摘要 :
This work aims at the assessment of soil erosion rate and its spatial distribution in hilly mountainous Nisava River Basin (South-eastern Serbia) with a surface area of approximately 2,848 km~2. The study was conducted using Unive...
展开
This work aims at the assessment of soil erosion rate and its spatial distribution in hilly mountainous Nisava River Basin (South-eastern Serbia) with a surface area of approximately 2,848 km~2. The study was conducted using Universal Soil Loss Equation (USLE) model due to its modest data demand and easy comprehensible structure. The erosion factors of USLE were collected and processed through a GIS-based approach. Landsat 7 Enhanced Thematic Mapper (ETM+) image and normalized difference vegetation index (NDVI) were used for the determination of crop management factor. The average annual soil loss was estimated at 27.0 t ha~(-1) year~(-1) classifying Nisava River Basin under very high erosion rate category. About 39.0 % of the watershed area was characterized by slight erosion rate (<5 t ha~(-1) year~(-1)), 7.7 % of the area was found to be under moderate erosion rate (5-10 t ha~(-1)), 13.8 % of the area is under high erosion rate (10-20 t ha"1), while around 17.5 % of the area was under very high erosion rate (20-40 t ha~(-1) year~(-1)). Severe erosion rate (40-80 t ha~(-1) year~(-1)) was observed at 14.2 % of the study area, whereas very severe erosion rate (>80 t ha~(-1) year~(-1)) described about 7.8 % of the watershed. The results of this work are in agreement with the soil erosion map of Serbia, the sediment yield measurements in the basin and with other, more detailed, studies in the watershed. Therefore, the presented methodology could be applied as a framework for the evaluation of erosion factors on soil resources in South-eastern Serbia when limited data are available. The outputs of these studies can be used for the identification of vulnerable areas on a cell basis and for planning of conservation practices.
收起
摘要 :
Main soil properties, contents, distribution and background limits of hot acid extractable forms of trace elements: Cd, Cr, Cu, Ni, Hg, Pb, Zn have been analysed in Branicevo Province in Eastern Serbia. Contents of selected trace ...
展开
Main soil properties, contents, distribution and background limits of hot acid extractable forms of trace elements: Cd, Cr, Cu, Ni, Hg, Pb, Zn have been analysed in Branicevo Province in Eastern Serbia. Contents of selected trace elements are relatively low and exploratory data analyses (EDA graphs) show that elements have asymmetrical distribution and great dispersion. This primarily applies to Cu, Cd, Hg, which at same time, have similar distribution patterns. Branicevo Province comprises 8 smaller districts, and is characterized by highly heterogenic natural conditions, which additionally complicate assessment of background limits. Different methods (classical [Mean+2Sdev], [Median+2MAD], box-plot and CDF) have been used for the evaluation of background limits, and for some methods besides natural, logtransformed values have also been used (Sdev - standard deviation, MAD - median of the absolute deviations from the data's median, CDF -cumulative probability plot). Values from [Median+2MAD] procedure have the lowest background limit, followed by the box-plot, while the classical method produces the highest background limits. Results for CDF, (where the background limits for all elements are approximately at cumulative 95%) are similar to those from logtransformed data of box-plot method (except for Cd and Ni). Thus, percentage of outliers in classical methods ranges from 1.1 to 4.2% for natural data (and 0.5-3.75 for logtransformed data), for box-plots method ranges from 0.8 to 11.0% (and 0.6-9.6%), and for [Median+ 2MAD] ranges from 3.4 to 22.0% (and from 1.4 to 15.8%). The smallest outliers percentage is for Cd, followed by Hg, than Cr and Ni, and it is higher for other elements. Outliers of Ni and Cr are most frequent in western disticts in Fluvisols of the Velika Morava River, Hg and Cd outliers are the commonest in the eastern district, while outliers of other elements are more evenly distributed. Since there is a statistically significant difference in distribution of trace elements per district, data have been arranged by homogeneous units, and then new, more realistic background limits have been determined.
收起
摘要 :
Exchangeable aluminium (Al_(KCI)) and CaCl_2-extractable aluminium (Al_(CaCl_2) approximately the same value in the prognosis of detrimental effect on plants. Additional, more in-depth research should show which of the two applied...
展开
Exchangeable aluminium (Al_(KCI)) and CaCl_2-extractable aluminium (Al_(CaCl_2) approximately the same value in the prognosis of detrimental effect on plants. Additional, more in-depth research should show which of the two applied methods of exchangeable
收起
摘要 :
Recently the cost of soil processing for agricultural production has been rapidly increasing because of expensiveness of agricultural machinery, energy, and agricultural chemicals. Intensive soil cultivation is costly and adversel...
展开
Recently the cost of soil processing for agricultural production has been rapidly increasing because of expensiveness of agricultural machinery, energy, and agricultural chemicals. Intensive soil cultivation is costly and adversely affects soil fertility due to accelerated mineralization of soil organic matter. By minimizing mechanical disturbance to the soil, costs can be reduced and the environment enhanced. About half of the global CO_2 emissions from the soil come from decomposition of the annual plant litter including agricultural crops. We studied methods of soil tillage that would help stabilize the yield of crops while maintaining soil fertility and saving energy and labour at the same time. Three types of crop cultivation experiments were studied: 1) cultivation intensity (simplified ST, common CT, and intensive IT); 2) tillage depth (shallow S, and deep D subsoil till), and 3) minimum MT, and zero till ZT. The results showed that under ST the soil biological parameters were more favourable than under CT and IT. Shallow subsoil till maintained higher levels of soil nutrients, and reduced CO_2 emission compared with the deep subsoil till. The minimum and zero tills positively influenced soil physical and biological properties through improvement in soil aggregate stability and soil enzymatic activity.
收起
原文获取