SOIL PHYSICAL PROPERTIES AND CROP PRODUCTIVITY OF AN ERODED SOIL AMENDED WITH CATTLE MANURE

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Abstract
Erosion changes soil properties, especially physical properties, mainly because it removes surface soil rich in organic materials and exposes lower soil layers. In 1988, a study was established to determine the effects of soil erosion and long-term manure applications on selected soil physical properties and corn (Zea mays L.) production. After 10 years of annual manure applications, soil core samples were collected in 7.6-cm increments at three depths, 0 to 7.6, 15 to 22.6, and 30 to 37.6 cm, to determine soil bulk density (ρb), hydraulic conductivity of saturated soil (Ks), and water retention. Bulk density and Ks increased slightly with erosion level. Water retention did not change in the surface 7.6 cm, but it did decrease with increasing erosion level at deeper depths. Long-term application of manure decreased ρb by 10%, whereas Ks was doubled in the top 7.6 cm of soil. Manure increased soil-water retention capacity and decreased differences in water retention between erosion levels, especially at low suctions (0 to 20 kPa). Soil carbon content correlated well with water retention and ρb. Corn grain yields in 1997, 1998, and 1999 were 15, 6, and 14% less, respectively, in the severe than in the slight erosion phase. Long-term manure additions increased corn grain yields by 19% in 1998 and by 25% in 1999. Increased yield from manure additions was likely related to an enhancement in water retention. Results from this study show that long-term manure application is a possible management alternative for restoring the physical properties and crop productivity of eroded soil.