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1.
Composition and properties of leachates from farmyard manure heaps Besides some rheological characteristics, the Ntotal, NH4+-N, NO3? -N, P, K+, dry matter and ash content, as well as chemical oxygen demand and conductivity of farmyard manure leachates were examined. The K+ concentration was highest with an average of 5921 mg l?1, followed by Ntotal (1139 mg l?1, 66% of it as NH4+-N and 4% NO3?-N) and P (334 mg l?1). All parameters were highest in leachates of fresh manure and lowest at the end of a 6 months storage period. During the storage, the P concentration in leachates showed a decrease of 67.7%, followed by a decrease in Nt (-57.3%) and K+ (-24.0%). In leachates from a manure with an relatively high initial Nt content of 0.51% and a low C:N ratio of 16.8 the Nt concentration was 0.5–1 times higher than that of a manure with 0.44% Nt and a C:N ratio of 19.9. The viscosity and the thixotropy of leachates were both relatively high at the beginning of the manure's storage period, which led to a strongly developed blocking of porous systems. These properties that contribute to explain the high retention rate of nutrients in the top soil layer at manure storage sites, decreased with an increase in storage time.  相似文献   

2.
Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO3-N l?1 in 1st year grass-clover to 20–50 mg NO3-N l?1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha?1 year?1 (from 0.9 to 1.4 livestock units ha?1) only increased leaching by 6 kg NO3-N ha?1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO3-N ha?1). Leaching losses were lowest in 1st year grass-clover (20 kg NO3-N ha?1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l?1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.  相似文献   

3.
Understanding the temporal distribution of NO3-N leaching losses from subsurface drained ‘tile’ fields as a function of climate and management practices can help develop strategies for its mitigation. A field study was conducted from 1999 through 2003 to investigate effects of the most vulnerable application of pig manure (fall application and chisel plow), safe application of pig manure (spring application and no-tillage) and common application of artificial nitrogen (UAN spring application and chisel plow) on NO3-N leaching losses to subsurface drainage water beneath corn (Zea mays L.)–soybean (Glycine max L.) rotation systems as a randomized complete block design. The N application rates averaged over five years ranged from 166 kg-N ha?1 for spring applied manure to 170 kg-N ha?1 for UAN and 172 kg-N ha?1 for fall applied manure. Tillage and nitrogen source effects on tile flow and NO3-N leaching losses were not significant (P?<?0.05). Fall applied manure with CP resulted in significantly greater corn grain yield (10.8 vs 10.4 Mg ha?1) compared with the spring manure-NT system. Corn plots with the spring applied manure-NT system gave relatively lower flow weighted NO3-N concentration of 13.2 mg l?1 in comparison to corn plots with fall manure-CP (21.6 mg l?1) and UAN-CP systems (15.9 mg l?1). Averaged across five years, about 60% of tile flow and NO3-N leaching losses exited the fields during March through May. Growing season precipitation and cycles of wet and dry years primarily controlled NO3-N leaching losses from tile drained fields. These results suggest that spring applied manure has potential to reduce NO3-N concentrations in subsurface drainage water and also strategies need to be developed to reduce early spring NO3-N leaching losses.  相似文献   

4.
Nitrate-N (NO3 ?-N) is a ubiquitous pollutant in both surface and groundwater in many agro-ecosystems. This has elicited a concerted effort to identify management strategies that mitigate NO3 ?–N pollution, without compromising crop yield. This study was conducted on a field site located at the Bio-Environmental Engineering Centre (BEEC) in Truro, NS, Canada during 1999 and 2000. The site has been used since 1997 to investigate the relative effect of inorganic versus organic fertilizer (liquid hog manure; LHM) applied at rates (70 kg N ha?1) on NO3 ?-N leaching from a carrot rotation system. NO3 ?-N concentrations were monitored in both the soil profile and in tile drainage effluents from eight treatment plots. The LHM treatment elicited significantly (P < 0.01) higher soil NO3 ?-N concentrations than inorganic fertilizer (IF) in June and October during 1999, but not 2000. The sampling date and soil depth were significant in most cases. Annual flow weighted averages (FWA) of NO3 ?-N in drainage water were generally greater for plots receiving LHM (15.4 and 10.5 mg L?1 for 1999 and 2000, respectively), when compared to IF (8.9 and 6.0 mg L?1 for 1999 and 2000, respectively), but the difference was significant (P < 0.05) only in 1999. Maximum NO3 ?-N concentrations in drainage water were similar for both treatments, while the LHM treatment had a significantly higher percentage of samples that were > 10 mg L?1. The total NO3 ?-N load was greater for the LHM treatment when compared to the IF treatment in 1999. Barley and carrot yields were unaffected by treatment applications.  相似文献   

5.
Environmental issues associated with intensive use of nitrogenous fertilizers have generated an interest in alternative management systems. An experiment was conducted to mitigate nitrate leaching from sandy soil using different waste materials such as charcoal, manure, sawdust, wood ash, and control (no amendment). Urea was applied at the rate of 300 kg nitrogen (N) ha?1. Nitrate was determined during six leaching events. During an incubation experiment, nitrate release was also determined in soil amended with charcoal at the rates of 0, 10, 20, and 40 t ha?1. Urea was applied at the rates of 0, 100, 200, 400, and 1000 ppm N. Results indicated that urea application increased nitrate (NO3) concentration in leachate. Soil amendments substantially reduced NO3 in leachates irrespective of the type of material used. Waste amendments differed for NO3 leaching as follows: charcoal < wood ash < sawdust < manure. Leaching of NO3 enhanced up to the fourth leaching event and thereafter reduced significantly. Nitrate retention in soil varied among material in the order of manure > charcoal > wood ash > sawdust. Nitrate accumulation occurred in the lower layer (25–50 cm) of soil column after the leaching process. Application of charcoal retained greater NO3 level as compared to control soil during an incubation. Enhanced urea applications also enhanced NO3 release. This experiment suggests that waste material can be viably recycled to mitigate NO3 concentration in water.  相似文献   

6.
Forty-two-day-old wheat (Triticum aestivum L. var. Asakazekomugi) plants were treated with complete, K-free (—K), Ca-limited (—Ca), and Mg-free (—Mg) nutrient solutions for 10 days using 2 mM NH4NO3 as the nitrogen source, which was replaced with 4 mM 15 NH4C1 or Na15NO3 for the subsequent 2 days to investigate the absorption, translocation, and assimilation of inorganic nitrogen in relation to the mineral supply. In another experiment plants were grown on NO3 ?, NH4 +, NH4N03, and K-free and Ca-limited NH4N03 nutrient solutions for 10 days, and then in the latter three treatments the nitrogen source was replaced with NO3 ? and half of the —K plants received K for 6 days to examine the changes in the nitrate reductase activity (NRA).

Wheat plants absorbed NH4 ?N and NO3-N at a similar rate. Influence of K on the absorption of N03-N was stronger than that on the absorption of NH4-N in wheat plants. The supply of K to the —K plants increased the absorption of NO3-N, while the absorption of NH4-N still remained at a lower rate in spite of the addition of K. A limited supply of Ca and lack of Mg in nutrient media slightly affected the absorption of NH4-N. The influence of K was stronger on the translocation of nitrogen from roots to shoots, while Ca and Mg had little effect. When K was supplied again to the —K plants the translocation of NO3,-N was more accelerated than that of NH4-N. Incorporation of NH4-N into protein was higher than that of NO3-N in all the tissues; root, stem, and leaf. Assimilation of NH4-N and NO3-N decreased by the —K and —Mg treatments.

Leaf NRA of wheat plants decreased in the —K and —Ca plants. Higher leaf NRA was found when K was given again to the —K plants than when the plants were continuously grown in K-free media. Replacement of NO3 ? with NH4 + as the nitrogen source caused a decline of leaf NRA, while the supply of both NH4 ?N and NO3-N slightly affected the leaf NRA.  相似文献   

7.
Zeolite minerals may improve nitrogen availability to plants in soil and reduce losses to the environment. A study was conducted to determine the influence of clinoptilolite (CL) on nitrogen (N) mineralization from solid dairy manure (224 kg N ha?1) in a sandy soil. Clinoptilolite was added to soil at six rates (0 to 44.8 Mg CL ha?1), each sampled during 11 sampling dates over a year. Over time, nitrate (NO3)-N increased, ammonium (NH4)-N decreased, but total inorganic N increased. Clinoptilolite did not influence the nitrification rates of initial manure NH4-N or mineralization of organic N (ON) over time. It is possible that adsorption of manure-derived potassium (K) outcompeted the NH4-N for CL exchange sites. The ON concentration was constant up to 84 days and then decreased by approximately 18% over the remaining time of the study across all treatments. Clinoptilolite use in this sandy soil did not alter mineralization of N from dairy manure.  相似文献   

8.
Extraction of soil nitrate nitrogen (NO3 ?-N) and ammonium nitrogen (NH4 +-N) by chemical reagents and their determinations by continuous flow analysis were used to ascertain factors affecting analysis of soil mineral N. In this study, six factors affecting extraction of soil NO3 ?-N and NH4 +-N were investigated in 10 soils sampled from five arable fields in autumn and spring in northwestern China, with three replications for each soil sample. The six factors were air drying, sieve size (1, 3, and 5 mm), extracting solution [0.01 mol L?1 calcium chloride (CaCl2), 1 mol L?1 potassium chloride (KCl), and 0.5 mol L?1 potassium sulfate (K2SO4)] and concentration (0.5, 1, and 2 mol L?1 KCl), solution-to-soil ratio (5:1, 10:1, and 20:1), shaking time (30, 60, and 120 min), storage time (2, 4, and 6 weeks), and storage temperature (?18 oC, 4 oC, and 25 oC) of extracted solution. The recovery of soil NO3 ?-N and NH4 +-N was also measured to compare the differences of three extracting reagents (CaCl2, KCl, and K2SO4) for NO3 ?-N and NH4 +-N extraction. Air drying decreased NO3 ?-N but increased NH4 +-N concentration in soil. Soil passed through a 3-mm sieve and shaken for 60 min yielded greater NO3 ?-N and NH4 +-N concentrations compared to other treatments. The concentrations of extracted NO3 ?-N and NH4 +-N in soil were significantly (P < 0.05) affected by extracting reagents. KCl was found to be most suitable for NO3 ?-N and NH4 +-N extraction, as it had better recovery for soil mineral N extraction, which averaged 113.3% for NO3 ?-N and 94.9% for NH4 +-N. K2SO4 was not found suitable for NO3 ?-N extraction in soil, with an average recovery as high as 137.0%, and the average recovery of CaCl2 was only 57.3% for NH4 +-N. For KCl, the concentration of extracting solution played an important role, and 0.5 mol L?1 KCl could fully extract NO3 ?-N. A ratio of 10:1 of solution to soil was adequate for NO3 ?-N extraction, whereas the NH4 +-N concentration was almost doubled when the solution-to-soil ratio was increased from 5:1 to 20:1. Storage of extracted solution at ?18 °C, 4 °C, and 25 °C had no significant effect (P < 0.05) on NO3 ?-N concentration, whereas the NH4 +-N concentration varied greatly with storage temperature. Storing the extracted solution at ?18 oC obtained significantly (P < 0.05) similar results with that determined immediately for both NO3 ?-N and NH4 +-N concentrations. Compared with the immediate extraction, the averaged NO3 ?-N concentration significantly (P < 0.05) increased after storing 2, 4, and 6 weeks, respectively, whereas NH4 +-N varied in the two seasons. In conclusion, using fresh soil passed through a 3-mm sieve and extracted by 0.5 mol L?1 KCl at a solution-to-soil ratio of 10:1 was suitable for extracting NO3 ?-N, whereas the concentration of extracted NH4 +-N varied with KCl concentration and increased with increasing solution-to-soil ratio. The findings also suggest that shaking for 60 min and immediate determination or storage of soil extract at ?18 oC could improve the reliability of NO3 ?-N and NH4 +-N results.  相似文献   

9.
Spinach (Spinacia oleracea cv. Okame) was grown in hydroponic pot culture with an Enshi nutrient solution amended with 0, 20, or 50% urea with or without nickel addition (Ni; 0.05 mg L-1), while the total concentration of N (17.33 mmol L-1) remained constant in all the cases to evaluate the effect of partial urea application, with or without the addition of Ni, on the absorption of NO3-N, urea-N, NH4-N, minerals (e.g. Ca, K, Mg, P) by plants. Fresh and dry weight of the shoots was highest when a 20% urea solution with Ni addition was used. The variation in spinach yield was related to the absorption of total-N by the plants. The absorption of total-N, attributed mainly to NO3-N and urea-N, differed between the treatments. In the case of short-term absorption, determination by using 15N-urea and 15N-KNO3 showed that, the urea-N absorption significantly increased with the increase in the urea concentration in the nutrient solution. When the urea solutions were used, regardless of Ni addition, the absorption of NO3-N was more than four times higher than that of urea-No The addition of Ni in the urea solutions stimulated and increased both urea-N and NO3-N absorption. In the case of long-term absorption, the NO3-N absorption decreased with the decrease of the NO3-N concentration when NO3-N was partially replaced with urea in the nutrient solution. The addition of Ni in the urea solutions resulted in the increase of the absorption of both urea-N and NO3-N, but the NO3-N absorption remained lower in all the treatments compared to the control. In the urea solutions, the absorption of urea-N with or without the addition of Ni increased at a lower rate over time (sampling stages). Application of urea, with or without the addition of Ni in the nutrient solution, increased Ca absorption but decreased K and Mg absorption, whereas, P absorption was unaffected. It is suggested that spinach could grow adequately in an Enshi nutrient solution modified with 20% urea with the addition of 0.05 mg Ni L-1, when urea totally replaced NH4-N and partially replaced NO3-N.  相似文献   

10.
Two field experiments were conducted to evaluate the use of relative chlorophyll content (RCC) in sweet corn leaves as an indicator of nitrate concentration in soil. Study objectives were (1) to evaluate the effect of manure types (chicken and dairy), rates (0, 168, 336, and 672 kg ha?1 equivalent N), and application frequency (one and two applications) of organic amendments on (a) nitrate nitrogen (NO3-N) concentration within and below the crop root zone and (b) the RCC of sweet corn leaves and (2) to quantify the relationship between RCC and NO3-N concentrations. The results showed a significant increase in NO3-N concentrations within and below the root zone and plant leaf RCC under chicken manure treatments. Manure application rates and frequency had a significant effect on both NO3-N concentration within and below the root zone and leaf RCC. It appears that leaf RCC can be used as an indicator of NO3-N availability for sweet corn cultivated under the study conditions.  相似文献   

11.
Corn requires high nitrogen (N) fertilizer use, but no soil N test for fertilizer N requirement is yet available in Quebec. Objectives of this research were (1) to determine the effects of soil nitrate (NO3 ?)-N, soil ammonium (NH4 +)-N, and N fertilizer rates on corn yields and (2) to determine soil sampling times and depths most highly correlated with yields and fertilizer N response under Quebec conditions. Soil samples were taken from 0- to 30-cm and 30- to 60-cm depths at seeding and postseeding (when corn height reached 20 cm) to determine soil NH4 + and NO3 ? in 44 continuous corn sites fertilized with four rates of N in two replications using a quick test (N-Trak) and a laboratory method. The N-Trak method overestimated soil NO3 ?-N in comparison with the laboratory method. Greater coefficients of determination were observed for soil NO3 ?-N analyses at postseeding compared with seeding.  相似文献   

12.
Abstract

A sandy soil was amended with various rates (20 – 320 g air-dry weight basis of the amendments per kg of air-dry soil) of chicken manure (CM), sewage sludge (SS), and incinerated sewage sludge (ISS) and incubated for 100 days in a greenhouse at 15% (wt/wt) soil water content. At the beginning of incubation, NH4-N concentrations varied from 50 – 280 mg kg?1 in the CM amended soil with negligible amounts of NO3-N. Subsequently, the concentration of NH4-N decreased while that of NO3-N increased rapidly. In soil amended with SS at 20 – 80 g kg?1 rates, the NO3-N concentration increased sharply during the first 20 days, followed by a slow rate of increase over the rest of the incubation period. However, at a 160 g kg?1 SS rate, there were three distinct phases of NO3-N release which lasted for160 days. In the ISS amended soil, the nitrification process was completed during the initial 30 days, and the concentrations of NH4-N and NO3-N were lower than those for the other treatments. The mineralized N across different rates accounted for 20 – 36%, 16 – 40%, and 26 – 50% of the total N applied as CM, SS, and ISS, respectively.  相似文献   

13.
测定土壤硝态氮的紫外分光光度法和镉柱还原法比较   总被引：2，自引：0，他引：2  
涂成  黄威  陈安磊  宋歌  陈春兰  王卫  谢小立 《土壤》2016,48(1):147-151
使用改进的紫外分光光度法(校正因素法)和基于镉柱还原的流动注射分析法(镉柱还原法)测定了中国10种不同类型土壤的NO3–-N含量,分析了两种方法的差异性及其适用性。统计分析表明,改进紫外分光光度法与镉柱还原法测定的结果具有极显著的相关性,测定样品的准确度介于89%~104%,具有可比性。在浓度适用上略有差异,对NO3–-N含量极低的土壤样品,采用镉柱还原法可提高精确度;对于NO3–-N含量高的土样选用紫外法可提高测定精确度,测定结果变异性低于镉柱还原法,且紫外法测定值都要高于镉柱还原法。从仪器操作及校准角度来看,紫外法测定操作过程简便,影响因子较少,对NO3–-N批量快速测定更为适用。  相似文献   

14.
The objective of this study was to investigate the effect of adding flue gas desulphurization gypsum (FGDG) on the transformation and fate of nitrogen during co-composting of dairy manure and pressmud of a sugar refinery. The ammonia absorption of FGDG was investigated. The changes in compost temperature, pH, electrical conductivity (EC), moisture, organic matter, the C/N ratio, Kjeldahl N, NH4+-N, NO2?-N, NO3?-N were assessed. The addition of FGDG did not significantly affect compost temperature, pH, EC, moisture, and organic matter degradation. However, the addition of FGDG significantly increased the NH4+-N content in the compost during the thermophilic phase, and the NH4+-N maximal content in the compost with FGDG (CP+G) was 59.9% more than that in the compost without FGDG (CP–G). FGDG was thought to create the formation of (NH4)2SO4 and the cation exchange between NH4+ and Ca2+. The NO2?-N content in the CP+G peaked on day 15, and was not observed in the CP–G. In the final compost products, the NO3?-N concentration in the CP–G was more than that in the CP+G, which was 1451 (CP–G) and 1109 mg·kg?1 (CP+G) dry material. This might be due to the NO2? accumulation in the CP+G, which accelerated N loss in the form of N2O. There is a strong correlation between N2O emission and NO2?-N accumulation in the composting process. Compared with the original N content in the compost mixture, the N loss in CP–G and CP+G were 15.0 and 10.8%, respectively. These results revealed that NH4+-N conservation effect was improved during the thermophilic phase and the total N loss was mitigated by adding FGDG into composting materials. FGDG could be utilized as a potential amendment to conserve nitrogen during composting.  相似文献   

15.
A correct determination of nitrogen (N) fertilization thresholds in wheat that is based on objective yield produces efficient use of this nutrient. Nitrogen fertilization recommendations for traditional wheat require determination of nitrate (NO3 ?)-N availability at 60 cm deep at planting time. However, this methodology is complicated, expensive, and time-consuming; thus, the determination of NO3 ?-N level at a lesser depth and at a different time would be desirable. The goals of this work were to determine available N in soil thresholds for traditional and French germplasm wheats and the feasibility of diagnosing N requirements by measuring NO3 ?-N at 40 cm deep, at planting or tillering times, in the southeastern Pampas. The experiments were factorial combinations of N rates and fertilization times (planting and tillering) at different sites and years during 2002–2006. Nitrogen fertilization significantly increased grain yield and protein content. French varieties presented greater grain yield (23%), lower protein content (11%), and greater yield per N unit, indicating greater N-use efficiency (NUE) than traditional varieties. A similar relationship was determined between grain yield and available N at both sampling depths. This might be explained by the strong association between NO3 ?-N content at 60 and 40 cm deep at both sampling dates. Maximum yield and available N determined at 60 or 40 cm soil deep showed that thresholds were lower for tillering than for planting, regardless of the genotype (152 and 174 kg of available N, respectively). Available N thresholds for 95% of maximum yield were less at 0–40 cm deep than at 0–60 cm deep (10 and 14 kg N ha?1 for traditional and French genotypes, respectively). The results of this experiment suggest the possibility of diagnosing N requirements for wheat by measuring NO3 ?-N content at 40 cm deep, instead of the usual 60 cm, for both traditional and French genotypes.  相似文献   

16.
Nitrogen (N) fertilizer use in cotton (Gossypium hirsutum L.) production is a potential source of nitrate (NO3 ?) contamination of soils, groundwater, and streams. The McConnell–Mitchell plots, a long-term study of cotton responses to N-fertilization and irrigation methods, were utilized to determine the NO3 ?-N in soil cropped to continuous cotton. The McConnell–Mitchell plots had a split-block experiential design. The main blocks of this test were irrigation methods. Each block of plots was irrigated using a single irrigation method for the entirety of the testing. Nitrogen fertilization rates were tested within each irrigation block. The soil NO3 ?-N content of two irrigation blocks, furrow flow (FI) and center pivot (CP), were compared to the dryland (DL) control block. Nitrogen treatments tested within each irrigation block ranged from 0 to 168.0 kg N ha?1 in 33.6-kg N ha?1 increments. Nitrogen treatments were tested for 18 years (1982 through 1999), discontinued for 4 years (2000 through 2003), and resumed in 2004. Soil samples were taken in the early spring (2000 and 2004) to a depth of 1.50 m in 0.15 m increments and analyzed for NO3 ?-N. Soil samples taken in 2004 were prior to any fertilization treatment. Irrigation method was found to influence the distribution of soil NO3 ?-N. Little accumulation of soil NO3 ?-N was observed in either irrigation block or under dryland production when N rates were less than 67.2 kg N ha?1. Distribution of soil NO3 ?-N in the FI block was significantly different with sample depth and N treatment but not the interaction of depth and treatment in both 2000 and 2004. Presumably, the small and close values of the means and the greater variability of interactions compared to main effects precluded significant interactions. Differences in soil NO3 ?-N in the FI block after suspending N treatments for 4 years were similar to those found in 2000, although the soil NO3 ?-N was generally depleted in 2004 compared to 2000. The distribution of soil NO3 ?-N in the CP-irrigated block was dependent on the interaction of sample depth with N treatment in both 2000 and 2004. Soil NO3 ?-N values and differences tended to be too small to be of discernable or practical importance under CP irrigation. The distribution of soil NO3 ?-N in the DL block was dependent on the interaction of sample depth with N treatment in 2000 and 2004. Soil NO3 ?-N was minimal in the three lowest N treatments (0, 33.6, and 67.2 kg N ha?1) in 2000. Greatest amounts of soil NO3 ?-N were found in conjunction with the 134.4 and 168.0 kg N ha?1 treatments both years. Depletion of soil NO3 ?-N was evident in the surface 0.45 m of the 100.8, 134.4, and 168.0 kg N ha?1 treatments under DL conditions in 2004.  相似文献   

17.
Alan Olness  B.W. Dewey 《Geoderma》1982,28(2):117-128
Fine-textured soil cores were saturated with KNO3 solutions, withdrawn at periodic in tervals and examined for mineral N forms. Reduction of NO3? was correlated with time using a first-order rate function. Instantaneous initial NO3?-N reduction rates were determined by taking derivatives of the rate function and setting t = 0. Duplicate experiments gave maximum NO3?-N reduction rates of 1.0 μ N/g soil/h or ? 100 kg NO3?-N/ha/day. Calculated NO3? reduction rates increased with depth down to 30 cm. Net NO3?-N reduction ceased between 48 and 96 h after which net NO3?-N production of 0.016 to 0.29 μg N/g soil/h (～1.5 kg N/ha/day/0 to 20 cm) occurred. Net NH4+-N mineralization ranged from about 0.03 to 0.05 μg N/g soil/h (3.5 to 4.0 kg N/ha/day/0 to 30 cm). Both instantaneous initial NO3?-N loss rates and N mineralization rates are similar to results of laboratory studies elsewhere on similar soil types. This procedure for estimating N-transformations may be useful where other techniques are either not adequate or not feasible for field use.  相似文献   

18.
Soil NH+4-N and NO?3-N at five soil depths (0–10, 10–20, 20–40, 40–60, 60–80 cm) and some environmental variables were measured in a field trial under fallow and wheat for 9 months.Significant linear and quadratic relationships were obtained relating soil NH+4-N, NO?3-N, NH+4-N + NO?3-N, and NH+4-N + NO?3 + total-N uptake by wheat to soil heat accumulation (temperature), moisture, and rainfall. R2 values generally decreased with soil depth and the maximum value (37%) was obtained for NO?3-N changes in the topsoil (0–10 cm).Although a considerable amount of variation in the inorganic values recorded is not included in the equations, our results suggest that the development of the above relationships particularly of the quadratic type are useful to predict crop requirements for N by measurement of environmental variables in the field.  相似文献   

19.
A greenhouse experiment was conducted for 130 days to assess the effect of application of uncoated urea (UA) and 3,4-dimethylpyrazole phosphate–coated urea (UDMPP) on mineral nitrogen (N) content [ammonium (NH4 +)-N and nitrate (NO3 ?)-N] in leachates and growing media. Charlotte rose plants grafted on Natal Briar were cultivated in four different media [soil, 100% burnt rice husks (100BRH), a mixture of 65% burnt rice husks and 35% coconut fiber (65BRH), and 100% coconut fiber (100CF)] and fertigated with UA or UDMPP at rate of 170 mg N·L?1. Results showed that fertilizer induced slight acidity in the leachate collected in all growing media. The use of DMPP diminished cumulative nitrate losses by ?65 and ?60%, in soil and coconut fiber leachates, respectively, as compared to the plots with UA. The UDMPP did not have any effect on nitrate losses in BRH media.  相似文献   

20.
Temporal variations of physical soil properties in the “Static Fertilization Experiment” The objective of the present paper was to observe short-term changes in physical soil properties of a differently fertilized loess-Chernozem. Samples were taken weekly from the plots with 17.2 g Corg kg?1 (unfertilized) and 25.0 g Corg kg?1 (NPK + farmyard manure) of the “Static Fertilization Experiment”, Bad Lauchstädt, and their moisture contents (θ), bulk densities (?d) and particle densities (?s) were determined. The soil moisture contents showed very similar variations in the two treatments. Clear differences between the unfertilized (≈ 16 Vol.-%) and the NPK + farmyard manure treatment (≈ 10 Vol.-%) only occurred during summer (means 25th–29th week). The values for ?d were lower in the NPK + farmyard manure plot (mean: –0.10 g cm?3). Similar short-term changes in ?d were found in both treatments and correlated to both, organic matter contents and composition (Corg, Nt, C/N). These data, however, gave no indication of reasons for the short-term changes in particle densities up to 0.09 g cm?3.  相似文献   

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