Relationship between Oil Palm Yield and Soil Fertility as Affected by Topography in an Indonesian Plantation

Abstract

Typically, Indonesian oil palm plantations rest on rolling topography. There is limited information on how topography affects soil fertility and oil palm yields. A study was conducted to evaluate these relationships in a commercial oil palm plantation located in South Sumatra, Indonesia. Two sites with differing past management history and fertility regimes were each partitioned into three topographic positions. At each topographic position, yields were recorded at 10‐day intervals over a period of 2 years. Leaf and soil samples were collected from corresponding points spaced at 36.4 m (x direction) and 8.7 m (y direction) using a systematic scheme. Leaf analysis was performed to quantify nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca), and soil analysis was carried out to determine pH, organic carbon (C), extractable P, exchangeable K, Mg, and Ca, effective cation exchange capacity (ECEC), and texture. The collected data were subjected to exploratory, univariate, and bivariate analyses, as well as analysis of variance. Empirical production functions based on measured variables were defined for each topographic position. Results showed that average yields at both study sites varied with topographic position. At site 1 (Sungai Pelepah Estate), the sideslope and the summit consistently gave higher yields than the toeslope. At site 2 (Sri Gunung Estate), a yield gradient was observed with the highest yield occurring at the toeslope and the lowest yield from the summit. Soil fertility varied across topographic positions at both sites. The measured leaf/soil variables showed varying levels of optimality/sufficiency across topographic positions. In most cases, leaf and soil variables showed comparable performance as yield predictors. Validation of the calibrated models showed reasonable accuracy for the toeslope of site 1 and all three positions at site 2.     

The impact of long-term cultivation and management history on the status and dynamics of cobalt in a savanna Alfisol in Nigeria

The status of cobalt (Co) in savanna soils of Nigeria is largely unknown, and a long-term experiment including inorganic fertilizer (NPK) and farmyard manure (FYM) and uncultivated land provided information on the way management affected the dynamics of Co in the soil. Total Co increased with increasing depth, whereas readily extractable Co decreased. The mean concentration of Co (5.6–7.9 mg kg⁻¹) was close to the mean value of 8 mg kg⁻¹ reported for soils worldwide, whereas the concentration of extractable Co was less than that reported in most soils. Regression analysis indicated that total Fe predicted up to 78% of the soil Co. The potentially available Co correlated strongly with pedogenic or reducible Mn oxides extracted with dithionite–citrate–bicarbonate. Mass balance calculations showed that fertilization with either NPK or FYM caused losses of between 0.8 and 1.1 g Co m⁻² after 50 years of cultivation against the uncultivated site as a reference. However, Co increased by 1.8 g m⁻² in the soil receiving FYM + NPK, suggesting that the Co of the soil was best maintained under this management probably because of incidental additions of Co in the manures. Furthermore, the positive Co balance in the FYM + NPK plot was partly enhanced by its larger contents of clay, Fe and pedogenic Mn oxides than in either the FYM or NPK plots. Clay, Fe and pedogenic oxides served as Co sinks in this particular savanna soil.     

Soil Solution Chemistry in Forests with Granite Bedrock in Japan

Soil solutions were taken from three forest areas with granite bedrock in Japan (Abukuma, Tateyama and Hiroshima) to investigate pH values, forms of Al and the molar BC/Al ratios. In each area, 10 sites were chosen for study. At each site, a target tree was selected, and two soil solution samples were taken from 10 cm depth at points 10 cm and 100 cm from the trunk of the tree to evaluate the effects of stemflow and throughfall on soil solution chemistry. Values of pH of samples taken 10 cm from the trunks (referred to as S samples) and 100 cm from the trunks (referred to as T samples) ranged from 3.66 to 6.52 and from 4.55 to 6.48, respectively. For Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) trees, S samples showed lower pH than T samples, whereas the inverse relation was observed for broadleaf trees. In the Abukuma and Tateyama areas, the concentrations of monomeric Al (Al_m) were mostly below 30 µmol L^?1. In the Hiroshima area, however, extremely high Al_m concentrations (up to 293 µmol L^?1) were observed at some sites. The molar ratio of BC (= Ca + Mg + K) to inorganic monomeric Al was higher than 1 for all samples, except for an S sample from the Hiroshima area having a ratio of 0.72.     

东北春玉米连作体系中土壤氮矿化、残留特征及氮素平衡

通过2年田间试验,在2种肥力、3种氮肥施用水平(不施氮N0,中量施氮N1,高量施氮N2)下,研究了吉林省春玉米连作体系中土壤氮素的矿化、残留特征及氮素平衡,并比较了种植不同玉米品种的效应。结果表明,德惠高肥力土壤中氮素两季总矿化量为203 kg/hm2,是新立城低肥力土壤的2.7倍。中量氮(N1)处理,2试验点2年土壤累计的氮素残留量为103～112 kg/hm2,对环境威胁较小;高量氮(N2)处理,新立城低肥力条件下土壤的氮素残留量为174 kg/hm2,且有下移趋势,而在德惠高肥力条件下,土壤的氮素残留量仅为107 kg/hm2。在新立城低肥力土壤上,施氮量在氮素输入项中起主要作用,在氮素输出项中,作物携出量并不随输入量的增加而有显著的变化,从而导致氮素盈余随着施氮量的增加而显著增加。氮盈余主要以残留Nm in积累在土壤剖面中,变幅为34.0%～88.4%。在德惠高肥力土壤上,土壤矿化氮在2个施氮处理中分别占氮素输入的28.3%和36.5%,在氮素输出中,氮肥表观损失量显著高于新立城,且氮盈余中以表观损失为主,变幅为54.3%～70.8%,平均为65.5%。两个试验点的氮素表观损失可能主要是由生物固持作用引起的肥料氮向土壤氮的转换。不同玉米品种对氮素矿化和表观利用率有一定的影响,在优化施肥中应加以考虑。     

Retention of cobalt by an oxisol in relation to the content of iron and manganese oxides

Abstract

The study aims at determining the cobalt retention properties of various soil components. Therefore, cobalt (Co) sorptions and extractions were carried out using an Oxisol sample before (untreated) and after successive removal of organic matter and active manganese (Mn) oxides (H₂O₂‐treated) and iron (Fe) oxides (H₂O₂+CBD‐treated). A synthetic goethite was included for comparison. Sorption of the four sorbents was determined over a range of Co concentrations (initially 10^‐8 M to 10^‐4 M), pH values (3 to 8) and reaction times (2 hours to 504 hours). The Co species sorbed was Co(ll), since oxygen exclusion during sorption had no effect on the amount sorbed. The pH‐dependent sorption curve (sorption edge) was shifted to lower pH at decreasing initial Co concentration and increasing reaction time. The displacements, in particular of the sorption edges corresponding to the lowest initial Co concentrations, to successively higher pH following removal of Mn oxides, organic matter and Fe oxides could be attributed to sorption onto sites of decreasing Co affinity [Mn oxides (and organic matter) > Fe oxides > kaolinite]. Extractions of sorbed Co at pH 5.5–7.5 with 2 M HCI showed that the extractability decreased with increasing sorption time and decreasing initial Co concentration. The untreated and H₂O₂‐treated soil samples retained sorbed Co at least as firmly as the synthetic goethite, whereas the H₂O₂+CBD‐treated sample (kaolinite) was clearly less effective. The results emphasized the importance of the soil Mn and Fe oxides for Co retention in soils but also the necessity of taken interior sorption sites into consideration.     

Soil phosphorus testing: 1. studies on spatial variation of colwell soil test phosphorus

Abstract

Spatial variation of soil test phosphorus (P) was studied by measuring soil‐test P for individual soil samples collected from uniform areas in south‐western Australia. The soil samples were collected using standard 10 cm deep by 2.5 cm diameter samplers. The Colwell alkaline bicarbonate soil test, the standard reagent adopted in Western Australia, was used. There were two parts to this study. In Part 1, 36 individual soil samples were collected on 20 m by 20 m grids within a uniform 100 m by 100 m area in paddocks on 16 different lateritic soil types. Superphosphate had been applied each previous year, using normal farmer practices, for either nine years at two sites or >20 years at the other sites. For pastures, fertiliser is usually applied to the surface. For crops, it is drilled with the seed at about 5 cm depth. In Part 2, 10 to 20 individual soil samples were collected at random locations within experimental plots (either 2 or 4.8 m wide by 30 m long) of five long‐term field experiments that were treated once only with different amounts of superphosphate applied from two to eight years previously. The P was applied to the soil surface and either incorporated through the soil with a rotary hoe or when sowing crops at 5 cm depth with tined implements, or the P was placed at 5 cm depth in bands that were 180 mm apart and the soil was not disturbed thereafter. For each site in Part 1, or each plot of each experiment in Part 2, soil‐test P for the individual soil samples varied, often markedly. Coefficient of variation was large. It was up to 56% for Part 1. For Part 2, it was up to 82% when P was incorporated into the topsoil, and up to 210% when P was banded in the soil. Spatial variation of soil‐test P is attributed to natural variation of soil physical, chemical, and mineralogical properties. Some of the variation may also be due to heterogenous mixing through the topsoil of fertiliser P applied in recent years. Soil‐test P is usually larger for recently applied fertiliser P.     

Soil fertility properties on Agave angustifolia Haw. plantations

This study examined the variations in soil physical, chemical and biological properties from Agave angustifolia fields in three sites with different topographic conditions (valley, hill and mountain), in Oaxaca, Mexico, associated with the tillage systems, disk ploughing (DP), animal drawn ploughing (ADP) and minimum tillage (MT), respectively. Plant ages were 1.5–3.5 years (class 1), 3.6–5.5 years (class 2) and 5.6–7.5 years (class 3). Soil samples were taken at two soil depths (0–20 and 21–40 cm) from plots of 4000 m² within each site and plant age classes, during the spring of 2005. The main changes in soil properties were found in the mountain site. Soil bulk density (2.0 g cm⁻³), cone penetration resistance (CPR) (3.96 MPa), 0.7 and 1.0 mm water stable aggregates (WSA) (28.3 g kg⁻¹ and 102.2 g kg⁻¹, respectively) were higher in the mountain site than in the hill and valley fields. This result is consistent with the rocky substrate beneath the shallow soil. Soil organic carbon (SOC) (23.9 g kg⁻¹), available N (23.1 mg kg⁻¹) and soil microbial biomass carbon (SMBC) (969.6 μg g⁻¹) at the mountain site showed the highest values, suggesting that MT practiced in this topographic condition favours the organic matter accumulation and biological activity. Soil microbial biomass carbon and SOC seem to be the soil properties that were mainly affected by the sites and soil management associated with them. For the three sites, SOC, P_Olsen, available N, exchangeable Na⁺ and SMBC were higher at 0–20 cm depth than at 21–40 cm depth within each site. Exchangeable Ca²⁺ and K⁺, P_Olsen and CPR increased with plant age. In contrast, available N decreased. Soil chemical properties were more affected by the age of the plant than physical and biological properties. Results reported here represent a reference of the fertility properties of soils cultivated with A. angustifolia, which could be used in further studies focused on management and tillage systems.     

Influence of high rates of topdressed KCl and K2SO4 on recovery of K,Cl, and SO4‐S by alfalfa and residual amount remaining in the soil

Abstract

This study was conducted to ascertain the percent of available K, Cl, and SO₄‐S recovered by alfalfa (Medicago sativa L. cv. ‘Vernal') herbage when various rates of K as KCl and K₂SO₄ were topdressed and also to determine where residual K, Cl, and SO₄‐S accumulated in the soil profile. An established stand of alfalfa growing on low fertility silt loam soil was topdressed in the spring of each of two harvest years with 0, 448, 896, 1344, and 1792 kg/ha of K as KCl or K₂SO₄. Four harvests were taken during each harvest year (1972 and 1973). Soil samples were taken during the autumn of 1973 to a depth of 91.4 cm in KCl‐fertilized plots, and to a depth of 76.2 cm in K₂SO₄‐fertilized and control plots.

Potassium recovery by alfalfa during two harvest years where K as KCl was applied at 448, 896, 1344, and 1792 kg/ha/yr was 56, 33, 20, and 17%, respectively. Recovery of available Cl from those same treatments was 30, 17, 12, and 10%, respectively. Where K as K₂SO₄ was applied at 448, 896, 1344, and 1792 kg/ha/yr, 55, 35, 27, and 22%, respectively, of available K was recovered. Recovery of available SO₄‐S from those same treatments was 16, 9, 7, and 5%, respectively. At the end of two years, a majority of the residual K was in the top 15.2 cm of soil. Residual Cl and SO₄‐S were concentrated at a depth of 30.5 to 76.2 cm in the soil profile.     

Contamination of pastures by polycyclic aromatic hydrocarbons (PAHs) in the vicinity of a highway

To assess PAH contamination pastures, grass and soil samples have been collected from 10 m (d1), 50 m (d2), and 150 m (d3) perpendicular to a French highway (70,000 vehicles per day) and at a control site in a rural area away from nearby contaminating sources. Total PAH concentration ranges from 767 ng/g dry weight to 3989 ng/g dry weight, according to the matrix and the distance from the highway. Distance is not a significant factor for PAH deposition on grass, while in soil it has an effect between d1 and d2 or d3. The total PAH concentration in highway samples is 8 times higher than in control site samples for grass and 7 to 4 times higher for soil. Fluoranthene, pyrene, and phenanthrene are the major PAHs in grass samples at the control site and the highway, but the concentrations are about 5 times higher near the highway. In soil samples collected near the highway, the values of concentrations between all compounds are not statistically different. PAH deposition on grass is linked to the physicochemical properties of the compounds, which lead to a specific distribution of each molecule (according to their volatility and the number of aromatic rings) while no specific behavior is revealed in soil.     

Sorption and desorption of cobalt by soils and soil components

The sorption of Co by individual soil components was studied at solution Co concentrations that were within the range found in natural soil solutions. Soil-derived oxide materials sorbed by far the greatest amounts of Co although substantial amounts were also sorbed by organic materials (humic and fulvic acids). Clay minerals and non-pedogenic iron and manganese oxides sorbed relatively little Co. It is considered that clay minerals are unlikely to have a significant influence on the sorption of Co by whole soils. Cobalt sorbed by soil oxide material was not readily desorbed back into solution and, in addition, rapidly became non-isotopically exchangeable with solution Co. In contrast, Co was relatively easily desorbed from humic acid and a large proportion of the Co sorbed by humic acid remained isotopically exchangeable. Cobalt sorbed by montmorillonite was more easily desorbed than that sorbed by soil oxide but less easily than that sorbed by humic acid. Cobalt sorption isotherms for whole soils at low site coverage were essentially linear and the gradients of isotherms increased with pH. A comparison of isotherm gradients for whole soils and individual soil components supported the suggestion that Co sorption in whole soils is largely controlled by soil oxide materials.     

Soil zinc and pH effects on zinc concentrations of corn plants

Abstract

Z1nc (Zn) deficiency of corn (Zea mays L.) has been detected in 20 or more states 1n the United States including Georgia. Since soil pH is a major factor in assessing the availability of soil Zn, this measurement has been included with acid extractable soil Zn in developing calibration Zn soil tests in North Carolina and Virginia. The objectives of this study were to develop a reliable soil test for Zn based on soil pH and Mehlich 1 soil Zn for corn gown on coarse‐textured soils and to compare our soil test values with those recently published from North Carolina where Mehlich 3 was the extractant. The study was conducted 1n 1979 to 1981 on a Tifton loamy sand (Plinthic Paleudult) site which had been used to study the influence of lime rates on micronutrient availability since 1970. Treatments consisted of four soil pH levels ranging from 5.3 to 6.6 and soil Zn levels ranging from 0.5 to 4.9 mg/kg. The Zn levels were established from the previous study where 5.6 kg Zn/ha had been applied annually for eight years (residual treatment) and by applying 3.36 or 6.72 kg Zn/ha during 1979, 1980 and 1981.

Soil Zn, corn shoot, and ear leaf Zn values were reflective of the amount of Zn applied except that the residual Zn treatment resulted in Zn concentrations > than the annual application of 3.36 kg Zn/ha. Zinc tended to accumulate in the soil and in corn leaf tissue more from the residual Zn than the recently applied Zn treatments, especially at the highest pH levels. Increasingly more soil Zn was required to increase corn shoot and ear leaf Zn one mg/kg as soil pH increased. In the initial year, each unit (kg/ha) of applied Zn increased corn shoot Zn approximately 4 units (mg/kg) at pH 5.3 and only 0.3 unit at pH 6.6. Zinc deficiency symptoms developed in corn shoots for the two highest soil pH levels in two of three years. Corn yields were increased by Zn only in 1980 and were increased by residual or applied Zn at pH levels of 6.2 and 6.6. Regression equations from these studies were utilized to develop predictive corn shoot and ear leaf Zn values over wide ranges in soil Zn and pH. Our field research data using Mehlich 1 extractant could possibly be used satisfactorily in North Carolina regression equations where Mehlich 3 was the extractant; however, certain limitations would need to be imposed in the North Carolina equations.     

Soil organic matter and land degradation in semi-arid area,Israel

Soil organic matter (SOM) was monitored at five research sites along a climatic transect extending from the Judean Mountains (mean annual rainfall 700 mm; annual mean temperature 17 °C) to the Dead Sea (mean annual rainfall < 100 mm; annual mean temperature 23 °C) in Israel. At four sites, representing four climatic regions, Mediterranean (site GIV), semi-arid (site MAL), mildly arid (site MIS) and arid (site KAL), four to eight soil samples were taken four times a year, in January, March, May and September, from 1992 through 1993 and 1994 and in April and August 2000. In the last 2 months soil samples were also taken from another site (MAB) in the semi-arid area. Comparison between the sites along the climatic transect shows that, except for site MAB, SOM increased significantly in both 0–2 cm and 2–10 cm, from the arid site, through the mildly arid site and the semi-arid site, to the Mediterranean site. Analysis of SOM temporal patterns of the two semi-arid sites (MAL and MAB) shows significant change from the normal SOM pattern in both the regional scale and the soil profile scale in one site (MAB). The a-normal pattern of SOM and the low soil aggregate stability at MAB indicates land degradation and it is attributed to overgrazing.     

Simple and fast technique to measure CO2 profiles in soil

We describe a simple method for sampling soil gas at different profile depths and analyzing CO₂ concentration in the gas sample. Soil gas samples were taken on the soil surface from each chosen depth through a gas circulation system and analyzed in situ with an infrared gas analyzer. The method is suitable for quickly handling a large number of soil gas samples in the field.     

Variabilité spatio-temporelle de l'aluminium chez l'epinette noire (Picea mariana)

Concentrations of metals in the environment have greatly increased in the past decade since large quantities of pollutants are released annually in to the atmosphere. Exposure of the population atmospheric pollutants is believed to be responsible for the development of a number of illnesses and there is an increasing need for bio-indicators which may serve as monitors of pollutants such as heavy metals. Many animal and plant species are used as bio-indicators. Certain species of trees are used as bio-indicators because they add an additional temporal dimension. By their growth rings, trees may reflect annual variations in metal concentrations in the environment. In general, conifers are preferred because of the primitive nature of their wood which decreases the lateral transfer of contaminants between rings and, thus, gives them a better potential for the evaluation of environmental contamination. The aim of this work is to evaluate black spruce (Picea mariana) as an historical indicator of Al deposition from the atmosphere. The territory studied extends to a radius of 10 km around the Alcan aluminum refinery at Jonquiere, Quebec, Canada. The sampling strategy was designed to determine the variability within an individual tree and to determine local and regional differences. Using an incremental corer, xylem samples were taken from trees at six sites at 5 and 10 km from the refinery. At each site, three samples were taken from each of five trees separated by 100 m. The wood samples, containing from 30 to 50 rings, were sliced into two-year sections which were dried and analysed for Al by neutron activation. This involved irradiation of each section in the neutron flux of a nuclear reactor followed by gamma-ray spectroscopy with a germanium detector. The Al concentrations were thus determined in over two thousand xylem sections with a precision of 5% at levels as low as 0.2 µg g^?1. The calculation of Kendall's τ for the Al concentrations in the three samples from each tree revealed correlations in 85% of the trees from the four sites situated along the line of the prevailing winds from the refinery. For the other two sites correlations were found in 40% of the trees. Higher Al levels were found in the growth rings of more recent years at all the sites. At each site the inter-tree variations in the Al concentrations in wood of a given age were about 50%. Among the six sites, the lowest concentrations were found by an SNK test, at the two which were away from the line of prevailing winds from the refinery. The highest concentrations were found at the site 10 km west of the refinery. This site is also 5 km from a paper mill. These results suggest that the trees most exposed to atmospheric contamination will contain high concentrations of Al. However, the temporal fluctuations of Al concentrations have not yet been related to fluctuations in industrial contamination. Moreover, the Al concentrations accumulated in the growth rings of black spruce could be related to the quantity of Al available in the soil, to the atmospheric release of NO_X and SO_X and to the natural pH of the soil which can induce chemical transformations, more particularly those related to the speciation and bio-availability of this metal. Although other variables must be taken into account, it appears that black spruce may be a useful historical monitor of environmental Al contamination once the relation between xylem concentration and atmospheric deposition is determined.     

黄土高原不同林龄苹果树根系吸水策略对降水的响应

在黄土高原陕西省长武塬区选取品种和管理手段均相同的3种林龄果园(尚未结果的5年幼龄果园、已结果的8年初果园和13年壮果园)苹果树,采用空间换时间的试验设计,分别于2015年7月12日和8月19日对0—500cm深度土壤及对应取样处的苹果树枝条取样,测定土样和枝条样中水分的稳定氢氧同位素,并利用贝叶斯模型量化降水前后不同土层对苹果林耗水的贡献。结果表明:(1)不同林龄苹果树降雨前后的主要水分来源深度不同。干旱时,13年壮龄果树的主要吸水深度比5年和8年果树深;而生长旺季,雨季降水只能补充未挂果的5年幼龄果园土壤水分消耗,即使降水量很大,也无法满足已经开始挂果的8年和13年果园土壤水分消耗。(2)在干旱期,5年和8年果树50%以上的水分来自表层0—100cm土壤,而13年果树50%的水分来自100—300cm土层。而降水后,5年和8年果树的主要水分来源变为100—300cm土层,贡献值在40%左右;13年果园的主要水分贡献层为0—100cm土层,贡献了近50%的水分。(3)3种林龄果树根系对300—500cm土层土壤水分的吸收对降雨的响应非常弱,降雨前后贡献率始终保持在30%。     

Reclamation of colliery spoil: the effect of amendments and grass species on grass yield and soil development

Results are presented of a field trial in which various methods for the reclamation of coarse colliery waste were tested. The site was divided into three blocks and each block received a different level of deep cultivation; however, these treatments appeared to have no long-term significant effect on grass yield. Within each cultivation block a number of treatments were superimposed. These included: amendments of soil and organic materials, deep placement of P fertilizer, and the use of different grass seed mixtures. Grass yield was measured annually for 6 years. At the end of that period soil samples were taken for analysis and tests were conducted in the field to measure the effects of treatments on the developing soil conditions. There was a general decline in grass yields during the course of the experiment. However, the rate of decline varied with the different treatments, being lower on amended spoil (i.e. treated with soil or organic materials) and on treatments sown with a seeds mixture containing S143 cocksfoot (Dactylis glomerata). Differences in the soil conditions resulting from the use of amendments were detected; in particular, the soil-amended plots had higher pH and exchangeable Ca and greater penetrability.     

Potassium uptake by soybean as affected by exchangeable potassium in soil

Abstract

Soybean (Glycine max (L.) Merrill) has been shown to have a great capacity to take K from soil, suggesting that it might absorb K from non‐exchangeable forms. In this paper, the effect of level of K fertilization on soil exchangeable K content and K uptake by soybean are discussed. The experiment was conducted on a Typic Haplortox (sandy loam), fertilized with 0, 40, 80, 160 and 240 kg K₂O/ha as KC1 or K₂SO₄. During five years before the experiment, half of the plots received those K rates annually and the other half only in the first three years, providing an opportunity to study the residual effect of applied K. Plant samples were taken at pod filling and at harvest. Soil cores were collected in 20 cm increments down to 80 cm deep at plant emergence, pod filling and after harvest. There was a residual effect of K, and 240 kg K₂O/ha applied in a 3‐year term led to the same yield and K uptake as 80 kg ICO/ha applied annually for 3 years. Fertilized plants absorbed 160% more K than unfertilized ones, but soil exchangeable K accounted for less than 50% of plant uptake; therefore the exchangeable pool must have been replaced in time for soybean uptake. On the other hand, the K recycled from the plant to the soil was not found in the exchangeable form. There was evidence of K leaching deeper than 80 cm, and in addition, the K recycled from the plants may have turned into non‐exchangeable forms in the soil.     

侵蚀性花岗岩坡地不同地貌部位土壤剖面风化特征研究

为揭示发育于侵蚀性风化花岗岩坡地上不同地貌部位土壤剖面的风化发育特征,在浙江省选择了典型的风化花岗岩坡地:浙江省嵊州市水土保持监测站为研究区,在监测站同一坡面不同侵蚀强度的坡顶、坡中、坡底选取3个典型的土壤剖面(140 cm),从下至上等距离(20 cm)采集土壤样品,共采集21个土样。进行了各层土壤基本理化特性和化学全量的分析,并分别计算了3个剖面不同层次的主要化学风化系数及总的风化强度,结果表明:(1)在强烈侵蚀的花岗岩风化残积坡地发育的土壤,总体发育成熟过程较弱,其进一步的发育与典型的地带性土壤的发育有很大的差异,侵蚀过程严重地影响了土壤的进一步成熟,侵蚀强度越大,则土壤发育越差。(2)土壤剖面总的风化强度不大,上下层的递变差异很小,脱硅富铝化过程随着剖面深度的增加风化程度越来越弱。(3)土壤剖面的化学分层不明显,各种风化指标均在60 cm左右形成了一个分界层,其上受水力侵蚀影响明显,其下呈现出的特性以继承残积母质为主。(4)不同地貌部位的风化发育程度排序为:坡底坡中坡顶,其与采样坡面的侵蚀强度排序正好相反。(5)风化程度与有机质和黏粒含量具有较为明显的正比关系,在侵蚀环境下,土壤的物理特性对风化的影响明显,在沉积环境下土壤有机质的影响大于黏粒含量的影响。总之,由于受侵蚀的影响,坡地土壤剖面的淀积层不发育,剖面呈现出的假淀积层不是由淋溶作用形成的,而是具有一定风化程度的风化残积层,结果导致发育于山地丘陵侵蚀性坡地的土壤层次划分不同于常规的土壤层次划分。     

用HRGC／HRMS测定开放式生活垃圾焚烧残余物及周边土壤中的PCDDs／PCDFs

以广东省东南沿海某开放式生活垃圾焚烧场为研究对象,用高分辨气相色谱／高分辨质谱同位素稀释法测定了垃圾焚烧场底灰、焚烧残余物及周边土壤中的多氯代二苯并对二嗯英和多氯代二苯并呋喃（PCDDs／PCDFs）。结果表明,PCDDs／PCDFs的总浓度为161～4670ng·kg^-1,毒性当量为1．10～45．8ngWHO1998-TEQ·kg^-1,其中采自垃圾焚烧场的3个样品浓度为30～45ngWHO1998-TEQ·kg^-1,剩余的土壤样品中有3个样品其浓度为4～35ngWHO1998-TEQ·kg^-1,其余的2个样品浓度〈4ngWHO1998-TEQ·kg^-1。对比加拿大的土壤指导性标准,75％的测定样品浓度高于该标准,即土壤背景浓度,有25％的样品低于此背景浓度。将垃圾焚烧场焚烧残余物作为土壤改良剂造成受施土壤的PCDDs／PCDFs污染严重,需引起有关部门的高度重视。     

Residual effect of phosphorus fertilizer when applied with the seed or banded

Abstract

Measurements of equilibrium phosphate (P) potentials were used to estimate the residual effect of P fertilizer on soil samples taken in the fall from a fertility experiment. After the harvest of spring wheat (Triticum aestivum L.) samples taken over the fertilizer band showed lower P potentials (higher P activity) than samples taken from the unfertilized soil or from areas 6.25 cm away from the fertilizer band. The reduction of equilibrium P potential was proportional to the amount of P applied in the spring for rates up to 17.4 kg P/ha with no further changes when 26.1 kg P/ha was applied. Solubility diagrams for this soil indicated that, at the rates of P fertilization used in this study, the increase in soil P was controlled by sorption processes, and that only at rates more than twice the highest one used would the precipitation of Ca‐P compounds control the concentration of P in solution.