% + Vermicompost + Humic acid (T6), RDF 100% + Vermicompost + Humic acid (T7), RDF 75% + Humic Acid + Arka microbial consortium (T8), RDF 100% + Humic Acid + Arka microbial consortium (T9), RDF 75% + Vermicompost + Arka microbial consortium (T10), RDF 100% + Vermicompost + Arka microbial consortium (T11), RDF 75% + Vermicompost + Humic Acid + Arka microbial consortium (T12), RDF 100% + Vermicompost + Humic Acid + Arka microbial consortium (T13).
 The treatment T13 recorded the maximum plant height (109.28 cm), number of branches plant-1 (18.74) and number of leaves plant-1 (136.94) were recorded for those plants applied with RDF 100% + Vermicompost + Humic Acid + AMC (T13) in 30, 60 and 90 days after transplanting. Similarly, maximum single flower weight (6.95 g), number of flowers plant-1 (58.42), flower yield plant-1 (312.63 g) and plot-1 (10.5 kg), estimated flower yield 13.86 t ha-1 and xanthophyll content (18.26 g kg-1 of petal meal). Hence, it is concluded that application of Vermicompost @ 5 t ha-1 + Humic acid @ 5 kg ha-1 along with Arka microbial consortium@ 12.5 kg ha-1 in addition with 100 % RDF (90:90:75 kg N, P2O5 and K2O kg ha-1) will be effective in increasing the growth, flower yield and xanthophyll content of African marigold.

Residual Effect of Green Manure on Soil Properties in Green Manure- Transplant Aman-Mustard Cropping Pattern

Background: Conventional monoculture or cereal-cereal sequence systems insist farmers to use excessive application of chemical fertilizer in agriculture resulting reduce the soil organic matter contents and structures. The inclusion of green manuring crops in a rotation is vital to improve the biochemical and physical properties of the soil via increasing the labile of organic matter and ultimately increased crops yield. Some complex molecules of green manuring crops takes a longer time of decomposition and thus nutrients reserve in soil and release latter which provide nutrients to the succeeding and following crops. So the current experiment aimed to study the residual effect of different in situ green manuring crops to the sub-sequent and following soil. Methods: The field experiment conducted during 2015 to 2016 with eight green manuring crops and rice and mustard was the subsequent and following crop. In situ incorporation of GM crops with 100% (F1) and 50% (F2) fertilizer, the prior and post-harvest soil (cropping pattern) of experiment field (0-15 cm) was collected and analyzed. Result: After two consecutive year, GM-T.aman-Mustard cropping pattern increased soil organic matter 0.04% to 0.07% and 0.02% to 0.03% (T1 and T2 with F1 and F2) and nitogen 0.05% (T1, T2 and T7 with F1 and F2) and K 0.2 to 0.5 meq/100 g (M. pudica with F1 and F2) and P 2 ppm to 15 ppm (T1, T2, T3 and T7 with F1 and F2) compared to initial soil. Rice yield with T1, T2, T3 and T6 shown higher with both fertilizer doses. Nitrogen fertilizer rates could be reduced after the incorporation of green manures in the succeeding and following crops.

Intensive agriculture, nitrogen legacies, and water quality: intersections and implications

More than a century of land-use changes and intensive agriculture across the Mississippi River Basin (MRB) has led to a degradation of soil and water resources. Nitrogen (N) leaching from the excess application of fertilizers has been implicated in algal blooms and the development of large, coastal ‘dead zones’. It is, however, increasingly recognized that water quality today is a function not only of the current-year inputs but also of legacy N within the watershed—legacy that has accumulated in soil and groundwater over decades of high-input agricultural practices. Although attempts have been made to quantify the extent to which soil organic nitrogen (SON) is being sequestered in agricultural soils with intensive fertilization, improved residue management, and the adoption of conservation tillage practices, the controls on accumulation dynamics as well as linkages between legacy N accumulation and water quality remain unclear. Here, we have used the process-based model CENTURY to quantify accumulation and depletion trajectories for soil N across a range of climate and soil types characteristic of the MRB. The model was calibrated against crop yield data and soil N accumulation data from a long-term field site. Model runs highlighted that under current management scenarios, N accumulation is greatest in regions with the highest crop yield, and this can be attributed to the higher residue rates with greater yields. We thus find that humans, through management practices, have homogenized spatial patterns of SON across the landscape by increasing SON magnitudes in warmer and drier regions. Results also suggest a regime shift in the relationship between soil organic N and N mineralization fluxes, such that N fluxes are greater now than in the 1930s, despite similar soil organic N magnitudes, mainly due to higher proportions of labile, unprotected soil organic matter. This regime shift leads to elevated N leaching to tiles and groundwater in landscapes under intensive agriculture.

Azolla Compost as an Approach for Enhancing Growth, Productivity and Nutrient Uptake of Oryza sativa L.

The excessive application of synthetic fertilizers can result in severe environmental risks, while composting green and fresh feedstocks can provide slow-release nutrients. Therefore, the aim of the current investigation was to study the effects of eight individual and combination treatments of azolla compost and NPK synthetic fertilizers (control = no fertilizer and compost; 100% NPK = full recommended dose of synthetic fertilizers as follows: 165 kg N ha−1, 37 kg P2O5 ha−1 and 50 kg K2O ha−1; 70% NPK; 40% NPK; 100% azolla compost (5 t DM ha−1); 50% NPK + 50% azolla compost; 70% NPK + 30% azolla compost and 40% NPK + 60% azolla compost) on rice growth, productivity and nutrient uptake in semi-arid agro-ecosystems. The results indicated that the combination of 40% NPK + 60% azolla compost or 50% NPK + 50% azolla compost resulted in the most optimal growth and the highest yield components. In addition, the application of 40% NPK + 60% azolla compost exhibited similar rice grain yields (10.76 t ha−1) as well as N, P, and K content and uptake compared with the full recommended dose of NPK fertilizer (100% NPK). This study declared that the utilization of azolla compost as an individual or combination application can reduce usage of synthetic fertilizers by up to 60% without significant reduction in the growth and grain productivity of rice.

Effects of different cropping systems on ammonia nitrogen load in a typical agricultural watershed of South China

The excessive application of agricultural irrigation water and chemical fertilizer has increased crop yields to help meet the demand for food, but it has also led to major water environment problem, i.e. non-point source (NPS) pollution, which needs to be addressed to achieve sustainable development targets. Although numerous studies have focused on the control and reduction of agricultural NPS pollution from the perspective of irrigation and fertilizer, the effects of different cropping systems on NPS pollution (ammonia nitrogen (NH3−N)) in the Dongjiang River Basin (DRB) were seldom assessed. Specifically, variation in the NH3-N load was simulated and analyzed at the annual and semi-annual scales under ten different cropping systems using the Soil and Water Assessment Tool (SWAT) model, which was calibrated and validated with satisfactory statistical index values in the DRB. The results indicated that the NH3-N load decreased, distinctly increased, slightly decreased when sweet potato, peanut, and rice were planted, respectively. Compared with mono-cropping, crop rotation could reduce the NH3-N load, and the planting sequence of crops could affect the NH3-N load to a certain extent. Planting peanuts in spring would dramatically increase NH3-N load. To evaluate NH3-N pollution, a critical threshold of NH3-N emission (5.1 kg·ha−1·year−1) was proposed. Meeting the NH3-N emission threshold cannot be achieved by altering the cropping system alone; additional measures are needed to reduce agricultural NPS pollution. This study facilitates the development of cropping systems and provides relevant information to aid the sustainable development of agriculture in the DRB.

Hydrogeochemistry of karst groundwater for the environmental and health risk assessment: The case of the suburban area of Chongqing (Southwest China)

Karst groundwater is a vital resource for drinking, living and irrigation purposes in karst agricultural areas of the world. Due to the vulnerability of karst aquifers, surface pollutants are easily transferred to the subsurface and make karst groundwater be deteriorated, thereby restricting the rational exploitation of karst groundwater resource. In view of this, 49 karst groundwater samples were collected from spring (SW) and underground river (URW) sites in the suburban area of Chongqing City and analyzed for various hydrochemical components. Particularly, the karst groundwater quality was comprehensively uncovered by combining characteristics of hydrogeochemical evolution and health risks caused by nitrate and fluoride. The results revealed that the karst groundwater was slightly alkaline in nature and the water types were mainly characterized by Ca-HCO3 accounting for 93.88% of the total samples due to the heavy dissolution of carbonate rock. The relatively high concentrations of Na+, SO42− and NO3− up to 271.88 mg/L, 277.94 mg/L and 56.94 mg/L were over the corresponding maximum acceptable limits for drinking water, which can be predominately attributed to the emissions of industrial park, dissolution of gypsum and pyrite and excessive application of chemical fertilizers. Although agricultural activities were stopped and chemical fertilizers were no longer applied during the sampling period, long-term application of fertilizers have a persistent adverse effect on the karst groundwater NO3−. The pollution index of the karst groundwater (PIG) revealed that the low pollution and potential pollution zones were noticed in the northwestern parts of the study area. With respect of the SW, all the total hazard index (HI) values were below 1 suggesting no significant health risk. On the contrary, HI values of 0.11–1.16 for adults, 0.15–1.61 for children and 0.17–1.83 for infants in the URW indicated significant noncarcinogenic health risks. Particularly, infants and children were more vulnerable to karst groundwater NO3− than adults. Furthermore, the noncarcinogenic health risks of karst groundwater can be mainly attributed to NO3−, confirmed by the higher contribution ratio (66.55%) to the HI values. Therefore, special and targeted measures need to be taken to decrease the NO3− concentration in agricultural area.

Single cell‐type transcriptome profiling reveals genes that promote nitrogen fixation in the infected and uninfected cells of legume nodules

Single cell‐type transcriptome profiling reveals genes that promote nitrogen fixation in the infected and uninfected cells of legume nodules

Effect of Seaweed Extract Supplement on Rice Rhizosphere Bacterial Community in Tillering and Heading Stages

Rhizosphere microbiota are conducive to soil nutrient cycling for plant growth. Long-term and excessive application of chemical fertilizer is harmful to agriculture. Seaweed extract is a good organic substitute for rhizosphere ecosystem and plant growth. We supplemented 5‰ seaweed extract powder to chemical fertilizer, and then studied its effect on rhizosphere bacteria of japonica rice (Oryza sativa L. subsp. japonica). In a short-term experiment, we compared the changes in rhizosphere bacteria among four treatments, i.e., no fertilizer (T1), chemical fertilizer only (T2), chemical fertilizer with 5‰ seaweed extract (T3), and less chemical fertilizer with 5‰ seaweed extract (80% of that of T3) (T4). Results show that seaweed extract supplement could affect the bacterial community in tillering and heading stages; the α-diversity of rhizosphere bacteria in the heading stage was obviously improved. In addition, seaweed extract supplement improved significantly the content of nitrate nitrogen (N), available phosphorus (P), and available potassium (K) in rhizosphere soil in the tillering stage, and, finally, increased the rice yield and quality mildly. Therefore, the seaweed extract supplement is shown to be a potential strategy to enrich the diversity of rhizosphere bacteria, which enhanced soil nutrient level, increased rice yield and quality, and also saved the use of chemical fertilizer.

Estimating Nutrient Uptake Requirements for Melon Based on the QUEFTS Model

Imbalanced and excessive fertilizer application has resulted in low yields and reduced nutrient use efficiency for melon production in China. Estimating nutrient requirements is crucial for effectively developing site-specific fertilizer recommendations for increasing yield and profit while reducing negative environmental impacts. Relationships between the yield and nutrient uptake requirements of above-ground dry matter were assessed using 1127 on-farm observations (2000–2020) from melon production regions of China. The quantitative evaluation of fertility of tropical soils (QUEFTS) model was used to estimate nutrient requirements. It predicted a linear increase in yield at balanced nutrient uptake levels until the yield reached approximately 60–80% of the potential yield. In order to produce 1000 kg of fruit, 2.9, 0.4 and 3.2 kg/ha of N, P and K (7.2:1.0:7.8), respectively, were required for above-ground parts, while the corresponding nutrient internal efficiencies were 345.3, 2612.6 and 310.0 kg per kg N, P and K, respectively, whereas 1.4, 0.2 and 1.9 kg of N, P and K were required to replace nutrients removed after harvest. The corresponding fruit absorption rates were 47.0%, 59.5% and 58.2%, respectively. Field validation experiments confirmed the consistency between observed and simulated uptake rates, indicating that this model could estimate nutrient requirements. These findings will help develop fertilizer recommendations for improving melon yield and nutrient use efficiency.

Characteristics and Driving Factors of Nitrogen-Use Efficiency in Chinese Greenhouse Tomato Cultivation

Excessive nitrogen fertilizer application in greenhouses could cause a significant variation in the nitrogen-use efficiency at the regional scale. This study aims to quantify agronomic nitrogen-use efficiency (AEN) and identify its driving factors across Chinese greenhouse tomato cultivation. Three hundred and forty-eight AEN values were obtained from 64 papers, including mineral nitrogen (MN) and mineral combined with organic nitrogen (MON) treatments. The average AEN values for the MN and MON treatments were 56.6 ± 7.0 kg kg−1 and 34.6 ± 3.5 kg kg−1, respectively. The AEN of the MN treatment was higher than that of the MON treatment for cultivation using soil with an organic matter content of less than 10 g kg−1 and the drip fertigation method. The AENs of the MN and MON treatments were divided into two segments according to the nitrogen application rate. The inflection points of the nitrogen application rate were 290 and 1100 kg N ha−1 for the MN and MON treatments, respectively. When the ratio of organic nitrogen to total nitrogen was less than 0.4, it was beneficial for improving the AEN. The soil organic matter content and the nitrogen application rate were the most critical factors determining the AEN. These results suggest that rationally reducing the nitrogen input and partially substituting mineral nitrogen with organic nitrogen can help improve the nitrogen-use efficiency.