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1.
Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha?1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO3? leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha?1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha?1 for the P1 treatment and 6058 kg TDS ha?1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry‐treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha?1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution.  相似文献   
2.
Although the effects of cover crops (CC) on various soil parameters have been fully investigated, less is known about the impacts at different stages in CC cultivation. The objective of this study was to quantify the influence of CC cultivation stages and residue placement on aggregates and microbial carbon (Cmic). Additionally, the influence of residue location and crop species on CO2 emissions and leached mineralized nitrogen (Nmin) during the plant degradation period was also investigated. Within an incubation experiment, four CC species were sown in soil columns, with additional columns being kept plant‐free. After plant growth, the columns were frozen (as occurs in winter under field conditions) and then incubated with the plant material either incorporated or surface‐applied. With CC, concentrations of large and medium macroaggregates were twice that of the fallow, confirming positive effects of root growth. Freezing led to a decrease in these aggregate size classes. In the subsequent incubation, the large macroaggregates decreased far more in the samples with CC than in the fallow, leading to similar aggregate size distributions. No difference in Cmic concentration was found among the CC cultivation stages. CO2 emissions were roughly equivalent to the carbon amounts added as plant residues. Comparison of columns with incorporated or surface‐applied residues indicated no consistent pattern of aggregate distribution, CO2 emission or Cmic and Nmin concentrations. Our results suggest that positive effects of CC cultivation are only short term and that a large amount of organic material in the soil could have a greater influence than CC cultivation.  相似文献   
3.
利用超声波对化肥控失材料(LCM)进行修饰改性,结果表明对硫酸铵的控失效果随处理时间呈现先升高然后降低的规律,峰值出现在5min.本文对其机理进行初步探讨.  相似文献   
4.
5.
肥料结构对红壤氮素淋失的影响及防治措施   总被引:9,自引:2,他引:9  
肥料结构是影响氮素淋失的重要因素。氮肥进入土壤后,其损失途径主要是氨挥发和反硝化的气态损失。但是,氮肥通过渗漏淋失对地下水(饮用水源)的污染,也不容忽视。为此,综述了近年来3种肥料结构(即单施无机氮肥、无机肥混施、无机肥与有机肥混施)对红壤区稻田土壤氮素淋失的影响的研究进展,并且提出了如何防止氮素淋失的对策  相似文献   
6.
疏勒河灌区新垦盐碱地洗盐定额试   总被引:2,自引:0,他引:2  
根据疏勒河灌区新垦盐碱地土壤含盐量高,需采用水平明沟排水冲洗改良的实际,开展了不同冲洗定额的洗盐效果试验研究,提出了排盐地区系数经验公式与冲洗定额对数函数计算公式。根据表层土壤含盐量高的特点,提出了以0~30cm土层作为冲洗改良盐碱地脱盐控制层的准则,并制定了相应的洗盐定额。  相似文献   
7.
为研究有机培肥对土壤优势流中养分淋失的影响,采用原状土柱模拟淋溶的方法,对土壤优势流中养分淋失的情况进行研究.结果表明,土壤经有机培肥后,明显降低了优势流中各种养分的淋失速度,从而使养分的淋失总量减少,为未施秸秆处理的1/3左右.有机培肥土壤对于淋溶液中养分浓度的影响表现为,在淋溶液中养分浓度总体降低的同时,各种养分的浓度降低的幅度又有所不同,其中对水溶性K和铵离子的效果最明显,而对硝态氮(NO-3-N)保持作用则相对差些.上述结果说明,有机培肥对减少土壤优势流造成的土壤养分淋失以及降低地下水污染都有一定的作用.  相似文献   
8.
Abstract

Soils under the main mangrove (Rhizophora racemosa and Avicennia germinans) forest in the Niger Delta, Nigeria, were characterized, and their capacities to retain heavy metals were examined by using soil column leaching experiments, using 20 mg L?1 Cu, 50 mg L?1 Zn, 20 mg L?1 Cd, and 100 mg L?1 Mn solutions. At the end of the leaching experiments, soil samples from each column were divided into two layers (0–5 cm and 5–10 cm) and analyzed for total metal retained. The fractionation of heavy metals in the surface soil samples (0–5 cm) was investigated by the sequential extraction technique. The study showed that the soils were influenced by tidal flow and characterized by the presence of very fine textured, thin (0–5 cm) to moderately thick (10–15 cm) layer of alluvium (mud) on the surface. The fibric soil material beneath the surface mud varies in thickness from about 70 to 100 cm, and beyond the histic layer is the plastic, very sticky, massive clay. In situ, the soils were neutral in reaction (pH 7.0–7.2), but became strongly acid (pH 3.3–4.8) upon drying. They are saline, high in soluble salts, highly reduced, with CEC that is low in the fibric layer, but high in the mineral, clayey subsoil horizon. The soils are saturated with water for much more than 30 days in a year and have fiber content that is more than 40 cm thick, with the fibric sphagnum constituting more than three‐fourths by volume to a depth greater than 90 cm. The soils, classified as Typic Sphagnofibrists, sequestered considerable amounts of copper (Cu), zinc (Zn), cadmium (Cd), and manganese (Mn) with most of the metals retained in the surface soils. The anthropogenic heavy metals were mostly adsorbed probably to the negatively charged sites of organics and clay. These loosely bound metals may be desorbed and reenter the aqueous phase, thus becoming a secondary source of metal pollution.  相似文献   
9.
Abstract

In a lysimeter study it was found that moderate rates of ammonium nitrate increased utilization percentages in spring wheat, and the leaching was 10% or less of added N. Over-optimal rates reduced utilization percentages and increased leaching to almost 50% of the highest doses. Late split application of calcium nitrate increased the percentage of N in grain. Furthermore, leaching of N was not reduced, but occurred somewhat later in the fall and winter seasons. Leaching of Cl? was more rapid and that of SO4 2- was delayed relative to the leaching of NO3 ?. Rather large negative N balances were obtained, also after over-optimal application rates, and total N content of the soil was reduced. Compared with the N0 treatment, differences in soil N residues amounted to 15–25% of added N in seven years. Gaseous losses had apparently taken place both from the added N and from soil N according to the total-N analysis.  相似文献   
10.
Return of high nitrogen (N) content crop residues to soil, particularly in autumn, can result in environmental pollution resulting from gaseous and leaching losses of N. The EU Landfill Directive will require significant reductions in the amounts of biodegradable materials going to landfill. A field experiment was set up to examine the potential of using biodegradable waste materials to manipulate losses of N from high N crop residues in the soil. Leafy residues of sugar beet were co‐incorporated into soil with materials of varying C:N ratios, including molasses, compactor waste, paper waste, green waste compost and cereal straw. The amendment materials were each incorporated to provide approximately 3.7 t C per hectare. The most effective material for reducing nitrous oxide (N2O) production and leaching loss of NO3? was compactor waste, which is the final product from the recycling of cardboard. Adding molasses increased N2O and NO3? leaching losses. Six months following incorporation of residues, the double rate application of compactor waste decreased soil mineral N by 36 kg N per hectare, and the molasses increased soil mineral N by 47 kg N per hectare. Compactor waste reduced spring barley grain yield by 73% in the first of years following incorporation, with smaller losses at the second harvest. At the first harvest, molasses and paper waste increased yields of spring barley by 20 and 10% compared with sugar beet residues alone, and the enhanced yield persisted to the second harvest. The amounts of soil mineral N in the spring and subsequent yields of a first cereal crop were significantly correlated to the lignin and cellulose contents of the amendment materials. Yield was reduced by 0.3–0.4 t/ha for every 100 mg/g increase in cellulose or lignin content. In a second year, cereal yield was still reduced and related to the cellulose content of the amendment materials but with one quarter of the effect. Additional fertilizer applied to this second crop did not relieve this effect. Although amendment materials were promising as tools to reduce N losses, further work is needed to reduce the negative effects on subsequent crops which was not removed by applying 60 kg/ha of fertilizer N.  相似文献   
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