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1.
采用土柱淋洗试验方法 ,对包膜尿素、尿素和硝酸铵在石碴土和粘壤质石灰性土壤中氮的行为进行了评价。结果表明 ,包膜尿素、尿素和硝酸铵的回收总氮量 (包括淋洗溶液中各种形态氮 ,土壤吸附的肥料氮和残余的肥料氮 )分别为施入总氮量的 90.5%、74.2 %、93.5%和91.5%、58.5%、91.1%。在 1750mL淋洗溶液中NO3--N分别占淋洗溶液中总氮量的 90%以上。在 7次淋洗干湿交替之后 ,土壤吸附的肥料氮 (NH4+-N和NO3--N)均不超过施氮总量的2.1% ;包膜尿素有62.7%和70.8%的氮以颗粒肥料存在于土壤中。 3种氮肥中包膜尿素较尿素和硝酸铵在土壤中释放持续的时间显著延长 ,尿素的氨挥发损失较高 ,硝酸铵淋失较快 相似文献
2.
Abstract. Less Intensive Farming and Environment (LIFE) management is a form of integrated farming which aims to meet farming's economic and environmental requirements. We used a farm-scale LIFE demonstration to measure nitrogen (N) leaching losses over a 6 year period (1995–2001) using ceramic suction cups and a meteorological model to give estimates of drainage volumes. Losses from the system averaged 49 kg N ha−1 , with an average drainage nitrate concentration of 15.5 mg N L−1 . Rainfall and its distribution strongly influenced the loss, and drainage N concentration only fell below the nominal target of 11.3 mg N L−1 (the EU limit for potable water) in the two wettest seasons. Crop type did not have a significant effect on either postharvest mineral N (PHMN) in soil or the leaching loss in the subsequent winter. However PHMN and overwinter N leaching declined with increasing crop yield. Overwinter crop N uptake increased with early sowing: leaching loss was only 5 kg N ha−1 under grass sown in early September. Measurements of PHMN, crop sowing date and drainage data were used to construct simple equations to predict average drainage N concentration under various scenarios. The large N loss from our site is partially attributable to soil type (shallow over limestone), indeed on similar soil the loss from a conventional farm nearby was greater. The LIFE practices of postharvest harrowing and late cereal sowing will minimize the need for agrochemical use but they stimulate mineralization and reduce plant N uptake in autumn, leaving more N at risk to leaching. Some assessment of all environmental impacts is needed if the benefits of integrated practices such as those used in LIFE are to be quantified. 相似文献
3.
Leaching column experiments were conducted to determine the degree of mobility of heavy metals (HMs) and nutrients after the addition of municipal solid sewage sludge (MSS) in a sandy‐loam soil. Treatments were (1) soil application of low metal content MSS, (2) soil application of metal‐enriched municipal solid sewage sludge (EMSS), and (3) control. The MSS application represented a dose of 200 Mg dry weight (dw) ha–1. Soil columns were incubated at room temperature for 15 d and were irrigated daily with distilled water to make a total of 557 mm. Leachates were collected and analyzed for HMs and nutrients. The Ni and Pb added to soil via MSS and EMSS were found to be leached through the 20 cm columns of calcareous sandy soil although Ni and Pb concentrations in the percolate were small relative to the total amounts of metals applied. Losses of K+ from the EMSS, MSS, and control were 92.5, 82.0, and 52.5 kg ha–1, respectively. Losses of Mg2+ were in the range from 104.4 (control treatment) to 295.2 kg ha–1 (EMSS), while the loss of Ca2+ was in the range from 265.0 (control treatment) to 568.2 kg ha–1 (EMSS). The results showed that the amounts of P leached from EMSS (3.02 kg ha–1) and MSS (2.97 kg–1 ha–1) were significantly larger than those from the control treatment (1.54 kg ha–1). The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate‐limited dissolution of hydroxyapatite, β‐tri‐Ca phosphate, and octa‐Ca phosphate. The results indicate that application of MSS to a sandy soil, at the loading rate used in this study, may pose a risk in terms of groundwater contamination with Ni, Pb, and the studied nutrients. 相似文献
4.
When potassium (K+) fertilizers are applied to the soil, K+ is subject to displacement through the soil profile. Leaching can play an important role in agricultural K+ losses that can decrease groundwater quality. To avoid overfertilization, estimation of K+ leaching from soil is important. The ability of the soils to retain K+ against leaching varies according to the adsorption coefficient of the soils. The aim of this study was to relate the K+ leaching from a wide range of calcareous soils to the values obtained from a sorption–desorption experiment. The soil columns were leached with 10 mM CaCl2 solution and the leachate was analyzed for K+. The breakthrough curves for K+ were different, and the amounts of K+ leached varied considerably between different soils. In these calcareous soils where crops are irrigated with water containing significant concentrations of Ca2+ and other cations, large amounts of K+ will be leached. Cumulative K+ leached after five pore volumes leaching with 10 mM CaCl2 was significantly (r = 0.776, p < 0.01) related to the equilibrium K+ concentration. The results of this study enabled us in many cases to estimate the K+ leaching from soil without conducting column experiments, minimizing the laborotary work. 相似文献
5.
Abstract. A field experiment on a coarse sand (1987–92) was conducted with spring barley ( Hordeum vulgare L.), in order to evaluate the effects of increasing N fertilization on nitrate leaching under temperate coastal climate conditions. The N fertilizer levels were 60 and 120 kg N/ha. The experiment was conducted on a 19-year old permanent field trial with continuous spring barley, initiated in 1968, and included treatments with ploughing in autumn or spring, with or without perennial ryegrass ( Lolium perenne L.) as a catch crop undersown in spring. Prior to 1987, the low and high levels of N fertilizer were 70 and 150 kg N/ha, respectively. To calculate nitrate leaching, soil water samples were taken from a depth of 0.8 m using ceramic cups. The average annual nitrate leaching from plots with 60 and 120 kg N/ha was 38 and 52 kg N/ha/y, respectively. The increased leaching associated with increasing fertilizer application was not caused by inorganic N in the soil at harvest, but rather by greater mineralization, mainly in autumn. Growing of a catch crop was relatively more efficient for reducing nitrate leaching than a long-term low fertilizer application. A 50% reduction in N application decreased average yield by 26%, while nitrate leaching decreased by 27%. 相似文献
6.
ABSTRACTWe studied (i) the pH buffer capacity (pHBC) of calcareous soils varied widely in calcite and texture, (ii) the contribution of soil properties to pHBC and (iii) the significance of using a model based on calcite dissolution to estimate the pHBC of calcareous soils. The pHBC of soils was measured by adding several rates of HCl to soils (100–6500 mM H+ kg–1), in a 0.01 M CaCl2 background and an equilibration time of 24 h. The pHBC (mM H+ kg–1 pH?1) varied from 55 to 3383, with the mean of 1073. The pHBC of the soils was strongly correlated with soil CaCO3 equivalent (calcite) (r = 0.94), sand (r = ?0.72), silt (r = 0.60), EC (r = 0.63), pH (r = 0.55), and weakly (r = 0.37) but significantly with clay content. The attained pHBC values indicated that calcite was probably the main buffer system in these soils. The chemical equilibrium model successfully predicted pH titration curves based on calcite dissolution, indicating buffering of acid inputs in the calcareous soils is dominated by calcite dissolution. The model can be used to simulate acidification of calcareous soils and to provide information for making environmental management decisions. 相似文献
7.
8.
Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies. 相似文献
9.
Abstract. Nitrate leaching from crop rotations supporting organic grain production was investigated from 1997 to 2000 in a field experiment at three locations in Denmark on different soil types. Three experimental factors were included in the experiment in a factorial design: (1) proportion of N2 -fixing crops in the rotation (crop rotation), (2) catch crop (with and without), and (3) manure (with and without). Three, four-course rotations were compared, two at each location. The nitrate leaching was measured using ceramic suction cells. Leaching losses from the crop rotation with grass–clover green manure and without catch crops were 104, 54 and 35 kg N ha−1 yr−1 on the coarse sand, the loamy sand, and the sandy loam, respectively. There was no effect of manure application or time of ploughing-in the grass–clover green manure crop on the accumulated nitrate leaching from the entire rotation. Catch crops reduced nitrate leaching significantly, by 30–38%, on the sandy soils. At all locations catch crops reduced the annual averaged nitrate concentration to meet drinking water quality standards in the crop rotation with green manure. On the coarse sand there was a time lag between the onset of drainage and the start of N-uptake by the catch crop. 相似文献
10.
Abstract. Four management systems combining high and low livestock densities (0.7 and 1.4 livestock units ha−1 ) and different types of organic manure (slurry and straw based FYM) were applied to an organic dairy crop rotation (undersown barley – grass–clover – grass–clover – barley/pea – oats – fodder beet) between 1998 and 2001. The effects of the management systems on crop yields and nitrate leaching were measured. In all four years, nitrate leaching, as determined using ceramic suction cups, was higher in the three crops following ploughing of grass–clover than under the barley or grass–clover. Overall, no significant differences in nitrate leaching were observed between the management systems. However, the replacement of the winter wheat crop used in the earlier experimental period (1994–97) by spring oats with catch crops in both the preceding and succeeding winters reduced nitrate leaching compared with the earlier rotation. Increasing the livestock density, which increased manure application by c. 60 kg total N ha−1 , increased crop yields by 7 and 9% on average for FYM and slurry, respectively. Yields were 3–5% lower where FYM was used instead of slurry. The experiment confirmed the overriding importance of grassland N management, particularly the cultivation of the ley, in organic dairy crop rotations. 相似文献
11.
J. Berntsen R. Grant J. E. Olesen I. S. Kristensen F. P. Vinther J. P. Mølgaard & B. M. Petersen 《Soil Use and Management》2006,22(2):197-208
Organic farming is considered an effective means of reducing nitrogen losses compared with more intensive conventional farming systems. However, under certain conditions, organic farming may also be susceptible to large nitrogen (N) losses. This is especially the case for organic dairy farms on sandy soils that use grazed grass–clover in rotation with cereals. A study was conducted on two commercial organic farms on sand and loamy sand soils in Denmark. On each farm, a 3‐year‐old grass–clover field was selected. Half of the field was ploughed the first year and the other half was ploughed the following year. Spring barley (Hordeum vulgare L.) was sown after ploughing in spring. Measurements showed moderate N leaching during the pasture period (9–64 kg N ha?1 year?1) but large amounts of leaching in the first (63–216 kg N ha?1) and second (61–235 kg N ha?1) year after ploughing. There was a small yield response to manure application on the sandy soil in both the first and second year after ploughing. To investigate the underlying processes affecting the residual effects of pasture and N leaching, the dynamic whole farm model farm assessment tool (FASSET) was used to simulate the treatments on both farms. The simulations agreed with the observed barley N‐uptake. However, for the sandy soil, the simulation of nitrate leaching and mineral nitrogen in the soil deviated considerably from the measurements. Three scenarios with changes in model parameters were constructed to investigate this discrepancy. These scenarios suggested that the organic matter turnover model should include an intermediate pool with a half‐life of about 2–3 years. There might also be a need to include effects of soil disturbance (tillage) on the soil organic matter turnover. 相似文献
12.
Abstract. The effect of nitrogen fertilizer inputs to cereal crops on nitrate leaching after harvest was tested on 21 experiments on sandy soils in England. At small nitrogen fertilizer rates leaching increased very little with increasing inputs, while at high rates more than half of any additional nitrogen could be accounted for as increase in nitrate leached. In many cases the response fitted two straight lines. Nitrogen offtake in grain also fitted two straight lines, with a form which complemented the leaching response. The gradient averaged 0.52 kg N in grain for every additional 1kg N applied below the break point, but only 0.05 kg/kg above. The break points were generally close to or above the economic optimum N input. The effect of inputs on leaching could he quantitatively related to nitrogen offtake in grain, assuming a constant ratio of nitrogen in grain to total nitrogen uptake. The results show that fields receiving N inputs in excess of the economic optimum cause a disproportionately large nitrate loss. However because of uncertainty in predicting the break point in advance, modest further reduction in leaching will occur by reducing inputs to somewhat below the expected economic optimum. 相似文献
13.
A. M. Matthews A. C. Armstrong P. B. Leeds-Harrison G. L. Harris J. A. Catt 《Soil & Tillage Research》2000,53(3-4):245-254
Both water movement and nitrate leaching in structured soils are strongly influenced by the nature of the macro-porosity. That macro-porosity can however also be manipulated by choice of tillage operations. In order to investigate the potential impacts of tillage on rates of nitrate leaching from structured soils, a model specific to these soils, CRACK-NP was developed. The model, its application and validation for an experimental site on a heavy clay soil (Verti-Eutric Gleysoil) at Brimstone Farm, Oxfordshire, UK, is described. The model considers the soil as a series of aggregates whose size is also the spacing of the macro-porosity. Water and solutes move in the macro-pores, but within the peds they move only by diffusion, internal infiltration and root uptake (evaporation). The model reflects the influence of diffusion limitation in the release of solutes to by-passing water. The model was then used to investigate the influence of variable ped spacings which were created by variations in tillage practices. The results both from the model and from the field data demonstrated that finer soil structures, which have larger surface contact areas and shorter diffusion path lengths, present greater opportunities for interaction between peds and the water moving around them, and so release more nitrates through the drainage waters. 相似文献
14.
Abstract. In organic farming, potassium (K) deficiency may become a significant problem due to nutrient import restrictions. Knowledge about potential K leaching in systems with different K budgets is therefore important for effective agricultural management. We investigated the effect of four organic farming systems (two livestock densities in combination with two types of organic manure) on crop yields, K leaching and K balances in a six course crop rotation from 1993/94 to 1997/98. Average K concentrations in soil water extracted by means of ceramic suction cups at 1 m depth were 0.6 mg K l−1 corresponding to a K leaching loss of 1.5 kg ha−1 yr−1 which was less than expected from values reported in the literature. Variation in K budgets from −12 to +30 kg ha−1 yr−1 did not affect K leaching. In an additional experiment with application of 988 kg K ha−1 as KCl, K leaching accounted for only 0.2% of the applied K although 40% of the accompanying Cl was leached. The main part of the applied K was retained in the topsoil. It was concluded that K leaching was a result of the fertilizer history rather than of the current K budget. 相似文献
15.
Nitrate leaching from arable and horticultural land 总被引：7，自引：0，他引：7
K. Goulding 《Soil Use and Management》2000,16(S1):145-151
16.
A greenhouse experiment was carried out to determine copper (Cu) desorption characteristics in ten bulk and rhizosphere soils (Typic Calcixerepts) amended with sewage sludge (1% w/w) using rhizoboxes. The kinetics of Cu desorption in the bulk and the rhizosphere soils were determined after successive extraction with DTPA‐TEA and 10 mM citric acid in a period of 1 to 504 h at (25 ± 1)°C. The results show that Cu extracted after 504 h using DTPA‐TEA were significantly (P < 1%) lower in the rhizosphere than the bulk soils. However, Cu extracted after 504 h using citric was significantly (P < 1%) higher in the rhizosphere than in the bulk soils. The results illustrated that, on average, citric acid extracted 56% more Cu from the bulk soils than DTPA‐TEA, and citric acid extracted 85% more Cu from the rhizosphere soils than DTPA‐TEA. Desorption kinetics of Cu in the two extractants was well described by power‐function, parabolic diffusion, and first‐order equations. The results show that a 10 mM citric acid extractant may be recommended to determine the kinetics of Cu desorption in calcareous soils amended with sewage sludge. 相似文献
17.
通过采集土壤溶液并分析其硝态氮（NO3^--N）含量,结合水量平衡方法,研究了华北太行山前平原小麦-玉米轮作农田在当前农民普遍采用的农业管理措施下土壤NO3^--N迁移、累积特征,计算了深层土壤水分渗漏与NO3^--N淋溶损失量。结果表明,土壤水分渗漏、NO3^--N的分布及其淋溶损失存在着明显的时空变异性,土壤水分的深层渗漏和NO3^--N的淋溶损失发生在玉米生长期间施肥灌水或降雨之后。在1998／1999和1999／2000两个作物轮作年中,土壤水分的深层渗漏损失分别为33～48mm（平均39mm）和90～92mm（平均90.7mm）,分别占降水＋灌溉总量的10％和19％;淋溶到根区之下的NO3^--N量（包括来自土壤和肥料的N）分别为N12kg hm^-2（范围N6～17kg hm^-2）和N61 kg hm^-2（范围N30～84kg hm^-2）,分别占施入肥料量的1．4％～4．1％和7．3％～20．3％。在玉米生长期间有较大潜力可调控灌溉与肥料用量,以提高水肥利用效率。 相似文献
18.
《Communications in Soil Science and Plant Analysis》2012,43(7):595-606
Abstract The effects of increasing levels of NaCl in the irrigation water on the foliar content of N, P, K, Ca, Mg, Fe, and Mn of six citrus seedling varieties were studied. The experiment was carried out under greenhouse conditions in a factorial design. Treatments consisted of addition of irrigation waters containing 1.5, 10, 20, and 40 me NaCl/l. Increasing salinity significantly decreased K and Mn contents and increased those of N and Mg. Leaf content of P, Ca, and Fe was not affected. Results also showed that seedling variety and sampling data had a significant effect on the mineral composition of the leaf. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(13-14):1877-1888
Abstract Highly calcareous soils are abundant in Iran. The calcium carbonate equivalent (CCE) of these soils reach up to 650 g kg?1. Although phosphorus (P) fertilizer is being widely used in these soils, little information, if any, is available about P status in such soils. The objectives of this study were to 1) determine inorganic P forms in 18 surface soils of southern Iran, 2) study P readsorption during different stages of fractionation schemes, 3) assess the ability of NaOH to extract aluminum (Al)‐P, and 4) evaluate the relationships between P availability indices and inorganic P forms. Eighteen soil samples with a wide range of physicochemical properties were selected for this study. Inorganic P forms was determined by sequential extraction with NaHCO3, NH4OAc, NH4F, NaOH, citrate dithionite (CD), and H2SO4, which are referred to as Ca2‐P, Ca8‐P, Al‐P, Fe‐P, occluded P (O‐P), and Ca10‐P. Phosphorus readsorption in different stages was determined by 1 M MgCl2. Furthermore, a fractionation scheme without an NH4F step was used to evaluate the ability of NaOH to extract Al‐P. NaHCO3 (Olsen‐P) and MgCl2‐extractable P (Exch‐P) were regarded as P-availability indices. The abundance of different P forms was in the order Ca2‐P<Fe‐P<Al‐P<O‐P<Ca8‐P<Ca10‐P. Ca2‐P was highly correlated with Olsen‐P and Exch‐P. Ca2‐P, Olsen‐P, and Exch‐P showed a relationship with CCE, citrate–bicarbonate–dithionite extractable Fe (Fed), and Al (Ald). Phosphorus readsorption appeared to be important only in the Ca8‐P step, and the content of readsorbed P was related to Ca8‐P, CCE, and clay content of the soils. In the present study, Al‐P and Fe‐P accounted for 10 and 5% of the sum of the inorganic P fractions, respectively, and Fe‐P showed a strong relationship with Feo, whereas Al‐P showed a significant relationship with oxalate‐extractable Al (Alo) and Ald. It was found that one extraction with NaOH is not a good indicator for Fe‐ and Al‐P, and the ability of NaOH to extract Al‐P was reduced with increase in Al‐P content. 相似文献
20.
This study was conducted to investigate the effect of time on chemical forms of P in 10 calcareous soils of western Iran. Phosphorus was added to soils at the rate of 200 mg kg?1 as KH2PO4. The samples were incubated for 1, 7, 15, 30, 60, 90 and 120 days at 25°C and constant moisture. After incubation, P was fractionated by the sequential extraction procedure: soluble and exchangeable P (NaHCO3-P) Al + Fe-P (NaOH-P), Ca-P (HCl-P) and residual P (Res-P). The distribution of added P into different fractions consisted of two phases involving initial rapid retention followed by a slow continuous retention. In general, the majority of the P applied entered mostly in the HCl-P and Res-P fractions. After 120 days incubation, the HCl-P fraction remained the most dominant in all soils. A combination of silt and sand content of the soils together explained between 88.5 and 83.3% of the variance inNaHCO3-P and HCl-P transformation rates, respectively, 76.6 and 72.8% of which is explained by silt alone. CaCl2-P and electrical conductivity (EC) together accounted for 66.3% of the variation in the rate constant of NaOH-P. The release rate of Res-P was not significantly related to soil properties. 相似文献