Search

The USDA Natural Resources Conservation Service has proposed the Soil Conditioning Index (SCI) to predict the consequences of management actions on the state of soil organic carbon (SOC), a soil quality indicator. The index was developed based on research in humid, temperate, loamy soils but has not been tested for many other conditions. In this project, we determined the effects of management on SCI, SOC, and other soil properties in semiarid, hot, sandy soils located in the Southern High Plains of western Texas. Agroecosystems studied included native rangeland, conservation grassland, cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) rotations, and high-residue forage sorghum (Sorghum bicolor L.). The sites included irrigated and dryland conditions under conventionally tilled and no-tillage practices. Mean SCI values varied from -1.49 for conventionally tilled dryland cotton to 2.15 for the conservation grassland. All native rangelands and conservation grasslands and no-tillage fields (dryland and irrigated) had positive SCI values, which indicates increasing organic matter levels. In contrast, all of the conventionally-tilled cotton fields had negative SCI values, indicating decreasing organic matter levels. The SCI was most strongly correlated with the residue equivalent value (r = 0.68) as estimated in the Revised Universal Soil Loss Equation but based on measured values and particulate organic matter carbon, POM-C (r = 0.57).The SCI showed which fields had the highest levels of POM-C and which fields used no-tillage or limited tillage from fields that had been aggressively tilled. Additional research is needed to adjust the SCI subfactors to better relate the index with SOC. [ABSTRACT FROM AUTHOR]

The article discusses a study which determined the effects of management on Soil Conditioning Index (SCI), soil organic carbon, and other soil properties in semi-arid, hot, sandy soils in the Southern High Plains (SHP) of western Texas. The researchers identified 16 field locations in six counties across the SHP that represented major cropping systems. It was found that particulate organic matter carbon of the surface soil of native rangeland was significantly greater than all other agroecosystems with the exception of the conservation grassland.

Wind erosion selectively winnows the fine, most chemically concentrated portions of surface soils and results in the inter-regional transport of fugitive dust containing plant nutrients, trace elements and other soil-borne contaminants. We sampled and analyzed surface soils, sediments in transport over eroding fields, and attic dust from a small area of the Southern High Plains of Texas to characterize the physical nature and chemical constituents of these materials and to investigate techniques that would allow relatively rapid, low cost techniques for estimating the chemical constituents of fugitive dust from an eroding field. From chemical analyses of actively eroding sediments, it would appear that Ca is the only chemical species that is enriched more than others during the process of fugitive dust production. We found surface soil sieved to produce a sub-sample with particle diameters in the range of 53-74 microm to be a reasonably good surrogate for fugitive dust very near the source field, that sieved sub-samples with particle diameters <10 microm have a crustal enrichment factor of approximately 6, and that this factor, multiplied by the chemical contents of source soils, may be a reasonable estimator of fugitive PM(10) chemistry from the soils of interest. We also found that dust from tractor air cleaners provided a good surrogate for dust entrained by tillage and harvesting operations if the chemical species resulting from engine wear and exhaust were removed from the data set or scaled back to the average of enrichment factors noted for chemical species with no known anthropogenic sources. Chemical analyses of dust samples collected from attics approximately 4 km from the nearest source fields indicated that anthropogenic sources of several environmentally important nutrient and trace element species are much larger contributors, by up to nearly two orders of magnitude, to atmospheric loading and subsequent deposition than fugitive dust from eroding soils.