Excessive Nitrogen Fertilization Research Articles

A Review of Two Emerging Rice Diseases, in the Major Rice Growing Areas of the World

The illness known as kernel smut, which is brought on by Tilletia horrida, is typified by the sooty black masses of teliospores or chlamydospores that replace rice grains. The color of the chlamydospores in kernel smut is different from that of rice fake smut, which is generated by Ustilaginoidea virens. Spore balls that are globose and velvety, with colors ranging from orangish yellow to greenish black, are the hallmark of false smut. Due to their irregular breakouts and little economic impact, kernel smut and fake smut which were first identified in the late 1870s and continued to persist are regarded as minor illnesses in many nations. However, in many nations, particularly the US, kernel smut and fake smut have become two of the most commercially significant illnesses affecting rice, including organic rice, in recent years. Grain production and quality have significantly decreased as a result of the growing use of sensitive rice cultivars particularly hybrids, excessive nitrogen fertilizer use, and short crop rotations. These factors have also led to a rise in kernel smut and fake smut. The distribution and economic significance of kernel smut are reviewed in this article, along with our current knowledge of the taxonomy, biology, and epidemiology of kernel smut and the genomics of the kernel smut fungus in comparison to fake smut and its causative agent. We also provide an update on the current management strategies of pathogen exclusion, cultivar resistance, fungicides, biological control, and cultural practices for kernel smut and false smut of rice.

In-Season Nitrogen Management in the Root Zone of Wheat in a Calcareous Soil Using the Response Index

ABSTRACT Excessive and inappropriate nitrogen (N) fertilizer applications on calcareous soils result in significant losses, necessitating a targeted approach for improved efficiency and yield. Field experiments were conducted over two seasons to develop a strategy for root-zone (RZ) N fertilization for wheat. In the first season, three methods of N fertilizer application were used: surface (SF), in the RZ at a depth of 10 cm (RZF10), and in the RZ at a depth of 20 cm (RZF20). The N fertilizer was applied in a range of 0–280 kg N ha−1. In the second season, another experiment was carried out to validate the results. The data showed that to achieve maximum yield levels, N fertilizer rates of 264 kg ha−1 for SF, 218 kg ha−1 for RZF10, and 183 kg ha−1 for RZF20 were required. The findings also revealed that relocating the application from the surface to depths of 10 and 20 cm resulted in an increase in recovery efficiency by 11.2% and 31.2%, respectively. A linear equation established the relationship between the response index at harvest (RI-Harvest) and the corrective N rate for RZF20. The in-season response index of the normalized difference vegetation index effectively predicted RI-Harvest, leading to the development of an empirical equation to predict the corrective N rate. The validation experiment demonstrated the effectiveness of the proposed strategy in adjusting N rates based on crop-specific needs. This approach allows growers to optimize profits by carefully applying N in the RZ, eliminating both excessive and inadequate use.

Effect of Synthetic Fertilizer on Diazotrophic Bacteria in Secondary Forest and Oil Palm Soils in Central Kalimantan

Soil microorganisms, especially diazotrophic bacteria, are vital for ecosystem sustainability, significantly contributing to nitrogen cycling and biodiversity conservation. Understanding the impact of different land-use practices on soil microorganisms, especially synthetic fertilizer addition, is essential for sustainable agriculture. This study compares soil properties, bacterial densities, and responses to fertilization in secondary forest soils and adjacent oil palm plantation soils located in PT Kerry Sawit Indonesia, Central Kalimantan. A greenhouse experiment was conducted using both secondary forest and oil palm plantation soils to evaluate the impacts of different synthetic fertilizers on nitrogen-fixing bacteria and soybean agronomic performance. Total soil bacteria and diazotrophic bacteria, essential for nitrogen fixation, were analyzed through microbiological assays and qPCR focusing on the nifH gene. Our findings show that oil palm plantation soils had higher levels of nitrogen, phosphate, and nitrate, while secondary forest soils had a higher abundance of diazotrophic bacteria. Furthermore, excessive nitrogen fertilization was found to reduce microbial density, negatively impacting plant sustainability, highlighting the importance of customized fertilizer management. The study highlights the intricate connections between land-use practices and microbial populations, providing valuable insights for balancing agricultural productivity with ecological sustainability.

Effects of Enhanced-efficiency Nitrogen Fertilizers on Soil Quality, Microbial Metabolism, and Soil Ecosystem Multifunctionality of Spring Maize Under White Plastic Film Mulching

Excessive nitrogen fertilizer application is the main driving force threatening soil health and reducing multiple soil functions. The enhanced-efficiency nitrogen fertilizers （EENFs）, such as urease inhibitors （NBPT）, nitrification inhibitors （DCD）, and coated controlled-release urea （RCN）, have been proven to be effective measures for reducing nitrogen fertilizer application. However, the effects of EENFs on soil quality （SQI）, microbial metabolic characteristics, and soil ecosystem multifunctionality （EMF） and their internal relationships are still unclear. Therefore, based on the field positioning experiment started in 2019 by Pengyang Experimental Station of Guyuan City, Ningxia Hui Autonomous Region, we studied the effects of different fertilization strategies （no nitrogen fertilizer （N0）, mineral nitrogen fertilizer （N200）, DCD, NBPT, and RCN） on SQI, soil enzyme stoichiometry, and EMF under white plastic film mulching. The results revealed that： ① Compared with that under N0, N200 and EENFs increased soil total nitrogen （TN）, microbial biomass carbon （MBC）, and microbial biomass nitrogen （MBN） contents. Compared to the SQI of N0 and N200, that of NBPT and DCD significantly increased by 59.97%-104.78% and 43.28%-83.42%, respectively, while RCN showed no significant change. ②EENFs can alleviate microbial carbon and nitrogen limitations better than N200 and increase soil EMF by 21.97% -51.53%. ③ The MBC, MBN, available nitrogen （AN）, available phosphorus （AP）, and water content （SWC） of soil factors were the common main factors affecting microbial C limitation, N limitation, and soil EMF. Moreover, the improvement in soil quality and alleviating microbial C and N limitation were conducive to improving soil EMF. Overall, the NBPT and DCD application under white plastic film mulching can achieve a win-win situation of soil health and EMF in the short term, which can provide references for optimizing local fertilization management measures.

Zeolite intervention in soil nitrate dynamics: insights from column experiments and modelling

ABSTRACT This study aims to address the harmful effects of excessive nitrogen fertilizer by investigating the mobility retardance effect of zeolite on nitrate movement in loam soil columns. Disturbed and undisturbed soil columns, treated with zeolite, as well as control soil columns, were analysed over a span of three years. Breakthrough curves generated from the experiments were evaluated using the HYDRUS1D code with mobile–immobile water (MIM) and dual-permeability (DP) models. Our findings highlight that zeolite application significantly reduced nitrate mobility, with recovery rates decreasing by 8% in disturbed and 11% in undisturbed columns. The DP model, which accurately reflects real soil water flow conditions, outperformed the MIM model in predictive accuracy. This research offers a novel long-term perspective on the benefits of zeolite in enhancing soil properties and mitigating nitrate leaching, recommending the DP model for superior prediction of contaminant transport in structured soils within the vadose zone.

The Effect of the Use of a Novel Urease Inhibitor Coated Urea on the Greenhouse Gas Emissions and Ammonia Volatilization Losses from a Maize Field

Nitrogen fertilizers are essential for enhancing agricultural productivity but are also major contributors to greenhouse gas (GHG) emissions and ammonia volatilization, which affect environmental sustainability. This study evaluated the effect of cashew nut shell liquid (CNSL)-coated urea on GHG emissions and ammonia losses from maize fields in the Indo-Gangetic Plains, known for excessive nitrogen fertilizer usage. A randomized block design was employed with four treatments: control (no nitrogen), prilled urea, neem-coated urea (NCU), and CNSL-coated urea (CCU). Gas samples were collected using the closed chamber method, and emissions of CO₂ and N₂O were analyzed via gas chromatography. Ammonia volatilization was measured using the forced air draft method. Results showed that the CCU treatment significantly reduced ammonia volatilization compared to prilled urea (15.84% reduction), with reductions of 9% to those observed with NCU. Moreover, CCU-treated plots exhibited reduced cumulative GHG and lower global warming potential (GWP) without compromising maize yields. Cumulative GHG emissions varied among the treatments in the order urea> CCU> NCU> Control. CCU treated plots exhibited a net GWP decrease of 8.59% compared to urea and an increase of 4.13% compared to NCU. These findings suggest that CNSL-coated urea can serve as an eco-friendly alternative to conventional urea, potentially mitigating environmental impacts associated with nitrogen fertilization. Further studies are recommended to assess the long-term efficacy of CNSL in various soil types and climatic conditions.

Evaluation of Nitrogen Fertilizer Supply and Soil Nitrate Thresholds for High Yields of Foxtail Millet

Foxtail millet is an important cereal crop in the North China Plain. However, excessive nitrogen fertilizer application over the years has led to declining yield and soil quality. This study investigated nutrient management strategies for foxtail millet based on crop yield levels and soil nutrient availability. In a field where targeted fertilization was conducted over six seasons, nitrogen fertilization effects and the dynamics of soil-available nitrogen were monitored continuously for two consecutive years (2022–2023) across five different foxtail millet varieties with varying yield levels. The study aimed to determine the optimal nitrogen application rate for achieving a high yield of foxtail millet, the minimum soil nitrate threshold required to maintain soil fertility, and the effective nitrogen application rate range for sustaining soil-available nitrate levels. Results showed that fertilization significantly affected dry matter weight during flowering, while variety affected dry matter weight at maturity. The average nitrogen application rate for achieving high yield across all five millet varieties was 141.3 kg·ha−1. Specifically, the average nitrogen application rate of nitrogen-efficient varieties achieving high yield (5607.32–5637.19 kg·ha−1) was 151.5 kg·ha−1, while the average nitrogen application rate of nitrogen-inefficient varieties achieving high yield (4749.77–4847.74 kg·ha−1) was 134.5 kg·ha−1. Soil NH4+-N and NO3−-N content increased when nitrogen application rate exceeded 360 kg·ha−1, posing environmental risks. To achieve high yield, soil nitrate levels would be maintained at an average of 17.23 mg·kg−1 (before sowing) and 9.75 mg·kg−1 (at maturity). A relationship between soil nitrate and nitrogen application rate was established: y = 867.5 − 50z (where y represents the optimal nitrogen application rate for high yield (kg·ha−1), and z represents soil NO3−-N content in the 0–20 cm layer before sowing, ranging from 10.0 to 17.35 mg·kg−1), which provided a practical method for nitrogen fertilization to achieve high yield of foxtail millet. In this study, the fertilization strategy was optimized according to soil nutrient level and yield targets, and the nitrogen application rate was controlled within 360 kg·ha−1 based on the soil nitrate nitrogen content, which will be instructive for reducing fertilizer use, maximizing fertilizer efficiency, and increasing yield.

Multi-omics analysis of excessive nitrogen fertilizer application: Assessing environmental damage and solutions in potato farming

Potatoes (Solanum tuberosum L.) are the third largest food crop globally and are pivotal for global food security. Widespread N fertilizer waste in potato cultivation has caused diverse environmental issues. This study employed microbial metagenomic sequencing to analyze the causes behind the declining N use efficiency (NUE) and escalating greenhouse gas emissions resulting from excessive N fertilizer application. Addressing N fertilizer inefficiency through breeding has emerged as a viable solution for mitigating overuse in potato cultivation. In this study, transcriptome and metabolome analyses were applied to identify N fertilizer-responsive genes. Metagenomic sequencing revealed that excessive N fertilizer application triggered alterations in the population dynamics of 11 major bacterial phyla, consequently affecting soil microbial functions, particularly N metabolism pathways and bacterial secretion systems. Notably, the enzyme levels associated with NO3- increased, and those associated with NO and N2O increased. Furthermore, excessive N fertilizer application enhanced soil virulence factors and increased potato susceptibility to diseases. Transcriptome and metabolome sequencing revealed significant impacts of excessive N fertilizer use on lipid and amino acid metabolism pathways. Weighted gene co‑expression network analysis (WGCNA) was adopted to identify two genes associated with N fertilizer response: PGSC0003DMG400021157 and PGSC0003DMG400009544.

Effects of Long-Term Application of Nitrogen Fertilizer on Soil Acidification and Biological Properties in China: A Meta-Analysis.

Soil acidification is a global environmental problem with significant impacts on agricultural production, environmental protection, and ecosystem health. Soil acidification is widespread in China, affecting crop yields, agricultural product quality, and biodiversity. Since the 1980s, much work has been done on acidic soils in China, but it is controversial whether excessive nitrogen fertilizer application can lead to soil acidification mechanisms. To address the above issues, we conducted a meta-analysis of 115 published papers to integrate and analyze the effects of N fertilizer application on soil acidification and biological properties from 1980 to 2024. We also quantified the effect of nitrogen fertilization on soil acidification and biological changes under different climatic conditions. The results showed that under long-term application of nitrogen fertilizers in China from 1980 to 2024, soil pH decreased by an average of 15.27%, and the activities of soil urease, nitrate reductase, nitrite reductase, catalase, glutamate dehydrogenase, and glutamate synthetase decreased by an average of 9.82-22.37%. The soil microbial community richness (Chao1 index) increased by 6.53%, but the community diversity (Shannon index) decreased by 15.42%. Among the dominant soil microorganisms, the relative abundance of bacteria decreased by an average of 9.67-29.38% and the abundance of gene expression of nifH, amoA-AOA, amoA-AOB, and qnorB decreased by 9.92-19.83%. In addition, we found that the mean annual temperature and rainfall impacted soil acidification via their effect on soil microbial diversity and community composition. This study provides a scientific basis for an in-depth understanding of the spatial and temporal variation of soil acidification and biological properties in China.

Optimization of ammonia nitrogen benchmarks and ecological risk assessment in monsoon freezing lakes based on species sensitivity distribution with Lake Chagan in northeastern China as an example

There is an urgent need to determine reasonable water-quality benchmarks and risk assessment results to accurately characterize the relationship between crop yield enhancement and ammonia nitrogen pollution caused by excessive nitrogen fertilizer application. Through the collection of monitoring data from 2016 to 2023 in Chagan Lake, the first development of ecological criteria for ammonia nitrogen and risk evaluation for Northeast China was carried out based on the secondary ecological risk models (the quotient value method and joint probability curve). In addition, the species sensitivity distribution (SSD) model is improved through the use of genetic algorithms to identify more suitable ammonia water-quality benchmarks for ecological risk assessment. The results showed that high ammonia nitrogen concentration in wet season is primarily influenced by agricultural irrigation and drainage activities, whereas the dry season is driven by low temperatures and the nitrogen and phosphorus concentrations. The biological benchmark of improved SSD model with a genetic algorithm has a maximum error reduction of 23.84 % compared with other distributions, which is more than twice that of the median water-quality benchmark under the traditional Class III water-quality standard and empirical formula. Risk evaluation using traditional water-quality standards leads to the overprotection of the biological environment. Evaluations using quotient value methods and joint probability curves yield consistent results. The severity of the ecological risk of ammonia nitrogen follows the order: wet season > flat season > dry season. Using a genetic algorithm to optimize SSD model can effectively reduce the uncertainty of the model, providing a more accurate and reasonable ammonia nitrogen water-quality benchmark. This study improves the evaluation of the ecological risk of ammonia nitrogen in Lake Chagan, provides ideas for reducing the uncertainty of the selection of ammonia nitrogen water-quality benchmarks, and effectively prevents the overprotection of the lake from ammonia nitrogen.

Research on Enhancing the Yield and Quality of Oat Forage: Optimization of Nitrogen and Organic Fertilizer Management Strategies

In the context of the increasingly serious issues of resource waste, soil degradation, and environmental pollution caused by excessive nitrogen fertilizer application worldwide, this study conducted a two-year field experiment in Qinghai Province to explore suitable nitrogen fertilizer management strategies for the region. Ten fertilization levels were set, incorporating varying ratios of conventional nitrogen fertilizer and organic fertilizer, as well as the proportion of base fertilizer and topdressing. The focus was on monitoring the forage yield, quality, and related physiological indicators of oats during the flowering and milk stages. The use of correlation analysis and the multi-criteria decision-making model TOPSIS was applied for comprehensive data evaluation to determine the optimal fertilization strategy. After systematic data collection and analysis, the results showed that when 75% conventional nitrogen fertilizer was combined with 4500 kg·hm−2 of organic fertilizer (F4), the oat yield during the milking stage reached its peak at 14,722.48 kg·hm−2. Additionally, the yield effect was optimal (13,677.34 kg·hm−2) when using 30% base fertilizer and 70% jointing fertilizer (D2). Regarding nutritional quality, the fertilization strategy combining 75% conventional nitrogen fertilizer with 4500 kg·hm−2 of organic fertilizer, along with 30% base fertilizer and 70% jointing fertilizer (F4D2), significantly reduced the content of acid detergent fiber (ADF), neutral detergent fiber (NDF), and coarse fiber (CF) in oats, while increasing the content of EE (crude fat) and CP (crude protein). This significantly improved the nutritional value of oats. Correlation analysis further revealed the positive effect of fertilization amount and fertilization period on oat yield, as well as a negative correlation with fiber content. Finally, through comprehensive evaluation using the multi-criteria decision-making model TOPSIS, we verified the superiority of the fertilization strategy.

Nitrogen rate is more important than irrigation rate in mitigating nitrogen leaching in flood-irrigated maize: A 6-year lysimeter experiment

Excessive nitrogen (N) fertilization and irrigation prevail in irrigated agriculture worldwide. However, little information is available that systematically evaluates grain yield, plant N uptake, residual soil NO3−-N (RSN), and N leaching under different irrigation–N regimes in an irrigated maize production system. To address such agronomic and environmental issues, a 6-year in situ lysimeter field trial was conducted in the Hetao Irrigation District of China with five treatments: 1) conventional irrigation (3,900 m3/ha) and local farmer fertilizer N rate (490 kg ha−1) (CON); 2) conventional irrigation and the recommended fertilizer N rate (420 kg ha−1) (RN); 3) deficit irrigation (2,730 m3/ha) and the recommended fertilizer N rate (SRN); 4) deficit irrigation and the recommended fertilizer N rate (with ∼ 10 % organic fertilizer N substitution) (SMN); and 5) conventional irrigation and controlled-release N fertilizer (270 kg ha−1) (CRF). Maize yield was not significantly different across treatments in 2015–2020. Averaged across years, SMN, SRN, and CRF significantly increased plant N uptake compared with that in CON by 28.84 %, 19.15 %, and 17.53 %, respectively. Residual soil NO3−-N at 0–90 cm was ranked as SRN > CON ≈ SMN > RN > CRF, whereas cumulative N in leachate from 2015–2020 (Nloss) in CON was 86.2 % to 187.1 % higher than that in other treatments. The Nloss in SRN was equivalent to that in RN and SMN, but Nloss in SMN decreased significantly compared with that in RN, indicating additive benefits of deficit irrigation and organic input on reducing N leaching. Structural equation modelling revealed that irrigation had greater effects on plant N uptake than those of fertilization, whereas N rate had a greater total effect on N leaching than that of irrigation. Overall, rampant excessive irrigation and N fertilization by farmers can be substantially reduced while maintaining grain yield and mitigating N leaching loss, with further benefits gained by applying controlled-release N fertilizer and manure in irrigated maize production.

Environmental transport of excess nitrogen fertilizer in peach orchard: Evidence arising from 15N tracing trial

In pursuit of high fruit yield, overwhelming amount of nitrogen (N) fertilizer was unreasonably applied in orchard, resulting in lower fertilizer N uptake and higher environmental loss. It is crucial to propose appropriate fertilization timing and optimal N management by clarifying fruit tree N uptake pattern in orchard systems. Here, a 15N isotope enrichment trial was conducted in peach orchard to assess the transport of applied synthesized fertilizer-N to the plant and environment in the Taihu Lake region. Ammonium sulfate ((NH4)2SO4, 10.12 atom % 15N), as the N source, was applied with four split applications at 382.5 kg N ha−1 during one plant growth cycle. Results showed N deriving from fertilizer (NDFF) accounted for 24.5% in leaves and 38.4% in fruits, respectively. During the annual growth cycle, the applied fertilizer-N uptake and utilization was higher in reproductive growth stage than vegetative growth stage. After harvest, 28.8% of applied fertilizer-N was absorbed by peach tree, 9.5% was lost to the environment through surface runoff, ammonia (NH3) volatilization and nitrous oxide (N2O) emission, 29.6% was retained in the 0–160 cm soil profile, the remaining 32.1% was unaccounted N including N leaching and N loss from the N removal progress. Generally, more applied fertilizer-N moved to the environment in high N input peach orchard. In order to promote optimal N management, the applied fertilizer-N rate should be reduced by 30% and emphasized on fertilization at the reproductive growth period according to tree N uptake pattern.

Optimizing the Mulching Pattern and Nitrogen Application Rate to Improve Maize Photosynthetic Capacity, Yield, and Nitrogen Fertilizer Utilization Efficiency.

Residual film pollution and excessive nitrogen fertilizer have become limiting factors for agricultural development. To investigate the feasibility of replacing conventional plastic film with biodegradable plastic film in cold and arid environments under nitrogen application conditions, field experiments were conducted from 2021 to 2022 with plastic film covering (including degradable plastic film (D) and ordinary plastic film (P)) combined with nitrogen fertilizer 0 (N0), 160 (N1), 320 (N2), and 480 (N3) kg·ha-1. The results showed no significant difference (p > 0.05) in dry matter accumulation, photosynthetic gas exchange parameters, soil enzyme activity, or yield of spring maize under degradable plastic film cover compared to ordinary plastic film cover. Nitrogen fertilizer is the main factor limiting the growth of spring maize. The above-ground and root biomass showed a trend of increasing and then decreasing with the increase in nitrogen application level. Increasing nitrogen fertilizer can also improve the photosynthetic gas exchange parameters of leaves, maintain soil enzyme activity, and reduce soil pH. Under the nitrogen application level of N2, the yield of degradable plastic film and ordinary plastic film coverage increased by 3.74~42.50% and 2.05~40.02%, respectively. At the same time, it can also improve water use efficiency and irrigation water use efficiency, but it will reduce nitrogen fertilizer partial productivity and nitrogen fertilizer agronomic use efficiency. Using multiple indicators to evaluate the effect of plastic film mulching combined with nitrogen fertilizer on the comprehensive growth of spring maize, it was found that the DN2 treatment had the best complete growth of maize, which was the best model for achieving stable yield and income increase and green development of spring maize in cold and cool irrigation areas.

Impacts of High-Frequency Chicken Manure Biochar Application on N2O and CH4 Emissions from Vegetable Field in Subtropical China

Vegetable production in Subtropical China is distinguished by excessive nitrogen (N) fertilization, frequent irrigation, and multiple crop rotations in a single year. The aforementioned variables are closely related to soil nitrous oxide (N2O) and methane (CH4) emissions. Hence, we conducted a field trial to measure N2O and CH4 emissions using static chamber–gas chromatograph. Four treatments were used: control (CK) with no fertilizer, 100% chemical N fertilization (CN), the conventional 30% chicken manure N plus 70%CN (CMN + CN), and 30% chicken manure biochar N plus 70%CN (CMBN + CN). The annual cumulative N2O emissions reached 12.4, 63.5, 111.8, and 44.1 kg N2O-N ha−1 for the CK, CN, CMN + CN, and CMBN + CN treatments, respectively. Compared to the CN and CMN + CN treatments, the CMBN + CN treatment reduced N2O emissions by 35.9%–65.7%, while it simultaneously increased the total vegetable yield by 16.1% compared to the CN treatment. Seven seasons mean N2O emission factors are 1.3% for CN, 3.8% for CMN + CN, and 0.9% for CMBN + CN. The CH4 emission was negligible, ranging from 0.07 kg CH4-C ha−1 for the CK treatment to 0.8 kg CH4-C ha−1 for the CN treatment. N2O emissions peaked under the conditions of an interior chamber temperature of around 31.9 °C and the water-filled pore space (WFPS) of the soil being approximately 60%. Future climate change will intensify, triggering higher N2O emissions from subtropical vegetable fields. CMB can be one of the best substitutes for direct chicken manure application as a soil supplement because it has a beneficial effect on improving vegetable yield and reducing N2O emissions in Subtropical China.

Integrating plant morphological traits with remote-sensed multispectral imageries for accurate corn grain yield prediction.

Sustainable crop production requires adequate and efficient management practices to reduce the negative environmental impacts of excessive nitrogen (N) fertilization. Remote sensing has gained traction as a low-cost and time-efficient tool for monitoring and managing cropping systems. In this study, vegetation indices (VIs) obtained from an unmanned aerial vehicle (UAV) were used to detect corn (Zea mays L.) response to varying N rates (ranging from 0 to 208 kg N ha-1) and fertilizer application methods (liquid urea ammonium nitrate (UAN), urea side-dressing and slow-release fertilizer). Four VIs were evaluated at three different growth stages of corn (V6, R3, and physiological maturity) along with morphological traits including plant height and leaf chlorophyll content (SPAD) to determine their predictive capability for corn yield. Our results show no differences in grain yield (average 13.2 Mg ha-1) between furrow-applied slow-release fertilizer at ≥156 kg N ha-1 and 208 kg N ha-1 side-dressed urea. Early season remote-sensed VIs and morphological data collected at V6 were least effective for grain yield prediction. Moreover, multivariate grain yield prediction was more accurate than univariate. Late-season measurements at the R3 and mature growth stages using a combination of normalized difference vegetation index (NDVI) and green normalized difference vegetation index (GNDVI) in a multilinear regression model showed effective prediction for corn yield. Additionally, a combination of NDVI and normalized difference red edge index (NDRE) in a multi-exponential regression model also demonstrated good prediction capabilities.

Water and nitrogen footprint assessment of integrated agronomic practice management in a summer maize cropping system

The footprints of water and nitrogen (WF and NF) provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen (Nr) loss in crop production. In this study, a field experiment over two years (2019 and 2020) compared three integrated agronomic practice management (IAPM) systems: An improved management system (T2), a high-yield production system (T3), and an integrated soil–crop management system (ISCM) using a local smallholder farmer's practice system (T1) as control, to investigate the responses of WF, Nr losses, water use efficiency (WUE), and nitrogen use efficiency (NUE) to IAPM. The results showed that IAPM optimized water distribution and promoted water use by summer maize. The evapotranspiration over the whole maize growth period of IAPM increased, but yield increased more, leading to a significant increase in WUE. The WUE of the T2, T3, and ISCM treatments was significantly greater than in the T1 treatment, in 2019 and 2020 respectively, by 19.8–21.5, 31.8–40.6, and 34.4–44.6%. The lowest WF was found in the ISCM treatment, which was 31.0% lower than that of the T1 treatment. In addition, the ISCM treatment optimized soil total nitrogen (TN) distribution and significantly increased TN in the cultivated layer. Excessive nitrogen fertilizer was applied in treatment T3, producing the highest maize yield, and resulting in the highest Nr losses. In contrast, the ISCM treatment used a reduced nitrogen fertilizer rate, sacrificing grain yield partly, which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery. The Nr level in the ISCM treatment was 34.8% lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8–63.1% in 2019 and 2020, respectively. Considering yield, WUE, NUE, WF, and NF together, ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

Acidification of European croplands by nitrogen fertilization: Consequences for carbonate losses, and soil health

Soil acidification is an ongoing problem in intensively cultivated croplands due to inefficient and excessive nitrogen (N) fertilization. We collected high-resolution data comprising 19,969 topsoil (0–20 cm) samples from the Land Use and Coverage Area frame Survey (LUCAS) of the European commission in 2009 to assess the impact of N fertilization on buffering substances such as carbonates and base cations. We have only considered the impacts of mineral fertilizers from the total added N, and a N use efficiency of 60 %. Nitrogen fertilization adds annually 6.1 × 107 kmol H+ to European croplands, leading to annual loss of 6.1 × 109 kg CaCO3. Assuming similar acidification during the next 50 years, soil carbonates will be completely removed from 3.4 × 106 ha of European croplands. In carbonate-free soils, annual loss of 2.1 × 107 kmol of basic cations will lead to strong acidification of at least 2.6 million ha of European croplands within the next 50 years. Inorganic carbon and basic cation losses at such rapid scale tremendously drop the nutrient status and production potential of croplands. Soil liming to ameliorate acidity increases pH only temporarily and with additional financial and environmental costs. Only the direct loss of soil carbonate stocks and compensation of carbonate-related CO2 correspond to about 1.5 % of the proposed budget of the European commission for 2023. Thus, controlling and decreasing soil acidification is crucial to avoid degradation of agricultural soils, which can be done by adopting best management practices and increasing nutrient use efficiency. Regular screening or monitoring of carbonate and base cations contents, especially for soils, where the carbonate stocks are at critical levels, are urgently necessary.

Silicon Fertilizer Addition Can Improve Rice Yield and Lodging Traits under Reduced Nitrogen and Increased Density Conditions

Reducing nitrogen fertilizer application, selecting a reasonable planting density, and adding silicon fertilizer can be used together to decrease excessive nitrogen fertilizer inputs in rice fields, reduce production costs, and ensure stable rice yield. However, the dynamics of the stem and internodes, as well as the changes in the physical and physiological characteristics of rice under a combination of these three strategies, are still unclear. In this study, we aimed to clarify these effects to improve the efficiency of rice production in northeastern China. A 2-year field experiment was conducted using five treatments: a conventional densification treatment (DM), a densification combined with reduced N input (−20%) treatment (DLM), and three densifications combined with reduced N input (−20%) and basal silicon fertilizer treatments (low fertilizer: DLMS1; medium fertilizer: DLMS2; and high fertilizer: DLMS3). This study revealed that the addition of silicon fertilizer improved rice yield compared to that under reduced nitrogen or increased density treatments alone, prevented excessive ineffective tillering after a density increase, and increased the number of productive panicles. Among the treatments, the DLMS3 treatment had the highest yields of 10.53 t/ha and 10.73 t/ha over the 2 years. Reducing nitrogen and increasing density reduced the weight and length of single panicles, while the addition of silicon fertilizer was beneficial for improving stem toughness, improving the physical and physiological characteristics of the plants and panicles, and enhancing plant bending resistance. Among the treatments, DLMS3 had the highest bending resistance, which increased by 440.1 g and 503.8 g compared to the lowest values in the DM treatment in 2020 and 2021, respectively. Nitrogen reduction resulted in the lowest lodging index values, with DLMS3 having the lowest values in both years, which decreased by 19.6% and 22.5% compared to the highest values in DM (2020) and DLM (2021), respectively. This study indicates that the application of 150.0 kg/ha silicon fertilizer in combination with reduced nitrogen and increased density (DLMS3) reduces the lodging index while ensuring rice yield, preventing a tradeoff between yield reduction and lodging due to a density increase or due to nitrogen reduction combined with a density increase and allowing for a reduction in nitrogen fertilizer input, which could ensure a uniform yield and an increase in lodging resistance. These results provide a scientific basis for rice cultivation measures that lead to high yield and lodging resistance while protecting the environment.

Nitrogen Utilization and Loss of the Tea Plantation System on Sloped Farmland: A Short-Term Response to Substitution with Organic Fertilizer

(1) Background: Excessive nitrogen (N) fertilizer application in tea plantations leads to challenges such as soil acidification and nitrogen loss, impending the sustainable development of the plantation system. Yet, there is a lack of research on blended fertilization strategies, and limited data regarding N loss when substituting with organic fertilizer. (2) Methods: A year-long field monitoring experiment was conducted to evaluate the effects of substituting compound fertilizer with organic fertilizer, specifically with respect to runoff N loss and uptake of chemical fertilizer N by tea trees. (3) Results: The annual runoff N loss ranged from 0.16 to 0.57 kg·hm−2 and accounted for a mere 0.22–0.48% of N from fertilizer applications. Substitution with organic fertilizer reduced runoff N loss by 21–53% and improved the tea tree utilization efficiency of chemical fertilizer N from 16% to 27%. A 50% organic fertilizer substitution (based on the amount of N) promoted a net soil N mineralization rate, creating an ammonium-rich environment favored by tea trees. (4) Conclusions: The positive effects of partially substituting N fertilizer with organic fertilizer in tea plantation systems on both N utilization efficiency and N loss were confirmed. If conditions permit, the study team would aim to expand the temporal scope of the study, and to investigate the impact of organic fertilizer substitution on N loss under various precipitation intensities.