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1.
In the arid and semi-arid regions, ridge tillage was often used as an alternative practice for wind erosion control on the croplands without sufficient crop residues left during the fallow period. Through wind tunnel experiments, wind erosion rate and vertical mass flux profile of blown sand under the simulated conditions of ridge tillage and flat tillage were studied in 15, 10, 10, 5, 3 min exposures at the wind velocities of 8, 10, 15, 20, 24 m s−1, respectively. The results for the soil tested indicate that the mean rate of wind erosion under flat tillage was 129.89 g m−2 min−1, while that under ridge tillage were 20–60% less. Under ridge tillage with different structures, average wind erosion rate had a positive correlation with the spacing between adjacent ridges. For the same ridge height, average wind erosion rate decreased with increasing ratio between the height of ridge and the width of furrow. For the same ratio between the height of ridge and the width of furrow, average wind erosion rate increased with increasing height of ridge. Power function relationships were found between wind erosion rate and wind velocity on all the simulated tillage conditions. A wind velocity of 15 m s−1 was the critical velocity, above which wind erosion rate increased rapidly for the soil and simulated tillage conditions tested. Compared with flat tillage, ridge tillage remarkably decreased wind erosion rates when wind velocities were beyond 15 m s−1. Under ridge tillage, the total mass of sand transported at a height of 0–20 cm above soil surface (Q0–20), and the fraction of that travelling at a height of 0–4 cm (Q0–4/Q0–20), were less man mat under flat tillage. For the same ridge height, Q0–4/Q0–20 increased with increasing ratio between the height of ridge and the width of furrow. For the same ratio between the height of ridge and the width of furrow, Q0–4/Q0–20 decreased with increasing height of the ridge. Sand transport rate under flat tillage decreased with increasing height by a negative exponential function, while negative linear functions were found under ridge tillage. Thus ridge tillage decreased the rate of wind erosion and sand transportation near soil surface, reduced the loss of soil nutrient caused by wind erosion and plant damage caused by blown sand abrasion, which make it an effective agricultural technology for wind erosion control in the arid and semi-arid regions.  相似文献   

2.
In the Horqin Sandy Land of eastern Inner Mongolia in northern China, wind erosion in farmland is very common in a period from thawing of frozen surface soil in mid-March to sowing of crops in the end of April, largely because of dry and windy weather. However, little is known about the magnitude of wind erosion and associated nutrient losses due to erosion and the addition of nutrients by airborne dust deposition to farmlands during this period. A field experiment was conducted in an Entisol with sand origin under corn (Zea mays L.) production to investigate daily changes in wind speed and wind erosion intensity (as measured by soil transport rate) over a period from 20 March to 30 April 2001. We also measured daily rates of airborne dust deposition during the spring seasons with the high frequency of dust storm occurrence. The rates of soil transport by wind varied greatly from 13.2 to 1254.1 kg ha−1 per day, averaging 232.1 kg ha−1 per day, largely attributable to great variation between days in wind speed within the study period. The potential losses of nutrients through wind erosion were 0.26–24.95 kg ha−1 per day (averaging 4.62 kg ha−1 per day) in organic matter, 0.02–1.64 kg ha−1 per day (averaging 0.31 kg ha−1 per day) in nitrogen and 0.01–0.7 kg ha−1 per day (averaging 0.13 kg ha−1 per day) in phosphorus. The mean rates of airborne dust deposition ranged from 4.0 to 48.9 kg ha−1 per day, averaging 19.9 kg ha−1 per day, during the spring seasons. The potential addition of organic matter, nitrogen and phosphorus by dust input to the experimental field was, on average, 0.54, 0.04 and 0.02 kg ha−1 per day, respectively. Although the addition was a fraction of the losses due to erosion, nevertheless, dust input in the spring seasons is one of the major suppliers of soil nutrition. The fact that the addition of nutrients by dust is about 1/10 of the losses of soil nutrients through wind erosion suggests that developing and adopting more effective management practices to reduce soil erosion losses and to improve soil fertility are crucial to achieve a sustainable agricultural system in a fragile, semiarid sandy land environment.  相似文献   

3.
Soil erosion contributes to the removal and redistribution of soil organic C from cultivated fields. The soil organic C content of wind erodible and water unstable aggregates is an important factor in determining the amount of carbon loss occurring in erosion processes. The relative distribution of organic carbon among aggregate size fractions may also affect the response of soils to erosion. Soil organic C distribution is dependent on the chosen management system. The effects of no-till, till, and grassland management systems on organic C content of erodible and non-erodible aggregates were examined in six Ustolls and two Usterts of central South Dakota. Organic C contents were related to dry- and wet-sieving to represent the potential influence of wind and water erosion on C loss in the absence of vegetative cover. Loss of aggregate stability in cultivated soils was associated with organic C loss. Most structural characteristics developed under tilled systems persisted after 6–16 years of no-till. Changes in distribution of organic C due to management systems were most evident in Ustolls where cultivation resulted in net soil C losses. Soil organic C was not significantly increased by the no-tillage practices applied in this on-farm study (in Ustolls 49 Mg ha−1 in no-till versus 41 Mg ha−1 in till, for 0–0.20 m depth). Soil properties of Usterts were less affected by land use and management practices due to the high shrink swell action and self-mixing. In both soil orders the greater concentration of organic C in the wind erodible (<1 mm) dry aggregate size fraction implies a high potential for organic C loss by erosion in addition to organic C loss from mineralization after tillage. Grassland when compared to cultivated topsoil showed the largest amounts of organic carbon stored and the minimal potential for erosion loss of soil organic C.  相似文献   

4.
5.
Sustainable agricultural use of cultivated desert soils has become a concern in Hexi Corridor in Gansu Province of China, because loss of topsoil in dust storms has been recently intensified. We chose four desert sites to investigate the effects of cultivation (cropping) on (i) soil organic C and its size fractions and (ii) soil aggregate stability (as a measure of soil erodibility). These parameters are of vital importance for evaluating the sustainability of agricultural practices.

Total organic C as well as organic C fractions in soil (coarse organic C, 0.1–2 mm; young organic C, 0.05–0.1 mm; stable organic C, <0.05 mm) generally increased with the duration of the cultivation period from 0 (virgin soil, non-cultivated) to more than 30 years (p < 0.05). Compared to total organic C in virgin soils (2.3–3.5 g kg−1 soil), significantly greater values were found after 10 to >20 years of cultivation (6.2–7.1 g kg−1 soil). The increase in organic C in desert soils following prolonged cultivation was mainly the consequence of an increase in the coarse organic C. The increase in total organic C in soil was also dependent on clay content [total organic C = 0.96 + 0.249 clay content (%) + 0.05 cultivation year, R2 = 0.48, n = 27, p < 0.001]. This indicates that clay protected soil organic C from mineralization, and also contributed to the increase in soil organic C as time of cultivation increased.

There was a significant positive correlation between aggregate stability and total organic C across all field sites. The water stability of aggregates was low (with water-stable aggregate percentage 4% of dry-sieved aggregates of size 1–5 mm). There was no consistent pattern of increase in the soil aggregate stability with time of cultivation at different locations, suggesting that desert soils might remain prone to wind erosion even after 50 years of cultivation. Alternative management options, such as retaining harvested crop residues on soil surface and excluding or minimizing tillage, may permit sustainable agricultural use of desert soils.  相似文献   


6.
The soils of alpine meadows and alpine grassland steppes, aeolian soils, coarse-grained soils, and farm soils cultivated from alpine grasslands in Tibet are typical soils that are suffering from different degrees of soil erosion by wind. Based on field investigations, wind tunnel experiments, and a 137Cs trace study, this work tested the erodibility of these soils by wind, simulated the protective functions of natural vegetation and the accelerative effects of damage by livestock, woodcutting, and cultivation on erosion, and estimated erosion rates from 1963 to 2001. The results indicated that alpine meadows have the strongest resistance to wind erosion, and that undamaged alpine meadow soils generally sustain only weak or no wind erosion. Alpine grassland steppes with good vegetation cover and little damage by humans exhibit good resistance to wind erosion and suffered from only slight erosion. However, soil erodibility increased remarkably in response to serious disturbance by livestock and woodcutting; wind erosion reached 33.03 t ha−1 year−1. The erodibility of semi-stabilized aeolian soil and mobile aeolian soil was highest, at 52.17 and 56.4 t ha−1 year−1, respectively. The mean erosion rates of coarse-grained soil with various levels of vegetation coverage and of farm soil were intermediate, at 45.85 and 51.33 t ha−1 year−1, respectively. Restricting livestock, woodcutting, and excessive grassland cultivation are the keys to controlling wind erosion in Tibet. In agricultural regions, taking protective cultivation and management to enhance surface roughness is a useful way to control wind erosion.  相似文献   

7.
土壤风蚀采沙器的结构设计与性能试验研究   总被引:4,自引:1,他引:3  
土壤风蚀是全球性土地退化的主要原因之一,也是世界上许多国家和地区的主要环境问题之一。为了准确认识和掌握风沙运动规律,有效指导防止风蚀措施的选择,该文研制了适用于野外采集风蚀土壤颗粒的采沙器,并在风洞内对其等动力性、高效率性及选择性进行了验证试验。试验结果表明:所研制的采沙器满足等动力特性要求;采集率为85.6%,可作为输沙量统一修订系数;采沙器更适用于采集以跃移形式运动的土壤颗粒。  相似文献   

8.
Several studies have shown the importance of organic material in the formation and stability of soil aggregates. The organic matter of soil (SOM) is affected among other factors by the application of farmyard waste and compost, as well as tillage and crop rotation. This paper examines the aggregation and stability of a sandy soil (Haplic Fluvisol) in the valley of Mexico when treated with either 40 Mg ha−1 of compost or urea (80 kg ha−1 of N) and sown to amaranth (Amaranthus hypochondriacus L.) under dryland conditions. The application of compost resulted in a significantly larger proportion of aggregates in the fractions >1 mm (1.0–2.0, 2.0–2.3, 2.3–4.7 mm) than in the smaller fraction (<1 mm). However the stability of the macroaggregates >1 mm in the compost treatment was not higher than in contrasting treatments which did not include organic matter. Compost, which was applied under drought conditions, did not increase the aggregate stability of the soil probably because of the restricted transformation of the compost and microorganism activity.  相似文献   

9.
Most of the tillage erosion studies have focused on the effect of tractor-plough tillage on soil translocation and soil loss. Only recently, have a few studies contributed to the understanding of tillage erosion by manual tillage. Furthermore, little is known about the impact of tillage erosion in hilly areas of the humid sub-tropics. This study on tillage erosion by hoeing was conducted on a purple soil (Regosols) of the steep land, in Jianyang County, Sichuan Province, southwestern China (30°24′N and 104°35′E) using the physical tracer method.

The effects of hoeing tillage on soil translocation on hillslopes are quite evident. The tillage transport coefficients were 26–38 kg m−1 per tillage pass and 121–175 kg m−1 per tillage pass respectively for k3- and k4-values. Given that there was a typical downslope parcel length of 15 m and two times of tillage per year in this area, the tillage erosion rates on the 4–43% hillslopes reached 48–151 Mg ha−1 per year. The downslope soil translocation is closely related to slope gradient. Lateral soil translocation by such tillage is also obvious though it is lower than downslope soil translocation. Strong downslope translocation accounts for thin soil layers and the exposure of parent materials/rocks at the ridge tops and on convexities in the hilly areas. Deterioration in soil quality and therefore reduction in plant productivity due to tillage-induced erosion would be evident at the ridge tops and convex shoulders.  相似文献   


10.
Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha−1 greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha−1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO2–C ha−1 d−1 but MBC increased by 90–224 g CO2–C ha−1 d−1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha−1 d−1, and PCM decreased by 10 g CO2–C ha−1 d−1 with rye to 79 g CO2–C ha−1 d−1 with blend, but MBC increased by 13 g CO2–C ha−1 d−1 with blend to 120 g CO2–C ha−1 d−1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.  相似文献   

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