NO3-N Accumulation Research Articles

Effects of Different Plastic Mulching Methods on Soil Water, Temperature and Nitrate Accumulation in a Dryland Winter Wheat Field

This study has investigated the effects of two different plastic mulching methods on soil water, temperature, and nitrate (NO3-N) accumulation in a dryland winter wheat field after one-year experiment. The drought-resistant wheat (Triticum aestivum) variety Chang-8744 was grown by (i) furrow planting with ridge mulching, (ii) bunch planting with flat mulching, and (iii) conventional flat planting without mulching (or control). Results showed that dryland winter wheat effectively utilized soil water down to 2 m depth, mainly in the first 140 cm. Plastic mulching increased the evapotranspiration during wheat growing season and mostly r flat plastic mulching, by ~18% over the value recorded in the control plots. Soil temperature of the 20-40 cm-layer was higher than the one recorded at 5-10 cm depth during seedling-overwintering stages. Ridge plastic mulching and flat plastic mulching increased soil temperatures at 5 cm, 10 cm, and 40 cm depths during seedling–overwintering stages with reference to the control (no mulching), then lowered them at the same depths during reviving–ripening stages. Residual NO3-N was always detected in the soil after harvesting irrespective of the mulching method. It was mainly concentrated in the first -60 cm accounting for ~50% of soil NO3-N accumulation within the 2-m profile. The highest soil NO3-N accumulation occurred under flat plastic mulching, which represented ~107% of the mean value of the remaining treatments. Finally, flat plastic mulching showed the greatest effects on soil water, temperature, and NO3-N accumulation in dryland wheat field.

Accumulation and leaching of nitrate in soils in wheat-maize production in China

Application rates of fertilizers in China often exceed crop requirements, resulting in high accumulation of nitrate (NO3) in the soil. Nitrate that has accumulated in soils is highly prone to leaching, directly threatening the quality of groundwater. A study was conducted to assess the magnitude of NO3 accumulation and leaching in China, to identify factors controlling NO3 accumulation and leaching, and to develop strategies that can be used to minimize NO3 leaching. Data were compiled from 212 studies conducted in China, amounting to 1077 observations of the NO3 content of the 0–100 cm soil profile in wheat and maize fields after harvest. Leaching of NO3 was significantly correlated with NO3 accumulation in the soil. NO3 leaching increased with 0.058 and 0.34 kg NO3-N ha−1 per season for wheat and maize, respectively, for every 1 kg ha-1 increase in NO3-N accumulation in 0–100 cm. This mainly related to lower precipitation during the wheat season and intensive rainfall in the maize season. Accumulation of NO3 in maize systems was 50% lower than for wheat when fertilized at the same rate, due to differences in rainfall between seasons. Soil NO3 accumulation was higher in heavy textured soils than in freely draining lighter textured soils, as most of NO3 leached out of 0–100 cm soil in lighter textured soils. Compared to flood irrigation, sprinkler irrigation increased NO3 accumulation by 17% and 152% for wheat and maize, respectively, due to lower irrigation and leaching rate. The level of nitrate accumulation in Chinese arable soils has become a significant hazard to drinking water, so good agricultural management is essential. Soil NO3 accumulation and leaching in China can be reduced by source and process control, such as reducing fertilizer application, using slow or controlled release forms of fertilizers, and regulating irrigation.

Long-term experiments on chernozem soil in the University of Debrecen

The impact of agrotechnical management practices (nutrient and water supply, crop rotation, crop protection, genotype) on the yields of winter wheat and maize and on the soil water and nutrient cycles was studied in long-term experiments set up in 1983 in Eastern Hungary on chernozem soil. The long-term experiments have shown that nitrogen fertilizer rates exceeding the N-optimum of winter wheat resulted in the accumulation of NO3-N in the soil. Winter wheat varieties can be classified into four groups based on their natural nutrient utilization and their fertilizer response. The fertilizer responses of wheat varieties depended on crop year (6.5–8.9 t ha-1 maximum yields in 2011–2015 years) and the genotypes (in 2012 the difference was ~3 t ha-1 among varieties). The optimum N(+PK) doses varied between 30–150 kg ha-1 in different crop years. In maize production fertilization, irrigation and crop rotation have decision role on the yields. The efficiency of fertilization modified by cropyear (in dry 891–1315 kg ha-1, in average 1927–4042 kg ha-1, in rainy cropyear 2051–4473 kg ha-1 yield surpluses of maize, respectively) and crop rotation (in monoculture 1315–4473 kg ha-1, in biculture 924–2727 kg ha-1 and triculture 891–2291 kg ha-1 yield surpluses of maize, respectively). The optimum fertilization could improve the water use efficiency in maize production.
 Our long-term experiments gave important ecological and agronomic information to guide regional development of sustainable cropping systems.

Role of agrotechnical elements in sustainable wheat and maize production

In conventional crop production the yield increasing was based on the huge industrial chemical inputs and new genotypes of cereals. This extreme external input use could modified the resilience, adaptive capacity and sustainability of different crop models. The effects of different crop management factors were studied in long- term experiments on chernozem soil in Eastern Hungary. The fertilizer responses of wheat varieties depended on the crop year (6.5-8.2 t ha-1 in 2011-2014 years) and the genotype (in 2012 the difference was 2.7 t ha-1 among genotypes). The optimum N(+PK) dose varied between 30-150 kg ha-1 in different crop years. The N-doses over optimum caused NO3-N accumulation in chernozem soil (from 32 mg kg-1 to 170 mg kg-1 ). In sustainable maize production the fertilization resulted high yield surpluses in average (2.0-4.1 t ha-1) and rainy (2.1-5.4 t ha-1) crop year in our long-term experiment (in 1986-2014 years). The yield increasing of irrigation were agronomically effective only in dry crop years (3.3-4.9 t ha-1) and they were very limited in average (1.2-1.3 t ha-1) and rainy (0-0.2 t ha-1) crop year (in 1986-2014 years) The optimum fertilization could improve WUE in maize production.

English

Little information is available on the role of optimized application of irrigation and N on crop N recovery and NO3-N build up and movement in soil profile. A field experiment was carried out to evaluate the effects of irrigation and N management practices on wheat yield, water and fertilizer use efficiency and NO3-N distribution in soil. The treatments included were three levels of irrigation; 0.7, 1.0 and 1.3% of the estimated evapo-transpiration (ETc) and four levels of N; 0, 110, 160 and 210 kg N ha in split plot design. The N was applied either in two splits (50% at sowing + 50% at maximum tillering) or three splits (50% at sowing + 25% at maximum tillering + 25% at spike initiation). Nitrogen applied at 110 kg ha in three splits produced higher wheat yield, N recovery and water use efficiency (WUE) than two splits. Further, application of N in three splits had considerably lesser accumulation of NO3-N in soil as compared to two splits. A significant irrigation effect was observed on grain yield, N recovery and WUE. The highest levels were achieved with water application according to crop water requirement (1.0 ETc). The deficit irrigation produced significantly lower grain yield (3.15 t ha) than full (3.80 t ha) and excessive (3.80 t ha) irrigations. Response of WUE to irrigation levels was in the order, 1.0 ETc (11.03 kg ha mm)>0.7 ETc (10.63 kg ha mm)>1.7 ETc (9.84 kg ha mm). Deficit irrigation resulted in higher build up of NO3-N in surface soil. In contrast, excessive irrigation resulted in greater concentration of NO3-N in lower depths of soil. The results from this research show that there is great potential for decreasing N leaching and increasing wheat crop yield and N use efficiency thorugh controlled irrigation and N application according to crop demand. © 2016 Friends Science Publishers

Use of the agricultural practice of pasture termination in reducing soil N2O emissions in high-rainfall cropping systems of south-eastern Australia

Conversion of long-term pasture to cropping was investigated for its effects on nitrous oxide (N2O) emissions in a 2-year field experiment in the high-rainfall zone of south-western Victoria. Early termination (pasture terminated 6 months before sowing) followed by winter (ETw) and spring (ETs) crops and late termination (pasture terminated 1 month before sowing) followed by a winter crop (LTw) were compared with continuous, mown pasture (MP). Emissions of N2O were measured with an automated gas sampling and analysing system. Emissions from MP were the lowest throughout the study, resulting in annual losses of 0.13kg N2O-N ha–1 in the first and the second years of the experiment. N2O-N loss was 0.6kgha–1 from treatments without fallow in both years (LTw in 2013 and ETs in 2014). In the first year, annual losses from previous fallow in ETw and ETs plots were 7.1 and 3.6kg N2O-N ha–1, respectively. Higher annual N2O losses from treatments with fallow periods continued in the second year of the study and were 2.0 and 1.3kg N2O-N ha–1 from ETw and LTw treatments, respectively. High emissions were associated with N mineralisation and the accumulation of NO3-N in the soil during the extensive fallow period after early pasture termination or wheat harvest. Soil water content was a key factor influencing the temporal fluctuations in N2O emissions. Low emissions occurred when water-filled pore space was <30%, whereas high emissions occurred when it was >65%, suggesting that denitrification was the major source of N2O emission. Crop grain yield was not affected by the duration of fallow (and therefore timing of pasture termination) in the first year, but was lower (P<0.05) in the treatment without fallow in the second year. Terminating pasture late rather than early, thus reducing the length of the fallow period, is a practical way of reducing N2O emissions from mixed pasture–cropping systems.

Numerical Evaluation of Nitrate Distributions in the Onion Root Zone under Conventional Furrow Fertigation

AbstractHYDRUS (2D/3D) model was used to simulate spatial and temporal distributions of nitrate-nitrogen (NO3-N) within and below the onion root zone under conventional furrow fertigation with the urea-ammonium-nitrate (UAN) liquid fertilizer. The simulated water contents in the furrow irrigated onion field agreed well with the measurements. Simulations produced similar patterns of the measured NO3-N concentration profiles throughout the growing season. NO3-N concentrations remained higher and accumulation of NO3-N was observed within the root zone. Higher NO3-N within the root zone was dependent on the rate of the UAN fertilizer application, quantity of NO3-N removed by root uptake, and NO3-N drainage fluxes below the root zone. Simulations also suggested that NO3-N below the root zone during different growth stages remained much higher than a recommended (for drinking water) standard concentration level (10 mg L−1). This resulted in higher NO3-N drainage fluxes, particularly during the fertigation even...

Effect of continuous application of inorganic nitrogen fertilizer on selenium concentration in vegetables grown in the Taihu Lake region of China

Vegetables provide an important source of selenium (Se) for many regions of China. Excess nitrogen (N) fertilizers are commonly used for vegetable production. In this regard, the effect of inorganic N-fertilizer application on the Se content in soils and plants was evaluated in vegetables produced in a polytunnel greenhouse vegetable system. Vegetables were continuously cultivated for 6 years in a microplot field experiment and treated annually with conventional N fertilizer (870 kg ha−1 inorganic fertilizer) and 0 kg N ha−1 as control treatment in polytunnel greenhouse vegetable system in the Taihu Lake region of China. Both treatments included 234 kg ha−1 N provided by manure. After each harvest, soil and vegetable samples were collected, and analyzed for soil NO3-N, Olsen-P, Se, phosphate extractable S and Se and vegetable Se. Six years of continuous application of inorganic N-fertilizer resulted in a significant accumulation of NO3-N, Olsen-P and extractable S in the soil over the course of the experiment. Soil NO3-N concentration accumulated up to 600 mg kg−1 with application of inorganic N-fertilizer, while soil phosphate extractable Se and vegetables Se concentration were significantly lower than that those grown in control treatments. The negative effect of continuous application of inorganic N-fertilizer on vegetable Se concentration may be a consequent of excessive accumulated soil NO3-N. When NO3-N concentration was greater than 300 mg kg−1, vegetable Se concentration was negatively correlated with soil NO3-N. The negative effect of continuous application of inorganic N-fertilizer on vegetable Se concentrations was likely the result of soil nitrate’s competitive or antagonistic effect on Se uptake by vegetables grown in an intensive polytunnel vegetable cultivation system.

滇池流域四县区土壤和农作物全氮分布特征及相关分析

氮素是构成一切生命体的重要元素。在作物生产中，作物对氮的需要量较大，土壤供氮不足是引起农产品产量下降和品质降低的主要限制因子。本研究运用半微量开氏法测定了滇池流域高新区马金铺、晋宁县上蒜镇、盘龙江松华坝、呈贡县斗南村四个县区的自然村的土壤和植物全氮含量，揭示滇池流域全氮的分布特征。结果表明：采样地区土壤全氮含量的范围是0.23 g/kg~3.97 g/kg，平均值为2.35 g/kg，在此范围内得出不同土地利用方式下土壤平均全氮含量：耕地 > 林地；不同种植模式下土壤平均全氮含量：大棚 > 传统。采样地区作物全氮含量的范围为9.77 g/kg~46.77 g/kg，平均值为25.74 g/kg，在此范围内得出不同过渡区作物平均全氮含量：坝平地 > 水源地 > 坡耕地；不同区域作物平均全氮含量：高新区马金铺 > 盘龙江松华坝 > 呈贡县斗南镇 > 晋宁县上蒜镇。对土壤和农作物全氮含量做双变量相关性双尾检验，Pearson相关性指数为0.559，分析表明，农作物全氮含量与土壤中的全氮含量相关。 Nitrogen is the essential element of all living organisms. Nitrogen is necessary for crop producing, and absence of Nitrogen in the soil is a major limited factor to lead the decreasing of crops gross production and property. Meanwhile, over fertilization with Nitrogen will cause eutrophication in the limnological ecosystem, accumulation of NO3-N to ground water, and poison damage. This ex-periment assayed the total nitrogen content in the soil and crops in four different regions, Dounan Town in Chenggong County, Shangsuan Town in Jinning County, Songhua Dam in Panlong District and Majinpu in High-Tech District, by semi-micro Kieldahl method to indicate the characteristic of the distribution of total Nitrogen in Dianchi Lake. The results demonstrate the total nitrogen con-tent in the soil in the sampling region is from 0.23 g/kg to 3.97 g/kg, and the mean is 2.35 g/kg. Meanwhile, the average total nitrogen content in the soil of cultivated land is higher than the woodland by the different land-using method. Furthermore, the average content of total nitrogen by green house growing is higher than the traditional growing method. The total Nitrogen content of crops in sampling region is from 9.77 g/kg to 46.77 g/kg, and the mean is 25.74 g/kg. In this range, the average total nitrogen content of transition regions crops varied as the following sequence: flat-farmland > sloped cultivated farmland > waterhead area farmland. In addition, and the total nitrogen content of crops in sampling regions varied as the following sequence: Majinpu in High-tech District > Songhua Dam in Panlong District > Dounan Town in Chenggong County > Shangsuan Town in Jinning County. The correlation coefficient of Pearson is 0.559 due to the two- way ANOVA test of the total nitrogen content in soil and crops, and according to the data analysis, the correlation of the total nitrogen content in crops and soils is significant.

Response of Different Brassica Vegetables to Manure Source , NO3-N Accumulation and Nitrate Reductase Activity in Plant

Response of Different Brassica Vegetables to Manure Source , NO3-N Accumulation and Nitrate Reductase Activity in Plant

Nitrate accumulation in forage brassicas

Previous research has shown that the application of fertilizer nitrogen (N) can lead to an accumulation of nitrate nitrogen (NO3-N) in forage brassicas, particularly when N application rates exceed that required to obtain maximum crop yield. However, there are no data examining the effect of timing of fertilizer application on NO3-N accumulation. An experiment was established in 2009 with four forage brassica crops (turnips, rape, kale and swedes) and three N fertilizer treatments (early N, late N and double N) at Lincoln, Canterbury, New Zealand. The N treatments, which differed among crops depending on crop duration, consisted of rates and timings of N fertilizer. For the turnips and rape, the early N treatment consisted of 200 kg N/ha applied 16 days after sowing; the late N treatment consisted of 200 kg N/ha applied 40 days after sowing; and the double N treatment consisted of 200 kg N/ha applied 16 days after sowing and a further 200 kg N/ha applied 40 days after sowing. For the kale and swedes, the early N treatment consisted of 400 kg N/ha applied 16 days after sowing; the late N treatment consisted of 400 kg N/ha applied 72 days after sowing; and the double N treatment consisted of 400 kg N/ha applied 16 days after sowing and a further 400 kg N/ha applied 72 days after sowing. There were differences in yield between species that reflected their growth duration but no yield differences between N treatments. Averaged across all species, plant NO3-N content was greater in crops that received the double rate of N than either the early or late N treatments. Importantly, the late N treatment (3.7 mg/g) accumulated almost double (P < 0.001) the plant NO3-N content of the early N treatment (2.0 mg/g). Averaged across all N treatments, the leafy crops (rape and kale) (5.5 mg/g) had nearly double (P < 0.001) the NO3-N content of the bulb crops (turnip and swedes) (2.9 mg/g). In general, the stems had the highest NO3-N content across all crops, followed by the bulbs. Leaves had the lowest NO3-N content. Overall, these results indicate that early application of fertilizer N could be used to minimize NO3-N accumulation in forage brassicas.

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)....

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.

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.

Organic versus conventional – a comparative study on quality and nutritional value of fruit and vegetable juices

The study presents a comparison of some nutritional values of juices made from organic and conventional apple, pear, blackcurrant, carrot, beetroot and celery. Higher soluble solids content (SSC) for organic juices than for conventional ones was recorded for blackcurrant (14.9% and 12.5%, respectively) and beetroot (12.3% versus 8.3%). The highest organic acids content was noted for blackcurrant (3.7 g malic acid 100 g− 1), whereas the lowest was for celery (0.57 g 100 g− 1 on average). Higher organic acids content was shown in apple, pear, and especially blackcurrant grown organically. Amounts of juice NH4-N content were lower in organic vegetable juices than in conventional ones. The conventional farming method favoured greater NO3-N accumulation for beetroot (846 mg NO3-N kg− 1 f.w.) than for organic juice (229 mg NO3-N kg− 1 f.w.). The data showed the organic juices to have polyphenols and ascorbic acid contents similar to, and antioxidant activity slightly higher than, conventional juices.

Short-Term Irrigation Level Effects on Residual Nitrate in Soil Profile and N Balance from Long-Term Manure and Fertilizer Applications in the Arid Areas of Northwest China

A field experiment was conducted to determine the effects of long-term applications of fertilizers and manure (1982 to 2003) and short-term irrigation level (2002 and 2003) on accumulation of nitrate nitrogen (NO3-N) in soil at Zhangye Oasis, China. The treatments included manure (M) and no manure (M0) as main plots; check (Ck), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + potassium (NPK) as subplots; and two amounts of irrigation (I1 and I2) as subsubplots. The application of N alone resulted in large NO3-N accumulation in soil, accounting for 6% of the applied N, and the lowest crop N recovery. Application of manure resulted in increased NO3-N in the soil profile compared to treatment with no manure, and the MN treatment resulted in the greatest amount of NO3-N in soil. Nitrogen applied with P and/or K reduced the amount of NO3-N in soil in both manure and no-manure treatments compared with N only. The unaccounted N was greatest (60%) in the N-alone treatment and lowest (30%) in the NPK treatment. When manure plus fertilizer were applied together, the unaccounted N ranged from 35%–42%. Based on results from only 2 years, greater amounts of irrigation (I2) caused greater leaching of NO3-N in the soil profile compared with I1, especially in treatments receiving manure. The implications of these findings are that these high amounts of accumulated NO3-N in surface and subsoil layers can be a potential threat to surface water, underground water, and air quality in the long run. This accumulated N in the soil profile can be used as a source of available N for future crops and should be recycled by using proper crop, soil, fertilizer, and water-management strategies/practices. The findings also suggest the need for further research to make an effective and efficient use of this accumulated NO3-N in the soil profile in order to save cost of N fertilizer application to future crops.

Nitrogen turnover of chernozem meadow soil in a long-term mineral fertilisation trial

The elaboration and introduction of an environment-friendly N fertilisation system requires studies on the soil N regime, and on NO 3 -N accumulation and leaching under field conditions. The present work aimed to provide data on the soil N balance and on the depth distribution and leaching of NO 3 -N in chernozem meadow soil, based on the results of an 18-year long-term mineral fertilisation experiment. The soil contained 3.0–3.2% humus and had good N-supplying ability. Averaged over 18 years, the plant N uptake on plots without N fertilisation was 126 kg ha −1 year −1 . At the 80 kg ha −1 N rate the soil N balance was negative, with a mean plant N uptake of 170 kg ha −1 year −1 and a low rate of NO 3 -N leaching was observed. At 160 kg ha −1 N the accumulated N balance was only slightly negative. In 7 of the 18 years plant N uptake was below 160 kg ha −1 . Under the given experimental conditions, considering the natural N-supplying capacity of the soil, the 160 kg ha −1 N fertiliser rate proved to be excessive, surpassing the N requirements of the potential crop yield in most years and resulting in NO 3 -N leaching. The N regime data indicated that the 240 kg ha −1 N rate represented over-fertilisation in the given location.

Accumulation of nitrate N in the soil profile and its implications for the environment under dryland agriculture in northern China: A review

Nitrate (NO3-) leaching and water contamination have become a worldwide concern. In this review, some examples are presented to show the extent and magnitude of NO3- accumulation in the soil profiles and its potential effects on contamination of ground water and surface water under dryland farming in northern China. Climatic and management factors affecting NO3- leaching are also discussed. In northern China, rainfall is relatively sparse, but the high intensity of precipitation and porous soils play an important role in the accumulation of NO3N in soil and its subsequent leaching in the soil profile. There is a risk of nitrate accumulation and leaching when high rates of fertilizer N are applied to improve crop yields, and it becomes even worse when conventional land use is changed from cereal crops to vegetable crops and fruit orchards. Under such conditions, shallow ground water might be polluted by NO3-. This suggests that more attention should be paid to prevent this problem by using best management practices, especially by controlling the amount of N fertilizer input, balanced fertilization, split N application, inclusion of crops with deep taproots in the rotation and minimizing summer fallow (especially tilled) frequency. Key words: Accumulation, contamination, dryland farming, ground water, leaching, nitrate, northern China

PERFORMANCE OF DUALEX IN SPRING WHEAT FOR CROP NITROGEN STATUS ASSESSMENT, YIELD PREDICTION AND ESTIMATION OF SOIL NITRATE CONTENT

Dualex and SPAD are devices developed for the purpose of testing crop nitrogen (N) status. These instruments were used in a wheat experiment in order to compare their respective performance in assessing leaf nitrogen (N) concentration, response to N topdressing application, soil nitrate (NO3)-N levels and in predicting grain yield. The experiment included different N rates in 2005 and 2006 in the Montérégie region of Quebec, Canada. Dualex readings correlated negatively with SPAD readings, leaf N concentration, soil NO3-N content and wheat grain yield. SPAD alone and the ratio of SPAD to Dualex measurements (Chl/Phen) were linearly related to N application rate but no effect of N application rate was found for individual Dualex parameters. However, both SPAD and Dualex readings were affected by year effects. The Dualex was also capable of indirect evaluation of in-season soil NO3-N accumulation and the prediction of wheat yield, but more so as Chl/Phen.

Nitrate Leaching in Two Irrigated Soils with Different Rates of Cattle Manure

Manure applied to irrigated land may potentially contaminate groundwater with NO3-N. An 8-yr field experiment was conducted in southern Alberta, Canada, to determine the effects of different rates of manure on NO3-N accumulation in two irrigated soil types and NO3-N leaching to shallow groundwater. An annual cereal silage was grown at each site and irrigation was based on soil moisture depletion. Treatments included a control, nitrogen fertilizer (NF) at 180 kg N ha(-1) yr(-1), and four rates of cattle (Bos taurus) manure (20, 40, 60, and 120 Mg ha(-1) yr(-1), wet-weight basis). Annual manure applications for 8 yr resulted in NO3-N accumulation in the soil profile at both sites. For every megagram of total N added from manure, NO3-N in the 0- to 1.5-m layer increased by about 50 kg ha(-1) at the coarse-textured (CT) site and by about 100 kg ha(-1) at the medium-textured (MT) site. Silage yield for all of the manure treatments was similar to yield for the NF treatment after the first 3 to 4 yr of annual manure applications. The greatest manure rate and NF treatments significantly increased NO3-N concentrations in groundwater at the CT site. Groundwater NO3-N concentrations were not adversely affected by manure or NF applications at the MT site. An annual cattle manure application rate of 20 Mg ha(-1) provided sufficient N for irrigated cereal silage production and minimized NO3-N leaching in a medium-textured soil.