Nitrate-nitrogen Losses Research Articles

Migration of Nitrate Nitrogen by Soil Profile

In the leached low-humus medium loamy chernozem of the central zone of the Kurgan region, losses of nitrate nitrogen through leaching with precipitation down the soil profile were noted. Losses increased with the use of increased doses of nitrogen fertilizers, as well as in variants with unilateral application of nitrogen fertilizers.

Study on the Influence of Canopy Density on Cycling of Soil Available N in Different Landform of Loess Plateau in China

In this paper, a total of 330 soil samples with 0-100cm soil depth of 66 planted square forest (10*10m) with different canopy density in the Loess Plateau were selected for the determination and analysis of soil N content in different soil layers, and the effects of different canopy density on soil N cycle under different topographic factors of planted forest were studied. The results showed as follows: (1) the migration mechanism of different N forms to the root surface was different, the migration of nitrate nitrogen to the root surface mainly depended on mass flow, there was enrichment phenomenon near the root, ammonium nitrogen mainly through diffusion, resulting in deficiency and loss in the near rhizosphere, and the leaching loss of nitrate nitrogen was affected by soil water and root growth. (2) The thickness, composition and decomposition rate of litter were different due to different canopy density, which affected the content of ammonium nitrogen and nitrate nitrogen in forest soil. (3) Although the change of different regions in this region was spatially different, keeping the stand cover in the middle and high range of 0.75-0.8 can be conducive to maintaining the balance between the consumption of soil nutrients by the stand and the supplement of nutrient consumption, which can also be conducive to the sustainable recovery and growth of the stand in this region.

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.

Effects of Biochar-Coated Nitrogen Fertilizer on the Yield and Quality of Bok Choy and on Soil Nutrients

This study was aimed at problems associated with low fertilizer using efficiency, excessive nitrate content of vegetables, and soil degradation in greenhouse vegetable production. A pot experiment was conducted to assess the effects of applying biochar-coated nitrogen fertilizer (BCNF) on the yield, quality, and nitrate content of bok choy (Brassica rapa subsp. Chinensis) as well as on soil nutrients in greenhouses. Four treatments were set up as follows: no nitrogen fertilizer application (BA), chemical nitrogen fertilizer application (CK), biochar-coated nitrogen fertilizer application (BCNF, the amount of nitrogen was equal to that of chemical fertilizer), and reduced biochar-coated nitrogen fertilizer application (D-BCNF, the amount of fertilizer was 80% of BCNF). Compared with the other treatments, BCNF treatment increased chlorophyll content, plant height, maximum leaf length, maximum leaf width, and other biological characters of bok choy. Compared with CK treatment, BCNF treatment increased the fresh weight of bok choy by 14.02%, while reducing the root–shoot ratio and nitrate content by 19.1% and 46%, respectively. It was further found that the application of BCNF could effectively increase the content of soil organic matter; reduce the leaching loss of nitrate nitrogen, exchangeable calcium and magnesium; and effectively improve nitrogen use efficiency. Therefore, the application of BCNF can not only reduce the loss of fertilizer nutrients, promote plant growth, and improve fertilizer utilization, but it can also improve soil nutrients, fix carbon, and reduce emissions. It is a new type of environmental protection fertilizer with application prospects.

Tackling policy leakage and targeting hotspots could be key to addressing the ‘Wicked’ challenge of nutrient pollution from corn production in the U.S.

Reducing nutrient loss from agriculture to improve water quality requires a combination of management practices. However, it has been unclear what pattern of mitigation is likely to emerge from different policies, individually and combined, and the consequences for local and national land use and farm returns. We address this research gap by constructing an integrated multi-scale framework for evaluating alternative nitrogen loss management policies for corn production in the US. This approach combines site- and practice-specific agro-ecosystem processes with a grid-resolving economic model to identify locations that can be prioritized to increase the economic efficiency of the policies. We find that regional measures, albeit effective in reducing local nitrogen loss, can displace corn production to the area where nitrogen fertilizer productivity is low and nutrient loss rate is high, thereby offsetting the overall effectiveness of the nutrient management strategy. This spatial spillover effect can be suppressed by implementing the partial measures in tandem with nationwide policies. Wetland restoration combined with split fertilizer application, along with a nitrogen loss tax could reduce nitrate nitrogen loss to the Mississippi River by 30% while only increasing corn prices by less than 2%.

Mitigating runoff nitrate loss from soil organic nitrogen mineralization in citrus orchard catchments using green manure.

Nitrate-nitrogen (NO3--N) loss is a significant contributor to water quality degradation in agricultural catchments. The amount of nitrogen (N) fertilizer input in citrus orchard is relatively large and results in significant NO3--N loss, compared to cropland. To promote sustainable N fertilizer management, it is crucial to identify the sources of runoff NO3--N loss in citrus orchards catchments. Particularly, we poorly know the sources of NO3--N and the mitigation mechanisms in these areas, which are highly polluted with NO3--N in water bodies. In this study conducted in central China, we conducted a field experiment with four treatments (CK: no N fertilizer; CF: conventional N fertilizer, 371.3kg N ha-1 yr-1 urea; OM: CF with organic manure; GM: CF with legume green manure) and a catchment-scale experiment in two citrus orchards (34.3%; 51.6%) catchments. To determine the source of runoff NO3--N loss, we used the dual isotope tracer method (δ15N and δ18O of NO3-) to identify the sources of NO3--N, and a 15-day incubation experiment to determine the potential and rate of soil N mineralization. Our findings revealed that soil organic nitrogen (SON) mineralization was the primary contributor to runoff NO3--N loss, and soil N mineralization potential (0.65⁎⁎⁎) and rate (0.54⁎⁎⁎) were the key factors impacting NO3--N loss. Interestingly, organic manure significantly increased 29.0% of NO3--N loss derived from SON in the runoff by enhancing soil N mineralization potential (+36.6%) and rate (+77.1%). But green manure mulching significantly reduced the soil N mineralization rate (-18.6%) compared to organic manure application, making it the most effective measure to reduce NO3--N loss (-12.4%). Our study highlights the critical role of regulating SON mineralization in controlling NO3--N pollution in surface waters in citrus orchard catchments.

Improving model capability in simulating spatiotemporal variations and flow contributions of nitrate export in tile-drained catchments

It is essential to identify the dominant flow paths, hot spots and hot periods of hydrological nitrate-nitrogen (NO3-N) losses for developing nitrogen loads reduction strategies in agricultural watersheds. Coupled biogeochemical transformations and hydrological connectivity regulate the spatiotemporal dynamics of water and NO3-N export along surface and subsurface flows. However, modeling performance is usually limited by the oversimplification of natural and human-managed processes and insufficient representation of spatiotemporally varied hydrological and biogeochemical cycles in agricultural watersheds. In this study, we improved a spatially distributed process-based hydro-ecological model (DLEM-catchment) and applied the model to four tile-drained catchments with mixed agricultural management and diverse landscape in Iowa, Midwestern US. The quantitative statistics show that the improved model well reproduced the daily and monthly water discharge, NO3-N concentration and loading measured from 2015 to 2019 in all four catchments. The model estimation shows that subsurface flow (tile flow + lateral flow) dominates the discharge (70–75%) and NO3-N loading (77–82%) over the years. However, the contributions of tile drainage and lateral flow vary remarkably among catchments due to different tile-drained area percentages and the presence of farmed potholes (former depressional wetlands that have been drained for agricultural production). Furthermore, we found that agricultural management (e.g. tillage and fertilizer management) and catchment characteristics (e.g. soil properties, farmed potholes, and tile drainage) play important roles in predicting the spatial distributions of NO3-N leaching and loading. The simulated results reveal that the model improvements in representing water retention capacity (snow processes, soil roughness, and farmed potholes) and tile drainage improved model performance in estimating discharge and NO3-N export at a daily time step, while improvement of agricultural management mainly impacts NO3-N export prediction. This study underlines the necessity of characterizing catchment properties, agricultural management practices, flow-specific NO3-N movement, and spatial heterogeneity of NO3-N fluxes for accurately simulating water quality dynamics and predicting the impacts of agricultural conservation nutrient reduction strategies.

Effectiveness of Saturated Buffers on Water Pollutant Reduction from Agricultural Drainage

Highlights Saturated buffers redistribute tile drainage water below riparian buffers to reduce nitrate-nitrogen loading. NRCS Conservation Practice Standard 604 guides saturated buffer design in the USA. Annual edge-of-field nitrate-nitrogen loss reductions averaged 46 ± 24% and 9.4 ± 5.9 kg N/ha/y. Further research on design, siting, and mechanisms will enhance performance. Abstract. It is a pivotal time in the development of saturated buffers as a conservation drainage practice. Field data have demonstrated that this practice can effectively reduce nitrate loads in subsurface drainage. The compilation and assessment of current knowledge for this relatively new practice is timely to help identify future opportunities. This review summarizes the state of the science for saturated buffers in the US within the context of this special collection’s emphasis on performance and cost. Suggested research areas are identified to improve understanding of saturated buffer function and performance and to refine design processes and criteria to accelerate adoption. As currently designed, saturated buffers removed an average of 46 ± 24% (mean ± sd) of the N load that would have otherwise entered receiving waters (9.4 ± 5.9 kg N removed/ha-y; n = 30 site-years). Cost efficiencies, which generally trended around $3 to $5/kg N removed per year, were considered relatively efficient compared to similar nitrate removal practices (range: $1.20 to $9.20/kg N/y), with planning level costs between $25 and $66/ha treated/y. As adoption is scaled, engineering design costs need to be considered unless the design model can be simplified. Future research should refine design processes, management, and siting criteria to facilitate scaled adoption for water quality goals. Additional studies on nutrient cycling within saturated buffers are needed to fill gaps about nitrogen and phosphorus dynamics and the role of buffer vegetation. Saturated buffers have significant nitrate reduction potential for tile-drained landscapes, but design adaptations may be needed to facilitate adoption in varied landscapes. Keywords: Denitrification, Edge-of-Field, Nitrate, Nonpoint-source pollution, Saturated riparian buffer, Subsurface drainage, Tile drainage, Water quality.

Rapid Response of Runoff Carrying Nitrogen Loss to Extreme Rainfall in Gentle Slope Farmland in the Karst Area of SW China

Nitrogen loss is the main reason for land quality degradation and productivity decline and an important factor in groundwater pollution. Extreme rainfall has occurred frequently in Karst areas of southwest China in recent years. It is of great significance to study the response of soil nitrogen loss to extreme rainfall in Karst areas to prevent and treat land quality degradation and non-point source pollution. In this study, field monitoring and indoor artificial rainfall simulation were used to study the loss characteristics of total soil nitrogen (TN), ammonium (NH4+-N) nitrogen, and nitrate-nitrogen (NO3−-N) in Karst bare slope farmland (slope angles of 5° and 10°) under extreme rainfall conditions. The results showed that: (1) Extreme rainfall (90 mm/h) increased the surface runoff, middle soil runoff, and underground runoff by 1.68 times, 1.16 times, and 1.43 times, respectively, compared with moderate rainfall (60 mm/h), so that nitrogen loss increased with runoff. (2) The loss of nitrate-nitrogen in surface, soil, and underground under extreme rainfall conditions was 223.99, 147.93, and 174.02% higher than that under moderate rainfall conditions, respectively; the nitrate losses were 203.78, 160.18, and 195.39% higher, respectively. Total nitrogen losses were 187.33, 115.45, and 138.68% higher, respectively. (3) The influencing factors of total soil nitrogen and nitrate-nitrogen loss in Karst slope farmland were slope > rainfall duration > rainfall intensity, while the influencing factors of ammonium nitrogen loss were rainfall duration > slope > rainfall intensity. Therefore, in controlling nitrogen loss in Karst slope farmland, changing slope degree and increasing farmland coverage may be useful measures to slow the nitrogen loss caused by extreme rainfall.

Modeling the impact of winter cover crop on tile drainage and nitrate loss using DSSAT model

Increasing demand for food has amplified the use of fertilizer. Intensive agriculture practices in the Upper Mississippi basin have been linked to the formation of a hypoxic zone in the Gulf of Mexico. Previous studies have recommended the use of winter cover crop in the maize-soybean rotation as an eco-efficient solution in reducing the nitrate-nitrogen (NO3-N) loss via a sub-surface drainage system. Therefore, the objective of this study is to evaluate the impact of cereal rye as a winter cover crop in the maize-soybean system on reducing nutrient loss via tile drainage using the DSSAT model. The experiments include four treatments with a combination of two different nitrogen (N) application timing with cover crop (CC) and without cover crop (NCC): fall-applied N without cover crop (FN), spring-applied N without cover crop (SN), fall-applied N with cover crop (FCC), and spring-applied N with cover crop (SCC). The calibrated DSSAT model was utilized to assess the impact of the cover crop by comparing NO3-N losses and cash crop yields between CC and NCC treatments for different N fertilization timings. The model calibrated for cereal rye biomass in the FCC treatment estimated the observed cereal rye growth for SCC treatment considerably well (R2 >0.91). The model successfully predicted the impact of cereal rye on nitrate loss and tile drainage with 43.6% and 45.4% (48.6% and 47.8% observed) nitrate loss reduction and 21.3% and 21.0% (30.2% and 19.4% observed) tile drainage volume reduction in fall and spring N application treatments, respectively. The results from this research suggest that DSSAT can predict the cereal rye growth and assess the soil water-nutrient dynamics in both CC and NCC systems. However, the model was not able to replicate the impact of cereal rye on the cash crop yields due to the higher N mineralization simulated in the CC compared to the NCC treatments. This could be due to the use of glyphosate to terminate the cereal rye and the presence of tillage radish along with the cereal rye. The glyphosate application hastens the decomposition process; however, it also reduces the overall residue. The chemical termination and intercropping feature are not available in the DSSAT model currently. The cereal rye hosted pathogens and pests might also be responsible for lowering maize yield in the observations.

Low irrigation water minimizes the nitrate nitrogen losses without compromising the soil fertility, enzymatic activities and maize growth

Nitrate nitrogen (NO3−_N) leaching increased with nitrogen (N) fertilization under high water supply to the field negatively affected the maize growth and performance. This study aimed to understand the mechanisms of NO3−_N leaching on a biochemical basis and its relationship with plant performance with 5 different doses (0, 200, 250, 300, 350 kg N ha− 1) of N fertilizers under low (60%; LW) and high (80%; HW) water holding capacity. Soil and plant enzymes were observed at different growth stages (V9, R1, R3, and R6) of the maize, whereas the leachates were collected at 10-days intervals from the sowing date. The LW had 10.15% lower NO3−_N leachate than HW, with correspondence increases in grain yield (25.57%), shoot (17.57%) and root (28.67%) dry matter. Irrespective of the irrigation water, RubisCo, glutamine synthase (GS), nitrate reductase (NR), nitrite reductase (NiR), and glutamate synthase (GOGAT) activities increased with increasing N fertilizer up to the V9 growth stage and decreased with approaching the maturity stage (R6) in maize. In HW irrigation, soil total N, GOGAT, soil nitrate (NO3−_N), leached nitrate (LNO3−_N), root N (RN), leaf N (LN) were positively correlated with N factors suggesting the higher losses of N through leaching (11.3%) compared to LW irrigation. However, the malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide (O2−), and proline were negatively correlated with the other enzymatic activities both under LW and HW irrigation. Thus, minimizing the NO3−_N leaching is possibly correlated with the LW and N300 combination without compromising the yield benefit and improving enzyme activities.

Efficacy of earthworm casts on sediment and nitrate loss with runoff in the Chinese Loess Plateau

The erosion of sediment and nutrients under rainfall conditions aggravated the degradation of soil quality in sloping farmland. It is very important to comprehensively control the sediment and nutrient loss of sloping farmland and improve the soil fertility of barren sloping farmland caused by soil erosion to improve the plant growth environment in the Loess Plateau of China. However, there is no research to combine the control of soil, water, and nutrient loss with the improvement of soil fertility. To address this issue, earthworm casts (ECs), an excellent organic soil amendment, was applied to the soil (silty loam). Ten rainfall simulation experiments were conducted in a 1.0 m × 1.0 m plot with two application methods (mixed and layered applications) and five application amounts (i.e., 0, 200, 400, 600, and 800 g/m2), and simulated rainfall for 1 h at a rate of 60 mm/h. The main results indicated that the ECs application significantly delayed the time of runoff initiation, reduced unit discharge and sediment yield rate in the early stage. The nitrate nitrogen concentration in runoff could be significantly reduced with the layered application method. The equivalent model of convection was more suitable for simulating nutrient transfer with runoff, and the effective mixing depth decreased with increased the ECs amounts. The ECs application increased the water content and nitrate nitrogen concentration of the soil profile from a depth of 0–20 cm and provided a suitable environment for vegetation growth. Runoff decreased by 18.16–33.47%, sediment decreased by 28.17–87.24%, and nitrate nitrogen loss in runoff decreased by 36.99–51.76% with the layered application. The layered application of ECs with 800 g/m2 had the significant regulation on runoff, sediment yield, and nitrate nitrogen loss. In conclusion, ECs can effectively improve the water erosion resistance of the soil, and enhance the water holding capacity and fertilizer retention capacity of the soil. The layered application of ECs can effectively control nitrogen loss with runoff. In the long run, ECs can provide sufficient nutrient sources for plant growth, improve regional vegetation carrying capacity, and fundamentally solve the problem of soil and water loss and soil degradation of bare slope farmland in the Loess Plateau of China.

Effect of Thaw Depth on Nitrogen and Phosphorus Loss in Runoff of Loess Slope

Seasonal freeze-thaw erosion is a form of soil erosion caused by the topographical characteristics and climatic factors of the hilly and gully loess regions. Seasonal freeze-thaw can damage the soil pores and cause its bulk density to change. The effects of thawing depth on runoff and Nitrogen and Phosphorus loss on the rainfall erosion of an artificial slope filled with loess soil were analyzed after a rainfall test that simulated the spring thaw period in China. The results showed that: (1) The maximum runoff yield was 33.35 mm at 4 cm thawing depth, and the minimum was 12.95 mm at 6 cm thawing depth. With the increase in runoff time, the slope infiltration rate had a decreasing trend. The loss rate of available and total Phosphorus increased with the increase in runoff rate. The rate of increase was fastest when the thawing depth was 4 cm. (2) The relationships between runoff rate and Nitrogen loss and Phosphorus loss rate can be explained by linear regression equations, and the loss rate increased as the runoff rate rose for all thawing depths. Within the 0–6 cm thawing depths, the loss of total phosphorus was the largest when the thawing depth was 4 cm, and the loss of available phosphorus was the smallest when the thawing depth was 6 cm. At the shallower thawing depths, the available Nitrogen loss represented a smaller proportion of the total Nitrogen loss compared to nitrate Nitrogen loss. However, there was a gradual rise in the available Nitrogen proportion in the total amount of inorganic Nitrogen as the thawing depth increased. (3) Total Phosphorus was the available Phosphorus with a quadratic function relationship with runoff energy and runoff power. Runoff energy mainly affected the total Nitrogen and available Nitrogen loss in runoff, whereas runoff power mainly affected total Nitrogen loss in runoff. The results of this paper can improve the understanding of runoff and Nitrogen and Phosphorus loss caused by runoff during freeze-thaw conditions.

赤红壤植蔗坡地坡面径流及溶解态氮磷流失特征

为探究南方高强度、高频次降雨下赤红壤区坡耕地土壤侵蚀及氮磷养分流失的特征，基于野外径流小区原位观测试验，通过测定自然降雨下赤红壤植蔗坡地坡面径流和溶解态氮磷流失量，探讨自然降雨下甘蔗种植对赤红壤坡面径流及溶解态氮磷流失的影响。结果表明：（1）2019年和2020年，径流量分别为1111.3 m³/hm²和3269.4 m³/hm²，硝态氮（NO₃^--N）流失量分别为1.39 kg/hm²和15.60 kg/hm²，铵态氮（NH₄⁺-N）流失量分别为0.37 kg/hm²和1.02 kg/hm²，可溶性磷流失量分别为0.20 kg/hm²和0.27 kg/hm²。2019年和2020年植蔗坡地径流及溶解态氮磷流失量均集中在6月份，占流失总量的45%以上，硝态氮（NO₃^--N）是径流氮素流失的主要形式，占79%以上。此外，2019年和2020年5月至8月，侵蚀性降雨场次分别为18次和23次，侵蚀性降雨量分别为407.8 mm和668.0 mm。（2）不同侵蚀性降雨条件下，植蔗坡地溶解态氮磷流失量及其浓度波动较大，甘蔗生长前期（5-6月）溶解态氮磷流失量及其浓度呈上升趋势，而生长后期（7-8月）则呈波动下降趋势。2019年和2020年观测期侵蚀性降雨的年内分布存在明显差异，均集中在6月份，占35%以上。（3）坡面径流量与降雨量和最大30 min降雨强度呈极显著的正相关关系，同时坡面径流量与径流中硝态氮、铵态氮及可溶性磷流失量均呈极显著正相关关系。研究结果有助于明晰南方赤红壤区蔗区坡面土壤侵蚀及养分流失特征。;The characteristics of soil loss and nutrient loss in sloping land are quitely different among different areas of China, and crop patterns also have significant impacts on these indicators. The objectives of this study were as follows:1) to explore the characteristics of soil erosion and nutrient loss in sloping land with planting sugarcane of lateritic soil; and 2) to analyze the impacts of sugarcane growing stage and natural rainfall characteristics on soil erosion and nitrogen and phosphorus loss characteristics. This research based on the in-situ observation test of runoff plot and measured the loss of runoff, dissolved nitrogen, and phosphorus in sloping land with planting sugarcane. The amounts and concentrations of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP) under individual natural rainfall during May to August in 2019 and 2020 were observed. The results showed that:(1) in 2019 and 2020, the runoffs, nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP) loss were 1111.3 m³/hm² and 3269.4 m³/hm², 1.39 kg/hm² and 15.60 kg/hm², 0.37 kg/hm² and 1.02 kg/hm², 0.20 kg/hm² and 0.27 kg/hm², respectively. The runoff and its dissolved nitrogen and phosphorus loss in sloping land with planting sugarcane under 2019 and 2020 were both concentrated in June, which accounted for more than 45%, and NO₃^--N was the main form of nitrogen loss in runoff, which accounted for more than 79% of total nitrogen loss. Besides, the times of individual erosive rainfall were 18 and 23, and the erosive rainfall amounts were 407.8 and 668.0 mm from May to August in 2019 and 2020, respectively. (2) The amounts of dissolved nitrogen and phosphorus loss and their concentrations in sloping land with planting sugarcane showed great fluctuation under different erosive rainfalls and stages of sugarcane growth. There were obvious differences in the annual distribution of erosive rainfall between observation period of 2019 and 2020, which were both concentrated in June, which accounted for more than 35% of total rainfall. In the early stage of sugarcane growth (from May to June), the losses of dissolved nitrogen and phosphorus and their concentrations showed an upward trend, while in the late stage of sugarcane growth (from July to August), they showed a fluctuating downward trend. (3) There was a significantly positive correlation between runoff and rainfall and maximum 30 min rainfall intensity, meanwhile, there was a significantly positive correlation between runoff and the loss of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP). The results can provide a theoretical basis for clarifying the soil erosion characteristics of sloping land with planting sugarcane in the lateritic soil region of southern China.

Rate and Timing of Meat and Bone Meal Applications Influence Growth, Yield, and Soil Water Nitrate Concentrations in Sweet Corn Production

Using local resources and minimizing environmental impacts are two important components of sustainable agriculture. Meat and bone meal (MBM), tankage, is a locally produced organic fertilizer. This study was conducted to investigate the response of sweet corn (Zea mays L. var. saccharata Stuart.) and soil water nitrate (NO3-N) concentration to MBM application at two locations, Waimānalo and Poamoho, on the island of O’ahu. The objectives were to determine effects of six application rates (0, 112, 224, 336, 448 and 672 kg N ha−1) and two application timings (preplant and split application) on: (1) sweet corn growth, yield, and quality, and (2) soil water nitrate concentration within and below the root zone. The split-plot was designed as four replicates randomly arranged in a complete block. Plant growth of roots and shoots, yield, and relative leaf chlorophyll content of sweet corn increased with increasing application rates of MBM in both locations. At Poamoho, yield was 13.6% greater in preplant versus split application. Nitrate-nitrogen losses were reduced by 20% at Waimānalo and 40% at Poamoho when MBM was applied in split applications. These findings suggest that MBM is an effective nitrogen source for sweet corn and a split application of MBM may reduce the potential for pollution.

SPECIAL ASPECTS OF MIGRATION OF WATER-SOLUBLE ORGANIC SUBSTANCE AND BIOGENIC ELEMENTS IN SOD-PODZOLIC SOIL DEPENDING ON FERTILIZATION SYSTEM AND MICROBIAL PREPARATIONS

Objective. To study special aspects of vertical migration of products of biological transformation of organic matter and biogenic elements in sod-podzolic soil under different modes of root nutrition of plants. Methods. Lysimetric experiment, agrochemical, mathematical and statistical. Results. Based on studies conducted in a long-term lysimetric experiment on sod-podzolic soil, periodically washed type of water regime was established, as a result of which 37 mm of moisture, 23 kg/ha of water-soluble humic substances, nitrogen (NO3–) 55 kg/ha, calcium oxide 91 kg/ha and magnesium oxide 26 kg/ha magnesium oxide is lost at the background without inoculation per crop rotation when using mineral fertilization system. The use of microbial preparations reduces the loss of these elements to 33 mm, 20 kg/ha, 52 kg/ha, 83 kg/ha and 25 kg/ha, respectively. It was established that the average infiltration of moisture from the layer 0–155 cm under crops of continuous sowing was 25–37 mm at the background without the use of microbial preparations and 22–33 mm at the background of inoculation. The mineral fertilizer system increased the losses of the soil solution by 9 mm and 7 mm versus the control variants, respective to the backgrounds. The lowest losses of productive moisture were reported in the variants where sidereal fertilizers were used. When replacing the mineral fertilization system with sidereal-mineral and organo-mineral fertilizers without compromising the yield of crop rotations, it is possible to reduce the loss of productive moisture by 1.5 times, reduce the loss of labile soil organic matter by 1.7–1.8 times, nitrate nitrogen by 8–10 %, calcium by 18–24 % and magnesium by 40–50 %. Due to the use of biopreparations, there is a reduction in losses of nitrate nitrogen by 5–18 %, magnesium — by 5–14 %, calcium — by 6–16 %. Conclusion. To reduce non-productive losses of moisture, water-soluble organic matter and biogenic element compounds, it is advisable to use green mass of green manures and microbial preparations at the background of the mineral system and fertilizer system NPK+manure. The use of microbial preparations helps to reduce the loss of nitrate nitrogen by 5–18 %, magnesium — by 5–14 %, calcium — by 6–16 %.

Effectiveness of Nutrient Management on Water Quality Improvement: A Synthesis on Nitrate-Nitrogen Loss from Subsurface Drainage.

Nutrient management, as described in NRCS Code 590, has been intensively investigated, with research largely focused on crop yields and water quality. Yet, due to complex processes and mechanisms in nutrient cycling (especially the nitrogen (N) cycle), there are many challenges in evaluating the effectiveness of nutrient management practices across site conditions. We therefore synthesized data from peer-reviewed publications on subsurface-drained agricultural fields in the Midwest U.S. with corn yield and drainage nitrate-N (NO3-N) export data published from 1980 to 2019. Through literature screening and data extraction from 43 publications, we obtained 577 site-years of data with detailed information on fertilization, corn yields, precipitation, drainage volume, and drainage NO3-N load/concentration or both. In addition, we estimated flow-weighted NO3-N concentrations ([NO3-N]) in drainage for those site-years where only load and volume were reported. Furthermore, we conducted a cost analysis using synthesized and surveyed corn yield data to evaluate the cost-effectiveness of different nutrient management plans. Results from the synthesis showed that N fertilizer rate was strongly positively correlated with corn yields, NO3-N loads, and flow-weighted [NO3-N]. Reducing N fertilizer rates can effectively mitigate NO3-N losses from agricultural fields; however, our cost analysis showed negative economic returns for continuous corn production at lower N rates. In addition, organic fertilizers significantly boosted corn yields and NO3-N losses compared to inorganic fertilizers at comparable rates; however, accurate quantification of plant-available N in organic fertilizers is necessary to guide appropriate nutrient management plans because the nutrient content may be highly variable. In terms of fertilizer application methods, we did not find significant differences in NO3-N export in drainage discharge. Lastly, impact of fertilization timing on NO3-N export varied depending on other factors such as fertilizer rate, source, and weather. According to these results, we suggest that further efforts are still required to produce effective local nutrient management plans. Furthermore, government agencies such as USDA-NRCS need to work with other agencies such as USEPA to address the potential economic losses due to implementation of lower fertilizer rates for water quality improvement.

The effect of the trench layout on the loss of nitrogen production and flow from the rainfall of oblique farmland

The oblique farmland in the northern part of China is often affected by rainfall, which arises out of the loss of a large amount of nitrogen, which causes the reduction of crop yield and the nutrient-rich pollution of river basins. Evaluating the impact of the trench farming layout on the loss of nitrogen production and flow of rainfall in sloping farmland can provide a scientific basis for the prediction and effective prevention and control of nitrogen loss in sloping farmland. Taking the oblique farmland of corn as the research object, nitrogen loss of distinctive ridges and the pitch of the ditches under natural rainfall conditions were continually observed by using the field prototype field observation test. According to the local farming tradition, three kinds of ridge and furrow trends should be set up, including horizontal ridge, vertical ridge and oblique ridge. The ridge and furrow spacing of the three tillage methods should be set at three levels, 40cm, 60cm and 80cm in turn. In addition, establish a field without ridge flat for blank control. Using the method of frequency statistics, it is calculated that the trench layout with the smallest nitrogen loss in each rainfall production stream is frequency in the annual rainfall production flow, and the trench layout with the smallest nitrogen loss is found from the overall trench layout and the same trench to different ridge spacing, and the same trench spacing to the three aspects of the trench layout. The results show that the optimal ridge and furrow layout with the minimum loss of nitrate nitrogen, ammonium nitrogen and total nitrogen is 60 cm ditch spacing in a horizontal ridge direction.

Evaluation of nitrogen loss reduction strategies using DRAINMOD-DSSAT in east-central Illinois

Agricultural system modeling has become an effective tool for analyzing and quantifying the effects of varying management practices and environmental conditions on crop production and nutrient export from croplands. The use of such modeling tools provides useful insights in identifying the most effective management practices for enhancing productivity, sustainability, and resiliency of agricultural systems. This study focuses on testing and application of an integrated field-scale process-based model, DRAINMOD-DSSAT, for simulating hydrology, nitrate-nitrogen (NO3-N) loss, and crop growth and yield responses in artificially drained croplands. The tested model was used to evaluate the effects of different N fertilizer application rates and timings in both conventional and controlled drainage conditions on crop yield and NO3-N losses in a poorly drained Drummer-Flanagan soil in east-central Illinois. The model was calibrated and validated for a corn [Zea Mays L.] – soybean [Glycine Max (L.)] rotation using 7 years (1992–1998) of field-measured tile drainage, crop yield, and NO3-N data. The graphical and statistical evaluations indicated very good model performance. Specifically, monthly tile drainage flow was predicted with modeling efficiency (NSE), index of agreement (d), and mean absolute error (MAE) of 0.85, 0.96, and 0.69 cm, respectively. Monthly NO3-N losses were predicted with NSE, d, and MAE of 0.82, 0.95, and 1.16 kg N ha−1, respectively. Corn and soybean yields were predicted with an absolute percent error (PE) of 1.84 and 12.07, respectively. The long-term model simulation results indicated that split N application of 50 % during spring-pre plant (S) and 50 % during side-dressing (SD) could increase crop yield and reduce N leaching losses compared to other tested N application methods: spring (S) only, fall-spring split (F-S), and fall-spring-side-dressing (F-S-SD). Further, applying 10 % and 20 % reduced N rates (194 kg N ha−1 and 174 kg N ha−1, respectively) in combination with S-SD split application in controlled drainage (CD) condition could reduce N leaching losses by 30 % and 33 %, respectively compared to the conventional application method. This study explored the effects of N fertilizer management on crop yield and nitrogen losses under two drainage conditions, and underscored the importance of N fertilizer application rates and timings for achieving yield goals while minimizing nitrogen export from drained agricultural fields. The results of the model simulations will be useful for stakeholders and policy makers while making decisions regarding promotion and adoption of best management practices for drained agricultural landscapes.

The effects of biodegradable and plastic film mulching on nitrogen uptake, distribution, and leaching in a drip-irrigated sandy field

Drip irrigation under plastic film mulching with applications of the N-fertilizer is an excellent agricultural strategy, resulting in saving irrigation water, improving N use efficiency, and increasing crop yield. However, the film residue and nitrate-nitrogen (NO3-N) losses are the leading cause of non-point pollution in agricultural fields. To promote the development of sustainable agriculture, the HYDRUS (2D/3D) model was first calibrated and then validated using experimental data from 2016 and 2017, respectively, collected in the drip-irrigated sandy field with plastic film mulching (PFM), biodegradable film mulching (BFM), and no film mulching (NFM). Additionally, the NO3-N spatial and temporal distributions, uptake, leaching, and use efficiency (NUE) under PFM, BFM, and NFM with 280 kg ha−1 of the N-fertilizer (the local recommendation) were evaluated using both observed and simulated data. These factors were also assessed under BFM with 210 (75 % of the recommended value) and 140 kg ha-1 (50 % of the recommended value) of the N-fertilizer. The results of numerical simulations were in good agreement with observations, with the RMSE, R2, and NSE during verification being 0.01-0.08 mg cm-3, 0.62-0.87, and 0.68-0.94, respectively. When the same amount of the N-fertilizer (280 kg ha−1) was applied in each treatment, there were no apparent differences in NO3-N concentrations in the soil profile, cumulative NO3-N uptake by corn (CNU), and cumulative NO3-N leaching (CNL) in the 100-cm soil depth between the BFM280 and PFM280 scenarios (the subscript indicates the amount of the N-fertilizer) during the early growing season (Day After Sowing [DAS] of 0–78 in 2016 and DAS of 0–92 in 2017). However, CNU and CNL were higher, and the NO3-N concentrations in the upper soil layer (0−40 cm soil layer) lower in these two scenarios than in the NFM280 scenario. The NO3-N concentrations in the topsoil layer (the 0−20 cm soil layer) in the BFM280 scenario were 3.9 % higher than in the PFM280 scenario during DAS 93–154 in 2017 due to the disintegration of the biodegradable film and 26.3 % lower during DAS 79–155 in 2016 because of intensive rainfall. Additionally, the highest NUE (50.9 kg kg-1, the average value for two years) was found when 75 % of the recommended N-fertilizer (210 kg ha−1) was applied. Therefore, an application of 210 kg ha−1 of the N-fertilizer in the BFM scenario can be recommended for sandy farmland to avoid plastic pollution, increase NUE, and effectively promote the development of sustainable agriculture.