土壤含水量和容重的空间变异及其分形特征

在小区面积为７．５ｍ×７．５ｍ的冬小麦农田，用烘干法和时域反射仪分别测定了表层０－１５ｃｍ土壤含水量和体积含水量，并用θｖ／θｇ求得土壤的容重。小区内测定网格单元为０．５ｍ×０．５ｍ。根据测定结果，用常规统计方法计算了均值，平均差，标准差，变异系数等传统统计特征值，并指出了用该方法表示土壤特性引起的困惑。     

一种地表径流模拟装置的研制与应用

为产生一种流经植被过滤带的薄层水流研制了一种往流模拟器（ＦＳＡ）。该装置取料容易，功能全，携带方便，性能稳定，变异系数小于１．５％，地表径流的试验流量为≥４Ｌ／ｍｉｎ，初始田间试验中，应用该装置向１ｍ × ５ ｍ的水牛草小区施用 ０．１ｍｇ／ｋｇ的莠去津溶液。草地的径流量相当于在 ５１ｍｍ降雨量情况下直接从 ３０ ｍ宽的坡上产生的径流量。在最初的 １５ ｍｉｎ内，流出的莠去津溶液的浓度降低，然后上升，最后稳定在输入浓度的 ８５％。稍加修正，ＦＳＡ可以为集中径流实验提供输入水流。     

黄土高原坡耕地土壤水分主要受控因子研究

通过对０°￣２５°坡耕地２４０ｃｍ以上土层１α内各层土壤水分状况每周的预测,结合同期降水资源,研究土壤水分在５－９月份的变化情况,从而得出土壤含水量随坡度增大呈减少趋势;距分水岭３０ｍ处土壤含水量最高（９％坡度）;土壤水分含量随雨量增大而增大;中等雨强降雨对土壤水分影响最大;高茬覆盖有利于增加土壤含水量,５－９月份,土壤月平均含水量呈正弦曲线变化的规律。     

通过地下滴灌管施用N^15标记肥料的装置

本文介绍一种通过地下滴灌管施用Ｎ＾１５肥料的新型装置。将叶用莴苣植于未施肥并设有地下滴灌装置的小区内（４．０６×５３．３４ｍ），此区含４条南北向的田块。设置六个小区（１．０２×２．００ｍ），在小区内将Ｎ＾１５注射装置与地下滴灌管连接起来。不同氮水平（７１－１７６ｋｇ·ｈａ＾－１）处理各重复三次，在生长季将含Ｎ＾１５１．６０和１．１５ａｔｏｍ％的尿素分五次分别施入低氮区和高氮区。然后在小区内或靠近小     

玄武岩发育土壤的磁化率及其机理解析

应用矿物磁测技术和Ｘ－射线衍分析对浙江和云南武岩发育土壤的磁化率机理进行了研究。浙江玄武岩发育土壤的ｘ为１００×１０＾－８￣５００×１０６－８ｍ＾３／ｋｇ,云南玄武岩发育土壤的ｘ在５００×１０＾－８￣２０００×１０＾－８ｍ＾３／ｋｇ,合成针铁矿的ｘ为３１．９×１０＾－８ｍ＾３／ｋｇ,赤铁矿ｘ为８４．５×１０＾－８ｍ＾３／ｋｇ,且合成氧化铁的ｘ随氧化铁的铝替代量增大而增加,土壤的磁一参数和Ｘ－射线衍     

梯田玉米有机肥最佳施用量的研究

施用２种有机肥（羊粪、猪粪）,并配施少量化肥,进行雨养梯田种植玉米的田间试验,结果表明,施有机肥后土壤总孔隙度、毛管孔隙度分别提高５．２％～１３．１％和３．６％～１０．０％,土壤容重降低１．８％～７．９％;雨后土壤含水量提高９．８％～１５．３％;玉米平均株高、平均茎粗分别增加０．１～６．５ｃｍ和０．１～０．５ｃｍ,玉米产量提高３３．５％～７７．２％。玉米产量与有机肥施用量呈３次方关系,并由此确定了     

西南山区农地土壤前期含水量对优先流的影响

在重庆四面山的4块农地上,通过前期洒水使样地具有不同的土壤前期含水量,应用优先流染色法和室内图像提取技术分析样地垂直剖面和水平剖面的土壤染色情况,并在染色过程中用TDR记录样地每层土壤含水量的变化,分析不同前期含水量下优先流的入渗深度及入渗速率,研究土壤前期含水量对优先流的影响。结果表明:(1)土壤前期含水量低的样地,湿润锋的渗透速率随土层深度的增加而增加,湿润锋平均入渗速率为1 520mm/h;土壤前期含水量高的样地,湿润锋的渗透速率随土层深度的增加而减小,湿润锋平均入渗速率为515mm/h;(2)土壤前期含水量较低的样地垂直剖面的染色示踪物平均最大入渗深度为56.00cm,大于前期含水量较高的样地的33.76cm,说明土壤前期含水量低的样地优先流渗透深度更大;(3)土壤前期含水量较高的样地,优先流主要发生在土壤A层和B层的20-30cm土层深度处,而前期含水量低的样地优先流在A层、B层和C层均有发生。而且土壤前期含水量较低的样地,垂直剖面每层的平均染色面积均大于前期含水量高的样地,说明土壤前期含水量较低的样地优先流现象更明显。     

封丘地区土壤水分扩散率的研究

本文研究了河南封丘地区代表性土壤的水分扩散率,结果表明:封丘地区3个土壤亚类的水分扩散率变化于1. 0×10-3 ~1. 5×10cm2 min-1之间;土壤水分扩散率存在着空间上的变异性,随土壤剖面深度增加而呈现出表土层高、中间土层低、底土层又升高的趋势;各土层土壤水分扩散率与土壤含水量呈指数函数变化关系,经统计分析均达到极显著水平;土壤容重、孔隙度及孔隙类型、土壤有机质含量和土壤粘粒含量均对土壤水分扩散率有不同程度的影响,而土壤全盐含量对其影响不大。     

五对小麦品种和突变体农艺性状的杂种优势和配合力效应比较分析

以５对小麦材料及其相应的突变体为参试亲本，组配成两套２×４ＮＣⅡ交配设计，对其Ｆ１的优势及配合力效应进行了对比分析，结果表明：除抽穗期的超中亲优势在第Ⅱ套组合中为负值外，其它性状的超中亲优势均为正值，一般而言，以突变体作亲本，其后代的实际表面优于以原始材料作亲本。８９００１８×７８－１－１和８９０１７４×核生２号两个组合对改善后代穗部性状最为有利。原丰５号×掖农７８－１和鲁麦２０号×原丰５号两个组     

区域土壤有机碳密度及碳储量计算方法探讨

土体中有机碳含量在纵向和横向上都具有空间相关性。本文利用曲周县四疃乡30个土壤剖面的有机碳含量数据,采用常见的纵向拟合方法建立了基于30个土壤剖面有机碳测定数据的对数函数拟合模型,计算得到研究区的土壤有机碳密度和碳储量分别为5.60kg C m-2和4.72×108kgC;又根据研究区土壤剖面中有机碳含量分布的不规则性特点,通过对土壤剖面层次的归一化处理,利用地统计横向插值方法,计算得到该区的土壤有机碳密度和碳储量分别为3.95kg Cm-2和3.33×108kgC。由于两种算法对数据的组织方式不同,得到的土壤有机碳密度和碳储量存在较大差异。两种方法适用于土壤有机碳在剖面中分布形式不同的土壤类型。     

Zeolite Effects on Immobile Water Content and Mass Exchange Coefficient at Different Soil Textures

The concern for groundwater pollution by agrichemicals through solute movement within the soil is widespread. Zeolite is a type of soil amendment that is utilized to improve physical properties of soil and ameliorate polluted soil. The high negative charge of the zeolite and its open space structure allows adsorption and access of heavy metals and other cations and anions. The objectives of this research were (i) to determine the effects of different application rates of zeolite (0, 2, 4, and 8 g kg^?1) on the immobile water content and mass exchange coefficient in a loam soil and then (ii) to determine the effects of optimum application rate of zeolite on the immobile water content and mass exchange coefficient of sandy loam and clay loam soils in saturated conditions by a mobile and immobile (MIM) model. In a disturbed soil column, a method was proposed for determination of MIM model parameters, that is, immobile water content (θ_im), mass exchange coefficient (α), and hydrodynamic dispersion coefficient (D_h). Breakthrough curves were obtained for different soil textures with different zeolite applications in three replicates, by miscible displacement of chloride (Cl^?1) in disturbed soil column. Cl^?1 breakthrough curves were evaluated in terms of the MIM model. The results showed that the pore water velocity calculated based on the total soil volumetric water content (θ_im+ θ_m) and real pore water velocity calculated based on the mobile water content (θ_m) increased in the loam soil with an increase in zeolite application rate, so that, between these different rates of zeolite application, the maximum value of pore water velocity and real pore water velocity occurred at zeolite application rates of 8.6 and 11.5 g kg^?1, which are indicated as the optimum application rates. However, the comparison between different soils showed that the zeolite application rate of 8 g kg^?1 could increase pore water velocity of sandy loam and loam soils by 31% more than that of clay loam soil. The immobile water content and mass exchange coefficient of loam soil were correlated with the zeolite application rate and reduced with an increase in the rate of applied zeolite. In a comparison between different soils at zeolite application rate of 8 g kg^?1, the immobile water contents of the zeolite-treated soil decreased by 57%, 60%, and 39% on sandy loam, loam, and clay loam soils, respectively, compared with the untreated soil. Furthermore, zeolite application could reduce mass exchange coefficient by 9%, 43%, and 21% on sandy loam, loam, and clay loam soils, respectively. A positive linear relationship was found between θ_im and α. Zeolite application increased real pore water velocity of sandy loam soil by 39% and 46% compared with loam and clay loam soils, respectively. In other studies there was a decrease in ammonium and nitrate leaching due to the zeolite application, and therefore, an increase in real pore water velocity due to zeolite application in sandy loam soil, as compared with the loam and clay loam soils, may not show more rapid movement of solute and agrichemicals to the groundwater.     

引入分维理论评价土壤对优势流的敏感性

Food dye Brilliant Blue was introduced as the tracer in a dye-tracing experiment to obtain dye profile patterns of sandy loam soil,aeolian sandy soil,percolating paddy soil and permeable paddy soil.The dyed soil profiles were then photographed and the photos were scanned into a computer.Edited with certain software,only the dyed areas were left on the profile photos,which indicted the preferential flow paths for water and solute transport.Fractal dimensions of the dye patterns were calculated according to Arnold‘s function.Soil particle size distribution was analyzed by pipette method.The regression analysis showed that there was significant relationship between soil clay content and fractal dimension D of the dye pattern of soil profile.Based on the experiment results,the possibility of introducing fractal dimension to estimation of soil sensitivity to preferential flow is discussed.     

A study of some tillage practices for sustainable crop production in India

Soil tilth has been defined in terms of a ‘Physical Index’ based on the product of the ratings of eight physical properties — soil depth, bulk density, available water storage capacity, cumulative infiltration or apparent hydraulic conductivity, aggregation or organic matter, non-capillary pore space, water table depth and slope. The Physical Index and a tillage guide were used to identify the tillage requirements of different soils varying in texture from loamy sand to clay in the semi-arid tropics. The physical index was 0.389 for a loamy sand, 0.518 for a black clay loam and 0.540 for a red sandy loam soil and the cumulative rating indices in summer and winter seasons were 45 and 44 for loamy sand, 52 and 51 for red sandy loam and 54 and 52 for black clay loam soils, respectively. The compaction of the loamy sand by eight passes of a 490 kg tractor-driven roller (0.75 m diameter and 1.00 m length) increased the physical index to 0.658 and chiselling of the red sandy loam and black clay loam increased the physical indices to 0.686 and 0.729, respectively. The grain yields of rainfed pearl millet and guar and irrigated pearl millet, wheat and barley increased significantly over the control (no compaction) yields by compaction.

The chiselling of the soils varying in texture from loamy sand to clay at 50 to 120-cm intervals up to 30–40 cm depth, depending upon the row spacing of seedlines and depth of the high mechanical impedance layer, increased the grain yields of rainfed and irrigated maize on alluvial loamy sand, rainfed maize on alluvial sandy loam and red sandy loam, rainfed sorghum on red sandy loam and black clay loam, irrigated sorghum on black clay loam and rainfed black gram on red sandy loam, pod yield of rainfed groundnut, tuber yield of irrigated tapioca and fresh fruit yield of rainfed tomato on red sandy loam and sugarcane yield on black clay soil, significantly over the yields of no-chiselling systems of tillage such as disc harrow and country plough.     

土壤电导率对时域反射仪测定土壤水分的影响

试验通过往土壤中加入电介质溶液 ,以及在不同粘粒含量土壤上用时域反射仪 (TDR)测定土壤含水量 ,研究结果表明 :在较低含水量情况下 (砂土 <0 1 5cm3cm- 3,砂质壤土 <0 .1 8cm3cm- 3) ,电导率的增加不易引起TDR测定值的明显偏差 ;但在较高含水量下 ,当溶液电导率增加到 8dSm- 1 (砂质壤土 )和 1 1dSm- 1 (砂土 )时 ,TDR测得的含水量值明显高于实际值。在较高电导率 ( <1 6dSm- 1 )下 ,K0 .5a 与实际含水量仍呈较好的线性关系 ,但电导率引起的介电损失影响了K0 .5a ～θ线性关系的斜率和截距。本文给出了考虑电导率影响的K0 .5a ～θ线性关系的校正方程。土壤粘粒含量的增加也会引起TDR测定偏差 ,在低含水量时测定值偏低 ,在高含水量时测定值偏高。粘粒含量 <5 0 %时 ,测定偏差 <0 .0 2cm3cm- 3。     

Salinity and sodicity affect soil respiration and dissolved organic matter dynamics differentially in soils varying in texture

The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3–4 times with solutions containing different concentrations of NaCl and CaCl₂ to reach almost identical electrical conductivity (EC_1:5) in both soils (EC_1:5 0.5, 1.3, 2.5 and 4.0 dS m^?1 in the sand and EC_1:5 0.7, 1.4, 2.5 and 4.0 dS m^?1 in the sandy clay loam) combined with two sodium absorption ratios: SAR < 3 and 20. Finely ground wheat straw residue was added (20 g kg^?1) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: ?2.92 MPa in sand (at EC 1.3) and ?2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8–9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR < 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation.     

Quantification of the effects of soil compaction on water flow using dye tracers and image analysis

Abstract. Soil compaction has long been considered to be a problem in arable land, primarily because it causes damage to soil structure, which can lead to serious reduction in crop yields. However, few studies have sought to investigate the effects of soil compaction on the water transport regime of modified soil pore systems. We attempted to quantify the effects of soil compaction on the initiation of preferential flow by using dye tracers and image analysis. A laboratory methodology involving rainfall simulation enabled us to quantitatively evaluate differences in the mechanisms of water flow between two soil types at several degrees of compaction. The results suggested significant differences in the types of water flow pathways between clay loams and sandy loams at different extents of compaction. In the sandy loam, it was concluded that a high degree of compaction led to an increased likelihood of preferential flow, whereas a more uniform movement of soil water occurred at less compaction. By contrast, preferential routing of soil water was recorded in the clay loam, except at the highest measured compaction. The results indicate that the visual techniques of dye tracing and image analysis could enable improved understanding of flow pathways of soil water associated with soil compaction.     

Straw incorporation and soil organic matter in macro-aggregates and particle size separates

Two field experiments in which straw has been removed or incorporated for 17 yr (loamy sand) and 10 yr (sandy clay loam) were sampled to examine the effect of straw on the C and N contents in whole soil samples, macro-aggregate fractions and primary particle-size separates. The particle size composition of the aggregate fractions was determined. Aggregates were isolated by dry sieving. Straw incorporation increased the number of 1–20 mm aggregates in the loamy sand but no effect was noted in the sandy clay loam. Straw had no effect on the particle size composition of the various aggregate fractions. After correction for loose sand that accumulated in the aggregate fractions during dry sieving, macro-aggregates appeared to be enriched in clay and silt compared with whole soil samples. Because of the possible detachment of sand particles from the exterior surface of aggregates during sieving operations, it was inferred that the particle size composition of macro-aggregates is similar to that of the bulk soil. The organic matter contents of the aggregate fractions were closely correlated with their clay + silt contents. Differences in the organic matter content of clay isolated from whole soil samples and aggregate fractions were generally small. This was also true for the silt-size separates. In both soils, straw incorporation increased the organic matter content of nearly all clay and silt separates; for silt this was generally twice that observed for clay. The amounts of soil C, derived from straw, left in the loamy sand and sandy clay loam at the time of sampling were 4.4 and 4.5 t ha^?1, corresponding to 12 and 21% of the straw C added. The C/N ratios of the straw-derived soil organic matter were 11 and 12 for the loamy sand and sandy clay loam, respectively.     

土石混合介质导气率变化特征试验

土壤中碎石的存在改变了土壤结构和孔隙分布,进而影响土壤通气性能。该文通过对碎石单粒径土石混合介质导气率变化特征研究,旨在探讨单粒径土石混合介质导气内在机理,为进一步研究复杂的野外土石混合介质的导气特性提供基础。为了研究土石混合介质中碎石对导气率的影响,该文通过试验研究,分析土壤颗粒小于2mm的样本(砂土、砂壤土、黏壤土)、碎石质量分数(10%、20%、30%、40%、50%)和碎石粒径(2～3、>3～5mm)对土石混合介质导气率的影响。结果表明:在土壤颗粒小于2mm的样本条件下,土壤导气率呈砂土>砂壤土>黏壤土;在相同碎石质量分数的土石混合介质中导气率呈砂壤土>砂土>黏壤土;碎石的存在改善黏壤土的导气性能,使黏壤土碎石混合介质的导气率大于黏壤土的导气率;降低了砂壤土和砂土的导气性能,且砂土的降低幅度远大于砂壤土;在砂壤土中碎石粒径2～3mm的导气率大于>3～5mm的导气率;在砂土中碎石质量分数30%之内,碎石粒径>3～5mm的导气率稍大于2～3mm的导气率,在40%则相反,但两种粒径下混合介质导气率差异不是很明显。     

Nitrogen availability to grain sorghum from organic and inorganic sources on sandy and clayey soil surfaces in a greenhouse pot study

In a greenhouse pot study, we examined the availability of N to grain sorghum from organic and inorganic N sources. The treatments were¹⁵N-labeled clover residues, wheat residues, and fertilizer placed on a sandy clay loam and loamy sand soil surface for an 8-week period. Soil aggregates formed under each soil texture were measured after 8 weeks for each treatment. Significantly greater ¹⁵N was taken up and recovered by grain sorghum in sandy clay loam pots compared with loamy sand pots. Greater ¹⁵N recovery was consistently observed with the inorganic source than the organic sources regardless of soil texture or time. Microbial biomass C and N were significantly greater for sandy clay loam soil compared with the loamy sand. Microbial biomass ¹⁵N was also significantly greater in the sandy clay loam treatment compared to the loamy sand. The fertilizer treatment initially had the greatest pool of microbial biomass ¹⁵N but decreased with time. The crop residue treatments generally had less microbial biomass ¹⁵N with time. The crop residues and soil texture had a significant effect on the water-stable aggregates formed after 8 weeks of treatments. Significantly greater water-stable aggregates were formed in the sandy clay loam than the loamy sand. Approximately 20% greater water-stable aggregates were formed under the crop residue treatments compared to the fertilizer only treatment. Soil texture seemed to be one of the most important factors affecting the availability of N from organic or inorganic N sources in these soils.Contribution from the MissouriAgricultural Experiment Station, Journal Series No.12131