Variation of Surface Soil Quality Parameters by Intensive Donkey-Drawn Tillage on Steep Slope

2000). Although these data are useful for soil erosion modeling, soil conservation planning, and the developFew direct measurements are made to quantify the erosion from ment of soil conservation practices on cultivated land upslope to lower field boundaries by intensive tillage. We conducted 50 plowing operations over a 5-d period using a donkey-drawn moldwith complex topography, it does not address variations board-plow on steep backslope in the Chinese Loess Plateau. Topoin surface soil quality as affected by soil redistribution graphic changes at different slope positions were quantified using due to tillage within a complex agricultural landscape. differential global positioning system (DGPS). Soil organic matter Quantitative data on the direct effects on surface soil (SOM), extractable P and N, and soil bulk density were measured quality indicators within the tilled layers of sloping land along a downslope transect after each 10-tillage series. Fifty operations at different spatial and temporal scales are needed to resulted in a decrease in maximum soil surface level (SSL) of 1.25 m establish a cause–effect relationship between soil redisin the upper slope position and an increase of 1.33 m at the bottom tribution by tillage and soil quality (Lal, 1999; Penof the slope. Slope gradients decreased from 37 to 14 at the upper nock, 1998). position and from 18 to 0 at the lower position. Surface soil bulk To assess the effects of tillage-translocated soil on density increased from 1.14 to 1.28 Mg m 3 in the upper slope and decreased from 1.10 to 1.03 Mg m 3 in the middle slope. Mean SOM surface soil properties and soil quality within the tilled concentrations in the upper and middle positions of the slope delayers, researchers have used modeling (Schumacher et creased from 8.3 to 3.6 g kg 1, mineral N from 43.4 to 17.4 mg kg 1, al., 1999; Lobb and Kachanoski, 1999; Van Oost et al., and Olsen-P from 4.5 to 1.0 mg kg 1. Intensive tillage resulted in a 2000), physical tracers (Poesen et al., 1997; Thapa et al., short-term increase in SOM and available nutrients in the lower por2001), fallout 137Cs technique (Li et al., 2000; Li and tion during the tillage operations. Geomorphologic evolution and Lindstrom, 2001), and long-term field studies (Sibbesen, landscape variability of dissected hillslopes are attributable to soil 1986). These studies are very helpful in demonstrating movement and resulting physical and fertility degradation induced by the potential effects of tillage-translocated soil on surintensive tillage. face soil properties and soil quality, but they have limitations because of three reasons. First, bulk soil movement predicted by existing tillage erosion models is not always O the last decade, researchers have measured in agreement with redistribution of soil nutrients (Schunet downslope movement of soil by tillage translomacher et al., 1999; Van Oost et al., 2000). Second, cation in a wide range of agricultural landscapes in physical tracers widely used in tillage experiments canNorth America (Lindstrom et al., 1990, 1992; Lobb et not be bound with soil particles and therefore do not al., 1995), Europe (Govers et al., 1994, 1996), and Asia adequately describe variations in soil physical and chem(Turkelboom et al., 1997, 1999; Thapa et al., 1999a, ical properties with tillage operations (Poesen et al., 1999b; Zhang et al., 2001). Significant progress has been 1997; Thapa et al., 2001). Third, long-term field investimade on quantifying relationships between tillage transgations do not distinguish between the net effects of location and tillage depth, tillage tools, slope gradient, tillage erosion from water erosion or other soil manageor slope curvature (Lindstrom et al., 1990, 1992, 2000; ment practices (Sibbesen, 1986), similar to fallout 137Cs Govers et al., 1994; Lobb et al., 1995; Dabney et al., 1999; technique (Li et al., 2000; Li and Lindstrom, 2001). Montgomery et al., 1999; Quine et al., 1999; Thapa et In our previous studies (Li et al., 2000; Li and Lindal., 1999a; Turkelboom et al., 1999; Van Muysen et al., strom, 2001), we indirectly estimated soil redistribution rates from tillage using tillage erosion prediction model Y. Li, Inst. of Agricultural Environment and Sustainable Develop(TEP), and then linked them to soil quality parameters ment, Chinese Academy of Agricultural Sciences, No. 12 Zhongguan(Li and Lindstrom, 2001). The key point for utilization cun South Street, Beijing 100081, China; G. Tian, Biosolids Utilization of the TEP is to assign an appropriate k-value (the and Soil Science Lab., Metropolitan Water Reclamation District of Greater Chicago, R&D Complex, 6001 W. Pershing Rd., Cicero, IL tillage transport coefficient per unit slope gradient) for 60804-4112; M.J. Lindstrom, USDA-ARS, N.C. Soil Conserv. Res. animal powered tillage, which is affected by many enviLab., 803 Iowa Ave., Morris, MN 56267; H.R. Bork, Ecology-Center, ronmental factors (Van Muysen et al., 2000). Moreover, Christian-Albrechts-Univers. Kiel, Schauenburger Str. 112, D-24118 the soil quality parameters measured in our previous Kiel, Germany. Received 30 Sept. 2002. *Corresponding author ([email protected]). Abbreviations: DGPS, differential global positioning system; SOM, Published in Soil Sci. Soc. Am. J. 68:907–913 (2004).  Soil Science Society of America soil organic matter; SSL, soil surface level; TEP, tillage erosion prediction. 677 S. Segoe Rd., Madison, WI 53711 USA