Changes in Soil Physical Properties Due to Organic Waste Applications: A Review

Land application of organic wastes such as animal manure, municipal wastes, and sewage sludge could alter the soil physical properties. Repeated substantial applications of waste increase the soil organic matter percentage. The available data on effects of waste applications on soil physical properties such as bulk density, water holding capacity at both field capacity and wilting point, and saturated hydraulic conductivity were summarized. Based on data from 12 different sources, 21 soil types, 7 waste types, and 8 crop types, a linear regression analysis of observed increases in soil organic C as a result of waste applications on percent reduction in bulk density indicated a highly significant relationship (r* = 0.69**). The results of an exponential multiple regression analysis of percentage sand and increase in organic C percentage on the percent increase in water holding capacity indicated that approximately 80% of the observed variations in percent increases in water holding capacity, at both field capacity and wilting point, could be attributed to variations in soil texture and soil organic C increases. The data on hydraulic conductivity as well as on infiltration rates are very limited and are not sufficient for quantitative analyses. The limitations of the available data were discussed in terms of identifying future research needs. Additional Index Words: bulk density, organic matter, water holding capacity, hydraulic conductivity. ' Paper no. 6041 of the Journal Series of the North Carolina Agric. Res. Serv., Raleigh, N.C. The use of trade names in this publication does not imply endorsement by the North Carolina Agric. Res. Serv. of the products named, nor criticism of similar ones not mentioned. This research was supported in part by the USEPA on a Grant no. R805011-0-1-0. Received 14 March 1980. ' Assistant Professor of Hydrology, New Mexico Inst. of Mining and Technol., Socorro, N. Mex.; Assistant Professor, AREC, Univ. of Florida, Sanford; Associate Professor, Dep. of Biol. and Agric. Eng., North Carolina State Univ., Raleigh; respectively. Khaleel, R., K. R. Reddy, and M. R. Overcash. 1981. Changes in soil physical properties due to organic waste applications: a review. J. Environ. Qual. 10:133-141. The soil has substantial capacity to treat and assimilate organic wastes. Applying wastes to land at agronomic rates for plant nutrient supply has been the traditional means of waste management. In recent years, there has been an increasing interest in disposal of wastes at rates far in excess of traditional agronomic rates. Application of wastes, either for plant nutrient supply or for disposal purposes, increases the C content of the soil. An increase in C content of the soil increases aggregation, decreases bulk density, increases water holding capacity, and hydraulic conductivity (e.g., Biswas and Khosla, 1971; Gupta et al., 1977; Kladivko and Nelson, 1979; Klute and Jacob, 1949; Mays et al., 1973; Salter and Haworth, 1961; Tiarks et al., 1974; Unger and Stewart, 1974; Volk and Ullery, 1973; Webber, 1978; Weil and Kroontje, 1979; Williams and Cooke, 1961). Furthermore, organic matter and soil aggregation are inversely related to runoff volumes and sediment loss (Wischmeier and Mannering, 1965; 1969). Several investigators, in monitoring runoff water quality from small plot-sized land application areas, reported less runoff volumes from these plots compared to control plots which received no wastes (Hensler et al., 1970; Long, 1979; McCaskey et al., 1971; Young, 1974; Young and Mutchler, 1976). The low runoff losses may be due to improved soil physical properties as a result of waste applications. Because of increased aggregation, less eroJ. Environ. Qual., Vol. 10, no. 2,1981 133 Table l--Pertinent information on various experiments. Location Percent C Years content of Waste type of waste study Soil type Crops grown Waste application Depth of rates incorpoMethod of metric tons ration, incorp@ ha" yr" cm ration Properties studied Remarks Reference Elk River, Minnesota Lafayette, Indiana Anaerobic 14.0 2 Hubbard coarse sludge sand {Udorthentic Haploborollsl 90.1% sand Anaerobic 19.4 1 Celina silt loam sludge {Aquic Haphdalfs}, 22.5% sand Mead, Cattle 32,0 2 Nebraska feadiot