Soil NO3-N Research Articles

Assessing Nitrogen Fertilization Strategies in Winter Wheat and Cotton Crops in Northern Greece

The management of fertilizer application is crucial for agricultural production and environmental safety. The objective of this study was to assess the efficiency of different fertilization strategies, applying fertilizers with and without nitrification inhibitors (NIs) in split application, in Greece. The assessment criteria used were based on crop yield, soil nitrogen (N) concentrations and economic efficiency. For this purpose two crops (winter wheat and cotton) were selected in order to explore the optimum fertilization strategy for each crop. Three treatments combining fertilizers with NIs were tested compared with conventional fertilization (CF). Slight differences in the quantity and the combination of fertilizers with NIs applied resulted in variable effects on crop yield, soil N and economic return. Split N application of 102 kg ha−1, with half of the total amount applied at seeding, resulted in higher grain yield of winter wheat, lower NO3-N in soil and higher economic return. This result reveals the importance of N application at seeding in wheat crop. Fertilization strategy with 109.5 kg N ha−1 and split P application resulted in higher cotton yield and higher economic profit. Split P application seemed to increase yield, even though it is not a common practise in the area.

Excessive Fertilization is Detrimental to Yield and Quality for Onion Grown on High Organic Matter Content Paddy Soils

Excess chemical fertilizer applications in historical onion (Allium cepa L.) cultivation areas in Korea may be detrimental to onion yield and quality. A field study was performed to evaluate the effects of chemical fertilizer rates and split applications on intermediate-day onion growth, yield, storage quality, and soil chemical properties in plants established in a paddy soil with high organic matter (OM) content. Rates of chemical fertilization, based on a soil test recommendation (192–13–213 kg·ha−1 N–P–K), and twice the recommended rate were applied and compared to a control treatment not receiving fertilizer. Treatments with twice the recommended rate were applied in three, four, or five splits. Preplant soil contained 46.3 g·kg−1 OM, 728 mg·kg−1 available phosphorus, and 17.3 mg·kg−1 nitrate nitrogen. The highest marketable yield, 58.1 Mt·ha−1, was achieved at the recommended rate, 7.3%–20.0% more than the double rates and the control. Increased fertilizer beyond the recommended rates and delayed split application times had no positive effect on onion growth or yield but increased culls and accumulated soil electric conductivity, OM, exchangeable K, and NO3-N content in soil at harvest. Soil NO3-N contents ranged from 110 to 316 mg·kg−1 for split applications at the double rates. The control yielded 40.8 Mt·ha−1, which was 70.2% of the highest yield. Storage quality was not affected due to treatment, although there were slight increases in bulb rot and physiological disorders at the double rate. Fertilizer applied at higher than the recommended rate for onion is not beneficial.

Simulation of nitrogen fate for greenhouse cucumber grown under different water and fertilizer management using the EU-Rotate_N model

The objectives of this study were to compare nitrate leaching for greenhouse vegetable grown under different water and fertilizer management, and to provide the best management practices (BMPs). A greenhouse cucumber experiment with different water and nitrogen management was conducted in Shouguang County of North China from 2009 to 2010. Seven different irrigation and fertilizer treatments were designed, including five treatments with furrow irrigation: no fertilizer (CK), organic manure (OM), conventional fertilizer (farmer's practice, FP), optimal fertilizer application (OPT), crop residues+farmer practice (CN), and two with drip irrigation: conventional fertilizer (RI) and crop residues+optimal fertilizer (OPTRI). The EU-Rotate_N model was used to simulate the greenhouse cucumber growth, water movement and N fate. Results indicated that the simulated values of cucumber dry weight, N uptake, soil water content and NO3-N concentration in the soil profile all agreed well with the observed values. Also, it was revealed that the irrigation method, amounts of fertilizer input and crop residues had significant effects on nitrate leaching and nitrogen use efficiency (NUE). Compared with that under the FP treatment, the amounts of nitrate leaching under the CN and RI treatments were decreased by 26–32% and 75–80%, respectively, whilst the amount of nitrate leaching under the OPT treatment could be reduced 32–36%. Nitrate leaching under the OPTRI treatment was the least, and the reduction was 79–86%. On the other hand, NUE was increased by 2–3%, 15–18% and 40–43% under the OPT, CN and RI treatments, respectively. The largest NUE occurred under the OPTRI treatment, about 314.5–337.4kgkg−1. It is concluded that the optimal fertilizer N, drip irrigation and straw incorporation are the effective measures for reducing N leaching and improving NUE. Amongst all the treatments, the OPTRI treatment yielded the lowest N leaching at the expense of a slight decrease in yield of greenhouse cucumber. Therefore, the OPTRI treatment should be recommended to farmers in order to reduce the risk of groundwater pollution and to develop sustainable vegetable production in the area.

Effect of legume or grass cover crops and nitrogen application rate on soil properties and corn productivity

Winter Cover Crops (WCC) into continuous agriculture in Uruguay could improve water erosion control, soil organic carbon, and crop productivity. On the other hand, could reduced soil water and nutrients interfering with cash crops. We conducted a four years field study on a clay loam (Typic Argiudol) in Uruguay to evaluate the effects of WCC on soil chemical properties, water content, soil N-nitrate with nitrogen variable rate at V6 on corn productivity. The six treatments consisted of Common Oat (Avena sativa L.), Annual Ryegrass (Lolium mutiflorum L.), Triticale (× Triticosecale wittmack), Egyptian clover (Trifolium alexandrinum L.), Pea (Pisum sativum L.), and no WCC. The highest corn yields were observed with no WCC (6.47 Mg ha-1), followed by legumes WCC (5.97 Mg ha-1) and grasses WCC (4.52 Mg ha-1). These differences were probably due to more soil water content at corn planting (35%) and soil NO3-N at corn planting and V6 (44 and 36%, respectively) in no WCC than overall WCC. The N yield response in V6 corn was highest in grass WCC (31%), followed by legume WCC (23%) and no WCC (7%). No soil organic carbon different were detected among treatments after four years with low risk of soil erosion. This result could be explained by similar carbon inputs (shoot and roots residue adding corn + cover crops) since the beginning of the experiment (averaged over treatments: 46.5 Mg ha-1). Farmers, who adopt use of WCC, could take disadvantage on low corn yield, therefore could increase cost by adding more N in corn.

Field and Laboratory Evaluation of the Cardy Nitrate-Nitrogen Meter for Measuring Soil Solution Nitrate Nitrogen in Hawaiian Soils

The estimation of plant-available nitrate nitrogen (NO3-N) is essential for any nutrient-management plan but can be time-consuming and expensive. However, the efficacy of rapid methods to determine soil NO3-N levels designed for grower use has received mixed reviews in the literature. Therefore, the objectives of this study were to (1) evaluate the Cardy electrode-based meter for measuring soil solution NO3-N concentrations under a perennial peanut living mulch in two mixed orchard systems on O'ahu and (2) determine the influence of soil type on measurement accuracy and precision under laboratory conditions. To achieve the first objective, 24 lysimeters were installed 15–30 cm deep at each of two fruit tree orchards with different soils and climate on Oahu island. For the second objective, a replicated column study was conducted, in which NO3-N solutions of varied concentrations were leached through three representative agricultural soils (Wahiawa, Loleka'a, and Waialua series). Field soil solution and column leachate were analyzed using the portable electrode-based meter and a standard laboratory colorimetric method. In the field samples, soil solution NO3-N ranged from <1 to 110 mg/L, and there was a strong correlation (r2 = 0.92) between the portable meter and colorimetric values. Similarly, a strong correlation between the Cardy meter and the laboratory methods was observed in the column study, although r 2 values varied with soil type. The data suggest that the Cardy meter can be used to rapidly and accurately measure soil solution NO3-N, if its concentrations are relatively high and concentrations of interfering ions such as chloride (Cl−) are low. Overall, the primary value of this rapid method may be in estimating relative changes in soil nitrate in response to nutrient management at a single site.

Cover crops and tillage influence soil organic matter and nitrogen availability in a semi-arid vineyard

Little attention has been given to the utilization of permanent cover crops in vineyard agroecosystems in semi-arid Mediterranean climatic conditions to increase soil organic carbon or its effects on N availability. We evaluated the effect of permanent cover crops with resident vegetation on labile organic matter fractions and inorganic N availability with respect to conventional tillage in a semi-arid vineyard. The field experiment was conducted on Typic Haploxerept soil, located in La Rioja area (Central River Ebro Valley). Soil samples were collected during June 2009, 5 years after covers crops were established. Soil organic carbon (SOC), water-soluble carbon (WSC), potentially mineralizable nitrogen (PMN), nitrate (N-NO3 −) and ammonium (N-NH4 +) were measured. At soil depths of 0–2.5 and 2.5–5 cm the cover crops increased SOC, WSC and PMN. So the results indicated a soil quality improvement. The cover crop treatment reduced soil N-NO3 − and increased the WSC to inorganic N ratio at 0–45 cm depth. PMN and WSC increments suggest a more active microbial biomass that could promote the immobilization and recycling of N-NO3 −, and therefore might partially explain the reduction in N-NO3 − pools under cover crops.

Content of soil mineral nitrogen as influenced by sample extraction and preservation

为探明影响土壤矿质氮测定的因素, 从棕壤、潮土和黄棕壤3种类型土壤中各采集10个经不同施肥处理的土样, 用连续流动注射分析仪测定经不同浸提剂以及不同保存方法处理后土样的NO₃-N和NH₄-N含量。结果表明: 不论是棕壤、潮土还是黄棕壤, 2 mol·L^-1 KCl提取硝态氮的数量与0.01 mol·L^-1 CaCl2提取的数量相关性均达到<i>P</i><0.01水平; 3种土壤各个土样硝态氮含量的测定值多表现为新鲜土<冷冻土<风干土; 将鲜样浸提后作短时间的冷冻处理, 其效果与鲜样24 h内的测定结果较接近; 土样不同保存方式以及浸提液的保存时间对3种土壤NH₄-N测定结果的影响规律不及NO₃-N明显。

Relationship between soil nitrate accumulation and in-season corn N nutrition indicators

Ziadi, N., Bélanger, G. and Claessens, A. 2012. Relationship between soil nitrate accumulation and in-season corn N nutrition indicators. Can. J. Plant Sci. 92: 331–339. Nitrogen management tools are required to optimize crop growth and yield while minimizing the likelihood of N losses to the environment. We previously determined that non-limiting N conditions for near maximum corn (Zea mays L.) grain yield are reached with the following threshold values for three in-season plant-based indicators of corn N nutrition determined at approximately the V12 stage of development: N nutrition index (NNI) = 0.88, leaf N (NL) concentration = 32.7 mg N g−1 leaf DM, and relative chlorophyll meter (RCM) values = 0.95. Our objective was to study the relationship between these plant-based indicators and soil NO3-N content in an effort to develop tools to reduce the likelihood of soil NO3-N accumulation without affecting grain yield. This study at 5 site-years in Québec consisted of six N fertilizer rates (20–250 kg N ha−1). The NNI, NL concentrations, RCM values, and soil (0–0.15 m) NO3-N content were measured weekly from July to early August, while soil NO3-N content to a 0.90-m depth was measured in late August and October. During the growing season from July to early August, the proportion of data points above the average soil NO3-N content was greater under non-limiting N conditions (NNI ≥ 0.88, NL concentrations ≥ 32.7 mg N g−1 leaf DM, or RCM values ≥ 0.95) than under limiting N conditions. Furthermore, the mean soil NO3-N content of the data points above the general average was much higher under non limiting than limiting N conditions in late August (167 vs. 78 kg NO3-N ha−1 for NNI and RCM; 166 vs. 112 kg NO3-N ha−1 for NL concentration) and October (68 vs. 49 kg NO3-N ha−1). High soil NO3-N accumulation during the season and at harvest occurs only when in-season plant-based N indicators are greater than their threshold values.

Relationship between soil nitrate accumulation and in-season corn N nutrition indicators

Ziadi, N., Belanger, G. and Claessens, A. 2012. Relationship between soil nitrate accumulation and in-season corn N nutrition indicators. Can. J. Plant Sci. 92: 331-339. Nitrogen management tools are required to optimize crop growth and yield while minimizing the likelihood of N losses to the environment. We previously determined that non-limiting N conditions for near maximum corn (Zea mays L.) grain yield are reached with the following threshold values for three in-season plant-based indicators of corn N nutrition determined at approximately the V12 stage of development: N nutrition index (NNI)=0.88, leaf N (NL) concentration =32.7 mg N g-1 leaf DM, and relative chlorophyll meter (RCM) values =0.95. Our objective was to study the relationship between these plant-based indicators and soil NO3-N content in an effort to develop tools to reduce the likelihood of soil NO3-N accumulation without affecting grain yield. This study at 5 site-years in Quebec consisted of six N fertilizer rates (20-250 kg N ha-1)....

Nitrogen and Phosphorus Leaching as Affected by Gypsum Amendment and Exchangeable Calcium and Magnesium

The loss of N and P by leaching is an important issue, especially on agricultural fields with subsurface tile drainage. The objective of this study was to evaluate how gypsum amendment and soil exchangeable Ca2+ and Mg2+ could affect the movement of P, NH4-N, and NO3-N in infiltrated water and soil. A column experiment was performed using a Miami silt loam soil, and the treatments were (i) control, (ii) gypsum applied at the surface, (iii) gypsum mixed into the 2.5-cm depth, and (iv) alteration of five different target exchangeable Ca/Mg ratios. A clear Plexiglas cylinder was filled with a 15-cm layer of soil; N, P, and K were applied in solution at the surface after the soil had been wetted and drained. Deionized water at a flow of 0.5 mL min(-1) was applied and eight leachate fractions, totaling about five pore volumes, were collected. Gypsum (5000 kg ha(-1)) applied at the surface and mixed into the 2.5-cm depth significantly decreased P and increased NH4-N concentration but had no significant effect on NO3-N leaching. Exchangeable Ca/Mg ratio treatments did not affect soluble nutrient losses; however, leaching of particulate P was significantly less in the Ca-treated soil than the Mg-treated soil. The overall practical conclusion of this study is that to control P transport, it is necessary to add gypsum even with a high soil exchangeable Ca/Mg ratio. The application of gypsum to the soil could be recommended as a best management practice to avoid water pollution by P; on the other hand, this could cause environmental problems by increasing the NH4 soil mobility.

Corn (Zea mays L.) Grain and Stover Yield as Affected by Soil Residual Mineral Nitrogen

Evaluation of nitrogen (N) dynamic in soil using regression equations is important for proper determination of N fertilization. A 3-year field experiment was conducted to (1) develop the best-fitted regression model relating corn grain and stover yield to soil residual ammonium (NH4)-N and nitrate (NO3)-N for corn yield prediction and (2) evaluate how such a model can be beneficial to the health of ecosystem by predicting the appropriate rates of N fertilization for corn production. Soil NH4-N and NO3-N were determined at corn harvest at the depths of 0–30 and 30–60 cm. Nitrogen fertilizer rates and soil mineral N accounted for a maximum of 93% variation in corn grain yield. Soil mineral N enhanced corn yield more than N fertilizer. Totals of 63.1 and 14.1 kg/ha of soil residual NO3-N and NH4-N were found in the 0- to 60-cm depth, indicating the importance of performing soil N tests.

Urea fertilizer forms affect grain corn yield and nitrogen use efficiency

Gagnon, B., Ziadi, N. and Grant, C. 2012. Urea fertilizer forms affect grain corn yield and nitrogen use efficiency. Can. J. Soil Sci. 92: 341–351. Controlled-release urea may be a good management strategy to increase the efficiency of N fertilizers. In a 3-yr study (2008–2010) conducted on a clay soil near Quebec City, Canada, we compared the effect of polymer-coated urea (PCU), nitrification inhibitor urea (NIU), dry urea and urea ammonium nitrate 32% (UAN) on corn yield, plant N accumulation and soil NO3-N remaining at harvest. Corn was fertilized with urea and PCU at 50, 100 and 150 kg N ha−1 in addition to an unfertilized control (0 N), and NIU and UAN at 150 kg N ha−1. Urea, PCU, and NIU were pre-plant broadcast whereas UAN was side-banded at the six-leaf stage of corn. Response to N fertilization occurred in all years, but the magnitude of the response varied with years. In wet years (2008 and 2009), PCU and NIU resulted in higher grain yield than urea, but the increase was greater for PCU (+0.8 to 1.6 Mg ha−1) than for NIU (+0.3 to 0.6 Mg ha−1). In a dry year (2010), no significant difference was found between urea, PCU and NIU. Yields and apparent N recovery were comparable for PCU and UAN except in the dry year, when plant N accumulation was much higher for the UAN treatment. At harvest, soil NO3-N was increased by PCU in all years. Economic analysis revealed that despite 30% higher cost, PCU gave comparable net returns at equivalent N rate than UAN in wet years. We conclude that controlled-release urea, particularly PCU, would be an additional option to farmers instead of sidedressed UAN application for fertilizing corn grown in eastern Canada.

Land-Use Effect on Selected Soil Quality Parameters

Land use is a key factor that affects soil quality. The purpose of the present study was to investigate changes of selected soil chemical properties related to soil function under different land uses. Five experimental sites arranged in a complete randomized blocks located within the Kalloni watershed (Lesvos Island, Greece) corresponding to different land uses (Pinus brutia forest, brushwood pasture, rain-fed olive grove, wheat, and maize) were compared for soil pH, electrical conductivity (EC), total nitrogen (N), nitrate N (NO3-N), Olsen phosphorus (P), and organic matter. Soil nitrate and P concentration were in the order corn > wheat > olive > pasture > forest. Soil EC and NO3-N showed significant within-year variability only in the corn and wheat systems. Corn and wheat had the lowest soil organic-matter content followed the order forest > pasture > olive grove = wheat = corn. However, total N did not significantly differ among land uses.

Urea fertilizer forms affect grain corn yield and nitrogen use efficiency

Gagnon, B., Ziadi, N. and Grant, C. 2012. Urea fertilizer forms affect grain corn yield and nitrogen use efficiency. Can. J. Soil Sci. 92: 341-351. Controlled-release urea may be a good management strategy to increase the efficiency of N fertilizers. In a 3-yr study (2008-2010) conducted on a clay soil near Quebec City, Canada, we compared the effect of polymer-coated urea (PCU), nitrification inhibitor urea (NIU), dry urea and urea ammonium nitrate 32% (UAN) on corn yield, plant N accumulation and soil NO3-N remaining at harvest. Corn was fertilized with urea and PCU at 50, 100 and 150 kg N ha-1 in addition to an unfertilized control (0 N), and NIU and UAN at 150 kg N ha-1. Urea, PCU, and NIU were pre-plant broadcast whereas UAN was side-banded at the six-leaf stage of corn. Response to N fertilization occurred in all years, but the magnitude of the response varied with years. In wet years (2008 and 2009), PCU and NIU resulted in higher grain yield than urea, but the increase was greater for PCU (+0.8 to...

Effect of legume or grass cover crops and nitrogen application rate on soil properties and corn productivity

Winter Cover Crops (WCC) into continuous agriculture in Uruguay could improve water erosion control, soil organic carbon, and crop productivity. On the other hand, could reduced soil water and nutrients interfering with cash crops. We conducted a four years field study on a clay loam (Typic Argiudol) in Uruguay to evaluate the effects of WCC on soil chemical properties, water content, soil N-nitrate with nitrogen variable rate at V6 on corn productivity. The six treatments consisted of Common Oat (Avena sativa L.), Annual Ryegrass (Lolium mutiflorum L.), Triticale (× Triticosecale wittmack), Egyptian clover (Trifolium alexandrinum L.), Pea (Pisum sativum L.), and no WCC. The highest corn yields were observed with no WCC (6.47 Mg ha-1), followed by legumes WCC (5.97 Mg ha-1) and grasses WCC (4.52 Mg ha-1). These differences were probably due to more soil water content at corn planting (35%) and soil NO3-N at corn planting and V6 (44 and 36%, respectively) in no WCC than overall WCC. The N yield response in V6 corn was highest in grass WCC (31%), followed by legume WCC (23%) and no WCC (7%). No soil organic carbon different were detected among treatments after four years with low risk of soil erosion. This result could be explained by similar carbon inputs (shoot and roots residue adding corn + cover crops) since the beginning of the experiment (averaged over treatments: 46.5 Mg ha-1). Farmers, who adopt use of WCC, could take disadvantage on low corn yield, therefore could increase cost by adding more N in corn.

Evolution of Soil Biochemical Parameters in Rainfed Crops: Effect of Organic and Mineral Fertilization

In organic farming, crop fertilization is largely based on the decomposition of organic matter and biological fixation of nutrients. It is therefore necessary to develop studies conducted to know and understand the soil biological processes for the natural nutrient supplies. The effect of three fertilizer managements (chemical with synthetic fertilizers, organic with 2500 kg compost ha−1, and no fertilizer) in a rainfed crop rotation (durum wheat-fallow-barley-vetch as green manure) on different soil biochemical parameters in semi-arid conditions was investigated. Soil organic matter, microbial biomass carbon, organic matter mineralization, CO2production-to-ATP ratio, and NO3-N content were analysed. Fertilization was only applied to cereals. The results showed the scarce effect of the organic fertilization on soil quality, which resulted more dependent on weather conditions. Only soil organic matter and NO3-N were affected by fertilization (significantly higher in the inorganic treatment, 1.28 g 100 g−1and 17.3 ppm, resp.). Soil organic matter was maintained throughout the study period by the inclusion of a legume in the cropping system and the burying of crop residues. In fallow, soil microbial biomass carbon increased considerably (816 ng g−1), and NO3-N at the end of this period was around 35 ppm, equivalent to 100 kg N ha−1.

Relationship between Soil Temperature and N Release in Organic and Conventionally Managed Vineyards

Soil temperature is a very easily measured parameter that influences nutrient availability in vineyards. We monitored soil temperature and plant-available nitrogen (N) in a study evaluating the potential of legumes as an interrow cover crop to supply N to Concord grape (Vitis labruscana Baily). Nitrogen sources used were hairy vetch (Vicia villosa subsp. villosa L.) and yellow sweet clover [Melilotus officinalis (L.) Lam] as green manure sources and either blood meal (in a certified organic vineyard) or urea (in a conventional vineyard) as soluble sources. Plant-available N was measured both continuously using ion exchange membranes (PRSTM) and point in time by soil sampling at regular intervals; both were analyzed for nitrate (NO3) N and ammonium (NH4) N, although negligible concentrations of NH4-N were detected. PRS NO3-N concentration varied by treatments because of differences in the chemical composition of the N source. Soil NO3-N concentration reached a peak between 520 and 550 degree-days with no significant differences by treatment or site. These findings are similar to results from incubation and field mineralization studies of organic amendments and suggest that N availability from organic sources in vineyards can be predicted using a degree-day-type model.

Accumulation and redistribution of residual chloride, nitrate, and soil test phosphorus in soil profiles amended with fresh and composted cattle manure containing straw or wood-chip bedding

Miller, J. J., Beasley, B. W., Drury, C. F. and Zebarth, B. J. 2011. Accumulation and redistribution of residual chloride, nitrate, and soil test phosphorus in soil profiles amended with fresh and composted cattle manure containing straw or wood-chip bedding. Can. J. Soil Sci. 91: 969–984. Limited research has compared the effect of fresh versus composted beef (Bos taurus) cattle feedlot manure containing straw or wood chips on accumulation and redistribution of residual chloride (Cl), NO3-N, and soil test P (STP) in soil profiles of the Great Plains region of North America. Barley (Hordeum vulgare L.) was grown (1999–2007) on an irrigated clay loam soil in southern Alberta where organic amendments and fertilizer were annually applied for 9 yr from 1998 to 2006. The field experiment was a factorial arrangement of two manure types (fresh versus composted feedlot manure), two bedding materials (straw versus wood-chips), and three application rates (13, 39, 77 Mg ha−1dry wt). There was also one inorganic (IN) fertilizer treatment and an unamended control. The soil profile (0–1.5 m) was sampled in the fall of 1999 to 2002, 2004, 2006, and 2007 and analyzed for residual soil NO3-N, Cl, and STP. Manure type had a significant (P≤0.05) effect on the accumulation of these chemicals, but there was an interaction with application rate (NO3-N), or with bedding and year (STP). The maximum accumulation of Cl after 9 yr was at the 0.6 to 0.9 m depth, but mean values at this depth were similar for the four organic amendments. The maximum accumulation of NO3-N after 9 yr (2007) was at the 0.3 to 0.6 m depth, and mean values at this depth were significantly greater by four- to sixfold for FM and CM with straw than wood-chips, which suggested greater N immobilization in soils with wood. Redistribution of Cl and NO3-N downward into the soil profile suggested a potential for leaching of these chemicals below the root zone. In contrast, soil test P did not accumulate below the 0.3 m depth, suggesting little potential for leaching. However, accumulation of soil test P at this depth was generally greater for the amendment treatments compared with inorganic fertilizer and was likely related to greater P applied in the amendments.

Effects of Soil Properties and Nitrogen Fertilization on Distribution of NO3-N in Soils of Eastern Poland

The effects of anthropogenic (nitrogen fertilization) and natural [soil texture, pH content of humus, ammonium nitrogen (N-NH4), and the available forms of phosphorus (P), potassium (K), magnesium (Mg)] factors on nitrate nitrogen (NO3-N) content and distribution were shown. The dependencies between these factors and the content of NO3-N in soil were estimated in three soil layers: 0–30 cm; 31–60 cm; 61–90 cm. The research was carried out in 2004–2006, and the soil samples were taken from 411 places throughout eastern Poland in two seasons: spring and autumn. The concentration of NO3-N significantly depended on the year of investigation, season of the year, and depth of sampling. Distribution of NO3-N in the soil profile indicates possibility of NO3 leaching during winter and early spring. The results also provide evidence that application of more than the optimum N rate considerably increases NO3-N, especially in soil with low humus content.

Two-Dimensional Analysis of Nitrate Nitrogen Movement under Drip Irrigation

The objective of this paper was to clarify the temporal and spatial two-dimensional variations of volu- metric water content and NO3-N concentration in soil under drip irrigation. A numerical model was used for estimating temporal and spatial movements of water and NO3-N in soil. Laboratory experiments were con- ducted to estimate the physical properties such as soil water retentivity and conductivity. A field observa- tion was conducted to evaluate the model accuracy. The temporal and spatial changes of volumetric water content and NO3-N concentration in soil were measured in a 1 m× 1m ×1 m lysimeter where NH4NO3 solu- tion was supplied in a row. The results of simulation calculated by the model agreed well with observed data. By using the model, temporal and spatial variations of soil water content and NO3-N concentration were calculated. The results described simultaneous movements of water and NO3-N spreading in a soil profile. The numerical model introduced here can be effective to estimate variations of water and NO3-N in soil.