Leaching Losses Research Articles

PH-Responsive Metal–Organic Framework for Targeted Delivery of Fungicide, Release Behavior, and Sustainable Plant Protection

A smart and environmentally friendly pesticide system was developed that could respond to environmental stimuli while mitigating environmental risks. In this study, thiabendazole (Thi), an effective fungicide, was loaded onto zeolitic imidazolate framework-8 (ZIF-8) using the impregnation method to fabricate a pH-responsive nano hybrid delivery system (Thi@ZIF-8). The results demonstrated that Thi@ZIF-8 had a rhombic dodecahedral morphology and a loading capacity of approximately 25%. Notably, the amount of Thi released from Thi@ZIF-8 at a pH of 5.0 reached 79.54%, which was higher than that at pH 7.0 and 9.0, for 251 h. Such pH-responsive release characteristics of Thi@ZIF-8 were probably related to the pH-dependent structure stability of ZIF-8. The release mechanism of Thi@ZIF-8 conformed to non-Fickian diffusion. Additionally, Thi@ZIF-8 showed a higher control efficacy against B. cinerea compared with Thi alone. Importantly, the ZIF-8 carrier could effectively reduce the leaching loss of Thi in soil and showed no negative effects on the three varieties of tomato seedlings, implying good biocompatibility. This work provides a novel and eco-friendly approach to control B. cinerea effectively that has great potential in modern sustainable agriculture.

Nutrient Management with Nitrogen Based Formulations for Enhancing Growth and Yield in Fodder Sorghum [Sorghum bicolor (L.) Moench

Fertilizers play a vital role in agricultural practices by boosting crop yield. Among various nutrient application methods, foliar application is one of the cost - effective method which allow rapid and efficient nutrient absorption through the stomata or cuticle, and subsequently into the cells. Applying nutrients through foliage offers several benefits, such as rapid nutrient absorption by plant tissues, improved transport to developing plant parts, elimination of leaching and fixation losses, regulated nutrient uptake by crops and enhanced nutrient utilization. Timely foliar application of nano fertilizers enhances crop output while reducing environmental risks. The current study aimed to evaluate the different concentrations of nano urea on growth and yield of fodder sorghum. The study was conducted at Instructional Farm, Vellayani, Thiruvananthapuram, Kerala during December 2023- February 2024. The field experiment was laid out in randomized block design with 13 treatments, replicated thrice. The treatments were T1:75% recommended dose of nitrogen (RDN) + nano urea (0.2%); T2:75% RDN+ nano urea (0.4%); T3:75% RDN + nano urea (0.6%);T4:100% RDN + nano urea (0.2%); T5:100% RDN + nano urea (0.4%); T6:100% RDN + nano urea (0.6%); T7:75% RDN + urea spray (2%); T8:100% RDN + urea spray (2%); T9: nano urea alone (0.2%); T10: nano urea alone (0.4%); T11: nano urea alone (0.6%); T12: KAU POP and T13: Control (without nitrogen). Both nano urea and urea spray were applied at 20 DAS and 40 DAS. Soil application of nitrogen was applied in three splits - 50% as basal, 25% at 20 DAS and 25% at 40 DAS. Full P and K were applied as basal. The study revealed that combined application of RDN along with nano urea 0.4% proved its superiority by registering higher growth and yield attributes such as plant height, stem girth, leaf: stem ratio, green fodder yield and dry fodder yield.

Effect of Microplastics and Straw Addition on Nitrogen and Phosphorus Leaching in Orange Orchard Soils

To explore the effects of microplastic input and straw addition on nitrogen and phosphorus leaching in orange orchard soil, indoor soil column leaching simulation experiments were conducted on orange orchard soil in Dangyang City, Hubei Province. The experiment analyzed the effects of different treatments on the leaching characteristics of soil nitrogen and phosphorus. The results showed that： ① The increase in microplastic input increased the leaching capacity of the soil （TN, NO3--N, NH4+-N, and TP） when only microplastic input was added. ② Under the addition of straw, the input of microplastics increased, which reduced the leaching amount of TN and NO3--N in the soil, and increased the leaching amount of NH4+-N and TP in the soil. ③ Under the input of microplastics, the key influencing factors of soil nitrogen and phosphorus leaching were soil bulk density and water content. Under straw addition, it was mainly affected by soil carbon and nitrogen content. Among them, microplastic input and straw addition significantly increased soil pH, but their path coefficients for nitrogen and phosphorus leaching were not significantly correlated. The results showed that the effects of polypropylene microplastic input and straw addition on soil nitrogen and phosphorus leaching were related to the amount of microplastics input and whether straw was added. The results showed that the input of microplastics would increase the amount of soil nitrogen and phosphorus leaching. Although nitrogen leaching loss caused by microplastic input could be reduced under straw addition, soil phosphorus leaching loss was significantly increased.

Water dispersible carbon nanomaterials reduced N, P, and K leaching potential in sandy soils: A column leaching study

Carbon nanomaterials (CNMs) — amendments with carbon in nanoscale form —could potentially enhance fertilizer delivery efficiency in agriculture, but their interaction with soil properties and nutrient co-mobility, especially in coarse-textured soils, remain poorly understood. We conducted a column leaching study in repacked soil columns to compare the co-leaching of novel water-dispersible CNMs and soil nutrients across two levels of CNMs applications (200 & 400 mg kg−1), two fertilization rates (low:80 mg kg−1 of N, P and K and high: 200 mg N kg−1, 100 mg P kg−1, 200 mg K kg−1, applied as ammonium nitrate, potassium phosphate, and potassium nitrate) and two soils (Spodosol with pH = 5.1, Alfisol with pH = 6.5). We imposed 12 leaching events to each column, with each leaching event adding water equivalent to the soil-pore volume (250 mL), resulting in cumulative leaching of 3000 mL of water through each column. CNMs applications reduced cumulative leaching losses of NO3-N (Spodosol: 8–12 %, Alfisol: 9–19 %), NH4-N (Spodosol: 2–14 %, Alfisol: 9–14 %), P (Spodosol: 23–27 %, Alfisol: 23–36 %) and K (Spodosol: 17–23 %, Alfisol: 24–26 %) compared to fertilized columns without CNMs. CNMs increased soil pH by up to 0.3 units (Spodosol) or 0.5 units (Alfisol), while lowering electrical conductivity by 15–20 % at the high fertilization rate in both soils. Columns with water-dispersible CNMs accumulated 25–30 % more total C in the base sections of the Alfisol compared to the Spodosol, indicating faster downward movement through the soil profile. Overall, we demonstrated that CNMs have the potential to reduce nutrient leaching in coarse-textured soils, which could be particularly beneficial in high-input intensive agricultural systems.

Spatial-temporal patterns of foliar and bulk soil 15N isotopic signatures across a heterogeneous landscape: Linkages to soil N status, nitrate leaching, and N2O fluxes

The natural abundance of plant and bulk soil 15N isotopic signatures provides valuable insights into the magnitude of nitrogen cycling and loss processes within terrestrial ecosystems. However, 15N isotopic signatures are highly variable in space due to natural and anthropogenic factors affecting N cycling processes and losses. To date, most studies on foliar and bulk soil 15N isotopic signatures have focused on N-limited forest ecosystems at relatively large spatial scales, while similar studies in N-enriched ecosystems at finer spatial scales are lacking. To address this gap and evaluate links between soil 15N isotopic signatures and ecosystem N cycling and loss processes (plant N uptake, N leaching, and gaseous loss), this study quantified foliar and bulk soil 15N isotopic signatures, soil physicochemical parameters, gaseous (N2O), and hydrological (NO3) N losses at 80 sites distributed across a heterogeneous landscape (∼5.8 km2). To account for the spatial-temporal heterogeneity, the measurements were performed in four campaigns (March, June, September 2022, and March 2023) at sites that considered different land uses, soil types, and topography. Results indicated that foliar and bulk soil 15N isotopic signatures were significantly (P < 0.05) more enriched in arable and grassland ecosystems than forests, suggesting a more open N cycle with significant N cycling and losses due to higher N inputs from fertilizers. Similar to soil inorganic N, N2O fluxes, and NO3 leaching rates, landscape-scale foliar and soil 15N isotopic signatures varied widely spatially, particularly at grassland and arable land (−3 to 9.0‰), with bivariate and multivariate analyses also showing significant relationships between landscape-scale soil 15N isotopic signatures and the aforementioned parameters (r2: 0.29 to 0.82). Based on these relationships, our findings suggested that foliar and bulk 15N isotopic signatures may capture fine-scale areas with persistently high and low environmental N losses (N2O fluxes and NO3 leaching) within a heterogeneous landscape.

Evaluating nitrogen dynamic and utilization under controlled-release fertilizer application for sunflowers in an arid region: Experimental and modeling approach

Traditional nitrogen fertilizers (TNF), such as urea, percolate easily in arid fields, posing low nitrogen use efficiency (NUE) and a high non-point pollution risk. Controlled-release fertilizers (CRF) exhibit significantly lower deep seepage, rendering it a favorable choice in arid fields due to its ability to enhance NUE through slow-release mechanisms. However, current models do not fully account for the soil nitrogen dynamics and crop interactions under controlled-release conditions, and lack quantification. This study improved the APSIM model by adjustment the urea hydrolysis rate to assess the impact of CRF and TNF applications on soil health, crop growth, and water quality. Calibration and validation were conducted through experiments in the Hetao Irrigation District of China from 2019 to 2020, with different nitrogen application rates (135, 225, and 315 kg/ha). The model accurately simulated soil NO3-N concentration (SNC), cumulative NO3-N leaching (CNL), nitrogen uptake (NU), and sunflower yield. During the validation process, R2 and Nash-Sutcliffe efficiency (NSE) values were both above 0.75. Results indicated that the average SNC, NU, and yield under CRF application were significantly higher than those under TNF application, with increases of 38.62%, 44.92%, and 18.38%, respectively. Notably, the proportion of soil nitrogen available (PSNA), a novel metric proposed in this study, was 159.50% higher in the 0–40 cm soil layer with CRF compared to TNF. Additionally, CNL and NO3-N leaching loss rate (NLLR) decreased by 25.76% and 25.77%, respectively. Scenario simulations indicated that the optimal fertilization strategy for this region is to use 180–193.5 kg/ha of CRF with a release period of 80–85.5 d to balance agricultural productivity and ecological protection. This study confirms the significant advantages of CRF in enhancing yield, improving nitrogen management, and promoting environmental sustainability, providing a scientific basis for CRF management strategies and supporting the shift towards more efficient and environmentally friendly agricultural practices.

Comparative research on monitoring methods for nitrate nitrogen leaching in tea plantation soils

Great concern has long been raised about nitrate leaching in cropland due to its possible environmental side effects in ground water contamination. Here we employed two common techniques to measure nitrate leaching in tea plantation soils in subtropical China. Using drainage lysimeter as a reference method, the adaptability of estimating drainage and nitrate leaching by combining the water balance equation with the suction cup technique was investigated. Results showed that the final cumulative leachate volume for the calculated and measured method was 721.43 mm and 729.92 mm respectively during the study period. However, nitrate concentration exerted great influence in the estimation of nitrate leaching from the suction cup-based method. The cumulative nitrate leaching loss from the lysimeter and suction cup-based method was 47.45 kg ha−1 and 43.58 kg ha−1 under lysimeter nitrate concentrations ranging from 7 mg L−1 to 13 mg L−1, 156.28 kg ha−1 and 79.95 kg ha−1 under lysimeter nitrate concentrations exceeding 13 mg L−1. Therefore, the suction cup-based method could be an alternative way of monitoring nitrate leaching loss within a range of 7–13 mg L−1 of nitrate concentrations in leachate. Besides, lower results occurred in suction cup samplers due to lack of representative samples which mainly leached via preferential flow when in strong leaching events. Thus, it is advisable to increase sampling frequency under such special conditions. The results of this experiment can serve as a reference and guidance for the application of ceramic cups in monitoring nitrogen and other nutrient-ion leaching in tea plantation soils.

Planted species influences soil phosphorus losses in a historically fertilized pasture system: A mesocosm study

AbstractThe gradual accumulation of phosphorus from historical fertilization can contribute to the eutrophication of surface waters by increasing the potential for subsurface leaching losses. Grazing lands areas are a priority for concern, and phytoremediation efforts in grazing lands have prioritized grasses that may be used as forage for cattle. This study investigated the influence of three different forage species—Paspalum notatum, Hemarthria altissima, and Cynodon nlemfuensis—on the loss of phosphorus in leachate from surface soils. The experiment used a nested pot mesocosm design that allowed us to monitor leachate volume and concentration biweekly over the course of 3 months. Pots containing P. notatum plants leached significantly more phosphorus than pots containing C. nlemfuensis or empty pots with no plants growing in them, despite losing an equivalent amount of water. H. altissima lost equivalent amounts of phosphorus in leachate water, but each H. altissima plant removed approximately 33.6 mg of phosphorus, approximately 2.5× that removed by P. notatum (13.4 mg). C. nlemfuensis had lower average leachate phosphorus concentrations at each biweekly sampling than either plant species (C. nlemfuensis‐P. notatum, padj = 0.001; C. nlemfuensis‐H. altissima, padj = 0.02), averaging only 0.110 ppm in leachate relative to 0.175 ppm and 0.200 ppm in pots beneath H. altissima and P. notatum, respectively. This, combined with C. nlemfuensis' slightly higher‐than‐average aboveground P content and overall aboveground biomass expression suggest it is the best possible phytoremediation candidate. As even minor leachate P loads can be critically threatening to neighboring oligotrophic water bodies, if the conservation of downstream environments is the priority, the short‐term threat of increased leachate must be considered. Further research is needed to explore the underlying mechanisms and field‐scale implications of these findings.

Iron-cobalt loading carbon nitride bimetallic catalyst activates peroxymonosulfate for bisphenol A degradation

In order to reduce metal leaching loss and carbon emissions, an active Peroxymonosulfate (PMS) catalyst (Fe/Co–CN) was prepared using a one-step thermal polycondensation method for the efficient treatment of wastewater containing bisphenol A (BPA). Fe/Co–CN has a low metal leaching (＜1 mg/L) and has good catalytic degradation performance for BPA. The degradation efficiency was 90.7% in 5 min and ∼100% in 10 min, which is much higher than single metal-loaded Fe–CN (77.2%) and Co–CN (73.2%). Nonradical species dominated by 1O2 and high-valent species were the main reactive oxygen species that degraded BPA in the Fe/Co–CN/PMS system. By strictly controlling the energy consumption during the synthesis and application of Fe/Co–CN, lower carbon emissions have been achieved than most catalysts reported. This achievement is of great significance for applying advanced oxidation methods to treat organic micro-pollutants and provides reference for the calculation of PMS catalysts carbon emissions.

12-year continuous biochar application: Mitigating reactive nitrogen loss in paddy fields but without rice yield enhancement

Numerous studies have documented the beneficial effects of short-term biochar application on soil carbon sequestration, greenhouse gas emissions reduction, and ecological functions enhancement. However, concerns persist regarding the impacts on soil reactive nitrogen (N) loss and crop yields under long-term biochar application (more than ten years), due to the irreversibility once biochar is incorporated into soils. This study presents the results of a 12-year field experiment in a rice-wheat rotation system with treatments including a control (CK, no corn straw or biochar), annual corn straw returning (CS, 6 Mg·ha−1·yr−1), and annual application of corn straw biochar pyrolyzed at 400°C at rates of 2.4, 6, and 12 Mg·ha−1·yr−1 (BC1, BC2, and BC3), investigating rice yields (2011–2022) and reactive N loss (2021–2022). The results showed that after 11 years of continuous biochar application until the 2021 rice season, alkaline hydrolysis N (AN, equivalent to an average of 347 kg N ha−1) within the 0–15 cm soil layer in biochar treatments was significantly higher than that of the CK (200 kg N ha−1), attributable to the biochar-induced enhancement of cation exchange capacity (CEC). The application of biochar reduced inorganic N leaching and NH3 volatilization losses by an average of 42.21 % and 30.85 %, respectively. However, N2O emission in the BC3 treatment was over 2 times as high as in the CK. Continuous biochar applications did not increase rice yield over the 12 rice seasons, as excessive soil AN level under biochar application reduced the rice harvest index. The results indicated that continuous biochar application was effective in reducing reactive N losses and increasing plant-available N supply, suggesting a potential to sustain rice production with lower fertilizer N inputs.

Mitigation of Nitrogen Losses in a Plant-Soil System through Incorporation of Nanocellulose and Zinc-Modified Nanocellulose.

Most nitrogen (N) applied to plants as fertilizer is lost through leaching. Here, nanocellulose was used in mitigating N leaching loss. Lettuce-cropped soil was treated with unmodified or Zn-modified nanocellulose (1-2% by wt) in combination with NPK, compared with urea and NPK-only treatments. Consecutive leaching, plant growth, plant N uptake, and soil nitrogen retention were assessed. Nanocellulose + NPK significantly (p ≤ 0.05) reduced N leaching, compared with urea and NPK-only. 1-and-2 wt % nanocellulose, as well as Zn-modified 1-and-2 wt % nanocellulose, reduced N leaching by 45, 38, 39, and 49% compared with urea and by 43, 36, 37, and 47% compared with NPK-only, respectively. Nitrogen leached mainly as NO3- (98.4%). Compared with urea and NPK, lettuce shoot mass was significantly (p ≤ 0.05) increased by 30-42% and by 44-57%, respectively, by all nanocellulose treatments, except for the Zn-modified 1 wt % nanocellulose. Leached N negatively correlated to biomass yield. Soil N retention was enhanced by the pristine and Zn-modified nanocelluloses between 27 and 94%. Demonstrably, nanocellulose can be utilized for mitigating N loss in soil and supporting crop production, resource management, and environmental sustainability.

Humic Acids Combined with Dairy Slurry as Fertilizer Can Increase Alfalfa Yield and Reduce Nitrogen Losses

Dairy slurry could be a significant source of nitrogen (N) for plants, but mismanagement can lead to atmospheric ammonia losses or nitrate leaching into groundwater. To make the use of dairy slurry efficient and reasonable, the loss of N pollution to the environment should be reduced. We used repacked lysimeters to comprehensively determine ammonia emission and N leaching losses in an alfalfa–soil system. The application of dairy slurry had no significant effect on alfalfa yield at the same rate of N application in comparison to chemical fertilizer, and adding humic acids significantly increased yield by about 12%. However, the application of dairy slurry increased the ammonia emission rate significantly, leading to an increase in the cumulative amount of ammonia emission, while the addition of humic acids reduced the ammonia emissions by 11%. Chemical fertilizer and dairy slurry application significantly increased nitrate leaching compared to the control treatment, while the addition of humic acids can significantly reduce ammonium N leaching. Dairy slurry was proven to be as effective as chemical N fertilizer in achieving the optimum biomass, and adding humic acids can significantly reduce N loss to the atmosphere and groundwater. This study showed the possibility of replacing chemical fertilizer with dairy slurry in alfalfa production and the advantages of humic acids’ addition to alfalfa to maintain production yield and improve environmental friendliness.

Hydrus-1D Model for Simulating Potassium Transport in Rice Crop Irrigated with Alternate Wetting and Drying Practice

ABSTRACT Potassium (K) is one of the essential nutrients that play a crucial role in rice fields; however, its availability, transport, and balance components can be influenced by alternating wetting and drying (AWD) irrigation practice. This study used the Hydrus-1D solute transport model to simulate K transport and balance components in AWD irrigated rice fields. Thirty lysimeter field experiment plots with three different irrigation treatments (No: no soil water stress, MS: mild soil water stress (400 cm), and SS: severe soil water stress (750 cm)) were used for rice cultivation. Daily measurements of soil matric potential head (SMPH) and ponding water depth (PWD) were recorded. Throughout the rice-growing season, leachate water samples from the surface (ponding water) and soil profiles were collected to measure K content. Using the lysimeter field experiment data, the Hydrus-1D model simulated K transport in the AWD rice field. The simulation results indicate that the K distribution predominantly occurred within the top puddled soil layer (0–20 cm) in AWD practice. This suggests that the recommended K fertilizer dose with a 4–5 cm PWD and SMPH of 400 cm optimizes K availability for rice while limiting K leaching loss. The Hydrus-1D model proves to be a valuable management tool, aiding in determining optimal K application rates and ponding water depths for AWD irrigation, ensuring sufficient K nutrients for rice, and controlling K loss for sustainable rice production.

Straw Returning Alleviates the Inhibition of Soil Nitrification Medicated by Ammonia-Oxidizing Archaea under Low Nitrogen Fertilization

Straw returning may stimulate soil microbial activity, thereby influencing microbial-mediated soil nitrification, which can lead to nitrate leaching and nitrogen (N) loss. However, its effects under long-term nitrogen fertilization remain unclear. At an experimental station with 34 years of fertilizer application (0, 135, and 270 kg ha−1 N), we investigated how nitrogen fertilization and straw returning affected the soil potential nitrification rate (PNR) and ammonia-oxidizing microorganisms (AOM). Our results suggest that N fertilization concurrently inhibits soil PNR, but this inhibition can be alleviated by straw returning, particularly with low nitrogen fertilization (p &lt; 0.05). Long-term N fertilization significantly decreased the abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and complete ammonia-oxidizing bacteria cladeB (CAOB-cladeB). Straw returning increased AOA abundance and diversity, especially with low or no fertilization (p &lt; 0.05). Furthermore, the partial least squares path model demonstrated that AOA abundance affected soil PNR by altering the AOA community. According to random forest analysis, soil pH and AOA beta diversity were the primary factors affecting soil PNR (explaining 10.76% and 10.03% of the variation, respectively). Overall, our findings highlight the importance of straw returning and AOA in soil nitrification under long-term nitrogen fertilization, emphasizing the need to consider these interactions for sustainable agriculture.

Influence of fertigation on soil-plant nutrition and crop productivity of shade grown Robusta coffee (Coffea canephora) in India

Coffee in Western Ghats grown under shade, soils are enriched with all the nutrients except phosphorus. The areas receive high rainfall, which leads to leaching loss and surface runoff of applied nutrients causing low fertilizer use efficiency. Improved agronomic practices are essential to address these issues. Fertigation is one such practice, having the potential to reduce extra chemical load by improving nutrient use efficiency. Hence, an attempt was made to study the impact of long-term fertigation on soil-plant nutrition and productivity of Robusta coffee. The trial was laid out in randomized complete block design (RCBD) with six treatments and four replications. Data on yield parameters and coffee yield indicated that significantly higher total number of nodes/branches, number of bearing nodes/branches, number of fruits/branches and coffee yield (49.1, 35.0, 758, and 2117 kg ha−1, respectively) were recorded in fertigation block supplied with 100% recommended dose of fertilizer (RDF) as water soluble fertilizer (WSF) which were statistically on par with 75% RDF (44.1, 29.4, 679, and 1821 kg ha−1, respectively). Similarly, higher major, secondary, and micro-nutrient content were noticed in leaf with fertigation at 75 and 100% RDF and also it was observed that, leaf Nitrogen (N), Phosphorus (P), and Potassium (K) content played a highly significant role in increasing coffee yield. The study results revealed that the quantum of N, P, and K fertilizer requirement could be brought down to the tune of 25% through fertigation as compared to the conventional soil application.

Quantification of nitrogen leaching losses by paddy cultivation under controlled and continual runoff conditions

In Asia, paddy is an important food crop that requires a high level of nitrogen, which is provided by straight chemical fertilizers that contribute a single nutrient, mainly urea. A study was conducted to quantify the leaching loss of nitrogen (as NO3--N) under two water management practices: controlled runoff and continual runoff in paddy cultivation at Low Country Intermediate Zone, Sri Lanka from 2015 to 2016 for four consecutive cropping seasons. Urea (N 46%) was applied as a sole source of Nitrogen at the rate of 225 kg ha-1. A randomized complete block design was employed with triplicates by two factors and two levels (cropping seasons; Yala, Maha, gradients; upper, lower). Lysimeters were arranged to collect leached water. The leachate from the study plots was collected weekly throughout the cropping period and the total amount of leached NO3--N for each cropping season was quantified. The leaching losses of NO3--N accounted under controlled runoff and continual runoff conditions were 8.6 kg ha-1 and 3.0 kg ha-1 respectively throughout the cropping period. It contributed to 8% and 3% of Nitrogen out of the total amount of applied N fertilizers in the same order. The water management practices and gradient effects were significant with respect to nitrogen leaching losses from paddy fields while cropping season had no effect on nitrogen leaching. A significant amount of nitrogen leaching losses could occur under the root zone, even though a controlled runoff situation posing possible threats of surface and groundwater pollution.

Does Soil Acidification Matter? Nutrient Sustainability of Timber Harvesting in Forests on Selected Soils Developed in Sediments of the Early vs. Late Pleistocene

With this study, our aim was to estimate the nutrient fluxes relevant for assessing nutrient sustainability as accurately as possible and to calculate nutrient balances for alternative forest management scenarios. Furthermore, we tested whether mapping units from existing geologic maps can serve as a basis for forest practitioners to estimate nutrient sustainability or whether more detailed data are needed. Positive fluxes include deposition and weathering, while negative fluxes include losses due to leaching and nutrient removal through timber harvesting in the balance. Weathering and leachate losses were modeled with a geochemical model. The SwissStandSim model was used to simulate the biomass growth under different harvesting and silvicultural strategies, allowing for sustainability to be assessed for each nutrient at a given intensity of use. This assessment was made per rotation period based on two criteria: (i) nutrient supply and (ii) total stocking volume. As a result, it can be noted that the accurate estimation of individual fluxes is essential for assessing the sustainability of forestry practices and that it needs detailed site-specific data. Various influencing factors turned out to be important, particularly the assumed depth of the root zone.

Using organic amendments in disturbed soil to enhance soil organic matter, nutrient content and turfgrass establishment

Disturbed soils, including manufactured topsoils, often lack physical and chemical properties conducive to vegetation establishment. As a result, efforts to stabilize disturbed soils with vegetation are susceptible to failure. Urban organic waste products such as wood mulch, composted leaf and yard waste, and biosolids are widely distributed as organic amendments that enhance sustainability and plant establishment. Correct use can be determined by examining soil properties such as pH; the concentration of soluble salts (SS); and plant available nutrients — particularly N, C and P; as well as root and shoot growth. This research examined the effects of three typical organic amendments on fertility, establishment, and nutrient loss. A manufactured topsoil was used as the base soil for all treatments, including a control unamended soil (CUT), and soil amended with either mulch (MAT), composted leaf and yard waste (LAT), or biosolids (BAT). A 2 % organic matter concentration increase was sought but not achieved due to difficulty in reproducing lab results at a larger scale. Results showed that LAT improved soil fertility, particularly N-P-K concentrations while maintaining a good C:N ratio, pH, and SS concentration. BAT was the most effective at enhancing shoot growth but results suggest that improved growth rates could result in increased maintenance. Additionally, biosolids were an excellent source of nutrients, especially N-P-K and S, but diminished root growth and N leachate losses indicate that N was applied in excess of turfgrass requirements. Therefore, biosolids could be used as fertilizer, subject to recommended rates for turfgrass establishment to prevent poor root growth and waterborne N pollution. To ensure establishment efforts are successful, MAT is not recommended without a supplemental source of soluble N. Altogether, study results and conclusions could inform others seeking to improve specifications for disturbed soil where turfgrass establishment is needed to stabilize soil.

Integration of QTL and transcriptome approaches for the identification of genes involved in tomato response to nitrogen deficiency.

Optimizing plant nitrogen (N) usage and inhibiting N leaching loss in the soil-crop system is crucial to maintaining crop yield and reducing environmental pollution. This study aimed at identifying quantitative trait loci (QTLs) and differentially expressed genes (DEGs) between two N treatments in order to list candidate genes related to nitrogen-related contrasting traits in tomato varieties. We characterized a genetic diversity core-collection (CC) and a multi-parental advanced generation intercross (MAGIC) tomato population grown in a greenhouse under two nitrogen levels and assessed several N-related traits and mapped QTLs. Transcriptome response under the two N conditions was also investigated through RNA sequencing of fruit and leaves in four parents of the MAGIC population. Significant differences in response to N input reduction were observed at the phenotypic level for biomass and N-related traits. Twenty-seven QTLs were detected for three target traits (leaf N content, leaf nitrogen balance index, and petiole NO3- content), 10 and six in the low and high N condition, respectively, while 19 QTLs were identified for plasticity traits. At the transcriptome level, 4752 and 2405 DEGs were detected between the two N conditions in leaves and fruits, respectively, among which 3628 (50.6%) in leaves and 1717 (71.4%) in fruit were genotype specific. When considering all the genotypes, 1677 DEGs were shared between organs or tissues. Finally, we integrated DEG and QTL analyses to identify the most promising candidate genes. The results highlighted a complex genetic architecture of N homeostasis in tomato and novel putative genes useful for breeding tomato varieties requiring less N input.

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.