施肥对蔬菜中硝酸盐含量的影响

通过对山东省蔬菜面积较大的潍坊和青岛市的蔬菜进行了取样分析及有关的试验,结果表明:依据国家标准(GB18406 1—2001)在所测的所有样品中,蔬菜硝酸盐含量均没有超标。而依据FAO/WHO(1973年)规定,瓜果类和根茎类蔬菜硝酸盐含量均不超标,而叶菜类有近30%超标,超标蔬菜达到了生食盐渍不宜,熟食允许的程度;同一种类蔬菜露天栽培比保护地栽培的硝酸盐积累量少;氮磷钾合理配合施用能减少蔬菜硝酸盐积累。本文提出了控制蔬菜硝酸盐积累的施肥措施。     

施用改良剂对大庆盐碱土的改良效果研究

为控制棚室土壤盐渍化进程,实现大庆盐碱土可持续利用。通过田间小区试验,在等量石膏、菌渣及硫酸铝基础上设置不同腐植酸用量处理,与定植前土壤盐分含量、p H值进行分析比较,以明确不同改良措施对盐碱土的改良效果。试验结果表明:施用4种改良剂的处理5(施用纯腐植酸1 050 kg/hm~2+石膏1 050 kg/hm~2+硫酸铝22.5 kg/hm~2+食用菌菌渣30 000 kg/hm~2)使土壤全盐量由试验前的1.665 g/kg降低到0.851 g/kg;p H值由改良前9.32降低到8.35,下降近1个单位,由碱性变为微碱性;与处理1相比,其番茄增产19.2%,每公顷棚室增效50 070.9元。相关分析表明,土壤全盐、p H值降低量均与纯腐植酸施用量呈一元二次回归关系。综上分析,处理5对盐碱土改良效果最佳,番茄产量、效益最高,是大庆盐碱棚室最优化的综合改良施肥措施。     

The effect on Cd contents and ethylene biosynthesis in tomato plants of adding cadmium sulphate to soil

Water, Air, & Soil Pollution - An experiment was carried out with increasing concentrations of Cd in soil on tomato (Lycopersicon esculentum Mill.) plants. The Cd contents of soil and in tomato...     

聚乳酸纤维沙障对表层土壤含水量的影响

在乌兰布和沙漠西南缘选择大小、走向相近的裸沙丘分别铺设聚乳酸纤维( PLA)沙障与麦草沙障,设计规格为1m×1m、2m×2m、3m×3m.从2008年开始连续3年对2种沙障不同规格、不同坡位表层土壤含水量进行测定,同时以未铺设任何沙障的裸沙丘作为对照,比较新型材料PLA沙障与传统沙障麦草沙障对表层土壤含水量的长时间影响.结果表明:1)PLA沙障与麦草沙障以及裸沙丘含水量都随年份的增加而增加,2类沙障含水量增长幅度明显优于裸沙丘;2)就沙障规格而言,长时间保持土壤水分,效果最好的是PLA沙障2m×2m规格:3)在0～10 cm深度,PLA沙障土壤含水量表现为迎风坡＞背风坡＞坡顶,麦草沙障与PLA沙障相反;4)在10～20 cm深度,PLA沙障土壤含水量表现为坡顶＞迎风坡＞背风坡,麦草沙障同样与PLA沙障相反.     

The effect of bulk density, water content and soil type on the diffusion of chloride in soil

The relative importance of soil bulk density, water content and potential on the self-diffusion and impedance factors of ³⁶C1 in a sandy loam and loamy clay were studied. The soil bulk densities used represented a range of conditions from freshly tilled seedbeds to compacted soils. The volumetric water contents and pF were the main factors controlling the soil impedance factors, with bulk density making a small but significant contribution.
Soil type affects the impedance factors through differences in anion exclusion volumes, the water contents of poorly connected pores that contribute little to the diffusion process, and tortuosity of the diffusion pathways.     

碱化土壤上磷石膏的施用效果

于１９９１～１９９５年在碱化草甸土上设置田间定位试验。结果表明,在施用氮磷化肥的基础上,配施磷石膏３～１８ｔ／ｈｍ２,玉米增产极为显著;土壤全氟量有所增加,但水溶性氟含量未见提高;玉米茎秆和籽粒中含氟量亦在允许范围内。     

钴对冬小麦幼苗生长及钴含量的影响

钴作为维B12的重要组成部分,参与人和动物的造血过程,对贫血有一定的治疗作用.反刍动物对钴有特殊的需要,钴不足则生长发育受到抑制,甚至死亡[1].钴的植物营养研究始于50年代中后期,前苏联在这方面作了大量的工作,施用钴已在大麦、牧草、糖用甜菜、菜豆、葡萄、马铃薯、棉花、玉米等多种作物上获得增产并改善了品质.现已证实,钴是蓝绿藻和微生物以及豆科植物的固氮作用所必需的,但是否为所有高等植物所必需尚无定论[1 - 3].近年来我国对钴在小麦、玉米、大豆、花生等作物的肥效也作了一些研究[4 - 10].本试验研究了盆栽条件下不同钴用量对冬小麦生长发育、生理活性、土壤和小麦植株中钴含量的影响,旨在进一步探明石灰性土壤上的钴肥肥效,为钴肥的开发利用提供依据.     

The effect of chloride and sulphate salts on the nitrate content in lettuce plants (Lactuca sativa L.)

The effect of chloride and sulphate on the nitrate accumulated in lettuce plants (Lactuca sativa L., cv. deci minor) under low light conditions was examined. The plants were grown on a complete nutrient solution for circa 45 days and then chloride was substituted for the nitrate in the nutrient solution. In another experiment, sulphate was substituted for the nitrate in the nutrient solution. Approximately 5 days later a reduction in growth occurred. The nitrate in the plants was not completely exhausted and was very slowly available for reduction both in the leaf blades and midribs. It was immaterial whether sulphate or chloride was substituted for nitrate in the nutrient solution. Chloride was taken up from the solution but sulphate was not. In plants in both treatments, sugars accumulated concomitantly with the decrease in nitrate content.

The actual nitrate reductase activity in the leaf blades decreased several days after the chloride and sulphate treatments began and was negligible on day 12. Nevertheless, the potential nitrate reductase activity of the treated plants was still 50% of the control.

It is suggested that the availability of nitrate from the storage pool is the limiting process for nitrate reductase activity, and is independent of the metabolic demand. For commercial growers it may be of advantage to use hydroponics in which the nitrate can be removed easily several days before harvest, to reduce high nitrate contents in vegetables, particularly under low light conditions.     

果园覆草技术及效应分析

1 果园覆草技术 覆草时间:果树覆草一般在春季整地施肥浇水基础上进行,也可在麦收后利用麦糠进行夏季覆盖.覆盖的物料种类包括各种杂草、麦秸、麦糠或稻草,铡成小段的玉米秸秆等.覆草数量:第一年用草量约15000～22500 kg/hm2,覆盖厚度15～20 cm,以后每年用量9000～12000 kg/hm2.覆草方法:覆草前先把果树树盘土壤扩穴深翻,整平后用草覆盖树盘.同时在果树根颈周围留出20 cm宽的空间,以防止夏天排捞和冬春火灾,覆盖后用少量土把草压实.为了防止初次覆盖后果树暂时缺氮,覆草前比常规多施尿素225～300 kg/hm2.覆盖3～4年后可把草翻入地下,同时进行新一轮覆盖.     

阿勒泰地区土壤有效硼含量状况与施硼效果

阿勒泰地区油葵、大豆、芸豆、甜菜、苜蓿等对硼敏感的经济作物及牧草种植面积已达7 79万hm2,占总播面积的75 2%。因此,对本区土壤有效硼含量及硼肥效果进行了探讨。1　土壤有效硼含量状况微量元素一般呈地带性分布,年际变化量小,在所辖的阿勒泰、布尔津、哈巴河、吉木乃、福海、青河等七县(市)共采集77个耕层土样。调查面积10 16万hm2。基本代表了阿勒泰地区的主要耕作土壤类型(前山丘陵海拔600～800m的栗钙土,戈壁平原及盆地的棕钙土,额尔齐斯河,乌伦古河两河河谷的灰潮土)。用ICP仪测定,全地区土壤耕层有效硼平均含量为0 54mg/kg,…     

Modelling the effect of soil water content and sorption on dye-tracer fluorescence

Fluorescent dye tracers are used to show concentration maps of tracer fronts, plumes and pathways on soil profiles and in monolith cross sections. The physical process of fluorescence from the exposed soil surfaces must be understood in order to retrieve accurately the concentration of such compounds. We found in a laboratory experiment that the fluorescence of quartz sand stained with Acid Yellow depends both on the tracer concentration and the soil water content. In this study, we investigate the dependence of fluorescence on the water content by using a radiative transfer model. The hypothesis of our modelling approach is that fluorescence depends on water content (1) because of the adsorption properties of the tracer and (2) because the microscopic distribution of the water phase changes the positioning and emission of the excited fluorescence molecules in the sample. Our model results show that both factors influence fluorescence to a similar extent, as observed in the Acid Yellow experiment. Because these results explain only part of the overall variation in the experiment, further factors, in addition to the postulated causes, have to be considered for determining concentration maps of fluorescent tracers from real soil profiles.     

The effect of soil water content and microbial activity on restoring the structure of a Vertisol

Soils with high clay content are susceptible to structural damage, if they are intensively cultivated. The structure of soils of the Vertisol group has the tendency to restore as a result of wetting and drying. Samples of a remoulded clayey soil were exposed to seven successive wetting/drying (w/d) cycles, in order to study the change of some structural features of the newly formed aggregates. To assess the effect of soil water content and microbial activity, two different matric water potential ranges were used under sterile and non-sterile conditions.

Aggregate size distribution depended on both the water potential range and microbial activity and approached to a steady state with increasing cycle number. The water stability of the 2–1 mm aggregates was affected by the activity of soil micro-organisms under wet conditions and by forces of mechanical nature when the soil was reaching dryness. All cases resulted in aggregates of reduced water stability with respect to the natural aggregates. The <50 μm aggregated particles initially preserved stability, but after a number of w/d cycles they collapsed at a rate, depending mainly on the water potential range.     

The effect of soil water content during land preparation on aspects of soil physical condition and cotton growth

In a field experiment on cracking clay soil, the effects of soil water content during pre-sowing land preparation and intensity of cultivations during the growing season on soil physical conditions and growth of a furrow-irrigated cotton crop were investigated. Before sowing, cultivations typical of local practice were imposed on soil in a ‘dry’, ‘moist’ and ‘wet’ state, representing three main treatments. During the season, three intensities of inter-row cultivation were superimposed on each of the three main treatments.Soil physical conditions and cotton plant growth were influenced by soil water content during pre-sowing land preparation, but not by subsequent inter-row cultivations. In soil prepared ‘dry’, after the first irrigation significantly more water was extracted by the crop than from either of the other two treatments. The morphology of the post-season soil profile of the land prepared ‘dry’ differed little from the unirrigated and uncultivated pre-season profile, whereas that of the land prepared ‘wet’ had altered considerably, being generally massive to a depth of 0.65 m. Cotton in the land prepared ‘dry’ grew tallest and had most green bolls of any main treatment on most weeks during the season. For most of the season, land prepared ‘dry’ or ‘moist’ had similar above-ground plant dry matter, both having greater amounts than the ‘wet’ treatment. Plant population per metre of row was equal in the ‘dry’ and ‘moist’ treatments, and lower in the ‘wet’. Yield differences were not recorded between treatments as there was high insect damage in the ‘dry’ treatment.     

The effect of soil moisture content on nitrogen transformation using OECD test guideline 216

One of the most important microbial processes in soil is the mineralisation of nitrogen in organic matter and this is vital for the maintenance of soil fertility. When performing a risk assessment for a substance that may enter the soil environment it is important to consider the potential effects the substance may have on the soil's microbial activity. The standardised test produced by the OECD (Organisation for Economic Co-operation and Development) (OECD, 2000) to address this requires that the soil moisture content should be maintained at between 40% and 60% of the maximum water holding capacity (MHC) with a range of ±5%. However, our investigations have suggested that the soil moisture content may adversely affect the performance of the test. The current research aimed to identify the moisture content range, within which the measured concentration of nitrate-N was sufficiently above background levels in soil. This moisture content range, which will be different for soils of different texture types, focused on a sandy loam soil fulfilling the criteria of the OECD 216 guideline (OECD, 2000). The nitrate-N yield and the EC₅₀ (the concentration causing 50% inhibition of nitrogen transformation) of the reference substance, nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine), were determined at varying soil moisture contents. The results indicate that the current OECD recommended upper limit for the soil moisture content (60% MHC) may be too high. The yield of nitrate-N and the EC₅₀ for nitrapyrin, were relatively constant between 20 and 40% MHC. Other reported data (Roberts et al., 2003) suggests that 50% MHC produced similar results. Therefore, we suggest that the OECD test be conducted between 20 and 50% MHC.     

湖南省稻田硒含量及硒肥施用效果

1957年Schwartz和Scott等人[1-2]相继证实硒(Se)是动物所必需的微量元素,但动物日摄取超过Se 2mg/kg就有中毒的危险[3-4].     

The effect of pH on the total and free ionic concentrations of mnganese, zinc and cobalt in soil solutions

Samples of five soils whose pH in the field had been adjusted to between 5.0 and 7.5 were incubated with water or 0.01 m CaCl₂ at 90% field capacity. Additional samples of the most acid soil were limed to various pH values immediately before incubation. Manganese, zinc and cobalt concentrations in the soil solutions, collected by displacement, decreased as the pH increased; the concentrations in calcium chloride solutions were higher than those in water solutions. The free divalent ions Mn²+, Zn²+ and Co²+ were the major metal species in solution at pH 5 but the proportion of the metals present as the free ion decreased as the pH increased. Differences in the manganese and zinc concentrations in the solutions were due not only to the pH of these solutions but also to the original pH of the soil in the field.     

The effect of initial soil water content and rainfall intensity on near-surface soil hydrologic conductivity: A laboratory investigation

This paper investigates the influence of rainfall intensity and initial soil water content on changes in the near-surface soil hydraulic conductivity. While numerous papers have examined surface sealing, this paper outlines two important innovations: the design and application of time-domain reflectometry probes with the ability to measure and record soil water content at very short time and length scales; the design and application of stainless steel tensiometers to measure soil water potential at the same, very short, time and length scales. These permit the Richards Equation to be applied and the near-surface hydraulic conductivity computed. An exponential curve was fitted to the temporal changes in hydraulic conductivity, as both a function of water potential or soil water content, with a high degree of fit. As rainfall intensity increased, the degree of scatter about the best-fit line increased, probably due to the ability of high intensity rainfall to disrupt the near-surface soil structure. While utilising deterministic models, such as the Richards Equation, may be appropriate at the column scale there are practical difficulties due to the very small length scale variability in each of the input variables. The experimental results detailed here indicate that even with data at very short time and length scales it is still not possible to utilize the Richards Equation, or at least, it may be difficult to transfer the laboratory results to the field due to the effect of the specific laboratory experimental conditions on the results.     

覆盖大豆绿肥腐解规律及其对土壤养分的影响

田间条件下采用覆盖尼龙袋的方法,研究了大豆绿肥的腐解规律及其对土壤养分的影响。结果表明,覆盖大豆绿肥随时间的延长逐渐腐解,在整个腐解过程中,前4周腐解得较快,以后腐解减慢,并且在种植玉米条件下比不种植玉米条件下腐解得快,但差异不显著。覆盖大豆绿肥经过玉米整个生长季(8周)的腐解,在种植玉米、不种植玉米的条件下的腐解率分别为54.2%和52.4%,其中前4周的腐解量分别占8周总腐解量的79.5%(种植玉米的条件下)和77.1%(不种植玉米的条件下)。覆盖大豆绿肥能明显提高土壤养分含量。     

水土保持先锋和牧草之王——紫花苜蓿

紫花苜蓿被人们誉为水土保持先锋和牧草之王,得到广泛重视。首先它的根深叶茂,四季可种,保水保土能力强,而且是最好的蜜源植物;其次是它的营养丰富,适口性好,家畜特别爱吃;再次是它生长迅速,根瘤菌极多,含氮磷钾丰富,是优良的绿肥作物;它的色鲜花美,还是绿化美化境境的奇花异卉。今天,要把紫花苜蓿提高到应有的地位,让它在发展农林牧副渔业中发挥应有的作用。