Reducing Fertilizer Application Research Articles

Growth and yield of maize in response to reduced fertilizer application and its impacts on population dynamics and community biodiversity of insects and soil microbes

In the North China Plain, farmers are using excessive amounts of fertilizer for the production of high-yield crop yield, which indirectly causes pollution in agricultural production. To investigate an optimal rate of fertilizer application for summer maize, the fertilizer reduction experiments with 600 kg/ha NPK (N: P2O5: K2O = 28: 8: 10) as normal fertilizer application (NFA), (i.e., 100F), were conducted successively during 2020 and 2021 to study the effects of reduced fertilizer rates, including 90% (540 kg/ha; i.e., 90F), 80% (480 kg/ha; i.e., 80F), 62.5% (375 kg/ha; i.e., 62.5F) and 50% (300 kg/ha; i.e., 50F) of NFA, on the plant growth of maize, the dynamics of key population abundances and community diversity of insects, and the composition and diversity of microbial community and finally to find out the N-metabolic enzymes’ activity in soil. Our findings revealed that the fertilizer reduction rates by 10% - 20% compared to the current 100% NFA, and it has not significantly affected the plant growth of maize, not only plant growth indexes but also foliar contents of nutrients, secondary metabolites, and N-metabolic enzymes’ activity. Further, there was no significant alteration of the key population dynamics of the Asian corn borer (Ostrinia furnacalis) and the community diversity of insects on maize plants. It is interesting to note that the level of N-metabolic enzymes’ activity and microbial community diversity in soil were also not affected. While the fertilizer reduction rate by 50% unequivocally reduced field corn yield compared to 100% NFA, significantly decreased the yield by 17.10%. The optimal fertilizer application was calculated as 547 kg/ha (i.e., 91.17% NFA) based on the simulation analysis of maize yields among the five fertilizer application treatments, and the fertilizer application reduced down to 486 kg/ha (i.e., 81.00% NFA) with a significant reduction of maize yield. These results indicated that reduced the fertilizer application by 8.83% - 19.00% is safe and feasible to mitigate pollution and promote sustainable production of maize crops in the region.

Optimizing phosphorus fertilization for two commonly grown ground covers: creeping jenny and periwinkle

Growing nursery plants in containers usually requires the addition of fertilizer to achieve optimal growth. However, misconceptions among growers often lead them to apply quantities of fertilizers exceeding the recommended dose, resulting in nutrient runoff and increased production costs. Reducing fertilizer application is beneficial to have healthy plants and environment as well as to save on fertilizer costs. In this study, we wanted to determine the minimal level of phosphorus (P) required to grow bedding plants i.e. Lysimachia nummularia ‘creeping jenny’ (moneywort) and Vinca minor ‘Bowles’ (periwinkle) in nursery. The plants were grown within a greenhouse in a mixture of peat moss, vermiculite, and rice hulls (3:1:1 v/v) substrates and subjected to various P treatments. The treatments included single dose of 1, 3, or 6 mg/L of P, double doses of 3 or 6 mg/L of P, or a control that received 6 mg/L of P at each irrigation. The results indicated that single dose of 6 mg/L of P had similar fresh weight compared to control in both taxa. Reducing P application further to a single dose of 1 and 3 mg/L reduced fresh weight and leaf area in both groundcovers however did not reduce their stem length or physiological parameters such as Soil Plant Analysis Development (SPAD) and normalized difference vegetation index (NDVI). Phosphorus concentration in the plant tissue at maturity was lower in all treatments than control for both the taxa. During the study period, control plants received 26 times the dose of P compared to plants receiving 6 mg/L of P once. Therefore, this study outlines the possibility of reducing P fertilizer application while growing these groundcovers in nurseries for sale.

How do price (risk) changes influence farmers’ preferences to reduce fertilizer application?

AbstractThe decision of farmers to reduce fertilizer applications and, thus, the achievement of agri‐environmental policy goals interacts with market price developments. In this study, we analyze how changes in price levels and volatility over time (i.e., 1991–2006 vs. 2007–2022) affected farmers’ preferences to reduce fertilizer application using statistical inferences of stochastic dominances. The analysis considers two cropping systems and fertilizer reduction measures: (i) grassland‐based milk production and the use of legumes and (ii) wheat production and the use of variable rate application. We show that the economic value of reducing fertilizer increased over time in both grassland‐based milk and wheat production. However, only in the case of wheat production was the reduction in fertilizer application observed as more risk‐reducing over time. In contrast, in grassland‐based milk production, the co‐movement of fertilizer and milk prices canceled out the increase in risk reduction. We conclude that changes in market price, along with agri‐environmental subsidies, can increasingly incentivize the reduction of fertilizer use.

Partial factor productivity and water use efficiency of ratoon pigeonpea under varied levels of irrigation, fertigation, and mulching

The scarcity of irrigation water and nutrients poses a serious challenge to the production of pigeonpea in the changing climate. Despite largest producer of pigeonpea, India is still not meeting the domestic pulses requirement. Exploiting the ratoon ability of pigeonpea in rainy and post-rainy seasons would produce higher grains with limited resources in shorter periods due to multiple harvests. Therefore, the present study was conducted to know the resource requirement of ratoon pigeonpea, partial factor productivity (PFP), and water use efficiency (WUE). Two irrigation levels (I 1= 0.50 and I 2=0.75 Crop Pan Evaporation), three nutrient levels (F 1 = 100%, F 2 = 75%, and F 3 = 50% of recommended dose of fertilizers; 25:50:25 kg N:P2O5:K2O ha−1) and two mulching levels (M 0 = without mulching, and M 1 = with mulching) were laid out in split-split plot design at University of Agricultural Sciences, GKVK, Bengaluru. Results revealed that a combination (I 2 F 1 M 1) of a higher level of irrigation (0.75 CPE) and 100% of recommended fertilizer through fertigation with mulching produced higher dry matter accumulation (190.16 g plant−1 at harvest) and nutrients (82.08, 17.37, and 78.35 kg total N, P, and K ha−1, respectively) uptake. Whereas, higher PFP of nutrients (58.12, 29.06, and 58.12 kg grain kg−1 of N, P, and K fertilizer nutrient, respectively) and WUE (21.07 kg ha-cm−1) were observed in higher irrigation with 50% of required fertilizer and mulching (I 1 F 3 M 1) as a result of higher yield and lesser resources used. Therefore, a concurrent supply of optimum irrigation and mulching could improve the PFP and WUE of ratoon pigeonpea even under reduced fertilizer application.

The Effect of Drainage and Subirrigation From a Small Drainage Water Recycling Reservoir on Corn and Soybean Yields in Eastern North Carolina

Highlights The Drainage Water Recycling (DWR) reservoir stored enough water to meet irrigation demand in three of four growing seasons. Subirrigation raised the groundwater table by an average of 15 cm. On average, DWR increased corn and soybean yields by 0.52 Mg ha-1 (8%) and 0.45 Mg ha-1 (17%), respectively. Subirrigation from the small size DWR reservoir did not protect corn from extended dry conditions during the growing season. Nutrients recycled back to the field via supplemental irrigation were not large enough to reduce fertilizer application rate. Abstract. Drainage water recycling (DWR) has been proposed as a source of supplemental irrigation to increase crop production resilience to extended and more frequent dry periods during the crop growing season; however, the system’s potential benefits have not been adequately quantified. The main objective of this study was to assess the performance of a DWR system for providing water for supplemental irrigation to corn and soybean at a research site in eastern North Carolina and quantify corn and soybean yield responses during 4 growing seasons (2018-2021) with varying weather conditions. Two treatments were implemented at the study site: DWR and the control (CT) treatment. The CT treatment was a 11.23 ha non-irrigated field that was primarily drained by a surface drainage system. The DWR treatment (11.48 ha) had a subsurface drainage system that provided drainage during the wet periods and subirrigation during the dry periods of the growing season. A small size reservoir (5,458 m3) was used to collect surface runoff and subsurface drainage and subirrigate the DWR treatment. Results showed that the DWR reservoir stored enough water to meet irrigation requirements in 3 of the four growing seasons and provided 5 to 73 mm of irrigation to the DWR treatment. Subirrigation raised the groundwater table by an average of 15 cm, which helped increase the upward movement of soil water to the root zone and meet crop evapotranspiration demand. DWR increased corn yields by 0.13 and 0.91 Mg ha-1 (1% and 79%) and soybean yields by 0.31 and 0.59 Mg ha-1 (9% and 30%). Subirrigation, which is generally less efficient than overhead irrigation methods, did not optimize the use of the limited water stored in the small reservoir and could not provide enough protection to corn against prolonged dry conditions in the 2019 growing season. The amount of nutrients recycled back to the field through subirrigation was not large enough to help reduce fertilizer application rate. Overall, the results demonstrated that DWR is a promising practice for increasing the resilience of crop production in the southeastern U.S. to the uncertainty in precipitation, which is expected to intensify by climate change. Monitoring the performance of DWR for longer periods with varying factors of weather, soil, and system design and management would help guide the design and management of the system to optimize the performance and minimize the implementation cost. Keywords: Drainage water management, Drainage water reuse, Irrigation reservoir, On-farm water storage, Subsurface drainage, Supplemental irrigation.

Accelerated integrated watershed management enhances agricultural carbon sequestration and water use efficiency in an endorheic basin

With the continuous promotion of integrated river basin management (IRBM) in endorheic watersheds, the oasis surface processes have undergone significant changes. However, these underlying surface characteristics have not been well integrated into models for simulating carbon-water flux thus far. In this work, a regional SWAT-TECO model was constructed by coupling the modified TECO simulator with irrigation, film mulching, and soil hydraulic redistribution processes within the SWAT framework. The results indicated that the carbon sequestration and water use efficiency (WUE) showed an increasing trend after IRBM implementation in Heihe endorheic basin. WUE was projected to improve under future climate change and can be further enhanced by a maximum of 6.37 % through improving irrigation water use efficiency by 20 %, maintaining existing planting scale, increasing film mulching by 20 %, and reducing fertilizer application by 10 %. These findings can guide the formulation of high-water efficiency agricultural management strategies in global endorheic basins.

Comparison of the effects of calcium ammonium nitrate and stabilized urea fertilizers on grass and silage yields and quality

AbstractEffects of Calcium Ammonium Nitrate (CAN) and Stabilized Urea (SU) fertilizers were compared for herbage yield and composition and silage composition of perennial ryegrass (Lolium perenne L.) swards over a two‐year study. The aim of this experiment was to establish the likely impacts of farmers transitioning to using SU fertilizers in order to reduce the nitrogenous emissions associated with silage production as the agriculture industry moves to address the challenges of climate change. Experimental plots of 7.5 m2 area were established in a randomized block experiment comprising 4 replicates of 18 treatments in a 3 × 6 factorial design (4 × 3 × 6 = 72 plots) for each of 3 silage harvest periods in 2018, and repeated in 2019. Herbage samples and yield measurements were collected weekly for weeks 2–7 post fertilizer application, and herbage harvested after seven weeks regrowth was ensiled and silage was analysed after 100 days. There were no significance differences overall between responses of CAN and SU fertilized plots in terms of grass dry matter (DM) yield and quality parameters (acid detergent fibre (ADF), ash, buffering capacity (BC), metabolisable Energy (ME), nitrate (NO32−), nitrogen (N), or water soluble carbohydrate (WSC) or silage quality parameters (DM, volatile corrected organic dry matter (VCODM), ammonia nitrogen as a fraction of total nitrogen (NH3‐N/ Total N), pH, crude protein (CP), lactic acid (LA), acetic acid (AA), propionic acid (PA), butyric acid (BA), ethanol, propanol, ADF, ash, WSC or dry matter digestibility (DMD). Numerous significant differences between week and between cut were identified for grass quality, silage quality and grass ensilability parameters, and in the grass DM yields recorded. However, in many instances there was no associated treatment effect identified. There were no significant interactions between CAN and SU treatments and either cut, or week for nitrate concentration or yield. Variance of nitrate concentration was highest at the third cut and indicates a reduction in the nitrogen use efficiency of the 3rd cut silage harvest, potentially demonstrating a need to reduce fertilizer application recommendations for late‐season silage harvests. Overall, the results of this study support the hypothesis that replacing the currently favoured CAN fertilizer products with SU will not impact production of grass silage in Northern Ireland, meaning SU can be confidently adopted by farmers as a mitigation strategy to reduce farm nitrogenous emissions without reducing levels of sward productivity. This study recorded average annual grass silage DM yields of 15.5 and 16.1 t DM/ha from the CAN and SU fertilizer treatments respectively, which were not significantly different. In addition, the yield gain response to the application of each fertilizer type were not significantly different at 21.51 and 23.24 kg of DM produced for every kg of N applied as SU or CAN respectively, relative to control plots receiving 0 nitrogen.

Long-term control of non-point source pollution by adjusting human environmental behavior in watershed-a new perspective.

The control of non-point source pollution is a major scientific and technological problem faced by mankind. We proposed a new approach to eliminate non-point source pollution, focusing on adjusting human environmental behavior. The implementation procedures are as follows: (1) Investigate the intention of pollution discharge behavior through interviews and questionnaires. (2) Carry out targeted intervention within the framework of social psychology to transform it into an environmentally friendly mode. (3) Calculate the amounts of pollutants produced and discharged before and after the intervention, and then evaluate the effect of the intervention on reducing pollution. (4) Based on successful interventions, a scheme can be developed to curb non-point source pollution. Aiming to reduce fertilizer use, a case study was conducted in Hetao Irrigation District, one of the three major Irrigation districts in China. The results showed that the interventions indirectly affected intention through attitude, subjective norm, and perceived behavioral control. The structural equation model explained 76.0% of the total variance of farmers' intention to reduce fertilizer application (SMC = 0.760), indicating effective intervention. Subsequently, a program to curb non-point source pollution was developed. This study can provide a key scientific and applied reference for the long-term control of non-point source pollution in watershed.

Foliar Mn and Zn Treatments Improve Apple Tree Nutrition and Help to Maintain Favorable Soil pH

The foliar application of micronutrients can improve primary nutrient uptake. As a result, foliar treatments can reduce fertilizer application rates and help to maintain the natural health of soil. Here, we report on the tentative implementation of this approach in an apple orchard located in a temperate climate (JSC “Dubovoye” 52°36′57.1″ N 40°17′04.1″ E; planted in 2002 according to the 6 × 4 m or 417 trees ha–1 cultivar (cv.) Bogatyr grafted on B118 (Budagovskii 118). Manganese treatments augmented foliar nitrogen content and, in certain seasons, foliar phosphorus, whereas zinc treatments enhanced foliar potassium. Low-rate chemical fertilizers application (once in 5 years) on the background of initial high-rate organic fertilization (60 t ha–1 manure) allowed us to retain the optimal soil pH in the experimental orchard.

Screening and promoting effect of grow-promoting fungi in rhizosphere of Angelica dahurica var. formosana

Excessive application of chemical fertilizer has caused many problems in Angelica dahurica var. formosana planting, such as yield decline and quality degradation. In order to promote the green cultivation mode of A. dahurica var. formosana and explore rhizosphere fungus resources, the rhizosphere fungi with nitrogen fixation, phosphorus solubilization, potassium solubilization, iron-producing carrier, and IAA-producing properties were isolated and screened in the rhizosphere of A. dahurica var. formosana from the genuine and non-genuine areas, respectively. The strains were identified comprehensively in light of the morphological characteristics and ITS rDNA sequences, and the growth-promoting effect of the screened strains was verified by pot experiment. The results showed that 37 strains of growth-promoting fungi were isolated and screened from the rhizosphere of A. dahurica var. formosana, mostly belonging to Fusarium. The cultured rhizosphere growth-promoting fungi of A. dahurica var. formosana were more abundant and diverse in the genuine producing areas than in the non-genuine producing areas. Among all strains, Aspergillus niger ZJ-17 had the strongest growth promotion potential. Under the condition of no fertilization outdoors, ZJ-17 inoculation significantly promoted the growth, yield, and accumulation of effective components of A. dahurica var. formosana planted in the soil of genuine and non-genuine producing areas, with yield increases of 73.59% and 37.84%, respectively. To a certain extent, it alleviated the restriction without additional fertilization on the growth of A. dahurica var. formosana. Therefore, A. niger ZJ-17 has great application prospects in increasing yield and quality of A. dahurica var. formosana and reducing fertilizer application and can be actually applied in promoting the growth of A. dahurica var. formosana and producing biofertilizer.

Integrating the Soil Microbiota and Metabolome Reveals the Mechanism through Which Controlled Release Fertilizer Affects Sugarcane Growth.

Root-soil underground interactions mediated by soil microorganisms and metabolites are crucial for fertilizer utilization efficiency and crop growth regulation. This study employed a combined approach of soil microbial community profiling and non-targeted metabolomics to investigate the patterns of root-associated microbial aggregation and the mechanisms associated with metabolites under varying controlled-release fertilizer (CRF) application rates. The experimental treatments included five field application rates of CRF (D1: 675 kg/ha; D15: 1012.5 kg/ha; D2: 1350 kg/ha; D25: 1687.5 kg/ha; and D3: 2025 kg/ha) along with traditional fertilizer as a control (CK: 1687.5 kg/ha). The results indicated that the growth of sugarcane in the field was significantly influenced by the CRF application rate (p < 0.05). Compared with CK, the optimal field application of CRF was observed at D25, resulting in a 16.3% to 53.6% increase in sugarcane yield. Under the condition of reducing fertilizer application by 20%, D2 showed a 13.3% increase in stem yield and a 6.7% increase in sugar production. The bacterial ACE index exhibited significant differences between D25 and D1, while the Chao1 index showed significance among the D25, D1, and CK treatments. The dominant bacterial phyla in sugarcane rhizosphere aggregation included Proteobacteria, Actinobacteriota, and Acidobacteriota. Fungal phyla comprised Rozellomycota, Basidiomycota, and Ascomycota. The annotated metabolic pathways encompassed biosynthesis of secondary metabolites, carbohydrate metabolism, and lipid metabolism. Differential analysis and random forest selection identified distinctive biomarkers including Leotiomycetes, Cercospora, Anaeromyxobacter, isoleucyl-proline, and methylmalonic acid. Redundancy analysis unveiled soil pH, soil organic carbon, and available nitrogen as the primary drivers of microbial communities, while the metabolic profiles were notably influenced by the available potassium and phosphorus. The correlation heatmaps illustrated potential microbial-metabolite regulatory mechanisms under CRF application conditions. These findings underscore the significant potential of CRF in sugarcane field production, laying a theoretical foundation for sustainable development in the sugarcane industry.

Spatial optimization of nutrient reduction measures on agricultural land to improve water quality: A coupled modeling approach

AbstractThe objective of this study is to identify the optimal spatial distribution of Best Management Practices (BMPs) to reduce total phosphorus (TP) runoff from agricultural land in the largest Canadian watershed draining into Lake Erie, the Great Lake most vulnerable to eutrophication. BMP measures include reduced fertilizer application, cover crops, buffer strips, and the restoration of wetlands. Environmental SWAT model results feed into a spatial optimization procedure using two separate objective functions to distinguish between public BMP program implementation costs (PIC) on the one hand and farmers’ private pollution abatement costs (PAC) on the other hand. The latter account for the opportunity costs of land retirement and changing land productivity. PAC are initially lower than PIC but exceed the latter after 30% of the annual TP baseline load is eliminated. This suggests that under optimal conditions existing grant and incentive payments cover the economic costs farmers face up to a maximum of 30% of the baseline load reduction. Imposing further reductions of up to 40% results in a cost to farmers of almost $52 million per year. This is 45% higher than the optimal solution based on PIC and therefore not deemed incentive‐compatible under the watershed's existing cost‐sharing scheme.

Effect of Nano Carbon and Nano Calcium Carbonate Application on Soil Nutrient Dynamics in Winter Wheat (Triticum aestivum L.)

ABSTRACT The application of nanomaterials in agriculture has considerable advantages, but its impact on the dynamic change of soil nutrients is still unclear. In the two-year experiment, the effects of nanocarbon (NC) and nano calcium carbonate (NCC) on the dynamic changes of soil nutrients in the wheat field were studied by setting the ratio of different nanomaterials and fertilizers. All treatments with NC and NCC applications positively affected soil nutrient effectiveness at 0–35 d after wheat anthesis, and the effect of NC+NCC was more significant. At 35 days after anthesis, soil available phosphorus (P), available potassium (K), organic matter (OM), and alkaline hydrolysis nitrogen (N) were elevated by 77.9%, 21.9%, 11.7%, and 7.0%, respectively, in the first year and 44.3%, 10.2%, 9.0%, and 7.6%, respectively, in the second year of treatment with 100% CF (complex fertilizer) + 50% NC + 50% NCC compared with control. The treatment with reduced fertilizer application also demonstrated a greater advantage. At 35 d after anthesis, 70% CF + 35% NC + 35% NCC had 54.3%, 11.5%, 8.4%, and 5.8% higher soil available P, available K, OM, and alkaline hydrolysis N, respectively, compared with the control, and 41.05%, 6.4%, 7.8%, and 5.4% higher the following year, respectively. In acidic soils, positively charged NC and NCC have a lasting effect on maintaining soil nutrients by adsorbing acid ions. Therefore, NC and NCC with compound fertilizer have favorable effects in maintaining soil nutrient content and improving fertilizer utilization.

Spatial Variability Analysis of Wheat Nitrogen Yield Response: A Case Study of Henan Province, China

The overapplication of nitrogen to wheat reduces profits and has adverse environmental consequences. Machine learning techniques are employed to identify the factors that hold the most potential in improving nitrogen recommendations. The database used in our analysis consisted of a formula fertilization project, the second soil census of China, and cultivated land fertility evaluation. The results showed that the wheat nitrogen yield response was mainly concentrated around 1300–2400 kg/ha in Henan Province, with the highest values observed in the southern and eastern regions and the lowest in the northern region. The soil nitrogen content, nitrogen fertilizer, wet nitrogen deposition, dry nitrogen deposition, and soil nitrogen supply capacity were mainly concentrated around 0.65–1.30 g/kg, 173–203 kg N/ha, 15–39 kg N/(ha yr), 7–49 kg N/(ha yr), and 105–150 kg N/ha, respectively. When comparing the spatial distribution of the soil nitrogen content, nitrogen fertilizer, and nitrogen deposition, we found that the soil nitrogen supply capacity emerged as the predominant factor controlling wheat grain production. Soil types, precipitation, and temperature demonstrated a notable positive correlation with the soil nitrogen supply capacity. Given this background, it would be unreasonable to rely solely on the soil nitrogen content as the standard for fertilizer management. Particularly in high-yield fields, our focus should be on preserving optimal soil fertility by placing greater emphasis on the soil nitrogen supply capacity rather than simply reducing fertilizer application during wheat growth.

Assessing and Mapping the Environmental Impacts of Best Management Practices in Nitrate-Vulnerable Areas

This investigation explores the impact of various management practices on nitrate leaching and crop yield in two specific areas in Slovenia. The issue of nitrate leaching from agricultural land is a worldwide threat to drinking water, and despite years of research efforts, universal solutions are still unknown. The two chosen study sites are significant because of their importance for agricultural production and because groundwater aquifers beneath are main sources of drinking water, which makes imposing mitigation measures challenging. One of the areas was reported to be of “bad” status according to the Water Framework Directive criteria, while the other is at risk of reaching this status if nitrate concentrations in groundwater continue to rise. This research used the SWAT model to simulate nitrate leaching and crop yield changes under different agricultural scenarios on different soil types. It aimed to accomplish two objectives: first, to identify parts of the case study areas where the existing combination of soil conditions and agricultural practices enables a high potential for nitrate leaching; second, to identify agricultural practices that decrease nitrate leaching from various soil types while maintaining crop yields in each area. By identifying the most vulnerable locations and the most promising practices, we generated a chart of best management practices for specific soil types as a guide that extension services can use to advise farmers on potential management improvements. The main findings demonstrate that reducing fertilizer application, both organic and inorganic, in areas where the rates exceed crop requirements may not have a significant impact on crop production. However, these reductions often resulted in a noticeable decrease in nitrate exports. The results also showed that soil type is crucially important and should always be considered when evaluating the effects of agricultural management on crop yields and nitrate leaching.

Do carbon farming practices build bioavailable nitrogen pools?

AbstractAgricultural soils contain large amounts of nitrogen (N), but only a small fraction is readily available to plants. Despite several methods developed to estimate the bioavailability of N, there is no consensus on which extraction methods to use, and which N pools are critically important. In this study, we measured six soil N pools from 20 farms, which were part of a multi‐year soil carbon sequestration on‐farm experiment (Carbon action, 2019–2023). The aim was to quantify the N pools and to evaluate if farming practices that aim to build soil carbon pools, also build bioavailable N pools. We also aimed to test if the smaller and rapidly changing N pools could serve as an indicator for the slower change in soil organic matter. The measured N pools decreased in size, when moving from total N (7700 ± 1500 kg/ha) to slowly cycling (Illinois Soil Nitrogen Test ISNT‐N: 1063 ± 220 kg/ha, autoclave citrate‐extracted ACE protein N: 633 ± 440 kg/ha), water‐soluble organic N (50 ± 17 kg/ha), potentially mineralizable N (33 ± 13 kg/ha) and finally readily plant available inorganic pools (nitrate and ammonium, total: 14 ± 8 kg/ha). In total, the measured pools covered only 18%–44% of total N, indicating a large unidentified N pool, which is either tightly bound to soil mineral fraction and not easily extractable or is bound to undecomposed plant residues and not hydrolysed by the methods. Of the large N pools (ISNT‐N, ACE protein and unidentified residual N), clay, carbon (C) and C:Clay ratios explained most of the variability (R2 = .90–.93), leaving a minor part of the variation to the management effect. A pairwise comparison of carbon farming and control plots concluded that farming practices had a small (3%–5%) but statistically significant (p &lt; .05) effect on soil total N and ISNT‐N pools, and a moderate and significant effect (18%, p &lt; .01) on potentially mineralizable N. The large variation in protein N, water‐soluble organic N and inorganic N reduced statistical significance, although individual C sequestration practices had large effects (−30% to +50%). In conclusion, carbon sequestration practices can build both slowly cycling N pools (ISNT) and increase the mineralisation rate of these pools to release plant available forms, resulting in an additional benefit to agriculture through reduced fertilizer application needs.

Effects of biochar in combination with varied N inputs on grain yield, N uptake, NH3 volatilization, and N2O emission in paddy soil.

Biochar application can improve crop yield, reduce ammonia (NH3) volatilization and nitrous oxide (N2O) emission from farmland. We here conducted a pot experiment to compare the effects of biochar application on rice yield, nitrogen (N) uptake, NH3 and N2O losses in paddy soil with low, medium, and high N inputs at 160 kg/ha, 200 kg/ha and 240 kg/ha, respectively. The results showed that: (1) Biochar significantly increased the rice grain yield at medium (200 kg/ha) and high (240 kg/ha) N inputs by 56.4 and 70.5%, respectively. The way to increase yield was to increase the rice N uptake, rice panicle number per pot and 1,000 grain weight by 78.5-96.5%, 6-16% and 4.4-6.1%, respectively; (2) Under low (160 kg/ha) N input, adding biochar effectively reduced the NH3 volatilization by 31.6% in rice season. The decreases of pH value and NH4+-N content in surface water, and the increases of the abundance of NH4+-N oxidizing archaea and bacteria (AOA and AOB) communities contributed to the reduction of NH3 volatilization following the biochar application; (3) Under same N input levels, the total N2O emission in rice season decreased by 43.3-73.9% after biochar addition. The decreases of nirK and nirS gene abundances but the increases of nosZ gene abundance are the main mechanisms for biochar application to reduce N2O emissions. Based on the results of the current study, adding biochar at medium (200 kg/ha) N level (N200 + BC) is the best treatment to synchronically reduce NH3 and N2O losses, improve grain yield, and reduce fertilizer application in rice production system.

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.