Influence of humic acid on water retention and nutrient acquisition in simulated golf putting greens

Humic substances are frequently applied to creeping bentgrass ( Agrostis palustris Huds.) on golf putting greens to improve turf health and are marketed to enhance nutrient acquisition and possibly aid in retaining water in drought prone environments, but information on the role of humic substances in increasing soil water retention is limited. Additionally, it is difficult to separate the beneficial effects of nutrients and other ingredients added to commercial humic formulations from the effects of the pure humic substance. In our study, pure humic acid, tannic and citric acids were added to simulated creeping bentgrass putting greens. The organic acids were applied at normalized carbon rates of 250 mg C per litre by watering solutions through an automated irrigation system. Volumetric water content (VWC) and irrigation frequency, shoot and root growth, and tissue nutrient concentration of the turf were measured. None of the organic acid treatments improved water retention in the simulated greens. The humic acid-treated greens required more frequent irrigation than the untreated greens indicating that they were drying out more quickly. In addition, the addition of humic acid did not result in an increased tissue concentration of nutrients in the creeping bentgrass, top growth or dry shoot mass compared with the other treatments. However, creeping bentgrass root length was greater in the greens treated with humic acid compared with the untreated control.     

Quantitative aspects of solid-state C-NMR spectra of humic substances from soils of volcanic systems

Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance spectroscopy (CPMAS ¹³C-NMR) represents one of the most powerful tools to investigate soil organic matter (SOM) mainly because of its inherent capacity to provide a semi-quantitative evaluation of carbon distribution. A critical parameter during acquisition of CPMAS ¹³C-NMR spectra is the contact time required to obtain the cross-polarisation between proton and carbon nuclei. The procedure to evaluate the best contact time for the acquisition of a quantitative CPMAS ¹³C-NMR spectrum is to perform Variable Contact Time (VCT) experiments. In this work the structural features of a number of purified humic substances from Italian and Costarican volcanic soils were investigated by CPMAS ¹³C-NMR spectroscopy after having performed preliminary VCT experiments. The VCT experiments showed that the average contact times vary according to the origin and chemical structure of the humic material. The optimal contact times (OCT) for nine humic samples were between 250 and 800 μs These values were different from the time of 1000 μs that is commonly applied as the best average contact time for humic materials. Moreover, by comparing the NMR data to those obtained by elemental analysis (C/H ratio), it appeared that the efficiency of the cross-polarisation between protons and carbons, and hence the contact time, is affected not only by the number of protons, but also by their distribution over the molecules. The evaluation of errors in quantitative estimation of the different carbons revealed that the use of OCT generally reduced by half the loss of signals occurring when the average contact time of 1000 μs is used in CPMAS ¹³C-NMR spectra of humic substances.     

土壤微生物膜对风沙土固沙保水特性的影响

土壤微生物膜胞外聚合物具有较强的黏结性,为增强风沙土抗蚀性,提高风沙土保水性提供了新途径。鉴于此,该研究采用室内控制试验设置6个微生物菌剂施用水平(0、1、3、5、7和10 g/kg),以期阐明土壤微生物膜对风沙土特性的影响。研究结果表明:1)施用微生物菌剂可产生土壤微生物膜,并胶结风沙土颗粒。2)试验结束时(第49 d),与对照组相比,不同菌剂施用处理的土壤容重降低0.54%～8.88%,孔隙度提高0.39%～3.91%,含水率显著提高0.11%～0.25%(P0.05),大团聚体质量分数增加5.59%～25.01%,土壤pH值由7.16显著增加至8.32～9.23(P0.05)。3)土壤多糖含量对土壤特性的解释率为47%,是影响土壤特性的关键因素。土壤微生物膜能够有效改善风沙土特性,增强风沙土抗蚀性,提高风沙土保水性,但较高的微生物菌剂施用量会增加土壤pH值,造成土壤盐碱化,建议微生物菌剂施用水平为1～5 g/kg。研究成果有利于深入理解微生物膜固沙保水机制,并可为沙化土地防治新技术研发提供重要理论依据和科技支撑。     

Effects of 'Agri-SC' soil conditioner on soil structure and erodibility: some further observations

Abstract. In field and laboratory experiments the conditioner‘Agri-SC’has shown improvements in the structure of loamy sand soils in east Shropshire, UK. It resulted in statistically significant decreases in soil bulk density values and increases in soil porosity and aggregate stability. Further experiments are in progress on both loamy sand and silt loam soils.     

Transferability of continuous‐ and class‐pedotransfer functions to predict water retention properties of semiarid Syrian soils

Hydraulic properties of soils, particularly water retention, are key for appropriate management of semiarid soils. Very few pedotransfer functions (PTF s) have been developed to predict these properties for soils of Mediterranean regions, where data are particularly scarce. We investigated the transferability of PTF s to semiarid soils. The quality of the prediction was compared to that for soils originating from temperate regions for which most PTF s were developed. We used two soil data sets: one from the Paris basin (French data set, n  = 30) and a Syrian data set (n  = 30). Soil samples were collected in winter when the water content was near field capacity. Composition and water content of the samples were determined at seven water potentials. Continuous‐ and class‐PTF s developed using different predictors were tested using the two data sets and their performance compared to those developed using artificial neural networks (ANN ). The best performance and transferability of the PTF s for both data sets used soil water content at field capacity as predictor after stratification by texture. The quality of prediction was similar to that for ANN ‐PTF s. Continuous‐ and class‐PTF s may be transferable to other countries with performances that vary according to their ability to account for variation in soil composition and structure. Taking into account predictors of composition (particle size distribution, texture, organic carbon content) and structure (bulk density, porosity, field capacity) did not lead to a better performance or the best transferability potential.     

Cattle manure effects on structural stability and water retention capacity of a granitic sandy soil in Zimbabwe

The evaluation of soil aggregate stability and water retention is important in the assessment of soil management options. A 3-year study was conducted in 1999 to determine the effects of two cattle manure application methods on soil aggregate stability and water retention capacity of a sandy soil (Haplic Lixisol). Manure application increased soil organic C by 10–38% in the 0–10 cm layer. Compared with the control, manure management treatments increased the aggregate stability of soil as measured by the mean weight diameter (MWD) and aggregates between 2 and 10 mm (AGG2) indices from 0.243 to 0.733–0.926 mm, and from 27.3 to 128.3–148.3 g kg⁻¹, respectively. The readily available water (RAW) capacity of the soil was significantly increased by manure addition, whereas the increase in AWC was not significant. The increase in water retention capacity in the soil was more affected at low suctions and this was related to the effects of manure on macroporosity. It was concluded that cattle manure was beneficial to the structural stability and water retention of this soil.     

2种高分子保水材料对土壤持水能力的影响

采用离心机法,研究聚丙烯酸钠与聚丙烯酰胺2种高分子化合物在5种使用浓度（占干土质量0、0．01％、0．08％、0．2％与1％）的条件下对3种土壤（砂土、壤土、黏土）持水能力的影响。结果表明：3种土壤在0．01—1．5MPa水吸力时,持水能力随着2种高分子材料用量的增加而增加,砂土的作用效果较壤土、黏土更显著;2种高分子材料与土壤质量比控制在8／10000～2／1000范围内其作用效果较好,该用量条件下高分子吸持水分平均可释放83．7％供植物吸收利用。2种高分子材料对土壤持水能力的作用效果基本相同。     

Effect of cultivation on physical speciation of humic substances and plant nutrients in aggregate fractions of crusting soil from Zimbabwe

The effects of clearing and cultivation of Rhodic Kandiustalf from Mazowe (Zimbabwe) were studied by quantifying humic substances and plant nutrients (available and exchangeable cations) in aggregate fractions. It was found that cultivation was associated with a relative depletion of plant nutrients in coarse aggregate fractions (i.e. a virtual migration of soil fertility towards microaggregate soil compartments). This effect was connected with the organic matter distribution patterns in the physical fractions: cultivation has led to a relative concentration of the colloidal fractions (humic acids and fulvic acids) in the microaggregates, accompanied by a selective depletion of the latter organic fraction. It is suggested that the increased physicochemical importance of the microaggregate fractions after cultivation may be an index for the disruption of the original soil structure leading to crust formation and it may also be related to the effect of ploughing on the humification processes and the mobility of the colloidal organic fractions. Received: 1 August 1996     

Effect of humic acid on growth and crop nutrient status of wheat on two different soils

The effect of plant-derived humic acid (PDHA) and coal-derived humic acid (CDHA) on wheat growth was tested on two alkaline calcareous soils in pots. Humic acid derived from plant and coal materials was applied at the rate 0 (control), 50 and 100 kg/ha to wheat in pots carrying two soils viz. clayey loam soil and sandy loam soil separately. Data was collected on plant growth parameters such as spike weight, grain and straw weight, and plant nutrients (macronutrients and micronutrients). Results showed that spike weight increased by 19%, 15%, and 26%, and 11% with application of PDHA at the rate of 50 and 100 mg/kg in clayey loam and sandy loam soil, respectively. Grain yield show an increase of 21% and 11% over control with application of PDHA and CDHA at the rate of 50 mg/kg on both soils, respectively, and 10% and 22% with application of PDHA and CDHA at the rate of 100 mg/kg on both soils.     

不同水分条件下保水剂对土壤持水与供水能力的影响

为探明水分条件对保水剂作用效果的影响,采用盆栽实验,测定冬小麦生长结束后不同水分条件下保水剂不同用量（T1：0、T2：27 mg/kg、T3：54 mg/kg、T4：81 mg/kg）处理的土壤持水、供水及导水性能等。结果表明：保水剂的施用均提高了土壤持水、供水、导水能力及土壤有效水含量。轻度胁迫条件下,以T3处理的持水能力、有效水含量及导水能力最强,而供水能力以T4处理为佳;充分供水条件下,随保水剂用量的增加,土壤持水能力、供水能力、有效水含量及导水能力均提高,但T3和T4处理间差异不显著。与轻度胁迫相比,充分供水条件下各处理的持水能力、供水能力及导水能力均较高,而有效水含量以轻度胁迫条件下的T3处理较高,较对照增加18.6%。从经济的角度考虑,2水分条件下以T3处理（54 mg/kg）效果为佳。     

不同类型层状土壤持水能力的研究

为了了解不同类型层状土柱持水能力,利用砂土和砂黄土2种土壤,设置3种不同厚度分层土柱(11.25、22.5、45 cm)和2种匀质对照土柱,测定了土柱自初始饱和条件下的排水过程;同时利用匀质土柱测定结果标定2种土壤水力参数,通过Hydrus-1D模型对不同类型层状土柱排水过程进行模拟分析,获得了不同类型层状土柱的田间持水量。结果表明,层状土柱持水能力随着分层厚度的减小而增加,当分层厚度减小到一定程度时土柱持水能力不再随着分层厚度的减小而增加,该临界厚度取决于下层粗质土壤对上层细质土的吸力与上层细质土壤进气吸力之间的相对大小。本试验所用2种土壤分层临界厚度大约在5 cm左右;土柱失水主要来自下层较粗质地土壤,由饱和时的0.385 cm~3/cm~3减小到0.04 cm~3/cm~3。上层细质土壤含水量随着分层厚度的减小而增加。研究结果可为干旱半干旱地区矿区恢复和污染物填埋提供理论指导。     

施用绿肥条件下减施化肥对土壤养分及持水供水能力的影响

以长期定位试验为基础,设置7个紫云英和化肥施用配比试验处理,以探索施用绿肥情况下减施化肥对土壤养分、持水和供水能力的影响。结果表明:在翻压紫云英条件下,即使不施化肥土壤氮也可基本得到满足,应适量施用化学钾肥,必须合理施用磷肥,以保证土壤全量和速效养分得到平衡和持续供给,化肥施用量减少未显著降低水稻产量;土壤持水、供水能力在处理间的趋势表现为:紫云英+40%化肥紫云英+60%化肥紫云英+80%化肥、紫云英+100%化肥单施100%化肥、单施紫云英CK,与CK相比,其它6个处理田间持水量提高了1.6%~15.4%,有效含水量增幅更大,平均提高1.5%~30.5%,说明紫云英化肥配施能显著提高土壤的持水、供水能力,且化肥施用量越少效果越好,而单施化肥或单施紫云英效果有限。因此,紫云英施用量一定时(22 500 kg/hm~2),化肥施用量应减少至40%甚至更低。     

基于流变学法研究容重和含水率对土壤结构力学稳定性的影响

土壤结构力学稳定性不仅与土壤质量和肥力密切相关,而且还与农业器具设计和农业水土工程建设紧密联系。该研究以黄土高原广泛分布的塿土和黄绵土为研究对象,采用振幅扫描试验模拟振荡荷载过程,研究土壤容重和含水率对土壤结构力学稳定性的影响。结果表明：1）随土壤容重的增加,土粒间接触点增多,使得剪切强度参数：线性黏弹区的剪切应力和储能模量均增加,土壤结构强度增强;黄绵土屈服点的剪切应变和塿土的积分z随容重增加先增大后降低,表明土壤颗粒存在一个最稳定的排列组合方式。同时,剪切强度参数对土壤容重的响应更为敏感。2）随含水率的增加,土壤颗粒间黏聚力和摩擦力降低,剪切强度参数：线性黏弹区的剪切应力、屈服点的剪切应力、最大剪切应力均降低,土壤结构强度降低;当剪切应变在线性黏弹区时,塿土的弹性随含水率的增加而增加,而较大的剪切应变下的塿土的弹性和黄绵土总的弹性随含水率增加均降低。3）对比2种土壤,因塿土的黏粒、有机质、阳离子交换量、比表面积等较高,增加了土粒间的胶结强度,使得塿土的弹性和剪切强度较高,而黄绵土结构更具脆性。该研究结果表明基于流变仪中的振幅扫描测试所获取的流变学参数能够定量表征土壤细观结构力学稳定性,为进一步深入认识土壤微观力学特性提供了丰富的评价参数。     

生物炭对云南典型植烟土壤持水性及烤烟产量的影响

为解决季节性干旱导致云南省烤烟减产的问题,开展了烟秆生物炭改善云南典型植烟土壤持水性的研究,进而为生物炭在烟叶生产中的推广应用提供依据。通过盆栽试验研究了穴施不同用量生物炭(0%、1%、4%、7%、11%干土重)对黄红壤(YR)、黄棕壤(YB)、赤红壤(LR)、水稻土(PD)和紫色土(PE)5种典型植烟土壤持水性的影响。结果表明:施用生物炭显著提升5种土壤持水性,一次浇水周期较对照延长1~5 d,对烤烟产量的影响因土壤类型而异。其中,1%~11%范围内,YR土壤持水性随着生物炭用量增加而降低,施用生物炭1%土壤持水性最好,与对照相比,烤烟生育期总补水量显著降低59.5%,土壤含水量平均下降速度显著下降50.4%,水分利用效率显著提高32.3%。但施用生物炭导致烤烟最高减产37.9%。YB土壤持水性随着生物炭用量增加呈升高趋势,施用生物炭11%最好,相比对照,烤烟生育期总补水量显著降低41.3%,水分利用效率显著提高93.3%,产量无显著提高。随着生物炭用量增加,LR土壤持水性先增加后降低,施用生物炭4%效果最好,烤烟产量和水分利用效率分别较对照显著提高46.2%和68.8%。随着生物炭用量增加,PD和PE的土壤持水性及烤烟产量呈现先增加后降低趋势,施用生物炭7%效果最佳,与对照相比,烤烟产量分别显著提高17.0%和55.6%,总补水量分别显著降低40.3%和26.8%,土壤含水量平均下降速度分别显著降低37.4%和36.5%,水分利用效率分别显著提高94.4%和121.7%。烟秆生物炭对于云南典型植烟土壤的保水效果明显,其最佳施用量视土壤类型而异。     

生物炭对东北黑土持水特性的影响

为探究生物炭对东北黑土持水特性的影响,系统研究3种添加比例(2%、5%、10%)、3种粒径(0.25、0.5、1 mm)的杨木炭和竹炭对3种质地东北黑土(壤土、砂壤土、砂土)田间持水量和含水率的影响规律,构建添加生物炭黑土的水分特征曲线,并采用Van-Genuchten和Broods-Corey模型进行拟合。结果表明:生物炭能显著提高不同质地东北黑土的持水能力,黑土的田间持水量与生物炭的添加比例呈显著正相关,而与生物炭的粒径呈负相关,0.5 mm和1 mm粒径的生物炭对黑土田间持水量的影响差异不显著,杨木炭显著优于竹炭,0.25 mm、10%添加比例的杨木炭对东北黑土持水能力的提高效果最优,壤土、砂壤土、砂土3种质地黑土的田间持水量和饱和含水率分别可提高64.97%、66.42%、69.39%和47.60%、38.93%、31.18%;Van-Genuchten模型能更精确的模拟添加生物炭黑土的水分特征曲线,最佳离心时间为100 min,三次函数曲线能够较好的拟合添加生物炭黑土的体积含水率与离心吸力之间的多元动态关系,为生物炭对各种质地东北黑土水分运动规律的深入研究提供理论依据。     

Plant-available water and integral energy for Medicago sativa and Bromus tomentellus in texturally different soils

Soil water availability is very crucial for pasture plants because their growth solely depends on the soil water storage. While plant-available water (PAW) is successfully related to plant growth, it is the energy required per unit mass of water, integrated over the PAW range, named the integral energy (E_I) that determines how easily plants can take up water from the soil. The soil water retention function was integrated over the PAW range to calculate the E_I. PAW and E_I were determined for Medicago sativa (alfalfa, a legume) and Bromus tomentellus (a grass) species in five texturally different soils of semi-steppe rangeland in central Zagros, western Iran. The PAW was calculated as the difference between field capacity and permanent wilting point (nominal h of 15,000 hPa or actual h obtained from PWP value determined in greenhouse). E_I values were calculated for the nominal and actual PAW values. M. sativa PAW and E_I values were more than those from B. tomentellus, indicating that M. sativa was able to tolerate higher soil matric suctions at similar conditions. Results showed predicting E_I only from basic soil properties is not accurate. PAW and E_I are dependent on plant species and soil type interactions, and environmental compatibility.     

Soil development on restored opencast coal sites with particular reference to organic matter and aggregate stability

Abstract. Organic indices and aggregate stability were measured in soils of similar texture on two restored opencast coal sites and on adjacent, undisturbed land in South Wales, UK. The aim was to assess rates of soil change over time, to relate these changes to conditions in undisturbed land and to evaluate organic-aggregation relationships across these range of soils. Several management factors were included in the comparisons.
Organic matter accumulated at the surface (0–7.5 cm) of restored soils, contents being greater than undisturbed soils after 21 years. However, this increase in total organic matter did not result in proportionate increases in carbohydrates and microbial biomass, nor did aggregate stability increase to the degree expected. Between 7.5 and 15 cm depth, rates of change were slower. Microbial metabolic quotient and respiration relative to total soil C were highest in recently (9 years) restored soils, intermediate in 21 year old restored soils and least for undisturbed soils.
Sewage (100t/ha) applied at reinstatement improved clay stability but had little effect on other parameters when measured 9 years later. Drainage of soils restored in 1972 reduced total organic content but its influence on other organic indices was more complex. Carbohydrate contents had the closest association with aggregate stability and microbial biomass.
Although the productivity of restored land may recover more quickly, findings suggest that rehabilitation of normal soil processes following surface mining may take much longer than the normal five year aftercare period.     

基于ANN的复垦土壤水分特征曲线的预测研究

为能较容易且更准确地获取复垦土壤水分特征曲线,将易测定的土壤特性如土壤质地、容重和饱和含水量作为输入变量,采用基于bagging算法的神经网络法建立了用于预测土壤水分特征曲线的土壤转换函数法(PTFs)模型,并对徐州矿区复垦土壤的水分特征曲线进行了预测,同时与普通BP算法预测精度进行了比较.研究结果表明所建立的PTFs参数模型具有较高的估计精度,bagging算法均方根预测误差比普通BP算法减少了7.5%～27.0%,说明该模型的建立与求解为复垦土壤水分特征曲线的预测研究提供了一条新途径.