Soil is a non‐renewable dynamic natural resource that is essential to life. Water movement, water quality, land use, and vegetation productivity all have relationships with soil. This article introduces many important soil concepts including development, classification, properties (physical, chemical, and biological), quality, and conservation. A general understanding of soil concepts and these interwoven relationships is essential to making sound land management decisions.

Core Ideas Total C and total N were greater at shoulder position for alfalfa than in the other two land uses. No observed differences for total C among land uses at backslope and footslope positions. Labile pools of C and N showed differences with land use and topographic positions. In general, labile C and N pools followed alfalfa > black walnut plantation > corn–soybean. Labile and bulk pools of carbon and nitrogen (C and N) play different functional roles in soil organic matter dynamics and nutrient cycling. The objectives of this study were to evaluate the (i) effects of land use [corn (Zea mays L.)–soybean [Glycine max (L.) Merr.], alfalfa (Medicago sativa L.), and black walnut (Juglans nigra L.) plantation] and (ii) vertical distribution of labile [potassium permanganate oxidizable carbon (POXC), water extractable organic carbon (WEOC), water extractable nitrogen (WEN)] and bulk [total carbon (TC), total nitrogen (TN)] pools of C and N in soil to a depth of 105 cm at different topographic positions within a watershed. Alfalfa had 10.02 to 14.86 Mg ha−1 greater TC than corn–soybean and black walnut plantation on the shoulder position in the surface horizon (0–15 cm), whereas the subsurface horizon (15–105 cm) showed no significant differences for TC measured at all topographic positions. Soil POXC was significantly higher in alfalfa than corn–soybean in the surface layer of 0 to 15 cm by 1748.6, 1904.03, and 2878.67 kg ha−1 at the shoulder, backslope, and footslope positions, respectively. However, no differences were observed for POXC at the shoulder position when all subsurface layers were combined at 15‐ to 105‐cm depth. In general, the labile pools of C and N showed differences with land use and topographic positions and followed alfalfa > black walnut plantation > corn–soybean. The study results suggest that for accurate assessment of land use on C and N gains and/or losses both bulk and labile pools should be measured including the entire root zone depth. Topographic differences should be accounted for assessing C and N pools at the watershed scale.

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Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.

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