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1.
Modeling spatial variation in productivity due to tillage and water erosion   总被引:5,自引:0,他引:5  
The advent of precision farming practices has heightened interest in managing field variability to optimize profitability. The large variation in yields across many producer fields demonstrated by yield–monitor–equipped combines has generated concern about management-induced causes of spatial variation in soil productivity. Soil translocation from erosion processes may result in variation in soil properties across field landscape positions that produce long-term changes in soil productivity. The objective of this study was to examine the relationships between soil redistribution caused by tillage and water erosion and the resulting spatial variability of soil productivity in a soil catena in eastern South Dakota. An empirical model developed to estimate tillage erosion was used to evaluate changes expected in the soil profile over a 50-year period on a typical toposequence found in eastern South Dakota and western Minnesota. Changes in the soil profile due to water erosion over a 50-year period were evaluated using the WEPP hillslope model. The tillage erosion model and the WEPP hillslope model were run concurrently for a 50-year period to evaluate the combined effect of the two processes. The resulting changes in soil properties of the root zone were evaluated for changes in productivity using a productivity index model. Tillage erosion resulted in soil loss in the shoulder position, while soil loss from water erosion occurred primarily in the mid to lower backslope position. The decline in soil productivity was greater when both processes were combined compared to either process acting alone. Water erosion contributed to nearly all the decline in soil productivity in the backslope position when both tillage and water erosion processes were combined. The net effect of soil translocation from the combined effects of tillage and water erosion is an increase in spatial variability of crop yields and a likely decline in overall soil productivity.  相似文献   

2.
A long‐term experiment comparing no‐till with conventional tillage systems across five rotations was evaluated 11 years after initiation. The objectives of the present paper are (1) to report differences in soil chemical properties (namely soil organic matter, total nitrogen, phosphorus, potassium and pH) that have resulted by converting from conventional to no‐till under contrasting cropping systems and (2) to draw tentative conclusions and recommendations on fertility status and fertilizer use and management. Soil in the no‐till system had increased surface soil organic C levels relative to conventional tillage regardless of rotation. In addition, depending on the rotation, the N and P content of the soil improved with no‐till compared with conventional tillage. In other words, no‐till has helped to retain soil organic matter (SOM), conserved more N, and resulted in increased extractable P and exchangeable K concentrations in the upper root‐zone. Hence, wheat produced in a no‐till system may receive more nutrients from decomposition of SOM and acidification of the seed zone. It is possible that lesser amounts of fertilizer nutrients will be needed because of the greater efficiency of nutrient cycling in no‐till systems relative to conventional systems. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

3.
It is found that the differentiation and degradation of soil depend on surface slope, water flow rate, and furrow length. The development of irrigation erosion on irrigated areas results in the formation of three zones: erosion, stabilization, and accumulation. The high slopes of irrigated plots favor an intense erosion-accumulation process. Depending on the surface slope and the water flow rate, 0.48–19.40 t of soil is washed away from 1 ha. Irrigation erosion affects the density and porosity of soils, and erosion on the slope is enhanced during the differentiation of soil varieties. The texture of soils becomes coarser in the upper erosion region and finer in the aggraded varieties. On the basis of the quantitative assessment of soil erosion rate, the possible losses in dry matter, humus, and essential nutrients are calculated, as well as their removal with water flows.  相似文献   

4.
Soil quality deterioration and consequent reduced productivity characterize the Vertisols in the highlands of Ethiopia. The problem is exacerbated by lack of appropriate land preparation alternatives for the major crops in the area. A field experiment was carried out for 6 years (1998–2003) at Caffee Doonsa in the central highlands of Ethiopia to evaluate alternative land preparation methods on the performance of wheat (Triticum durum Desf.), lentil (Lens culinaries Medik L) and tef (Eragrostis tef L) grown in rotation. Four methods of land preparation (broad bed and furrow, green manure, ridge and furrow and reduced tillage) were arranged in a randomized complete block design with three replications on permanent plots of 22 m by 6 m. Broad bed and furrow significantly increased the grain yield of lentils by 59% (from 1029 to 1632 kg ha−1) as compared to the control. On the other hand, reduced tillage resulted in the highest grain yield of wheat (1862 kg ha−1) and tef (1378 kg ha−1) as compared to 1698 kg ha−1 of wheat and 1274 kg ha−1 of tef for the control although the increase was not statistically significant. A gross margin analysis showed that BBF is the most profitable option for lentil with 65% increase in total gross margin. On the other hand, RT resulted in 11 and 8% increase in gross margin of wheat and tef, respectively as compared to the control. Based on the agronomic and economic performances best combinations of crop and land preparation method were: lentil sown on broad bed and furrow, and wheat and tef sown after reduced tillage.  相似文献   

5.
Validation of spatially distributed models using spatially distributed data represents a vital element in the development process; however, it is rarely undertaken. To a large extent, this reflects the problems associated with assembling erosion rate data, at appropriate temporal and spatial scales and with a suitable spatial resolution, for comparison with model results. The caesium-137 (137Cs) technique would appear to offer considerable potential for meeting this need for data, at least for longer timescales. Nevertheless, initial attempts to use 137Cs for model validation did not prove successful. This lack of success may be explained by the important role of tillage erosion in redistributing soil within agricultural fields and, therefore, contributing to the 137Cs-derived soil redistribution rates. This paper examines the implications of tillage erosion for the use of 137Cs in erosion model validation and presents an outline methodology for the use of 137Cs in model validation. This methodology acknowledges and addresses the constraints imposed by the need to: (1) separate water and tillage erosion contributions to total soil redistribution as represented in 137Cs derived rates; (2) account for lateral mixing of 137Cs within fields as a result of tillage translocation; (3) simulate long-term water erosion rates using the model under evaluation if 137Cs-derived water erosion rates are to be used in model validation. The methodology is dependent on accurate simulation of tillage erosion and tillage translocation. Therefore, as greater understanding of tillage erosion is obtained, the potential for the use of 137Cs in water erosion model validation will increase. Caesium-137 measurements remain one of the few sources of spatially distributed erosion information and, therefore, their potential value should be exploited to the full.  相似文献   

6.
This study reports the results of a series of experiments that were set up on agricultural land in central Belgium to investigate soil translocation and erosivity resulting from a secondary tillage operation using an implement sequence of a rotary harrow and seeder. Aluminium cubes were used as tracers of soil movement. Results show that soil displacement resulting from tillage with such an implement sequence is far from insignificant. This is mainly related to the relatively shallow tillage depth as well as to the loose initial soil condition of such secondary tillage operations. The calculated value for the tillage transport coefficient k (123 kg m−1 per tillage operation) is comparable with k-values from implements that are considered to be more erosive, like mouldboard and chisel implements. In conclusion, this study shows that tillage erosion not only results from relatively aggressive tillage operations such as mouldboard and chisel passes, but that secondary operations contribute significantly to soil displacement and tillage erosion.  相似文献   

7.
我国水土流失日益严重,已成为制约构建和谐社会的重大生态环境问题[1]。因此,土壤侵蚀的监测研究显得格外重要且十分紧迫。磁性示踪技术作为土壤侵蚀监测研究的一种新手段,具有很多优点[2-3],近年来逐渐得到广大科研工作者的重视。  相似文献   

8.
Large amounts of soil are eroded annually from tilled, hilly upland soils in the humid tropics. Awareness has been increasing that much of this erosion may be due to tillage operations rather than water-induced soil movement. This field study estimated soil translocation and tillage erosion for four tillage systems on Oxisols with slope gradients of 16–22% at Claveria, Misamis Oriental, Philippines. Soil movement was estimated using ‘soil movement tracers' (SMT) which consisted of painted 12-mm hexagonal steel nuts. The SMT were buried in three replicate plots of the following tillage treatments: (1) contour moldboard plowing in the open field (MP-open); (2) contour ridge tillage in the open field (RT-open); (3) contour moldboard plowing plus contour natural grass barrier strips (MP-strip); and (4) contour natural grass barrier strips plus ridge tillage (RT-strip). Two hundred SMT were placed at the 5-cm depth at 5-cm spacings on 10 rows and 20 columns in two microplots within each plot. The microplots were oriented with the boundaries running downslope and along the contour of each 8-m-wide × 38-m-long (downslope) tillage plot. After tilling the land for four successive corn (Zea mays L.) crops (20 tillage operations), the SMT were manually excavated and their positions recorded. Recovery of SMT ranged from 82% to 85%. Displacement of SMT was directly related to slope length, percent slope, and tillage method. Mean displacement distance of SMT during the four corn growing seasons was 3.3 m for MP-open, 1.8 m for RT-open, 1.5 m for the RT-strip, and 2.2 m for MP-strip. Based on tillage operations associated with two corn crops per year, mean annual soil flux was estimated to be 241, 131, 158 and 112 kg m−1 for MP-open, RT-open MP-strip, and RT-strip, respectively. Compared to the mean annual soil loss for MP-open of 63 Mg ha−1, soil loss was reduced by 30%, 45%, and 53% for the MP-strip, RT-open, and RT-strip systems, respectively. Both ridge tillage and natural grass barrier strips reduced soil displacement, soil translocation flux, and tillage erosion rates.  相似文献   

9.
Abstract

The investigations aimed to: 1) evaluate water erosion rates on undulating slopes in Lithuania under different land use systems; 2) study changes in soil physical properties on the differently eroded slopes; and 3) better understand relationships between soil physical properties and soil erodibility. Research data were obtained on loamy sand and clay loam Eutric Albeluvisols located on the undulating hilly relief of the ?emai?iai Uplands of Western Lithuania. The results of 18 years of water erosion investigations under different land use systems on slopes of varying steepness are presented. Attention is focused on changes in soil physical properties in relation to soil erosion severity. Measured water erosion rates in the field experiments were: 3.2–8.6 m3 ha?1 yr?1 under winter rye, 9.0–27.1 m3 ha?1 yr?1 under spring barley and 24.2–87.1 m3 ha?1 yr?1 under potatoes. Perennial grasses completely prevented water erosion, while erosion-preventive grass-grain crop rotations (67% grasses, 33% cereal grains) decreased soil losses by 75–80% compared to the field crop rotation, containing 17% tillage crops (potatoes), 33% grasses and 50% cereal grains. The grain-grass crop rotation (33% grasses and 67% cereal grains) decreased soil erosion rates by 23–24%. The percentage of clay-silt and clay fractions of arable soil horizons increased, while the total soil porosity and moisture retention capacity decreased with increased soil erosion. Phytocenoses, including sod-forming perennial grasses and grass-grain crop rotations, led to changes in the physical properties of eroded soils; soil bulk density decreased and percentage total porosity and moisture retention capacity increased. The grass-grain crop rotations increased the water-stable soil structure (measured as water-stable soil aggregates) by 11.03 per cent units and sod-forming perennial grasses increased aggregate stability by 9.86 per cent units compared with the grain-grass crop rotation on the 10–14° slope. Therefore, grass-grain crop rotations and sod-forming perennial grasses decreased soil erodibility and thus could assist both erosion control and the ecological stability of the vulnerable hilly-undulating landscape.  相似文献   

10.
渭北旱塬侵蚀退化土壤生产力的恢复与评价   总被引:3,自引:0,他引:3  
土壤侵蚀会降低生产力,威胁农业生产,因此,对土壤生产力进行恢复和评价具有重要意义。通过人工剥离熟土层,模拟研究不同侵蚀程度下的土壤生产力,选取施肥和覆盖表土2种恢复措施,对其土壤生产力的恢复情况展开研究并进行评价。结果表明:1)土壤侵蚀能够使土壤的理化性状恶化,施肥和覆土均能很好地改善土壤密度和孔隙度等,并能够增加土壤有机质及其他养分的质量分数。2)土壤侵蚀会降低作物产量,在不施肥下,每侵蚀1cm熟土层,玉米产量平均下降1.27%,施肥下每侵蚀1 cm熟土层,玉米产量比对照平均增加0.87%;而每覆盖1cm熟土层,玉米产量平均增加0.91%,但并不能完全补偿侵蚀造成的产量损失。3)利用土壤生产力指数模型(PI模型)计算出了不同措施下的生产力指数,发现:无肥下侵蚀的生产力指数最低,平均每侵蚀1 cm熟土层,生产力指数下降2.17%,施肥下平均每侵蚀1 cm熟土层,生产力指数比无肥增加1.09%,而平均每覆盖1 cm熟土,生产力指数增加1.29%;表明覆土较施肥更易提高土壤生产力。4)对产量和生产力指数进行相关性分析,得出二者具有很好的正相关关系,说明用生产力指数来衡量土壤生产力的高低是可行的。  相似文献   

11.
12.
Under tropical meteorological conditions, the volume of soil explored by plant roots is crucial for crop growth as it allows increased water and nutrient use efficiency. We hypothesized that, under different irrigation intervals, leguminous mulch can extend the duration between irrigation events but maintain crop performance, because decreased evaporative fluxes also reduce constraints to root exploration imposed by mechanical stress. We evaluated the combined effects of leguminous mulch and irrigation intervals on soil physical properties to determine whether the growth and productivity of maize were modified in a structurally fragile tropical soil. The experiment involved the following treatments: 4‐day irrigation intervals with soil mulched (4C) or bare (4S), 6‐day irrigation intervals with soil mulched (6C) or bare (6S), 8‐day irrigation intervals with soil mulched (8C) or bare (8S) and 10‐day irrigation intervals with soil mulched (10C) or bare (10S). Mulch decreased soil penetration resistance and increased to 4 days the favourable time for root development in drying soil. Relative to bare soil, mulch with a 6‐day irrigation interval almost doubled nitrogen uptake post‐tasselling, which decreased nitrogen remobilization and increased the crop growth rate during this stage. These conditions had a positive effect on the transpiration rate and stomatal conductance as well as on the growth and yield of maize. A 6‐day irrigation interval with mulch compared to 4 days with bare soil resulted in similar conditions for root development, but greater uptake of nitrogen (102.73–78.70 kg/ha) and better yield (6.2–5.3 t/ha), which means greater efficiency in nitrogen and water use.  相似文献   

13.
发展保护性耕作技术 有效防治耕地土壤侵蚀   总被引:3,自引:0,他引:3       下载免费PDF全文
 我国是世界上人均耕地最少的国家之一,人均耕地仅为0.093 3 hm2,不到世界平均水平的40%。同时,我国也是世界上耕地土壤侵蚀最严重的国家之一,全国耕地土壤侵蚀面积为4 033万hm2,占耕地总面积的33.15%。仅坡耕地每年产生的土壤流失量约达15亿t,占全国土壤侵蚀总量的33%。耕地土壤侵蚀已对我国的粮食安全、生态安全和经济社会可持续发展构成了严重威胁。论述了水土保持领域发展保护性耕作技术的重要意义、产生与发展、主要技术内容与技术模式及保护性耕作技术的生态、经济和社会效益。发展保护性耕作技术,是水土保持的新理念,对于有效防治耕地土壤侵蚀和非点源污染具有重要意义。  相似文献   

14.
Since the 1970s and 1980s, the vineyard areas in the Mediterranean region of north east Spain have undergone profound transformation to allow greater mechanization. This has involved land levelling, deep ploughing and the elimination of traditional soil conservation measures. Recently the EU Common Agricultural Policy encourages this through the vineyard restructuring and conversion plans (Commission Regulation EC No 1227/2000 of 31 May 2000) by subsidizing up to 50% of the cost of soil preparation such as soil movement and land levelling. A clear example of the problems that this causes is in the Penedès vineyard region (Catalonia, north east Spain), and the present research analyses the changes in soil properties caused by erosion, deep ploughing and land levelling. The study was carried out in an area of 30 000 ha for which a Soil Information System at a scale of 1:50 000 was developed based on 394 field observations (89 soil profiles and 251 auger hole samples down to 120 cm). The results show that 74% of the described soil profiles are disturbed with evidence of soil mixing and/or profile truncation due to erosion, deep ploughing and/or land levelling. The evidence from the topsoils is mainly the presence of fragments of calcic or petrocalcic horizons, marls and sandstones. Other important properties for crops such as organic matter (OM) content and soil depth show statistically significant differences between disturbed soils and undisturbed soils (22.3–33.3% OM content depletion and 35.1% soil depth reduction). These results confirm that the soils of the region are significantly altered by mechanical operations which also influence soil erosion and contribute to global warming effect through depletion of soil OM.  相似文献   

15.
Soil erosion is a major threat to global economic and environmental sustainability. This study evaluated long-term effects of conservation tillage with poultry litter application on soil erosion estimates in cotton (Gossypium hirsutum L.) plots using RUSLE 2.0 computer model. Treatments consisting of no-till, mulch-till, and conventional tillage systems, winter rye (Secale cereale L.) cover cropping and poultry litter, and ammonium nitrate sources of nitrogen were established at the Alabama Agricultural Experiment Station, Belle Mina, AL (34°41′N, 86°52′W), beginning fall 1996. Soil erosion estimates in cotton plots under conventional tillage system with winter rye cover cropping declined by 36% from 8.0 Mg ha−1 year−1 in 1997 to 5.1 Mg ha−1 year−1 in 2004. This result was largely attributed to cumulative effect of surface residue cover which increased by 17%, from 20% in 1997 to 37% in 2004. In conventional tillage without winter rye cover cropping, soil erosion estimates were 11.0 Mg ha−1 year−1 in 1997 and increased to 12.0 Mg ha−1 year−1 in 2004. In no-till system, soil erosion estimates generally remained stable over the study period, averaging 0.5 and 1.3 Mg ha−1 year−1with and without winter rye cover cropping, respectively. This study shows that cover cropping is critical to reduce soil erosion and to increase the sustainability of cotton production in the southeast U.S. Application of N in the form of ammonium nitrate or poultry litter significantly increased cotton canopy cover and surface root biomass, which are desirable attributes for soil erosion reduction in cotton plots.  相似文献   

16.
A. R. Dexter   《Geoderma》2004,120(3-4):215-225
The index of soil physical quality, S, which was introduced in Part I is applied to problems of agricultural soil mechanics, especially soil tillage and hard-setting. S is equal to the slope of the water retention curve at its inflection point. The retention curve must be plotted as the logarithm (to base e) of the water potential against the gravimetric water content (kg kg−1). The use of S is illustrated with examples of soils with different friabilities, tillage at different water contents and the aggregate size distribution resulting from tillage. It is shown that friability, and hence the ease of working of the soil, is linearly and positively correlated with S. It is also shown in a short theoretical study that S can be used in a simple equation for estimation of the hard-setting behaviour of soil on drying. In combination with pedo-transfer functions, this enables the hard-setting behaviours of soils of different textures to be predicted and shows how hard-setting may be expected to increase with soil compaction. However, the predictions of hard-setting should be considered as speculative until they have been tested experimentally.  相似文献   

17.
《Applied soil ecology》2010,46(3):254-261
Soil microorganisms mediate many important biological processes for sustainable agriculture. The effect of a polymer-coated controlled-release urea (CRU, ESN®) on soil microbial communities was studied at six sites across western Canada from 2004 to 2006. Fertilizer treatments were CRU, urea and an unfertilized control. Timing of fertilizer application (fall vs. spring) was studied in 9 of the 18 site-years (combinations of sites and years). Wheat (Triticum aestivum L.), canola (Brassica napus L.) and barley (Hordeum vulgare L.) were grown in rotation at five sites, and silage corn (Zea mays L.) was grown in all 3 years at one site, under conventional tillage (CT) or zero tillage (ZT). The fertilizers were side-banded at 50–60 kg N ha−1 for wheat, barley and canola, and broadcast at 150 kg N ha−1 for corn. Microbial biomass C (MBC) and bacterial functional diversity and community-level physiological profiles (CLPPs) were determined at about the flowering stage of each crop. In situ CO2 evolution (soil respiration) was measured, and microbial metabolic quotient (qCO2) determined, at one site in 2 years. In the rhizosphere, fertilizer effects on MBC and functional diversity were observed in 1 and 5 of 18 site-years, respectively; and in bulk soil in 4 site-years each. These effects were usually positive relative to the control. CRU increased MBC or functional diversity more than urea in 3 site-years, but the opposite was observed in 1 site-year. Time of fertilizer application affected MBC in 1, and functional diversity in 2, of 9 site-years in the rhizosphere, and no effects were observed in bulk soil. Fall-applied fertilizer increased MBC more than spring-applied fertilizer, but the opposite was observed for functional diversity. Tillage affected MBC and functional diversity in 4 and 5 of 18 site-years, respectively, in the rhizosphere, and in 3 and 4 site-years in bulk soil. Tillage effects were usually in favour of ZT. There were no treatment effects on CO2 evolution, but an interactive effect of fertilizer and tillage on qCO2 was observed in 1 year when qCO2 in the control treatment was greater than that in either fertilizer treatment under CT, but urea increased qCO2 relative to the control under ZT. Shifts in CLPPs were sometimes observed where the treatment effects described above were not significant. Notwithstanding the limitations of culture-dependent CLPPs, most fertilizer effects on soil microbiological properties were not statistically significant. Therefore, these fertilizers probably did not adversely affect most soil biological processes.  相似文献   

18.
R. Lal 《Geoderma》1976,16(5):419-431
Erosion-induced changes in the physical characteristics of the surface soil under different soil and crop management treatments were monitored over a period of two years. These studies were conducted on field runoff plots established on natural slopes of 1, 5, 10 and 15%. The soil and crop management treatments consisted of bare-fallow, maize-maize (plowed and mulched), maize-maize (plowed), maize-cowpeas (no-till) and cowpeas-maize (plowed).Soil erosion increased the gravel content and decreased the silt and clay contents of the surface horizon. The moisture retention capacity of the surface soil decreased significantly. The infiltration rate decreased from 3.5 cm/min on all plots in February 1972 to 0.2 cm/min under bare-fallow, to 0.6 cm/min under maize-maize (mulch), to 1.5 cm/min under maize-cowpeas (no-till) and to 0.1 cm/min under maize-maize (plowed) in February 1974. Maize yields on the mulch and no-till treatments were maintained while those on plowed plots declined. Artificial soil removal resulted in significant reductions of maize and cowpea yields.  相似文献   

19.
《CATENA》1998,32(1):55-70
Spatial patterns in surface soil moisture during dry and wet weather conditions have been recorded over a 3.68 ha gully catchment in central Spain. During dry weather conditions this spatial pattern was characterised by areas of relatively wet and dry soil, forming a mosaic of areas with contrasting hydrological response. Semi-variogram analysis has indicated that these areas are spatially isolated and unconnected, with the effect that surface runoff from source areas within the catchment may be re-absorbed by surrounding areas which act as sinks for overland flow. Consequently during dry weather conditions, variation in the soil's physical and hydrological properties, as reflected by spatial differences in soil moisture, may be advantageous in minimising widespread catchment runoff and erosion, by creating spatial isolation of runoff producing areas and by promoting discontinuity in hydrological pathways. During wet weather conditions, however, extensive saturation, exceeding a catchment wetness threshold, increased spatial continuity in hydrological pathways, regardless of the spatial variation in soil hydraulic properties, resulting in widespread runoff and erosion. Management strategies should therefore aim to raise this wetness threshold value, by improving the soils physical and hydrological properties. The creation of a mosaic pattern of areas with contrasting hydrological response may prove to be an effective management strategy in runoff and erosion control in semi-arid environments.  相似文献   

20.
Monitoring chemical and physical changes during thermal flavor generation   总被引:1,自引:0,他引:1  
On-line techniques were developed to monitor chemical and physical changes occurring during the heating of skim milk powder (SMP). Atmospheric pressure chemical ionization mass spectrometry (APCIMS) followed the generation and release of volatile compounds from SMP in a packed-bed reactor. Operating conditions were optimized to avoid condensation of high boiling compounds such as maltol, and the system was highly reproducible (CV < 7%). Differential scanning calorimetry (DSC) of SMP identified a potential glass transition at an onset temperature of 67.9 degrees C and a series of exothermic events that were related to different stages of the Maillard reaction. No lactose crystallization was found after heating. Using a heated stage reflectance FTIR device, spectra were obtained at different temperatures. Analysis of the data showed a correlation between the intensity ratio at wavenumbers 1017 and 1064 cm(-1) and the glass transition measured by DSC. This FTIR system was not sensitive enough to detect Maillard intermediates. Combining data from the three techniques provides a fuller picture of the physical changes during the Maillard reaction and their effects on the chemical reactions.  相似文献   

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