Sodicity and salinity in a Brazilian Oxisol cultivated with sugarcane irrigated with wastewater

Changes in soil sodicity-salinity parameters are one of the most characteristic alterations after treated sewage effluent (TSE) irrigation in agro-systems. Considering the importance of these parameters for agricultural management, as well as the economical value of sugarcane for Brazil, the present study aimed at evaluating effects on soil sodicity and salinity under tropical conditions over 16 months of TSE irrigation in a sugarcane plantation at Lins, São Paulo State, Brazil. Soil samplings were carried out in February 2005 (before planting), December 2005 (after 8 months of TSE irrigation) and September 2006 (after 16 months of TSE irrigation) following a complete block design with four treatments and four replicates. Treatments consisted of: (i) control, without TSE irrigation; (ii) T100, T150 and T200, with TSE irrigation supplying 100% (0% surplus, total of 2524 mm), 150% (50% surplus, total of 3832 mm) and 200% (100% surplus, total of 5092 mm) of crop water demand, respectively. Compared to initial soil conditions, at the end of the experiment increases of exchangeable sodium (from 2.4 to 5.9 mmol_c kg⁻¹), exchangeable sodium percentage (ESP) (from 8 to 18%), soluble Na (from 1.4 to 4.7 mmol L⁻¹) and sodium adsorption ratio (SAR) of soil solution (from 3.6 to 12.6 (mmol L⁻¹)^0.5) were found in the soil profile (0-100 cm) as an average for the irrigated plots due to high SAR of TSE. Associated with the increments were mostly significant increases in clay dispersion rates at depths 0-10, 10-20 and 20-40 cm. Electrical conductivity (EC) of soil solution increased during the TSE irrigation period whereas at the end of the experiment, after short term discontinuation of irrigation and harvest, EC in the topsoil (0-10 and 10-20 cm) decreased compared to the previous samplings. Moreover, despite increasing sodicity over time mainly insignificant differences within the different irrigated treatments were found in December 2005 and September 2006. This suggests that independent of varying irrigation amounts the increasing soil sodicity over time were rather caused by the continuous use of TSE than by its quantity applied. Moreover, also plant productivity showed no significant differences within the TSE irrigated plots. The study indicates that monitoring as well as remediation of soil after TSE irrigation is required for a sustainable TSE use in order to maintain agricultural quality parameters.     

Simulating soil water flow and nitrogen dynamics in a sunflower field irrigated with reclaimed wastewater

Soil water flow and nitrogen dynamics were simulated in sunflower field during and after the growing period, in Northern Greece. Soil water and nitrogen dynamics were evaluated using a one-dimensional simulation model based on the Galerkin finite element method. We examined the effects of irrigation with reclaimed wastewater and nitrogen fertilizer applications on plant growth, water and nitrogen distribution in the soil profile, water and nitrogen balance components and nitrogen leaching to groundwater. The model simulated the temporal variation of soil water content with reasonable accuracy. However, an over estimation of the measured data was observed during the simulation period. Relatively good agreement was found between the simulated and measured NH₄-N and NO₃-N concentrations over time and depth, whereas fluctuations at greater depths were relatively small. Most of the cumulative nitrate-N leaching (44.7 kg N ha⁻¹) occurred during the winter.     

Components of the water balance in soil with sugarcane crops

The objective of this study was to analyze the components of the water balance in an Ultisol, located in the municipality of Jaboticabal, SP, Brazil (21°20′20″S, 48°18′35″W), that was cultivated with sugarcane. The monitoring was performed during the agricultural cycle of the first ratoon between 11/16/2006 and 7/9/2007. Three treatments were established in four blocks with doses of ammonium sulfate, as follows: Treatment 1 (T₁), without fertilizer; Treatment 2 (T₂), 100 kg ha⁻¹ of nitrogen (N) and 114 kg ha⁻¹ of sulfur (S); and Treatment 3 (T₃), 150 kg ha⁻¹ of N and 172 kg ha⁻¹ of S. Rainy precipitation (P) in the area was measured with a rain gauge. The soil water storage (H) and the soil water storage variations (ΔH) were determined by the gravimetric method, and the internal drainage (D)/capillary rise (CR) at a depth of 0.9 m was quantified by the water flux density using the Darcy–Buckingham equation. The actual evapotranspiration (ET_a) was calculated as follows: ET_a = P − D + CR ± ΔH. During the study period, the amount of rainfall was 1406 mm, 121 mm greater than the historic average for the region (1285 mm), with a notable peak in the month of January of 402 mm (historic average: 251 mm). The internal drainage was 300 mm under T₁, 352 mm under T₂, and 199 mm under T₃, and this was relevant during times with elevated P, when the actual H was greater than the field capacity H. The actual evapotranspiration (T₁: −897.7 mm, T₂: −847.5 mm, and T₃: −970.8 mm) and the water use efficiency (T₁: −131.3 kg mm⁻¹, T₂: −146.6 kg mm⁻¹, and T₃: −127.5 kg mm⁻¹) did not differ among the treatments. The dispersion of D was greater than the other components of the water balance, especially during the period of elevated P, with the errors of this process propagated in the estimation of ET_a. Despite of this propagated standard deviation of ET_a, it accounted less than 15% of the total ET_a, showing that the method may be conveniently used in field studies with sugarcane crops.     

Reclaimed wastewater: Effects on citrus nutrition

The effects of irrigation with reclaimed wastewater (RWW) were compared with well water (WW) on citrus (Citrus paradisi Macfad. X Citrus aurantium L.) nutrition. The deviation from the optimum percentage (DOP) index of macro- and micro-nutrients were used to evaluate the nutritional status: optimal (DOP = 0), deficiency (DOP < 0) or excess (DOP > 0). After 11 years of RWW irrigation the influence on nutrient concentration in plants decreased in the order: B > Zn > Mn = Ca > Cu > Mg > P > K. Reclaimed wastewater irritation positively affected citrus nutrition as it rendered the concentration of macro-nutrients, i.e. P, Ca, and K. closer to their optimum levels (ΣDOP_macro = 7). However micro-nutrients tended to be excessive in plants (ΣDOP_micro = 753) due to imbalanced supply of these elements in the RWW, particularly, for B and Cu. Citrus groves with long-term RWW irrigation may exercised caution in monitoring concentrations of B and Cu to avoid plant toxicity and soil quality degradation.     

Simulation of heat and water transfer in a surface irrigated, cropped sandy soil

Field experiments were conducted to validate a one-dimensional numerical Simple Soil Plant Atmospheric Transfer (SiSPAT) model that simulates heat and water transfer through the root zone of a surface irrigated, cropped sandy soil. The model accounts for the dominant processes involved in water and heat transfer in a cropped soil. Model validation used field experimental data from 2004 and suggested that the SiSPAT model could be successfully applied to predict soil water and temperature dynamics of a cropped soil in experimental conditions. Validation resulted in high values of model efficiency (ME), and low values of root mean square deviation (RMSD) and mean bias error (MBE) between the simulated and measured values. Model predictions were obtained using field experimental data from 2005 and showed that the SiSPAT model reproduced reasonably well the experimental distributions of soil moisture and temperature. Minor discrepancies between the predicted and measured data during the prediction period can probably be attributed to the uncertainties in soil water content and soil temperature probe measurements. In addition, the influence of irrigation water temperature on water and heat transfer was ignored in the model. This could have contributed to deviations between the simulated and measured values during the experiment. Prediction results indicated that the variability of the water and heat transfer fluxes following a surface irrigation in different stages of the crop (wheat) growth season resulted from the difference in net radiation reaching the cropped soil due to the varying shielding factor as controlled by leaf area index (LAI), root water uptake, meteorological conditions and soil water regime. Furthermore, an interaction between water and heat transfer through the root zone in the cropped soil could be observed during the prediction period.     

Oxyfertigation of a greenhouse tomato crop grown on rockwool slabs and irrigated with treated wastewater: Oxygen content dynamics and crop response

This work assesses the seasonal dynamics of the substrate oxygen content and the response to nutrient solution oxygen enrichment (oxyfertigation) of an autumn-spring tomato crop grown on rockwool slabs and irrigated with treated wastewater of very low dissolved oxygen (DO) content under Mediterranean greenhouse conditions. DO values in the nutrient solution were clearly higher for the oxygen-enriched (14.6 mg L⁻¹) tomato crop than for the non-enriched one (4.5 mg L⁻¹). However, DO values in the substrate solution were similar for both oxygen treatments (mean seasonal values of 5.1 and 4.8 mg L⁻¹ for the enriched and the non-enriched one, respectively), except for a short crop period at the end of the cycle when they were significantly higher for the oxygen-enriched crop. For both treatments, substrate DO values were highest for the winter period and decreased progressively during the spring period, reaching minimum values of around or below 3 mg L⁻¹ at the end of the spring. The oxygen enrichment of the nutrient solution did not affect any of the irrigation and fertigation parameters evaluated in the tomato crop: water uptake, volumetric water content of the substrate, electrical conductivity (EC) or nutrient concentration in the leached nutrient solution. Moreover, the oxygen enrichment of the nutrient solution did not affect the aboveground biomass and the biomass partitioning, the fresh weight of total and marketable tomato fruits or the tomato fruit quality parameters. Overall, it appears that oxygen deficiency conditions did not occur as the substrate DO values were higher than, or about, 3 mg L⁻¹ throughout most of the tomato crop cycle for both treatments and the rockwool slabs maintained good aeration conditions throughout the whole cycle.     

养殖废水灌溉对玉米地土壤水溶性碳及其剖面分布的影响

为了研究养殖废水灌溉对土壤水溶性碳量及其占总有机碳量比例的剖面分布的影响,设置水质和灌溉量处理,测定了玉米地土壤总有机碳和水溶性碳量,分析了水溶性碳占总有机碳比例及其剖面分布特征。结果表明,总有机碳及水溶性碳量在土壤表层较高,且随着土层加深均有所减少。养殖废水灌溉条件下的土壤总有机碳和水溶性碳量总体上比清水灌溉处理的高,这说明在一定范围内养殖废水灌溉更有利于土壤中有机碳量的增加。清水灌溉条件下,灌水量为640 m~3/hm~2时土壤总有机碳量最高;灌水量为760 m~3/hm~2时水溶性碳量最高。养殖废水灌溉条件下,灌水量为880 m~3/hm~2时土壤总有机碳和水溶性碳量均为最高。由于土壤中的总有机碳在土壤深层分布较少,且随土层加深土壤总有机碳量下降幅度减小,水溶性碳占总有机碳的比例随土层深度加深而逐步增加。养殖废水灌溉有利于土壤总有机碳、水溶性碳量的增加,并可促进二者在土壤表层的积累。     

Partial root-zone irrigation enhanced soil enzyme activities and water use of maize under different ratios of inorganic to organic nitrogen fertilizers

Partial root-zone irrigation (PRI) is an effective water-saving irrigation method but the heterogeneous soil moisture distribution that may affect soil enzymatic activities and crop water use. With pot-grown maize, we investigated the dry mass accumulation, crop water-use efficiency and the activities of four major soil enzymes from jointing to grain filling stages of maize plants subjected to PRI and also different ratios of inorganic to organic N fertilizers. Three irrigation methods, i.e. conventional irrigation (CI), alternate PRI (APRI) and fixed PRI (FPRI) and three ratios of inorganic to organic N, i.e. 100% inorganic (F₁), 70% inorganic + 30% organic (F₂) and 40% inorganic + 60% organic (F₃), were applied. Compared to CI, PRI reduced total dry mass and water consumption of maize by 9.5 and 15.7%, respectively, which led to an increase of canopy water-use efficiency by 7.4%. Within the same irrigation method (CI, APRI or FPRI), added organic N increased total dry mass and canopy WUE. During the whole period, maximal soil catalase, urease and acid-phosphatase activities occurred in the wet root-zone of PRI, but maximal invertase activity occurred in the dry root-zone of PRI. When organic N was the most (F₃), APRI increased soil catalase, urease and invertase activities at jointing stage if compared to CI, but PRI reduced the acid-phosphatase activity from jointing to filling stages. Soil catalase, urease and invertase activities generally increased with more organic manure, but the maximal acid-phosphatase activities occurred under moderate amount of organic N (F₂). Our results indicate that APRI increases canopy WUE and the catalase, urease and invertase activities in its wet zone and organic N plays a major role in enhancing canopy WUE and soil enzymatic activities.     

Yield and water-production functions of two durum wheat cultivars grown under different irrigation and nitrogen regimes

Wheat (Triticum durum L.) yields in the semi-arid regions are limited by inadequate water supply late in the cropping season. Planning suitable irrigation strategy and nitrogen fertilization with the appropriate crop phenology will produce optimum grain yields. A 3-year experiment was conducted on deep, fairly drained clay soil, at Tal Amara Research Station in the central Bekaa Valley of Lebanon to investigate the response of durum wheat to supplemental irrigation (IRR) and nitrogen rate (NR). Three water supply levels (rainfed and two treatments irrigated at half and full soil water deficit) were coupled with three N fertilization rates (100, 150 and 200 kg N ha⁻¹) and two cultivars (Waha and Haurani) under the same cropping practices (sowing date, seeding rate, row space and seeding depth). Averaged across N treatments and years, rainfed treatment yielded 3.49 Mg ha⁻¹ and it was 25% and 28% less than half and full irrigation treatments, respectively, for Waha, while for Haurani the rainfed treatment yielded 3.21 Mg ha⁻¹, and it was 18% and 22% less than half and full irrigation, respectively. On the other hand, N fertilization of 150 and 200 kg N ha⁻¹ increased grain yield in Waha by 12% and 16%, respectively, in comparison with N fertilization of 100 kg N ha⁻¹, while for cultivar Haurani the increases were 24% and 38%, respectively. Regardless of cultivar, results showed that supplemental irrigation significantly increased grain number per square meter and grain weight with respect to the rainfed treatment, while nitrogen fertilization was observed to have significant effects only on grain number per square meter. Moreover, results showed that grain yield for cultivar Haurani was less affected by supplemental irrigation and more affected by nitrogen fertilization than cultivar Waha in all years. However, cultivar effects were of lower magnitude compared with those of irrigation and nitrogen. We conclude that optimum yield was produced for both cultivars at 50% of soil water deficit as supplemental irrigation and N rate of 150 kg N ha⁻¹. However, Harvest index (HI) and water use efficiency (WUE) in both cultivars were not significantly affected neither by supplemental irrigation nor by nitrogen rate. Evapotranspiration (ET) of rainfed wheat ranged from 300 to 400 mm, while irrigated wheat had seasonal ET ranging from 450 to 650 mm. On the other hand, irrigation treatments significantly affected ET after normalizing for vapor pressure deficit (ET/VPD) during the growing season. Supplemental irrigation at 50% and 100% of soil water deficit had approximately 26 and 52 mm mbar⁻¹ more ET/VPD, respectively, than those grown under rainfed conditions.     

Contribution of runoff to incomplete off season soil water refilling in a Mediterranean vineyard

The dynamics of soil water was investigated in a Mediterranean vineyard during the 2003-2007 period in order to identify the inter-seasonal modification of water storage due to intercropping. The intercrop was a mixture of tall fescue and rye grass. Soil water content was measured on 3 m soil profiles (plus one 5 m profile) as was runoff from local stands.Great variations in soil refilling were observed over the years, for both the bare soil and intercrop treatments. The complete refilling occurred once and it was associated with a rise of the water table up to less than 2 m from the soil surface in the low part of the field. During the other years, the wetting front was identified between 1 m and 2.3 m at spring in the bare soil treatment, deeper in the lowest part of the field. The available soil water content at bud-break was influenced by the topography. A higher infiltration was observed in the intercropped treatment. Runoff kinetics was compared to rainfall kinetics in a selection of three rain events differing by duration and intensity. The curve number method was used to perform the analysis of runoff at a 1-day time-step rather than the quarter of an hour time-step of the registrations. With this method, the time limitation of water balance studies for Mediterranean vineyards would be partially removed.     

Optimal coupling combinations between irrigation frequency and rate for drip-irrigated maize grown on sandy soil

This study was conducted over 2 years (2007 and 2008) to establish the optimal combinations between irrigation frequency and rate for drip-irrigated maize using water production functions and water use-yield relationships. A field experiment was conducted using a randomized complete block split plot design with four irrigation frequencies (F₁, F₂, F₃ and F₄, irrigation events once every 1, 2, 3 or 4 days, respectively) and three drip irrigation rates (I₁: 1.00, I₂: 0.80, and I₃: 0.60 of the estimated evapotranspiration, ET) as the main and split plots, respectively. Our results show that yield variables and water use efficiencies (WUEs) increased with increasing irrigation frequency and rate, with non-significant differences between F₁ and F₂ in yield variables and between I₁ and I₂ in WUEs. Moreover, the combination between various irrigation frequencies and rates had an important effect on yield variables and WUEs, with the highest values being found for F₁I₂ and F₂I₁ and the lowest for F₃I₃ and F₄I₃. The F₁I₃ treatment had grain yield and yield components values similar to those obtained for the F₃I₂ and F₄I₁ treatments and WUEs values similar to those obtained for the F₂I₁ and F₂I₂ treatments. Seasonal yield response factors (k_y) were 1.81 and 1.86 in 2007 and 2008, respectively. Production functions of yield versus seasonal crop ET were linear for all combinations of irrigation frequency and rate and for all irrigation frequency treatments with the exception of the F₁ treatment, which instead showed a second order relationship. The relationship between WUE and grain yield was best represented by a power equation. In conclusion, we identified the optimal coupling combinations between irrigation frequency and water application rate to achieve the maximum yield and WUEs under either sufficient (F₂I₁) or limited irrigation (F₁I₃) water supplies.     

Summer cover crop impacts on soil percolation and nitrogen leaching from a winter corn field

The impacts of a leguminous summer cover crop (sunn hemp; Crotalaria juncea) on nitrogen leaching from a corn (Zea mays L.) field was evaluated by direct measurements of soil water content and nitrogen balance components, complemented by direct and inverse modeling as an exploratory tool to better understand water flow and nitrogen balances in the soil. Water and nitrogen inputs and outputs were measured during winter corn production in an experimental field located in the south Miami-Dade basin in southern Florida (USA). Data from the last two seasons (2001-2002 and 2002-2003) of a 4-year study are presented. The field was divided into six 0.13 ha plots. One-half of the plots were rotated with sunn hemp (CC plots) during the summer while the remaining plots were kept fallow (NC plots). Sweet corn management was uniform on all plots and followed grower recommended practices. A numerical model (WAVE) for describing water and agrochemical movement in the soil was used to simulate water and nitrogen balances in both types of plots during the corn seasons. The hydrodynamic component of WAVE was calibrated with soil water data collected continuously at three depths, which resulted in accurate soil water content predictions (coefficients of efficiency of 0.85 and 0.91 for CC and NC plots, respectively). Measured components of the nitrogen balance (corn yields, estimated nitrogen uptake, and soil organic nitrogen) were used to positively assess the quality of the nitrogen simulation results. Results of the modeled water balance indicate that using sunn hemp as a cover crop improved the soil physical conditions (increase in soil water retention) and subsequently enhanced actual crop evapotranspiration and reduced soil drainage. However, nitrogen simulation results suggest that, although corn nitrogen uptake and yields were slightly higher in the CC plots than in the NC plots, there were net increases of soil N content that resulted in increased N leaching to the shallow aquifer. Therefore, the use of sunn hemp as cover crop should be coupled with reductions in N fertilizer applied to the winter crop to account for the net increase in soil N content.     

Nitrogen and phosphorous concentrations in runoff from a purple soil in an agricultural watershed

Nutrient loss from purple soils has been reported to increase pollution of the Yangtze River. However, few studies have addressed the variations of nutrient concentration in runoff during natural rainstorms in the regions. Nitrogen and phosphorus concentrations in runoff waters from a small agricultural watershed, in the purple soil region of southwest China, were investigated for four natural rainstorms occurred in a conventional double cropping system (wheat-corn) and another six rainstorms in a new triple cropping system (wheat-corn-sweet potato). The NO₃⁻ concentrations in runoff for the observed rainstorms generally varied from 1.0 to 3.5 g m⁻³, which were noticeably affected by flow rates. A significant logarithmic correlation between NO₃⁻ concentrations and flow rates for each rainstorm was identified. In contrast, the concentrations of NH₄⁺ and dissolved reactive phosphorus (DRP) in runoff fluctuated substantially without a noticeable trend for each rainstorm. Positive linear correlation between the concentrations of DRP and sediment for each rainstorm tested was found under the circumstances of double cropping system. In addition, the ratios of NO₃⁻ to NH₄⁺ for the loss amount in 10 rainstorms varied from 1 to 7 for the triple cropping system and 16-29 for the double cropping system. Furthermore, the ratios of the sum of NO₃⁻ and NH₄⁺ to DRP for the loss amount in 10 rainstorms ranged from 12 to 79 depending on the cropping systems. Nitrate nitrogen was proved to be the main form of inorganic nitrogen loss in runoff water in the purple soil region. Compared with the conventional double cropping system, the new triple cropping system tends to cause more NH₄⁺ loss. These findings would help develop the effective erosion control strategies and select a suitable cropping system to reduce potential pollution hazards.     

Water and salt regulation and its effects on Leymus chinensis growth under drip irrigation in saline-sodic soils of the Songnen Plain

Field experiments were carried out to investigate water and salt management and its effects on Leymus chinensis growth under drip irrigation on saline-sodic soils of the Songnen Plain, China. The ECe of the experiment soil here is 15.2 dS/m and SAR_e is 14.6 (mmol_c L⁻¹)^1/2. The threshold of soil matric potential (SMP) was preset in different treatments (−5, −10, −15, −20 and −25 kPa) to control the timing of the irrigation cycle using vacuum tensiometers buried at 0.2 m depth immediately under drip emitters. Drip irrigation frequency and soil matric potential significantly influenced water and salt distributions and L. chinensis growth. In the root zone, the soil water content increased with the SMP, but at deeper layers there were no significant differences in soil water content due to the effect of groundwater. Electrical conductivity showed that there was a low-salt zone near the emitters and that drip irrigation inhibited the buildup of salts in the root zone. There was more leaching of salts for −5 and −10 kPa treatments than for the −15, −20 and −25 kPa treatments. After two years of drip irrigation, the surface salts were well leached, and had moved down with the water to depths below 40 cm. The pH of each treatment was a little decreased and the soil nutrient of S1-S5 were all increased after reclamation, but there were no obvious differences of the five treatments. The best growth was achieved with soil matric potentials of −5 and −10 kPa: the plant height, number and length of spikes, number of tillers, coverage and aboveground biomass all attained their maximum values during the growth periods of L. chinensis, with no significant differences between those two treatments. Thus, in the Songnen Plain, drip irrigation can be used on transplanted L. chinensis for restoration of saline-sodic soils. The results provide theoretical and technological guidance for sustainable reclamation salt-affected soil and the quick restoration and reconstruction of saline-sodic grassland.     

Olive mill wastewater irrigation of maize: Impacts on soil and groundwater

The environmental impact of irrigating a maize field with weathered olive mill wastewater (OMW) for 5 years was assessed. The use of the weathered OMW added the following concentrations of nutrients to the field: 11.8 t/ha/yr carbon, 1033 kg/ha/yr total nitrogen, 23.8 kg/ha/yr phosphorous and 4161 kg/ha/yr potassium. The maize field received 6 times more nitrogen, 50 times more potassium and 2 times less phosphorous than the recommended fertilization rates. The presence of carbon increased microbial activity for organic nitrogen breakdown and the decomposition rate of organic nitrogen. No significant increase was observed of heavy metal accumulation in the soil. Electrical conductivity in the soil remained below the salinization threshold. No direct exposure values were exceeded. No impact on groundwater quality was observed. Irrigation of crops like maize with weathered OMW could be part of a viable decentralized solution for olive mill wastewater use in areas with low organic matter and high irrigation demand.     

Comparison of nitrogen and irrigation strategies in tomato using CROPGRO model. A case study from Southern Italy

The CROPGRO simulation model was calibrated for processing tomato in Southern Italy with a 2002 data set and validated with three independent data sets with acceptable results. Subsequently this model was combined with 53 years of local historical weather data and it was used as a research tool to evaluate the benefits, risks and costs of 23 different interactive irrigation and/or N-management scenarios. Irrigation water was applied (i) on reported dates with 3 and 5 days intervals and application rates of 15 and 25 mm or (ii) with automatic irrigation initiated at residual soil moisture levels in the upper 30 cm of the soil profile of 25, 50, or 75%. Three amount levels of N application (100, 200 and 300 kg ha⁻¹ as ammonium nitrate) were considered. A simple economic analysis, including tomato marketable yield and price, irrigation and nitrogen cost and other fixed production costs, was used to estimate expected net return for each management scenario.     

Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO₃) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO₃-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha⁻¹), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO₃-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO₃-N leaching out of the 60-cm soil layer was 8.43 kg N ha⁻¹, for the 142 kg N ha⁻¹ and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO₃ concentration at the 60 cm depth was 46 and 138 mg l⁻¹, respectively. Based on our findings, it is possible to control NO₃ leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.