Soil Nitrogen Dynamics Research Articles

Key determinants of soil labile nitrogen changes under climate change in the Arctic: A meta-analysis of the responses of soil labile nitrogen pools to experimental warming and snow addition

The Arctic terrestrial ecosystems are undergoing rapid climate change, causing shifts in the dynamics of soil nitrogen (N), a pivotal but relatively underexplored component. To understand the impacts of climate change on soil labile N pools, we performed meta- and decision-tree analyses of 391 observations from 38 peer-reviewed publications across the Arctic, focusing on experimental warming and snow addition. Soil dissolved organic nitrogen (DON), ammonium (NH4+), and nitrate (NO3-) pools under experimental warming exhibited overall standard mean differences (SMDs) ranging from −0.08 to 0.02, with no significance (P > 0.05); however, specific conditions led to significant changes. The key determinants of soil labile N responses to warming were experimental duration and mean annual summer temperature for DON; annual precipitation, soil moisture, and sampling timing for NH4+; and soil layer for NO3-. Snow addition significantly increased all labile N pools (overall SMD = 0.23–0.36; P < 0.05), influenced by factors such as sampling timing and vegetation type for DON; experimental duration and soil moisture for NH4+; and soil pH for NO3-. By consolidating and reprocessing datasets, we not only showed the overall responses of soil labile N pools to climate manipulation experiments in Arctic tundra ecosystems but also identified key determinants for changes in soil N pools among environmental and experimental variables. Our findings demonstrate that warming and snow-cover changes significantly affect soil labile N pools, highlighting how the unique environmental characteristics of different sites influence terrestrial N cycling and underscoring the complexity of Arctic N dynamics under climate change.

Sustainable Soil Management for Climate Resilience: Long-Term Management Effects on Soil Carbon Sequestration and Nitrogen Dynamics in a Semi-Arid Tropical Inceptisol of India

Sustainable Soil Management for Climate Resilience: Long-Term Management Effects on Soil Carbon Sequestration and Nitrogen Dynamics in a Semi-Arid Tropical Inceptisol of India

Soil nitrogen dynamics affected by coffee (coffea arabica) canopy and fertilizer management in coffee-based agroforestry

Nutrient management in coffee-based agroforestry systems plays a critical role in soil nitrogen (N) cycling, but has not been well documented. The objective of this study was to evaluate the effect of coffee canopy management and fertilization on soil N dynamics. This study used a randomized complete block design (2 × 3 × 2) with four replications. There were three factors: 1) coffee canopy management (T1: Pruned, T2: Unpruned), 2) fertilizer type (O: Organic, I: Inorganic; M: 50% Organic + 50% Inorganic), and 3) fertilizer dose (D1: low, D2: medium, D3: high). Soil N dynamic indicators (i.e., total N, ammonium (NH4+), nitrate (NO3−), net N-NH4+, net N-NO3−, soil microbial biomass N) were measured at two soil sampling depths (0–20 cm and 20–40 cm). Results showed that pruning increased soil total N and microbial biomass N (MBN) by 10–56% relative to unpruned coffee trees. In contrast, the unpruned coffee canopy had 15–345% higher NH4+, NO3−, net N-NH4+, net N-NO3−, and microbial biomass N concentration than pruned coffee. Mixed fertilizer application increased NO3− and net N-NH4+ accumulation by 5–15% relative to inorganic and organic fertilizers. In addition, medium to high dose fertilization led to a 19–86% higher net N-NO3− concentration and microbial biomass N as compared to low dose fertilization. The treatment of no pruning and mixed fertilizer at low to medium doses was the optimal management strategy to maintain soil available N, while pruning combined with organic fertilizer has the potential to improve soil total N and MBN.

Modeling maize growth and nitrogen dynamics using CERES-Maize (DSSAT) under diverse nitrogen management options in a conservation agriculture-based maize-wheat system

Agricultural field experiments are costly and time-consuming, and often struggling to capture spatial and temporal variability. Mechanistic crop growth models offer a solution to understand intricate crop-soil-weather system, aiding farm-level management decisions throughout the growing season. The objective of this study was to calibrate and the Crop Environment Resource Synthesis CERES-Maize (DSSAT v 4.8) model to simulate crop growth, yield, and nitrogen dynamics in a long-term conservation agriculture (CA) based maize system. The model was also used to investigate the relationship between, temperature, nitrate and ammoniacal concentration in soil, and nitrogen uptake by the crop. Additionally, the study explored the impact of contrasting tillage practices and fertilizer nitrogen management options on maize yields. Using field data from 2019 and 2020, the DSSAT-CERES-Maize model was calibrated for plant growth stages, leaf area index-LAI, biomass, and yield. Data from 2021 were used to evaluate the model's performance. The treatments consisted of four nitrogen management options, viz., N0 (without nitrogen), N150 (150 kg N/ha through urea), GS (Green seeker-based urea application) and USG (urea super granules @150kg N/ha) in two contrasting tillage systems, i.e., CA-based zero tillage-ZT and conventional tillage-CT. The model accurately simulated maize cultivar’s anthesis and physiological maturity, with observed value falling within 5% of the model’s predictions range. LAI predictions by the model aligned well with measured values (RMSE 0.57 and nRMSE 10.33%), with a 14.6% prediction error at 60 days. The simulated grain yields generally matched with measured values (with prediction error ranging from 0 to 3%), except for plots without nitrogen application, where the model overestimated yields by 9–16%. The study also demonstrated the model's ability to accurately capture soil nitrate–N levels (RMSE 12.63 kg/ha and nRMSE 12.84%). The study concludes that the DSSAT-CERES-Maize model accurately assessed the impacts of tillage and nitrogen management practices on maize crop’s growth, yield, and soil nitrogen dynamics. By providing reliable simulations during the growing season, this modelling approach can facilitate better planning and more efficient resource management. Future research should focus on expanding the model's capabilities and improving its predictions further.

Aerated irrigation improves soil gross nitrogen transformations in greenhouse tomato: Insights from a 15N-tracing study

Aerated irrigation (AI) significantly influences soil nitrogen (N) dynamics and biochemical characteristics, which are crucial for enhancing N absorption and utilization efficiency. However, AI’s potential effects and mechanisms on gross soil N transformations remain unclear. In this study, a 15N tracing incubation experiment was conducted with four treatments, each receiving an equivalent N input (150 kg N ha–1): (1) AINPK, chemical fertilizer under AI; (2) AIOM, organic fertilizer (OM) under AI; (3) AINPK+OM, chemical fertilizer (75 % of applied N) with organic fertilizer (NPK+OM) under AI; (4) NPK, chemical fertilizer (NPK) under traditional drip irrigation. The results revealed that AINPK significantly increased crop yield by 12.42 %, gross N mineralization by 2.58-fold, and gross nitrification by 1.27-fold compared to NPK. The AIOM and AINPK+OM significantly increased yield by 18.74–12.34 %, gross N mineralization by 1.14–1.27-fold, and autotrophic nitrification by 1.05–1.11-fold compared to AINPK. The AIOM exhibits the highest rate of NH4+ immobilization, being 1.16–1.26-fold greater than the other three treatments. Moreover, AINPK significantly reduced the turnover time of organic N compared to NPK, and the turnover time of organic N of AIOM and AINPK+OM was shorter than AINPK. Overall, AI increased gross N mineralization and gross nitrification rates, enhancing soil N availability. AINPK and AIOM elevated the NH4+ immobilization rates compared to NPK, while the AIOM and AINPK+OM also enhanced NO3– immobilization rates, stimulating inorganic N retention capacity. Therefore, based on the N transformation dynamics observed in this study, AIOM and AINPK+OM, which accelerate organic N turnover, enhance N availability and retention capacity, and increase crop yields, are recommended for crop production in greenhouse tomato.

Effect of crop rotation on nitrogen leaching with the lysimetric waters in vulnerable areas

Abstract. Climate change is known to subject the functioning of agroecosystems to high levels of biotic and abiotic stress and has a significant impact on agricultural production worldwide. Crop rotation is believed to be one way of adapting agriculture to climate change compared to monoculture This study aimed to examine the maize-wheat rotation impact on soil nitrogen dynamics and leaching losses. A study has been carried out on the experimental field of Tsalapitsa, Plovdiv region on Fluvisol. In this maize-wheat rotation experiment, we compared three fertilization treatments with increasing nitrogen and phosphorus rates to a control with no fertilization. In 2020, grain maize (Zea mays L.) FAO group 310, was grown with fertilizer rates (T0N0P0; T1N120P80; T2N160P120; T3N200P160). In the period 2020/2021, wheat, (Triticum aestivum L.), was grown with the following fertilizer variants – (Т0 N0P0; Т1N100P60; Т2 N140P100; Т3 N180P140). The field plots were equipped with modification of Ebermayer type of lysimeters, which collect water from 100 cm depth of soil profile. The volume of lysimetric waters was calculated, the nitrogen content and its leaching were analyzed. The study found that the lysimetric water volume after maize cultivation was 75.95 liters per square meter, approximately 2.5 to 3 times higher than that observed after wheat cultivation. Nitrogen content varied with fertilization rates, ranging from 10.8 to 37.5 mg/L for maize and 8.73 to 23.58 mg/L for wheat. The losses of the element with drainage runoff with the first crop were – 5.6-28.5 kg.ha-1, and with wheat – 1.2-6.3 kg.ha-1, respectively. It was established that when cereal crops were grown the losses of nitrate nitrogen out of the root zone were significantly reduced.

Influence of woodchip size and nitrogen fertilization on carbon dioxide and nitrous oxide emissions from soils amended with orchard biomass

AbstractIncorporating large amounts of woody biomass into soil, such as in whole orchard recycling (WOR), can promote carbon sequestration, nutrient recycling, and ecosystem health in agricultural fields. Yet uncertainty regarding the effects of WOR on soil carbon (C) and nitrogen (N) dynamics influences management decisions. The objective of this research was to evaluate the effects of woodchip (WC) size and interaction with N fertilization on carbon dioxide (CO2) and nitrous oxide (N2O) emissions. An 8‐month incubation experiment incorporating WC (4% w/w, equivalent to ∼40 tons per acre) in four sieved sizes (0.2–1.6, 1.6–3.2, 3.2–6.4, and 6.4–12.7 mm) with and without N applications was conducted. All treatments with WC showed that CO2 emission peaked within the first week, then decreased drastically afterward. The CO2 peak delayed as the peak value decreased (WC size increased). The finest WC (&lt;1.6 mm) yielded the lowest total CO2 emissions and resulted in the greatest increase in soil C at the end of incubation. Nitrogen application reduced total CO2 emissions by 1% in the smallest WC size and by 8%–9% for those larger than 1.6 mm. The N2O emissions spiked following each fertilizer application with lowest total emissions from the smallest WC size, suggesting substantial N immobilization. The results imply that larger WC sizes can delay C mineralization and reduce initial N immobilization risks, but the smallest WC size may have stabilized and increased soil organic carbon. This research increased our understanding on WC mineralization that can be used in WOR management.

Carbon persistence of soils with long‐term biosolids amendments in California agroecosystems

AbstractBiosolids can build soil organic matter, but their ability to increase carbon and nitrogen in persistent fractions in deep soil is not well understood. We aimed to assess the mechanisms that influence soil carbon and nitrogen dynamics at three sites—Sacramento (irrigated, grazed grassland), Solano (rainfed, grazed grassland), and Merced (feed cropping system with alfalfa–corn rotation)—where soils were amended with biosolids for 20 years using density fractionations, organomineral extractions, and correlations between calcium and soil organic carbon at three depths (0–10, 30–50, and 75–100 cm). We found that amended soils had higher carbon and nitrogen content in the free‐ and occluded‐light fractions at all depths relative to the control in the Sacramento and Solano sites; however, the Merced site had a greater relative increase of carbon and nitrogen associated with the heavy fraction. Effect sizes show that biosolids increase carbon and nitrogen content in free‐ and occluded‐light fractions in the surface soil (0–10 cm), and in both light and heavy fractions in the deep soil layer (75–100 cm). Ratios of carbon to iron and aluminum show that chelation is an important mechanism of carbon stabilization in Sacramento and Solano sites throughout the soil profile. No (0–10 cm) to negative (75–100 cm) correlations were observed between calcium and soil carbon in the amended soils in the Merced site. Our results indicate that, while biosolids are typically incorporated at shallow depths, long‐term application of biosolids can increase the amount of free‐ and occluded‐light carbon fractions in deep soil.

Exploring the Combined Effects of Different Nitrogen Sources and Chabazite Zeolite-Tuff on Nitrogen Dynamics in an Acidic Sandy-Loam Soil

Volcanic tuffs rich in chabazite zeolites have been extensively examined for their potential to enhance soil properties and increase fertilizer efficiency, both in their natural state and when enriched with nitrogen (N). However, there is a scarcity of data regarding their utilization in acidic sandy soil, particularly when used alongside organic fertilizers. This paper presents the findings of a 50-day laboratory incubation study that investigated the dynamics of N pools in an acidic sandy-loam agricultural soil treated with various N sources. These sources included urea, N-enriched chabazite zeolite tuff, and pelleted composted manure applied at a rate of 170 kg N/ha. Additionally, the N sources were tested in combination with chabazite zeolite tuff mixed into the soil to assess its role as a soil conditioner. The results revealed distinct behaviours among the tested N sources, primarily impacting soil pH and N dynamics. Soil fertilized with manure exhibited slow N mineralization, whereas N-enriched zeolite displayed a more balanced behaviour concerning net NO3−-N production and NH4+-N consumption. Both N-enriched zeolite and urea temporarily altered the soil pH, resembling a “liming” effect, while pelleted manure facilitated a prolonged shift towards neutral pH values. Considering the water adsorption capacity of zeolite minerals, caution is advised when adjusting water content and employing combustion methods to measure soil organic matter in zeolite-treated soil to avoid potential inaccuracies. In summary, N-enriched chabazite zeolite tuff emerged as a valuable N source in acidic sandy-loam soil, offering a promising alternative to synthetic fertilizers and showcasing a sustainable means of N recycling.

A review of the influence of heat drying, alkaline treatment, and composting on biosolids characteristics and their impacts on nitrogen dynamics in biosolids-amended soils

Application of biosolids to agricultural land has gained increasing attention due to their rich nutrient content. There are a variety of treatment processes for converting sewage sludge to biosolids. Different treatment processes can change the physicochemical properties of the raw sewage sludge and affect the dynamics of nutrient release in biosolids-amended soils. This paper reviews heat drying, alkaline treatment, and composting as biosolids treatment processes and discusses the effects of these treatments on biosolid nitrogen (N) content and availability. Most N in the biosolids remain in organic forms, regardless of biosolids treatment type but considerable variation exists in the mean values of total N and mineralizable N across different types of biosolids. The highest mean total N content was recorded in heat-dried biosolids (HDB) (4.92%), followed by composted biosolids (CB) (2.25%) and alkaline-treated biosolids (ATB) (2.14%). The mean mineralizable N value was similar between HDB and ATB, with a broader range of mineralizable N in ATB. The lowest N availability was observed in CB. Although many models have been extensively studied for predicting potential N mineralization in soils amended with organic amendments, limited research has attempted to model soil N mineralization following biosolids application. With biosolids being a popular, economical, and eco-friendly alternative to chemical N-fertilizers, understanding biosolids treatment effects on biosolids properties is important for developing a sound biosolids management system. Moreover, modeling N mineralization in biosolids-amended soils is essential for the adoption of sustainable farming practices that maximize the agronomic value of all types of biosolids.

Drive soil nitrogen transformation and improve crop nitrogen absorption and utilization - a review of green manure applications.

Green manure application presents a valuable strategy for enhancing soil fertility and promoting ecological sustainability. By leveraging green manures for effective nitrogen management in agricultural fields can significantly reduce the dependency of primary crops on chemical nitrogen fertilizers, thereby fostering resource efficiency. This review examines the current advancements in the green manure industry, focusing on the modulation of nitrogen transformation in soil and how crops absorb and utilize nitrogen after green manure application. Initially, the influence of green manure on soil nitrogen transformation is delineated, covering processes such as soil nitrogen immobilization, and mineralization, and losses including NH3, N2O, and NO3 --N leaching. The review then delves into the effects of green manure on the composition and function of soil microbial communities, highlighting their role in nitrogen transformation. It emphasizes the available nitrogen content in the soil, this article discussing nitrogen uptake and utilization by plants, including aspects such as nitrogen translocation, distribution, the root system, and the rhizosphere environment of primary crops. This provides insights into the mechanisms that enhance nitrogen uptake and utilization when green manures are reintroduced into fields. Finally, the review anticipates future research directions in modulating soil nitrogen dynamics and crop nitrogen uptake through green manure application, aiming to advance research and the development of the green manure sector.

Dynamics and microbial characteristics of nitrogen and carbon in saline-alkali paddy soil under different fertilization

The expansion of saline-alkali paddy fields, coupled with the application of large amounts of nitrogen (N) fertilizers, has given rise to a host of environmental concerns. While N and carbon (C) are vital indicators for assessing soil fertility, their dynamic characteristics in saline-alkali paddy soil remain obscure. To address this knowledge gap, we established paddy mesocosms with five distinct N-fertilizer treatments: control without N-fertilizer (CK), urea (U), urea with inhibitors (UI), organic–inorganic compound fertilizer (OCF) and C-based slow-release fertilizer (CSF). The objective was to monitor the dynamic changes of various N and soil organic-C (SOC) during a 137-day rice growing season, and to clarify the microbiological characteristics. By the end of the rice growing season, soil ammonia-N (NH4+-N) concentrations were UI > OCF > CSF > U > CK, and UI had a significant difference (p < 0.05) with all the other four treatments. Soil nitrate-N (NO3−-N) concentrations in OCF and CSF treatments were 5.64 ± 1.25 mg kg−1 and 6.81 ± 0.29 mg kg−1, respectively, significantly (p < 0.05) higher than U and UI treatments. NH4+-N showed a negative correlation with NO3−-N regardless of the N-fertilizer types, and a significant (p < 0.01) positive relationship with alkali-hydrolyzable N (AHN). A significant (p < 0.01) positive relationship existed between total-N (TN) and Bacteria 16S rRNA gene. The SOC had a significant (p < 0.05) positive relationship with mcrA gene. During the entire rice growing season, CSF treatment had lower mean TN and SOC concentrations than all the other treatments, and exhibited the highest TN and total organic-C (TOC) content in rice. In summary, the UI can increase the residual NH4+-N in saline-alkali paddy fields, and the CSF is a better choice for growing rice.

The Impact of Long‐Term Tillage Systems on Soil Carbon and Nitrogen Dynamics and Other Nutrient Contents

The Impact of Long‐Term Tillage Systems on Soil Carbon and Nitrogen Dynamics and Other Nutrient Contents

Measuring and modelling the impact of outdoor pigs on soil carbon and nutrient dynamics under a changing climate and different management scenarios

AbstractA mixed agricultural system that integrates livestock and cropping is essential to organic, agroecological, and regenerative farming. The demand for improved welfare systems has made the practice of outdoor rearing of pigs very popular; it currently makes up 40% of the UK pig industry and has also been integrated into arable rotations. Besides the benefits of outdoor production systems, they also potentially pose environmental risks to farmlands, such as accumulation of nitrogen and phosphorus in the soil, soil erosion and compaction and carbon loss. Despite this, the impact of outdoor pigs and arable crop rotations on soil health has been under‐researched relative to other livestock species. This study was conducted at the University of Leeds Research Farm from 2018 to 2020 using a combined experimental and modelling approach to understand the impact of outdoor pigs on soil carbon and nutrient dynamics. The physio‐chemical properties of arable soil were measured prior to the introduction of the pigs and after introducing the pigs at the end of first and second years, consecutively. There was assessment of control sites (without pigs, mowing once a year) and pig pens (pigs in a rotation with arable crops). The soil was sampled at two different depths, 0–10 cm and 10–20 cm. It was observed that measured soil organic carbon (SOC) stocks in the soil depths of 0–10 cm and 10–20 cm layer were decreased by 7% and 3%, respectively, in the pig pens from 2019 to 2020, and total available nitrogen and phosphorus were significantly higher in pig pens than the control sites. Hence, at a depth between 0 and 20 cm, the average total available nitrogen was 2.51 and 2.68 mg kg−1 in the control sites and 21.76 and 20.45 mg kg−1 in the pig pens in 2019 and 2020, respectively. The average total available phosphorus at 0–20 cm was 26.54 and 37.02 mg kg−1 in control sites and 48.15 and 63.58 mg kg−1 in pig pens during 2019 and 2020, respectively. A process‐based model (DayCent) was used to simulate soil carbon and nitrogen dynamics in the arable rotation with outdoor pigs and showed SOC stock losses of – 0.09 ± 0.23 T C ha−1 year−1 using the future climate CMIP5 RCP 8.5 scenario for 2020 to 2048. To reduce this loss, we modelled the impact of changing the management of the pig rotation and found that the loss of SOC stock could be decreased by shortening the period of pig retention in the field, growing grass in the field, and leguminous crops in the crop rotation.

Glucose input profit soil organic carbon mineralization and nitrogen dynamics in relation to nitrogen amended soils

Exogenous carbon (C) inputs stimulate soil organic carbon (SOC) decomposition, strongly influencing atmospheric concentrations and climate dynamics. The direction and magnitude of C decomposition depend on the C and nitrogen (N) addition, types and pattern. Despite the importance of decomposition, it remains unclear whether organic C input affects the SOC decomposition under different N-types (Ammonium Nitrate; AN, Urea; U and Ammonium Sulfate; AS). Therefore, we conducted an incubation experiment to assess glucose impact on N-treated soils at various levels (High N; HN: 50 mg/m2, Low N; LN: 05 mg/m2). The glucose input increased SOC mineralization by 38% and 35% under HN and LN, respectively. Moreover, it suppressed the concentration of NO3−-N by 35% and NH4+-N by 15% in response to HN and LN soils, respectively. Results indicated higher respiration in Urea-treated soils and elevated net total nitrogen content (TN) in AS-treated soils. AN-amended soil exhibited no notable rise in C mineralization and TN content compared to other N-type soils. Microbial biomass carbon (MBC) was higher in glucose treated soils under LN conditions than control. This could result that high N suppressed microbial N mining and enhancing SOM stability by directing microbes towards accessible C sources. Our results suggest that glucose accelerated SOC mineralization in urea-added soils and TN contents in AS-amended soils, while HN levels suppressed C release and increased TN contents in all soil types except glucose-treated soils. Thus, different N-types and levels play a key role in modulating the stability of SOC over C input.

Modeling the daily dynamics of grass growth of several species according to their functional type, based on soil water and nitrogen dynamics: Gras-Sim model definition, parametrization and evaluation

Gras-Sim model, through the environmental conditions and the dynamics of water and nitrogen in the soil, enables the prediction of the biomass yield in permanent grasslands. It was developed from existing models and simulates the dynamics of several grass species grouped into plant functional types (PFTs) A and B. Model inputs include weather data, fertilizer application, soil data, and cutting management. In contrast to previous models, Gras-Sim proposes a complete nitrogen balance at the field scale as well as a new formalism to estimate actual evapotranspiration based on the crop coefficient (Kc) for a better prediction of biomass production even under moderate stress. Gras-Sim was evaluated in this paper on the basis of data from experiments conducted between 2010 and 2018, on 3 sites fairly representative of the soil and climate conditions in Wallonia (Belgium). The relative root mean square error (RRMSE), normalized deviation (ND), and model efficiency (EF) across all cuts, sites, and PFTs were 29 %, 2 %, and 71 % respectively, for biomass production. Gras-Sim is a simple and efficient model that can be used as a starting point for the design of a decision support tool for better management of permanent grasslands.

Ground Cover Rice Production System Affects Soil Water, Nitrogen Dynamics and Crop Growth Differentially with or without Climate Stress.

The ground cover rice production system (GCRPS) has been proposed as a potential solution to alleviate seasonal drought and early low-temperature stress in hilly mountainous areas; clarifying its impact on crop growth is crucial to enhance rice productivity in these areas. A two-year (2021-2022) field experiment was conducted in the hilly mountains of southwest China to compare the effects of the traditional flooding paddy (Paddy) and GCRPS under three different nitrogen (N) management practices (N1, zero-N fertilizer; N2, 135 kg N ha-1 as a urea-based fertilizer; and N3, 135 kg N ha-1 with a 3:2 base-topdressing ratio as urea fertilizer for the Paddy or a 1:1 basal application ratio as urea and manure for GCRPS) on soil water storage, soil mineral N content and crop growth parameters, including plant height, tiller numbers, the leaf area index (LAI), aboveground dry matter (DM) dynamics and crop yield. The results showed that there was a significant difference in rainfall between the two growth periods, with 906 mm and 291 mm in 2021 and 2022, respectively. While GCRPS did not significantly affect soil water storage, soil mineral N content, and plant height, it led to a reduction in partial tiller numbers (1.1% to 31.6%), LAI (0.6% to 20.4%), DM (4.4% to 18.8%), and crop yield (7.4% to 22.0%) in 2021 (wet year) compared to the Paddy. However, in 2022 (dry year), GCRPS led to an increase in tiller numbers (13.7% to 115.4%), LAI (17.3% to 81.0%), DM (9.0% to 62.6%), and crop yield (2.9% to 9.2%) compared to the Paddy. Structural equation modeling indicated that GCRPS significantly affected tiller numbers, plant height, LAI, DM, and productive tiller numbers, which indirectly influenced crop yield by significantly affecting tiller numbers and productive tiller numbers in 2022. Overall, the effects of GCRPS on soil water and N dynamics were not significant. In 2021, with high rainfall, no drought, and no early, low-temperature stress, the GCRPS suppressed crop growth and reduced yield, while in 2022, with drought and early low-temperature stress and low rainfall, the GCRPS promoted crop growth and increased yield, with tiller numbers and productive tiller numbers being the key factors affecting crop yield.

Soil protein: A key indicator of soil health and nitrogen management

AbstractMonitoring soil nitrogen (N) dynamics in agroecosystems is foundational to soil health management and is critical for maximizing crop productivity in contrasting management systems. The newly established soil health indicator, autoclaved‐citrate extractable (ACE) protein, measures an organically bound pool of N. However, the relationship between ACE protein and other N‐related soil health indicators is poorly understood. In this study, ACE protein is investigated in relation to other soil N measures at four timepoints across a single growing season along a 33‐year‐old replicated eight‐system management intensity gradient located in southwest Michigan, USA. On average, polyculture perennial systems that promote soil health had two to four times higher (2–12 g kg−1 higher) ACE protein concentrations compared to annual cropping and monoculture perennial systems. In addition, ACE protein fluctuated less than total soil N, NH4+‐N, and NO3−‐N across the growing season, which shows the potential for ACE protein to serve as a reliable indicator of soil health and soil organic N status. Furthermore, ACE protein was positively correlated with total soil N and NH4+‐N and negatively correlated with NO3−‐N at individual sampling timepoints across the management intensity gradient. In addition, ACE protein, measured toward the end of the growing season, showed a consistent and positive trend with yield across different systems. This study highlights the potential for ACE protein as an indicator of sustainable management practices, SOM cycling, and soil health and calls for more studies investigating its relationship with crop productivity.

Hydrological and Biogeochemical Controls of the Seasonality of Particulate and Dissolved Nitrogen Exports During Rainfall Events From a Forested Watershed in Monsoon Asia, Japan

AbstractFew studies have investigated the effects of hydrological conditions such as rainfall magnitude and soil nitrogen dynamics on nitrogen export from forests during rainfall events. In this study, the seasonal export of particulate and dissolved nitrogen during 24 rainfall events (range: 3.0–417 mm) in a temperate monsoon forest watershed in Japan was measured along with the seasonality of the soil nitrate () pool size and the nitrification rate. The increase in nitrogen export with increasing streamflow was larger for particulate nitrogen than for and dissolved organic nitrogen, but was always the most abundant nitrogen component exported, even during extreme rainfall. For all rainfall events in summer, measured exports were higher than the averaged exports, regardless of rainfall magnitude or preceding rainfall. Nitrification activity in the soil was high in summer because of the high temperature and wet conditions of the soil. Nitrification also occurred in the upper slope in summer, whereas during other seasons it is hindered by dry conditions. These results indicate that nitrogen dynamics in the soil also affect export during rainfall. Comparisons with previous studies suggested that the effects of soil nitrogen dynamics on concentrations in stream water may be stronger during rainfall than during base flow conditions. They also showed that regions with wet summers due to rainfall are more sensitive to export, compared with other regions, and that increased summer rainfall can have a particularly large impact on nitrogen export from forest watersheds.

Long-term conversion of upland to paddy increased SOC content and N availability in a sand dune of Japan

Land use change driven by anthropogenic activities has greatly affected terrestrial C and N cycling; however, it remains unclear how dynamics of soil organic carbon (SOC) and nitrogen (N) availability respond to long-term land use change in sand dunes. Here, we investigated the changes in SOC, total nitrogen (TN), and their aerobic and anaerobic decomposition or mineralization in a vinyl film paddy, compared with dry land use and management changes (LUMCs) (original upland, greenhouse, and agricultural forest (tree area)) in Shonai sand dunes, northeast Japan. The vinyl film paddy had been singly cultivated for 54 years. Soil samples were collected from five soil depths (0–10, 10–20, 20–30, 30–40, 40–50 cm) to compare the effects of depth and LUMC among the four treatments. The C decomposition (Dec-C) was assessed as the aerobic CO2 production and anaerobic methane and CO2 productions. Meanwhile, N mineralization (Min-N) was determined as aerobic NH4+ and NO3– production and anaerobic NH4+ production. The results showed that the vinyl film paddy increased SOC and TN contents, Dec-C and Min-N than upland and greenhouses at 0–30 cm depth but lower levels than the tree area at all depths. The arithmetic mean for all depths showed the aerobic Dec-C in the paddy (216.0 mg kg−1) was higher than the corresponding anaerobic Dec-C (192.8 mg kg−1). Conversely, the aerobic Min-N (35.9 mg kg−1) was lower than the anaerobic Min-N (75.7 mg kg−1). There were significantly positive correlations among SOC, TN, aerobic and anaerobic Dec-C and Min-N, whereas the paddy had steeper slope than other three LUMCs. Conclusively, our results indicated that long-term conversion of upland to vinyl film paddy increased SOC and TN accumulation and N availability (Min-N) in Shonai sand dunes, which can be applied as an effective agricultural practice to improve fertility of coastal sandy soils.