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1.
Rain-fed agriculture is widespread in Inner Mongolia, northern China, where wind erosion of farmland is very common because of sandy soil and dry, windy weather. However, very little is known about the effects of wind erosion on soil physical and chemical properties in this region. A field experiment was conducted in sandy farmland, where erosional and depositional gradients were established to evaluate the effects of wind erosion and leeward sand accumulation on soil texture, nutrient content, soil water, and soil temperature. The research showed that long term wind erosion could result in significant soil coarseness, infertility and dryness. Severe erosion reduced clay by 59.6%, organic C by 71.2%, total N by 67.4%, total P by 31.4%, available N by 64.5%, available P by 38.8%, and average soil water content by 51.8%, compared with non-eroded farmland in the study region. The sand fraction (particles > 0.05 mm), pH and ground-surface temperature increased by 6.2%, 3.7%, and 2.2 °C, respectively. Accumulated sand also caused a decrease in nutrients and soil water content. Under severe sand accumulation, clay was reduced by 2.0%, organic C by 19.3%, total N by 21.7%, total P by 13.7%, available N by 52.5%, and average soil water content by 26.6%. The sand fraction, pH, available P, and ground-surface temperature increased by 0.2%, 0.9%, 5.8% and 2.8 °C, respectively.  相似文献   

2.
黑土区土壤侵蚀厚度对土地生产力的影响及其评价   总被引：5，自引：2，他引：3  
刘慧  魏永霞 《农业工程学报》2014,30(20):288-296
为了研究黑土区土壤侵蚀厚度对土地生产力的影响,采用盆栽试验,人为剥离黑土表层0、5、10、15、20、25和30 cm土壤以模拟侵蚀厚度不同的耕层土壤,分析土壤侵蚀厚度对土壤理化性质、大豆生物性状和水分利用效率等指标的影响。并对TOPSIS(technique for order preference by similarity to ideal solution)模型进行改进,用于评价侵蚀厚度不同的土壤的土地生产力。结果表明:土壤全N、碱解N、全P、速效P、有机质含量和土壤田间持水率均随侵蚀厚度的增加而递减,土壤容重随侵蚀厚度的增加而递增。土壤侵蚀厚度对大豆生长有显著影响,随着侵蚀厚度的增加,大豆减产率呈"S型"曲线递增,产量、耗水量呈"Z型"曲线递减,水分利用效率呈指数曲线关系递减。改进的TOPSIS模型对不同侵蚀厚度下土地生产力的评价结果较为理想,计算的土地生产力指数随土壤侵蚀厚度的变化呈"Z型"曲线,与大豆产量的变化趋势相同,且二者呈指数函数关系,决定系数达0.996,均方根误差为0.65。研究结果可为黑土区土壤侵蚀防治提供理论依据。  相似文献   

3.
Soil losses affect the physical, chemical and biological soil properties and as a consequence reduce soil productivity. Erosion reduces or eliminates root-explorable soil depth and crop available water, selectively decreases the nutrient and organic matter content, and exposes soil layers with unsuitable characteristics for crop growth. Yield is hence assumed to be a function of root growth, which in turn is a function of the soil environment. In order to evaluate the water erosion impact on soil properties and productivity, a study was carried out on a Typic Haplustalfs soil, with sorghum (Sorghum bicolor (L) Moench), located in Chaguaramas in the Central Plains of Venezuela. Four different study locations with the same soil type, with slopes ranging from 3% to 6% and with different levels of erosion were selected: Chaguaramas I (slightly eroded), Chaguaramas II, (moderately eroded), Chaguaramas III (moderately eroded), and Chaguaramas IV (severely eroded). A sorghum–livestock farming system was introduced 30 years ago. Secondary tillage with a disc harrow (without mulch on the topsoil) was applied for seedbed preparation. Fertilizers and pesticides were applied uniformly over the entire fields. Soil samples from each horizon were analysed for particle size distribution, water retention, bulk density, pH and organic matter content. The relative production potential was estimated using the Productivity Index developed by Pierce et al. [Pierce, F.C., W.E. Larson, R.H. Dowdy and W.A. Graham. 1983. Productivity of soils: assessing long-term changes due to erosion. Journal of Soil and Water Conservation. 38 39–44.], and adapted to the methodology proposed by Delgado [Delgado F. 2003. Soil physical properties on Venezuelan steeplands: applications to conservation planning. The Abdus Salam International Centre for Theoretical Physics. College on Soil Physics. 11 pp.] for Venezuelan soil conditions. The Productivity Index (PI) could estimate the tolerable rate of soil productivity loss. A soil erosion risk was assessed by the Erosion Risk Index (ERI) taking into account the soil hydrological characteristics (infiltration–runoff ratio), rainfall aggressiveness and topography (slope). The Productivity Index (PI) and the Erosion Risk Index (ERI) were used to classify the lands for soil conservation priorities, for conservation requirements and for alternative land uses. The results showed that: (a) the Productivity Index (PI) decreased with increasing level of erosion, (b) the Productivity Index (PI) was mainly affected by changes in available water storage capacity, bulk density and pH, (c) the erosion risk (ERI) was strongly affected by slope gradient and rainfall aggressiveness, (d) the areas were classified as critical lands and super-critical lands, with high to very high soil conservation requirements, depending on the level of soil erosion.  相似文献   

4.
Application of crop residues to soil and reduced or no tillage are current management practices in order to achieve better water management, increase soil fertility, crop production and soil erosion control. This study was carried out to quantify the effect of wheat straw mulching in a no tilled Fluvisol under semi-arid conditions in SW Spain and to determine the optimum rate in terms of cost and soil protection. After a 3-years experiment, mulching application significantly improved physical and chemical properties of the studied soil with respect to control, and the intensity of changes was related to mulching rate. The organic matter content was generally increased, although no benefit was found beyond 10 Mg ha−1 year−1. Bulk density, porosity and aggregate stability were also improved with increasing mulching rates, which confirmed the interactions of these properties. Low mulching rates did not have a significant effect on water properties with respect to control, although the available water capacity increased greatly under high mulching rates. After simulated rainfall experiments (65 mm h−1 intensity), it was found that the mulch layer contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rain water during storms. Mulching contributed to a reduction in runoff generation and soil losses compared to bare soil, and negligible runoff flow or sediment yield were determined under just 5 Mg ha−1 year−1 mulching rate. It was observed that during simulations, the erosive response quickly decreases with time after prolonged storms (30 min) due to the exhaustion of available erodible particles. These results suggest that the erosive consequences of intermediate intensity 5-years-recurrent storms in the studied area could be strongly diminished by using just 5 Mg ha−1 year−1 mulching rates.  相似文献   

5.
陕北坡耕地土壤侵蚀对土壤性质的影响研究   总被引：7，自引：0，他引：7       下载免费PDF全文
研究分析黄土高原北部坡耕地土壤侵蚀对土壤性质影响结果表明,山坡中、上部为土壤侵蚀最强烈地带,坡顶侵蚀较弱;土壤全N、碱解氮、速效钾与水蚀和耕作侵蚀间呈线性相关关系,而土壤有机质、速效磷和阳离子代换量则与水蚀和耕作侵蚀无显著相关性。  相似文献   

6.
为明确黄土高原旱作麦田长期保护性耕作对土壤肥力和土壤原核微生物的效应,以位于山西省临汾市实施保护性耕作26年的小麦田为试验基地,采用Illumina Hiseq 2500高通量测序等手段,开展了不同耕作措施[免耕覆盖（NTS）、深松免耕覆盖（SNTS）和传统耕作（TT1）]对土壤理化性质和土壤原核微生物多样性的影响分析。研究结果表明：1）NTS和SNTS处理比TT1处理显著提高了土壤全氮、碱解氮、速效磷及速效钾的含量,降低了土壤pH,提高了土壤贮水能力和水分含量,降低了0~10 cm土层的土壤容重,但提高了10~20 cm土层的土壤容重;同时,SNTS处理显著增加了土壤的有机质含量。2）Illumina Hiseq高通量16S rRNA基因V4区测序结果表明：NTS和SNTS处理比TT1处理显著降低了绿弯菌门的相对丰度;NTS比SNTS处理显著降低了土壤中疣微菌门和绿弯菌门的相对丰度;NTS处理显著增加了土壤原核微生物群落的多样性,但未显著改变原核微生物群落的丰度;SNTS对原核微生物群落的多样性和丰富度均未有显著改变;NTS处理的显著性差异物种（Biomarker）高于其他2个处理;其他原核微生物门的相对丰度,在3个处理间尚未有明显差异。3）聚类分析可见：NTS和SNTS处理与TT1处理的微生物群落结构差异较大;NTS处理与SNTS处理间的微生物群落结构差异较小。4）CCA分析可知：土壤pH、有机质、速效氮、速效磷、速效钾含量对土壤原核微生物群落遗传多样性的变化起着重要作用;与TT1处理相比,NTS和SNTS处理在一定程度上改变了土壤原核微生物群落结构,但仍存在结构的相似性。综上所述,长期进行NTS和SNTS处理对黄土高原旱地麦田土壤微生物多样性、丰富度以及土壤肥力因子等的正效作用明显。  相似文献   

7.
Soil movement by tillage redistributes soil within the profile and throughout the landscape, resulting in soil removal from convex slope positions and soil accumulation in concave slope positions. Previous investigations of the spatial variability in surface soil properties and crop yield in a glacial till landscape in west central Minnesota indicated that wheat (Triticum aestivum) yields were decreased in upper hillslope positions affected by high soil erosion loss. In the present study, soil cores were collected and characterized to indicate the effects of long-term intensive tillage on soil properties as a function of depth and tillage erosion. This study provides quantitative measures of the chemical and physical properties of soil profiles in a landscape subject to prolonged tillage erosion, and compares the properties of soil profiles in areas of differing rates of tillage erosion and an uncultivated hillslope. These comparisons emphasize the influence of soil translocation within the landscape by tillage on soil profile characteristics. Soil profiles in areas subject to soil loss by tillage erosion >20 Mg ha−1 year−1 were characterized by truncated profiles, a shallow depth to the C horizon (mean upper boundary 75 cm from the soil surface), a calcic subsoil and a tilled layer containing 19 g kg−1 of inorganic carbon. In contrast, profiles in areas of soil accumulation by tillage >10 Mg ha−1 year−1 exhibited thick sola with low inorganic carbon content (mean 3 g kg−1) and a large depth to the C horizon (usually >1.5 m below the soil surface). When compared to areas of soil accumulation, organic carbon, total nitrogen and Olsen-extractable phosphorus contents measured lower, whereas inorganic carbon content, pH and soil strength measured higher throughout the profile in eroded landscape positions because of the reduced soil organic matter content and the influence of calcic subsoil material. The mean surface soil organic carbon and total nitrogen contents in cultivated areas (regardless of erosion status) were less than half that measured in an uncultivated area, indicating that intensive tillage and cropping has significantly depleted the surface soil organic matter in this landscape. Prolonged intensive tillage and cropping at this site has effectively removed at least 20 cm of soil from the upper hillslope positions.  相似文献   

8.
Biotic soil parameters have so far seldom played a role in practical soil assessment and management of grasslands. However, the ongoing reduction of external inputs in agriculture would imply an increasing reliance on ecosystem self-regulating processes. Since soil biota play an important role in these processes and in the provision of ecosystem services, biological soil parameters should be an integral part of soil assessment. The general objective of the current study is to investigate to what extent biotic soil parameters provide additional value in soil quality assessment of grassland on sandy soils. We measured abiotic and biotic soil parameters together with process parameters underlying ecosystem services in 20 permanent production grasslands. Cross-validated stepwise regression was used to identify abiotic and biotic soil parameters that explained the soil ecosystem services soil structure maintenance, water regulation, supply of nutrients, and grassland production, respectively.Process parameters underlying the ecosystem service soil structure maintenance such as bulk density and the percentage of sub-angular blocky elements were mainly influenced by SOM and its qualities. The correlations between penetration resistance at 0-10 cm and the percentage of soil crumbs with earthworms suggested a relationship to earthworm activity. Parameters underlying the service of water regulation showed no clear relationship to biotic soil parameters. Water infiltration rate in the field was explained by the penetration resistance at 10-20 cm. Process parameters underlying the service of nutrients’ supply such as the potentially mineralizable C and N were mainly determined by soil total N. The potential C and N mineralization were more related to biotic soil parameters, whereby each parameter was the other’s antithesis. The grassland production without N fertilization viz. the nitrogen supply capacity of the soil measured as N yield, was mainly explained by soil organic matter (SOM) and soil moisture, and to a lesser extent by soil total N. One gram of SOM per kg of dry soil corresponded to 3.21 kg N yield ha−1, on top of a constant of 15.4 kg N ha−1. The currently applied calculations in the Dutch grassland fertilization recommendation, underestimated in 85% of the production grasslands, the measured nitrogen supply capacity of the soil by on average 42 kg N ha−1 (31%). This legitimizes additional research to improve the currently applied recommendations for sandy soils. The response of N yield to N fertilization ranged from 35 to 102%. This wide range emphasizes the importance of a better recommendation base to target N fertilizer. The response of N yield to N fertilization was predicted by the total number of enchytraeids, the underlying mechanism of which needs further investigation on different soil types. This knowledge can be important for the optimal use of fertilizer and its consequences for environmental quality.  相似文献   

9.
渭北旱塬不同程度土壤侵蚀及生产力恢复试验   总被引：2，自引：0，他引：2  
土壤侵蚀会降低生产力,影响作物产量,因此,恢复土壤生产力是人们普遍关注的问题。采用人工模拟土壤侵蚀方法,对侵蚀状况下的土壤进行生产力研究,并配以施肥探索土壤生产力的恢复情况。结果显示：I）施肥可以改善土壤的物理性状,侵蚀土壤的含水量降低,密度增加,孔隙度减小;2）在无肥下,土壤中有机质及其他养分质量分数均随侵蚀程度的加深而减少,施肥可以增加土壤中有机质及各养分的质量分数,但施肥后各养分的质量分数整体上仍呈现出随侵蚀深而降低的趋势;3）土壤侵蚀会减少玉米的生物量,平均每侵蚀1am土层,玉米生物量下降0．38％,施肥可以在一定程度上弥补侵蚀所造成的损失;4）同生物量的变化情况,玉米产量也呈现出随侵蚀程度加深而逐渐下降的趋势,每流失1cm土层,玉米产量平均下降2．49％,施肥能够提高一定的玉米产量,在剥离地表20cm、剥离地表10cm、原状未扰动土和覆盖10cm表土4种不同的地表处理下,常规施肥下的玉米产量比无肥分别提高2．44％、2．13％、1．50％和1．23％,过量施肥比无肥分别提高2．99％、2．56％、1．98％、1．14％。  相似文献   

10.
In soil-mantled landscapes, downslope sediment transport occurs via disturbance-driven processes that vary with climate and vegetation change. To help constrain the long-term (? 10 yr) pattern and rate of soil mixing and transport in forests, we analyzed the distribution of tephra grains in soil along a hillslope transect in the Blue Mountains, SE Washington. Deposited within a loess mantle, tephra associated with Mt. Mazama (7.7 cal. kyr B.P.) serves as a marker bed for estimating erosion and transport rates. Moving downslope, the buried tephra horizon is progressively exhumed and becomes increasingly mixed in the upper soil layer, reflecting disturbance and transport via tree root growth and turnover. This pattern also implies increasing erosion rates downslope and our hillslope transect becomes increasingly convex coincident with progressive exhumation of the tephra layer. This systematic correspondence between topographic form, specifically, local convexity, and surface lowering is consistent with theoretical models for which soil transport rates depend on slope inclination. From our analysis, calibrated coefficients for a linear, slope-dependent transport model are on the order of 10− 3 m2yr− 1, consistent with previous work in forested loess-mantled landscapes. In addition, our results reveal both the high degree of soil mixing over millennial timescales and the local variability of mixing in forested landscapes. Furthermore, the results enable us to quantify the amount of energy expended by trees in mixing and transporting soil and the net sediment transport fraction of the net primary productivity NPP of the ecosystem.  相似文献   

11.
Biochemical characterization of urban soil profiles from Stuttgart, Germany   总被引：1，自引：0，他引：1  
The knowledge of biochemical properties of urban soils can help to understand nutrient cycling in urban areas and provide a database for urban soil management. Soil samples were taken from 10 soil profiles in the city of Stuttgart, Germany, differing in land use—from an essentially undisturbed garden area to highly disturbed high-density and railway areas. A variety of soil biotic (microbial biomass, enzyme activities) and abiotic properties (total organic C, elemental C, total N) were measured up to 1.9 m depth. Soil organic matter was frequently enriched in the subsoil. Microbial biomass in the top horizons ranged from 0.17 to 1.64 g C kg−1, and from 0.01 to 0.30 g N kg−1, respectively. The deepest soil horizon at 170-190 cm, however, contained 0.12 g C kg−1 and 0.05 kg N kg−1 in the microbial biomass. In general, arylsulphatase and urease activity decreased with depth but in three profiles potentially mineralizable N in the deepest horizons was higher than in soil layers directly overlying. In deeply modified urban soils, subsoil beside topsoil properties have to be included in the evaluation of soil quality. This knowledge is essential because consumption of natural soils for housing and traffic has to be reduced by promoting inner city densification.  相似文献   

12.
Municipal solid waste (MSW) composts have been used to maintain the long-term productivity of agroecosystems and to protect the soil environment from overcropping, changes in climatic conditions and inadequate management; they also have the additional benefit of reducing waste disposal costs. Since MSW may contain heavy metals and other toxic compounds, amendments cannot only influence soil fertility, but may also affect the composition and activity of soil microorganisms. The effects of MSW compost and mineral N amendments in a 6-year field trial on some physical-chemical properties, enzyme activities and bacterial genetic diversity of cropped plots (Beta vulgaris-Triticum turgidum rotation) and uncropped plots were investigated. The compost was added at the recommended and twice the recommended dosage (12, 24 t ha−1). Amendments of cropped plots with MSW compost increased the contents of organic C from 13.3 to 15.0 g kg−1 soil and total N from 1.55 to 1.65 g kg−1 soil. There were significant increases in dehydrogenase (9.6%), β-glucosidase (13.5%), urease (15.4%), nitrate reductase (21.4%) and phosphatase (9.7%) activities. A significant reduction in protease activity (from 3.6 to 2.8 U g−1 soil) was measured when a double dose of compost was added to the cropped plots. No dosage effect was detected for the other enzymes. Changes in the microbial community, as a consequence of MSW amendment, were minimal as determined using denaturing gradient gel electrophoresis, rDNA internal spacer analysis and amplified ribosomal DNA restriction analysis of bacteria, archaea, actinomycetes, and ammonia oxidizers. This indicates that there was no significant variation in the overall bacterial communities nor in selected taxonomic groups deemed to be essential for soil fertility.  相似文献   

13.
Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha−1 y−1, and urban sewage sludge at two different rates, 10 t ha−1 y−1 and 100 t ha−1 every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg−1 in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last application, the organic C content and the microbial biomass content remained higher in sludge-treated soils than in the control. In contrast, the proportion of labile organic matter was significantly lower in sludge-treated soils than in manure-treated and control soils. The labile organic matter of sludge extracts appeared less humified than that of manure-treated and control soils.  相似文献   

14.
Considerable amounts of soil organic matter (SOM) are stabilized in paddy soils, and thus a large proportion of the terrestrial carbon is conserved in wetland rice soils. Nonetheless, the mechanisms for stabilization of organic carbon (OC) in paddy soils are largely unknown. Based on a chronosequence derived from marine sediments, the objectives of this study are to investigate the accumulation of OC and the concurrent loss of inorganic carbon (IC) and to identify the role of the soil fractions for the stabilization of OC with increasing duration of paddy soil management. A chronosequence of six age groups of paddy soil formation was chosen in the Zhejiang Province (PR China), ranging from 50 to 2000 years (yrs) of paddy management. Soil samples obtained from horizontal sampling of three soil profiles within each age group were analyzed for bulk density (BD), OC as well as IC concentrations, OC stocks of bulk soil and the OC contributions to the bulk soil of the particle size fractions. Paddy soils are characterized by relatively low bulk densities in the puddled topsoil horizons (1.0 and 1.2 g cm− 3) and high values in the plow pan (1.6 g cm− 3). Our results demonstrate a substantial loss of carbonates during soil formation, as the upper 20 cm were free of carbonates in 100-year-old paddy soils, but carbonate removal from the entire soil profile required almost 700 yrs of rice cultivation. We observed an increase of topsoil OC stocks from 2.5 to 4.4 kg m− 2 during 50 to 2000 yrs of paddy management. The OC accumulation in the bulk soil was dominated by the silt- and clay-sized fractions. The silt fraction showed a high accretion of OC and seems to be an important long-term OC sink during soil evolution. Fine clay in the puddled topsoil horizon was already saturated and the highest storage capacity for OC was calculated for coarse clay. With longer paddy management, the fractions < 20 μm showed an increasing actual OC saturation level, but did not reach the calculated potential storage capacity.  相似文献   

15.
Soil moisture characteristic curves were determined in long-term trials at the agronomic research center of Saria (latitude 12°16′ N, longitude 2°09′ W) in West-central Burkina Faso. The agronomic treatments combined soil tillage with organic and chemical fertilizers. The twin values for soil moisture and water potential showed that on ploughed plots, moisture content was higher at low suction and lower at high suction than the hand hoed plots. Moisture contents were higher for extreme suctions (pF < 1.5 and >3) on plots that received high dose of animal manure. The bush fallow plots behaved as a ploughed plot at low suction and like a hand hoed plot at the high suction. Field capacities were around 9.50% (g/g) and 8% (g/g), respectively, for hand hoed and ploughed plots, while the wilting points for both were of 5–6% (g/g). Organic matter input improved field capacity and soil water content at wilting point but not the useful available water (UAW). The UAW ≥10 mm on the fallow and the control, while it was <9 mm on the other treatments in 0–20 cm soil layer. Soil structural modifications induced by tillage and organic matter input explained these differences in soil hydrologic regime.  相似文献   

16.
Effectiveness of geotextiles in reducing runoff and soil loss: A synthesis   总被引：1，自引：0，他引：1  
Despite geotextiles having potential for soil conservation, limited scientific data are available to assess the effects of geotextiles in reducing runoff and water erosion. Hence, the objective of this review is to analyse the effects of plot length (L) and other possible affecting factors [cover percentage (C, %), slope gradient (S), rainfall duration (D), rainfall intensity (I), sand, silt and clay contents, soil organic matter (SOM) content and geotextile type (natural or synthetic)] on the effectiveness of geotextiles in reducing soil and water loss, based on reported experimental data. From linear regressions, C (%) and soil sand, silt and clay contents are found to be the most important variables in reducing SLR (ratio of soil loss in bare plots to that in geotextile treated plots) for splash, C (%) for interrill and D (min) for rill and interrill erosion processes, respectively. Soil clay and silt contents and D are key variables in decreasing RR (ratio of runoff from bare plots to that from geotextile treated plots) for interrill, and clay content for rill and interrill erosion processes, respectively. The linear relationship between mean b-value (geotextile effectiveness factor in reducing soil loss) and L of all studies was not significant (P > 0.05). The same is true for the relationship between L and SLR, and L and RR. However, when L is added to an equation as an interaction term with C (%), geotextile cover is significantly (P < 0.05) more effective in reducing SLR on shorter plots than longer ones for both interrill and rill and interrill erosion processes. Buffer strip plots (area coverage ∼ 10%) with Borassus and Buriti mats have the highest b-values.  相似文献   

17.
《CATENA》2006,65(2-3):297-306
Soil losses affect the physical, chemical and biological soil properties and as a consequence reduce soil productivity. Erosion reduces or eliminates root-explorable soil depth and crop available water, selectively decreases the nutrient and organic matter content, and exposes soil layers with unsuitable characteristics for crop growth. Yield is hence assumed to be a function of root growth, which in turn is a function of the soil environment. In order to evaluate the water erosion impact on soil properties and productivity, a study was carried out on a Typic Haplustalfs soil, with sorghum (Sorghum bicolor (L) Moench), located in Chaguaramas in the Central Plains of Venezuela. Four different study locations with the same soil type, with slopes ranging from 3% to 6% and with different levels of erosion were selected: Chaguaramas I (slightly eroded), Chaguaramas II, (moderately eroded), Chaguaramas III (moderately eroded), and Chaguaramas IV (severely eroded). A sorghum–livestock farming system was introduced 30 years ago. Secondary tillage with a disc harrow (without mulch on the topsoil) was applied for seedbed preparation. Fertilizers and pesticides were applied uniformly over the entire fields. Soil samples from each horizon were analysed for particle size distribution, water retention, bulk density, pH and organic matter content. The relative production potential was estimated using the Productivity Index developed by Pierce et al. [Pierce, F.C., W.E. Larson, R.H. Dowdy and W.A. Graham. 1983. Productivity of soils: assessing long-term changes due to erosion. Journal of Soil and Water Conservation. 38 39–44.], and adapted to the methodology proposed by Delgado [Delgado F. 2003. Soil physical properties on Venezuelan steeplands: applications to conservation planning. The Abdus Salam International Centre for Theoretical Physics. College on Soil Physics. 11 pp.] for Venezuelan soil conditions. The Productivity Index (PI) could estimate the tolerable rate of soil productivity loss. A soil erosion risk was assessed by the Erosion Risk Index (ERI) taking into account the soil hydrological characteristics (infiltration–runoff ratio), rainfall aggressiveness and topography (slope). The Productivity Index (PI) and the Erosion Risk Index (ERI) were used to classify the lands for soil conservation priorities, for conservation requirements and for alternative land uses. The results showed that: (a) the Productivity Index (PI) decreased with increasing level of erosion, (b) the Productivity Index (PI) was mainly affected by changes in available water storage capacity, bulk density and pH, (c) the erosion risk (ERI) was strongly affected by slope gradient and rainfall aggressiveness, (d) the areas were classified as critical lands and super-critical lands, with high to very high soil conservation requirements, depending on the level of soil erosion.  相似文献   

18.
The submontaneous tract of Punjab comprising 10% of the state, is prone to soil erosion by water. Soils of the area are coarse in texture, low in organic matter and poor in fertility. High intensity rains during the monsoon season result in fertile topsoil removal. There is an urgent need to control soil erosion in this region so as to improve soil productivity. A field study was conducted to estimate the effect of tillage and different modes of mulch application on soil erosion losses. Treatments comprised two levels of tillage, viz. minimum (Tm) and conventional (Tc) in the main plots and five modes of straw mulch application, viz. mulch spread over whole plot (Mw), mulch spread on lower one-third of plot (M1/3), mulch applied in strips (Ms), vertical mulching (Mv) and unmulched control (Mo), in subplots in a replicated split plot design. Rate of mulch application was 6 t ha−1 in all modes. Compared with Mo, Mw reduced runoff by 33%. Runoff and soil loss were 5 and 40% higher under Tc than under Tm. Though other modes of straw mulch application (M1/3, Ms and Mv) controlled soil loss better than Mo, their effectiveness was less than Mw. Tm was more effective in conserving soil moisture than Tc. Compared with Mo, Mw had 3–7% higher soil moisture content in the 0–30 cm soil depth under Tm. Minimum soil temperature of the surface layer was 1.4–2.4 °C lower under Mw than under Mo. Straw mulching reduced maximum soil temperature and helped in conserving soil moisture. Minimum tillage coupled with Mw was highly effective in reducing soil erosion losses, decreasing soil temperature and increasing moisture content by providing maximum surface cover.  相似文献   

19.
Soil aggregation is of great importance in agriculture due to its positive effect on soil physical properties, plant growth and the environment. A long-term (1996-2008) field experiment was performed to investigate the role of mycorrhizal inoculation and organic fertilizers on some of soil properties of Mediterranean soils (Typic Xerofluvent, Menzilat clay-loam soil). We applied a rotation with winter wheat (Triticum aestivum L.) and maize (Zea mays L.) as a second crop during the periods of 1996 and 2008. The study consisted of five experimental treatments; control, mineral fertilizer (300-60-150 kg N-P-K ha−1), manure at 25 t ha−1, compost at 25 t ha−1 and mycorrhiza-inoculated compost at 10 t ha−1 with three replicates. The highest organic matter content both at 0-15 cm and 15-30 cm soil depths were obtained with manure application, whereas mineral fertilizer application had no effect on organic matter accumulation. Manure, compost and mycorrhizal inoculation + compost application had 69%, 32% and 24% higher organic matter contents at 0-30 cm depth as compared to the control application. Organic applications had varying and important effects on aggregation indexes of soils. The greatest mean weight diameters (MWD) at 15-30 cm depth were obtained with manure, mycorrhiza-inoculated compost and compost applications, respectively. The decline in organic matter content of soils in control plots lead disintegration of aggregates demonstrated on significantly lower MWD values. The compost application resulted in occurring the lowest bulk densities at 0-15 and 15-30 cm soil depths, whereas the highest bulk density values were obtained with mineral fertilizer application. Measurements obtained in 2008 indicated that manure and compost applications did not cause any further increase in MWD at manure and compost receiving plots indicated reaching a steady state. However, compost with mycorrhizae application continued to significant increase (P < 0.05) in MWD values of soils. Organic applications significantly lowered the soil bulk density and penetration resistance. The lowest penetration resistance (PR) at 0-50 cm soil depth was obtained with mycorrhizal inoculated compost, and the highest PR was with control and mineral fertilizer applications. The results clearly revealed that mycorrhiza application along with organic fertilizers resulted in decreased bulk density and penetration resistance associated with an increase in organic matter and greater aggregate stability, indicated an improvement in soil structure.  相似文献   

20.
以新疆奇台县绿洲不同耕种时间土壤含盐量为研究对象,运用聚类分析与相关分析法对其含盐量变化规律、盐分剖面类型及其影响因素进行了研究。结果表明:在荒地转化成人类熟作的农田(5 a以上)过程中,土壤剖面盐分特征变化依次为表聚型、均匀型、震荡型和底聚型。未耕地土壤含盐量高,是典型的盐渍土,且表层聚集现象明显,含盐量在表层(0～20 cm)占整个剖面的34.31%。耕种5 a、10 a的土壤,多为底聚型盐分剖面。随耕种时间加长,土壤各层含盐量的活跃程度变化依次为活跃层、次活跃层和较稳定层;土壤含盐量与有机质含量的关系由极显著正相关转变为极显著负相关,而与土壤pH的关系变化则相反。有耕作活动的土壤盐渍化发生了逆向演替,耕种10 a土壤平均含盐量仅为未耕地的20.90%,脱盐速度随着时间的增加而减小,由早期(0～3 a)的1.56 g kg-1a-1,下降为后期(5～10 a)的0.04 g kg-1a-1。  相似文献   

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