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1.
The effects of soil bunds on runoff, losses of soil and nutrients, and crop yield are rarely documented in the Central Highlands of Ethiopia. A field experiment was set up consisting of three treatments: (i) barley‐cultivated land protected with graded soil bunds (Sb); (ii) fallow land (F); and (iii) barley‐cultivated land without soil bund (Bc). For 3 years (2007–2009), the effect of soil bunds on runoff, losses of soil and nutrients, and crop productivity was studied. Daily runoff and soil and nutrient losses were measured for each treatment using standard procedures while barley yield was recorded from the cultivated plots. The results showed that Sb brought about significant reduction in runoff and soil losses. Plots with Sb reduced the average annual runoff by 28 per cent and the average annual soil loss by 47 per cent. Consequently, Sb reduced losses of soil nutrients and organic carbon. However, the absolute losses were still high. This implies the need for supplementing Sb with biological and agronomic land management measures to further control soil erosion. Despite these positive impacts on soil quality, Sb do not increase crop yield. Calculated on a per‐hectare basis, Sb even reduce crop yield by about 7 per cent as compared with control plots, which is entirely explained by the reduction of the cultivable area by 8·6 per cent due to the soil bunds. Suitable measures are needed to compensate the yield losses caused by the construction of soil bunds, which would convince farmers to construct these land management measures that have long‐term beneficial effects on erosion control. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

2.
Abstract

Laboratory and field experiments were conducted at the Regional Research Station of Kandi Area, Ballowal Saunkhri, Punjab, India, to determine the immediate influence of artificial topsoil removal (simulated erosion) on selected soil properties, maize (Zea mays) growth and yield, and restoration of crop productivity with nitrogen (N) fertilization. For the laboratory experiment, soil samples (0–15 cm) were obtained after removing 0, 6, 12, and 18 cm of a sandy loam topsoil from a cereal grain cropped field. In the field experiment, topsoil was removed at 0, 6, 12, and 18 cm in main plots, and six N treatments at rates of 0, 40, 80, 120, 160, and 200 kg N ha‐1 were applied in subplots. Topsoil removal greatly decreased mineralized N, N mineralization potential and rate constant, and increased time for half mineralization of N. Bulk density and penetration resistance increased as a result of topsoil removal and infiltration capacity of the soil decreased. Total profile water was more at the time of harvest than at sowing in the plots where topsoil was removed, but the water expense efficiency decreased. Both grain and straw yield of maize decreased substantially as a result of adverse effect of topsoil removal on plant height, mass and depth of root, length and girth of cob, and thousand grain weight. Nitrogen application improved maize growth and yield, but the crop responded to higher doses of N on eroded plots than the uneroded plots, and yields on eroded plots did not match to those obtained on uneroded plots at any level of N application. In conclusion, artificial surface soil erosion deteriorated soil properties governing maize productivity. More N was required where topsoil had been eroded, but N application alone did not restore crop yield to that level obtained from uneroded soil. Therefore, there is a need to look for and quantify other factors also to improve soil productivity.  相似文献   

3.
Soil degradation by accelerated erosion is a serious problem and will remain so during the 21st century, especially in developing countries of the tropics and subtropics. Yet, its extent, severity, and economic and environmental impacts are debatable. Estimates of global and regional land area affected are tentative and subjective. Results of field measurements are often technique‐dependent. Considerable progress has been made in modeling soil erosion, yet field validation of these models remains to be done for principal soils and ecoregions. Similar to the land area affected, estimates of erosional impacts on crop yield, productivity and soil quality are tentative and subjective. Further, erosion‐induced losses on crop yield are scale‐dependent because of the compensatory beneficial effects on yields from depositional sites, and technology‐dependent because of the masking effects of input such as fertilizers and irrigation. Erosion caused changes in soil carbon dynamics and non‐point source water pollution are important environmental impacts. While erosion (e.g., detachment and transport) can lead to emission of trace gases into the atmosphere, deposition can bury and sequester some of the carbon. In addition to improving the database on the land area affected, there is also a need to assess erosional impacts on productivity and soil C balance at the watershed, regional, and global scale. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

4.
The effect of soil erosion on spring barley growth was studied on a deep loamy soil in East Anglia,England,in 1992,Soil erosion was simulated by three levels of soil desurfacing,7.5,18and 30cm with three replicates.Significant differences in crop height,ground cover and crop yield were observed between the three levels of desurfacing.Soil desurfacing also has a singnificant effect on soil moisture at the 20cm depth.The interaction between soil removal and crop performance affected soil moisture at the depths of 50 and 100cm,No significant differences were found in runoff and sediment etween the three topsoil removals due to very dry growing season.Regression equations were developed between spring barley yield and soil desurfacing Spring barley grain yield declined by 97.6kg/ha per cm soil desurfacing.  相似文献   

5.
Soil compaction can affect crop growth and greenhouse gas emission and information is required of how both these aspects are affected by compaction intensity and weather. In this paper we describe treatments of compaction intensity and their effects on soil physical conditions and crop growth in loam to sandy loam cambisol soils. Soil conditions and crop performance were measured over three seasons in a field experiment on soil compacted by wheels on freshly ploughed seedbeds. Ploughing buried the chopped residues of the previous crop. After ploughing, traffic was controlled such that the experimental plots received wheel traffic only as treatments. The overall objective was to discover how the intensity and distribution of soil compaction just before sowing influenced crop performance, soil conditions and emissions of nitrous oxide. Compaction treatments were zero, light compaction by roller (up to 1 Mg m−1) and heavy compaction by loaded tractor, (up to 4.2 Mg). The experiment was located at Boghall, near Edinburgh (860 mm average annual rainfall) for the first two seasons under spring and winter barley (Hordeum vulgare L.) and in a drier area at North Berwick (610 mm average annual rainfall) for the third season under winter oil-seed rape (Brassica napus L.). Heavy compaction in dry soil conditions had little effect on crop growth. However, in wet conditions heavy compaction reduced air porosity, air permeability and gas diffusivity, increased cone resistance and limited winter barley growth and grain yield. Heavy compaction in wet conditions reduced winter barley yields to 7.1 Mg ha−1, in comparison to 8.8 Mg ha−1 in the zero compaction treatment. The compaction status of the top 15 cm of soil seemed to be particularly important. Loosening of the top 10 cm of soil immediately after heavy compaction restored soil conditions for crop growth. However, zero seed bed compaction gave patchy and uneven crop emergence in dry conditions. Both zero and light compaction to a target depth of 10 cm gave similar crop productivity. Maintenance of a correct compaction level near the soil surface is particularly important for establishment and overwintering of barley and oil seed rape.  相似文献   

6.
During 2005–2007, studies were carried out in two field experiments in southwest Sweden with separately tile‐drained plots on a sandy soil (three replicates) and on a clay soil (two replicates). The overall aim was to determine the effects of different cropping systems with catch crops on losses of N, P and glyphosate. Different times of glyphosate treatment of undersown ryegrass catch crops were examined in combination with soil tillage in November or spring. Drainage water was sampled continuously in proportion to water flow and analysed for N, P and glyphosate. Catch crops were sampled in late autumn and spring and soil was analysed for mineral N content. The yields of following cereal crops were determined. The importance of keeping the catch crop growing as long as possible in the autumn is demonstrated to decrease the risk of N leaching. During a year with high drainage on the sandy soil, annual N leaching was 26 kg/ha higher for plots with a catch crop killed with glyphosate in late September than for plots with a catch crop, while the difference was very small during 1 yr with less drainage. Having the catch crop in place during October was the most important factor, whereas the time of incorporation of a dead catch crop did not influence N leaching from either of the two soils. However, incorporation of a growing catch crop in spring resulted in decreased crop yields, especially on the clay soil. Soil type affected glyphosate leaching to a larger extent than the experimental treatments. Glyphosate was not leached from the sand at all, while it was found at average concentrations of 0.25 μg/L in drainage water from the clay soil on all sampling occasions. Phosphorus leaching also varied (on average 0.2 and 0.5 kg/ha/yr from the sand and clay, respectively), but was not significantly affected by the different catch crop treatments.  相似文献   

7.
The adoption of conservation agriculture (CA), based on minimal soil movement, permanent soil cover with crop residues or growing plants and crop rotation has advanced rapidly in the Americas and Australia over the last three decades. One of the immediate benefits of CA in dryland agriculture is improved rainfall-use efficiency through increased water infiltration and decreased evaporation from the soil surface, with associated decreases in runoff and soil erosion. This paper focuses on the effect of CA techniques on soil moisture relations in two researcher-managed trials in Zambia and Zimbabwe. In 2005/2006 and 2006/2007, we found significantly higher water infiltration on both sites on CA fields compared to conventionally ploughed fields. At Henderson Research Station, Zimbabwe, on a sandy soil, a direct seeded CA treatments had a 49% and 45% greater infiltration rate than the conventionally tilled plots after a simulated rainfall in both seasons. At Monze Farmer Training Centre, Zambia, on a finer-textured soil, the same treatment had 57% and 87% greater infiltration rate than the conventionally tilled control treatment in both seasons. Treatments that included reduced tillage and surface residue retention had less water runoff and erosion on runoff plots at Henderson Research Station, Zimbabwe. On average, soil moisture was higher throughout the season in most CA treatments than in the conventionally tilled plots. However, the full potential of CA in mitigating drought was not evident as there was no significant drought period in either season. Results suggest that CA has the potential to increase the productivity of rainfall water and therefore reduce the risk of crop failure, as was apparent at the Monze Farmer Training Centre, Zambia, in 2005/2006 when a period of moisture stress at tassling affected CA treatments less than the conventionally tilled treatment.  相似文献   

8.
Black soils, originally characterized by a deep, dark A‐horizon, are widespread in the Northeast Plain of China and have been one of the most fertile agricultural resources in the country. However, more than a half‐century of intensified management degraded its productivity, mainly with the loss of the dark‐coloured A‐horizon by rainfall erosion. Using the Revised Universal Soil Loss Equation (RUSLE), the rainfall erosion losses of black soils in YuShu and DeHui counties of Jilin Province were estimated. The rate of loss of thickness of the A‐horizon of black soils and the time over which the A‐horizons of some black soils in the region might be lost were evaluated. The results showed that about 4–45 t ha−1 topsoil could have been lost each year under corn (Zea mays L.) production. Soybean (Glycine max L. Merr) production would double the losses. Soil losses were directly related to soil type, tillage practices and crop grain yields. The thickness of the A‐horizon of black soils in the region decreased at rates of 0ċ5–4ċ5 mm yr−1, depending on soil type and management practices. Corn production may have resulted in an annual loss of 8ċ3 million tonnes of topsoil from black soils alone in Jilin Province; soybean production could have greatly increased this loss. Traditional intensified farming can accelerate the degradation of black soils; conservation tillage has great potential to prevent rainfall erosion losses for the same soils. Accordingly, to preserve and restore the productivity of black soils, conservation tillage is appropriate and should be adopted in Jilin. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

9.
10.
Land degradation mapping by remote sensing in the arid region of India   总被引:1,自引:0,他引:1  
Abstract. In arid regions of India, cultivation of marginal areas and overgrazing of pastures have resulted in degradation of land. Accelerated wind erosion on sandy surfaces and water erosion on the shallow soils of piedmont areas are both common. Landsat Thematic Mapper sub-scenes have been used to map the type, extent and degree of degradation. In an area of over 5000 km2, 42% was affected by wind erosion and 50% by accelerated water erosion. A quarter of the whole area needs urgent attention for soil conservation.  相似文献   

11.
斥水土壤中的水热运动规律与数值模型   总被引:5,自引:2,他引:5  
斥水土壤很难被雨水湿润,影响种子发芽出苗而造成农业减产。由于地表干燥而引起风蚀水蚀,造成土地退化。这一问题在澳大利亚、荷兰、新西兰与美国引起重视。斥水土壤中水分分布往往是无规律的“指状”,到目前为止,没有成功的数学模型。作者从研究斥水土壤地区的耕作工程实践出发,采用沟种之后,水分的分布就有了规律性。开沟播种时,耕作机械把表层斥水性特别强的土壤推到垄上而形成几乎不透水的垄,下雨时雨水只能从沟中渗入形  相似文献   

12.
利用野外模拟降雨试验,研究了粗质地土壤裸地和苜蓿地在不同坡度(5°,15°,25°)、不同前期含水量(低、中、高)条件下坡面降雨产流、产沙的过程及其特征,以此探究该区退耕还草效益。结果表明:3种坡度条件下裸地和苜蓿地的产流过程在不同前期含水量下均为先增大后趋于稳定,不同坡度之间的径流量差异不显著,但泥沙流失量随着坡度的增大而显著增加,在降雨过程中先增大达到峰值趋于稳定波动,裸地的波动幅度大于苜蓿地。2种处理的前期含水量对径流量以及平均入渗率的影响均达显著水平,裸地在相同的坡度下,前期含水量由低水平增加到中水平、低水平增加到高水平,径流量分别增加38.2%~52.8%,39.7%~42.8%,苜蓿地径流量分别增加27.3%~77.8%,45.5%~91.1%。坡度对泥沙流失量及含沙率影响显著,在相同的前期含水量下,裸地由5°增加到15°,15°增加到25°的泥沙流失量分别增加96.3%~268.7%,6.9%~40.3%,苜蓿地的泥沙流失量分别增加81.1%~384.2%,61.7%~169.9%。在相同坡度和前期含水量下,苜蓿地的径流量和泥沙流失量均显著低于裸地。研究结果表明粗质地土壤前期含水量和坡度显著影响坡地土壤侵蚀过程和总量,植被不但因为冠层拦截而减少径流,而且因为耗水量增加,降低了土壤前期含水量而减水减沙。  相似文献   

13.
[目的] 开展柴达木盆地的土壤侵蚀现状调查研究,旨在为柴达木盆地土壤侵蚀防治和青藏高原环境治理提供科学依据。[方法] 考察组分别于2019,2020,2021年7月3次赴柴达木盆地,沿德令哈市、格尔木市、都兰县一带,对选取的77个样地内不同土地利用类型植被、土壤、侵蚀特征和水土保持措施进行了调查和分析。[结果] 柴达木盆地以风蚀为主,在作物生长季,耕地没有明显的风蚀现象,说明作物的水土保持效果显著。不同利用类型土地的平均土壤风蚀速率大小顺序为:沙地>耕地>撂荒地>灌草地;土壤侵蚀沟多出现于山前洪积扇和山坡上的灌草地,洪积扇上的沟蚀较为严重;植物沙堆分布广泛,种类多样,沙堆体积与植物冠幅相关性强,植物拦沙作用明显。同时,该区还存在部分耕地因灌溉系统管理不善而造成土壤侵蚀和地下水位上升大;种植枸杞的沙田管理不到位,水土保持措施不完善,水土保持投入不足等问题。[结论] 柴达木盆地土壤侵蚀类型复杂多样,需要在加强水土保持工作的同时,完善灌溉系统的维护,加强土壤盐渍化治理和沙田保育,切实保障柴达木盆地的土地资源可持续性。  相似文献   

14.
Abstract. Each year since 1986 information has been collected about the farming systems at intersections of a nationwide 7 km square grid in Denmark. These management data and corresponding soil analyses were used in the model DAISY to simulate water and nitrogen dynamics. The model was validated with respect to harvested dry matter yield and nitrogen content in the soil. Simulated nitrate leaching from farmland areas from 1 April 1989 to 31 March 1993 was related to precipitation zones, soil type, fertilizer strategies and cropping systems. The mean simulated nitrate leaching for the whole of Denmark was 74 kg N/ha/yr, with a large yearly variation in the period considered. The simulated nitrate leached from soils with a sandy subsoil corresponded to 51% of the applied fertilizer, twice that leached from soils with a loamy subsoil. The application of pig manure resulted in average leaching losses of 105 kg N/ha/yr. The simulated nitrate leaching losses at sites where only artificial fertilizer was applied were in the following order: cereal with undersown grass < crop followed by winter cereal or winter rape < cereal or rape without a catch crop < root crops without a catch crop. Where only artificial fertilizers were applied, the simulated mean annual leaching was 59 kg N/ha from spring barley and 40 kg N/ha from winter wheat. A map of simulated nitrate leaching in Denmark was produced using a Geographical Information System.  相似文献   

15.
针对黄土丘陵区的土地可持续利用问题,引入目前国际上较先进的水土流失与土地利用规划模型APEX和AV-SWAT,利用GIS技术及陕北安塞县纸坊沟小流域定位站多年的连续观测资料,对模型在黄土丘陵区的适用性进行了初步验证。通过对该类型地区的水土流失量、作物产量、植被生物量等方面的测算,结果表明模型模拟计算的水土流失量与实际观测量的误差小于10%,5年加权平均的作物模拟产量与实测值的差异不显著。从而为该类型区土地可持续利用方法论提供了新的计算工具,也使得更大尺度上的土地可持续利用设计成为可能。  相似文献   

16.
Abstract. The 296 soil associations of the National Soil Map of England and Wales are placed into five categories of erosion risk. These are based on land use, landform and soil properties and take into account the extent of erosion in the uplands, and its frequency, extent and rates in the lowlands. Erosion of arable land is by water or wind, but in the uplands frost action and disturbance by sheep are also important. A large proportion of arable England (36%) is at moderate to very high risk of erosion, including much of the better drained and more easily worked land, especially sandy soils. In the uplands thin soils or deep peats are most at risk. If land use changes, because of increasing intensification of agriculture or in response to climatic changes, many soil associations will become more at risk of erosion.  相似文献   

17.
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.
Nitrate leaching as influenced by soil tillage and catch crop   总被引:1,自引:0,他引:1  
Because of public and political concern for the quality of surface and ground water, leaching of nitrate is of special concern in many countries. To evaluate the effects of tillage and growth of a catch crop on nitrate leaching, two field trials were conducted in spring barley (Hordeum vulgare L.) under temperate coastal climate conditions. On a coarse sand (1987–1992), ploughing in autumn or in spring in combination with perennial ryegrass (Lolium perenne L.) as a catch crop was evaluated. Furthermore, rotovating and direct drilling were included. The experiment was conducted on a 19-year-old field trial with continuous production of spring barley. On a sandy loam (1988–1992), ploughing in autumn or in spring in combination with stubble cultivation and perennial ryegrass, in addition to minimum tillage, was evaluated in a newly established field trial. For calculation of nitrate leaching, soil water isolates from depths of 0.8 or 1.0 m were taken using ceramic cups. No significant effect of tillage was found on the coarse sand; however, a significant effect of tillage was found on the sandy loam, where leaching from autumn ploughed plots without stubble cultivation was 16 kg N ha−1 year−1 higher than leaching from spring ploughed plots. Leaching was significantly less when stubble cultivation in autumn was omitted. Leaching on both soil types was significantly reduced by the growth of a catch crop which was ploughed under in autumn or in spring. It was concluded that soil cultivation increased leaching on the sandy loam but not on the coarse sand, and that the growth of perennial ryegrass as a catch crop reduced leaching on both soil types, particularly when ryegrass was ploughed under in spring.  相似文献   

19.
In Scandinavia high losses of soil and particulate-bound phosphorus (PP) have been shown to occur from tine-cultivated and mouldboard-ploughed soils in clay soil areas, especially in relatively warm, wet winters. The omission in the autumn of primary tillage (not ploughing) and the maintenance of a continuous crop cover are generally used to control soil erosion. In Norway, ploughing and shallow cultivation of sloping fields in spring instead of ploughing in autumn have been shown to reduce particle transport by up to 89% on highly erodible soils. Particle erosion from clay soils can be reduced by 79% by direct drilling in spring compared with autumn ploughing. Field experiments in Scandinavia with ploughless tillage of clay loams and clay soils compared to conventional autumn ploughing usually show reductions in total P losses of 10–80% by both surface and subsurface runoff (lateral movements to drains). However, the effects of not ploughing during the autumn on losses of dissolved reactive P (DRP) are frequently negative, since the DRP losses without ploughing compared to conventional ploughing have increased up to fourfold in field experiments. In addition, a comprehensive Norwegian field experiment at a site with high erosion risk has shown that the proportion of DRP compared to total P was twice as high in runoff water after direct drilling compared to ploughing. Therefore, erosion control measures should be further evaluated for fields with an erosion risk since reduction in PP losses may be low and DRP losses still high. Ploughless tillage systems have potential side-effects, including an increased need for pesticides to control weeds [e.g. Elytrigia repens (L.) Desv. ex Nevski] and plant diseases (e.g. Fusarium spp.) harboured by crop residues on the soil surface. Overall, soil tillage systems should be appraised for their positive and negative environmental effects before they are widely used for all types of soil, management practice, climate and landscape.  相似文献   

20.
Abstract

Four rates of straw (0, 4, 8 and 12 t ha?1 yr?1) were incorporated in a field experiment with continuous spring barley. The experiment was conducted on a sandy soil (5.5% clay) and a sandy loam soil (11.2% clay). After eight years, the straw incorporation was combined with catch-crop growing with and without winter application of animal slurry and also spring fertilization with mineral fertilizer (0, 50, 100 or 125 kg N ha?1 yr?1). The combined experiment was conducted for three lyears on the sandy soil and for four years on the sandy loam soil. The effects on barley dry matter yield and N uptake are presented together with the long-term effects of the straw incorporations on crop growth and soil C and N. Grain yield on the sandy loam was unaffected by straw incorporation. On the sandy soil the highest straw application rates reduced grain yield in the unfertilized barley. When the barley received mineral fertilizer at recommended levels (100 kg N ha?1 yr?1), grain yield on this soil was also unaffected by the high straw rates. Including a catch crop had a positive effect on the grain yield of barley on both soils. The total N uptake in grain and straw generally increased with straw application up to 8 t ha?1 yr?1. With the highest straw application rate (12 t ha?1 yr?1), the total N uptake decreased but still exceeded N uptake in barley grown with straw removal. The barley accumulated higher amounts of N when a catch crop was included. The total N uptake in the barley was significantly higher after animal slurry application. The extra N uptake, however, was much lower than the amounts of N applied with the slurry. Incorporation of straw had only a small influence on N uptake after slurry application. The straw, therefore, was not able to store the applied N during winter. In the two four-year periods before the combined experiment, grain yield on the sandy loam was generally negatively affected by straw incorporations. In the second period, N uptake began to show a positive effect of the straw. On the sandy soil, grain yield and N uptake during the whole period were generally positively affected by the straw incorporations except for the highest straw rate (12 t ha?1 yr?1). The sandy loam soil showed higher increases in C and N content after the repeated straw incorporations and catch-crop growing than the sandy soil. When application of animal slurry was combined with the catch crop, no further increases in soil C and N were found relative to soil where a catch crop was grown without slurry application. Large amounts of the N applied with the slurry may therefore have been lost by denitrification or nitrate leaching.  相似文献   

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