Soil Changes Resulting from Cropping1

TLDR: In this paper, the authors evaluated the changes in chemical and physical properties of a Keith silt loam (fine-silty, mixed, mesic, Aridic Argiustolls) that may be attributed to cropping.

Abstract: from various cropping systems and the uniqueness of a longThe need to document further the changes in soil properties time cultivated field adjacent to huffdograss (Buehloe dactyloides) pasture prompted us to evaluate sail-property changes of a Keith silt loam ( fine-silty, mixed, mesic, Aridic Argiustolls 1, characteristic of that pasture and field. In the fall of 1973, we ples were obtained from the pasture (newly broken sod) and brake the sod of the buffalograss pasture for analysis. Soil samthe adjacent cultivated field. The wet aggregates from the pasture were stabler as mmpared with the cultivated field for both flash and vacuum wetting. However, the dry aggregates from the cultivated field were slightly stabler than those from the pasture. The average clod densities were 1.7 and 1.3 g a 3 from the tilled and pasture soils, respectively. The pasture soil was also much more permeable. The constant infiltration rate (after 6 hours of infiltration) averaged 0.95 and 0.13 of the general deterioration of many of the physical properties cm hr-1 for pasture and cultivated soils, respectively. Because of its soil, the cultivated field will require special management Consideration. Additional Indez Words: tillage, soil structure, infiltration, organic matter. s . . . OIL'S PHYSICAL PROPERTIES generally deteriorate if a Soil 1s mtenslvely cultivated. Page and Willard (1946) found cultivation resulted in a loss of pore space and a corresponding increase in weight per unit-volume of soil. Other workers (van Bavel and Schaller, 1950; Wilson and Browning, 1945) observed decreased aggregation of soil under continuous corn. Olmstead (1946), who compared aggregation of soil from virgin buffalograss pasture with that of plots broken from virgin buffalograss (Buchloe ducfyzone the tilled plots had lost approximately 80% of their hides) prairie about 1902, found that in the surface-tilled initial aggregation-a decrease sufficient to account for decreased crop yields. Harris et al. (1966) summarized their review of "Dynamics of Soil Aggregation" by reporting that a soil's aggregate status usually deteriorates rapidly if the soil is repeatedly cropped with annuals that supply little organic matter to the soil, require extensive cultivation, and provide minimal vegetative cover. deteriorated soil structure (Cary and Hayden, 1973.) MidHowever, not all continuous row-cropping systems have dleton (1952) reported tilling the soil at its most favorable moisture content usually will improve (or change very little) its structure because the aggregates formed from the joining of individual particles then will tend to countereration with the Kansas Agric. Exp. Sta. Dept. of Agronomy 'Contribution from the Agric. Res. Serv., USDA, in coopContribution no. 1461: Colby Branch Sta. no. 54. Paper presented before Div. S6 , Soil Sci. Soc. Am., Chicago, Ill. November 1974. Received 20 Jan. 1975. Approved 14 Mar. 1975. zSoil Scientist and Engineering Technician, USDA, ARS, NCR, Manhattan, Kansas, and Superintendent, Colhy Exp. Sta., Colby, Kansas. balance those disrupted by implement action. Harris et al. (1966) concluded grasses and perennial crops with extensive root systems, a continuous supply of readily decomposable organic matter, and effective protective coverage improve soil aggregation. The change in soil properties from various cropping systems needs to he further documented. In this study, we evaluated the changes in chemical and physical properties of a Keith silt loam (fine-silty, mixed, mesic, Aridic Argiustolls) that may be attributable to cropping. The study was possible because a field cultivated for many years is adjacent o the buffalograss pasture being brought under cultivation. METHODS AND PROCEDURE The newly broken sod, cultivated for a few years about the native pasture continuously. The main plant species (and apturn of the century (from 1913 or 1914 until 1973), was in proximate percentages) in the pasture included: 55% buffalograss, 20% western wheatgrass (Agropyron smithir), 17% red three-awn (Arisfidn longiseta), 5% tall dropseed (Sporobolus), laneous weeds-prairieconeflower (Ratibida Raf.), gumweed 1% little barley (Hordeum pusillum Nutt.), and 2% miscel(Grindelia Willd.), fetid marigold (Dyssodia papposa (vent.) Hitche.), and firewied (Epilobium angrrsrifolirrm L.). In the fall of 1973, the sod was chiseled 83 cm on center, approximately 20 cm deep. After chiseling, the soil was prepared for plowing by disking twice-io level the area and break up sod clumps-and then plowed 15 cm deep and left for the winter, In early spring of 1974, a roller packer was used twice to level and prepare a seedbed for spring barley, planted in late February. The cultivated field has been cropped for more than 60 years. Early cropping sequence included forage sorghum (Sorghum wheat fallow. Starting in 1959 the sequence has been: bicolor (L..) Moench.), wheat (Triticum aestivum L.), and 1959-summer-fallow 1960-fallowed wheat 1967-summer-fallow 1961-summer-fallow 1968-fallowed Lancer wheat 1962-fallowed wheat 1969-summer-fallow 1963-summer-fallow 1970-fallowed Shawnee wheat 1964-fallowed grain sorghum 1972-nonirrigated spring barley 1971-irrigatedsugar beet 1965--summer-fallow 1973-irrigated corn 1966-fallowed Scout wheat Sails from the field with a long-time cropping history and from the field previously in grass pasture will be referred to as "tilled" and "sod." ple from both sod and tilled fields at 0to 15-, 15to 30-, and We obtained a composite (at least 10 suhsamples) soil sam30to 60-cm depths. The samples were analyzed for chemical properties at the Kansas State Univ. Soil Testing Laboratory. cultivated and grassed sites were allowed to air-dry, we deterAfter about 10 kg of soil obtained from the plow layer of the mined their dry-aggregate stability and size distribution by dry sieving according to Chepil's method (1951, 1952, 1958), using a sieve described by Lyles et al. (1970). To determine wet-aggregate stability (of soil wetted both by vacuum and by direct immersion) of the 2.0and 0.84-mm size fraction obtained from the dry sieving, we used the method described by Kemper (1965). except we used a 15.2-cm-diameter sieve and a 30-g soil sample. Our mechanical sieving machine lowered and raised the sieve holder throngh a distance of 2.7 cm 25 X each minute. 964 965 S ~ I D M O R E ET AL. : SOIL CHANGES RESULTING FROM CROPPING Table 1-Chemical properties of the sod and tilled Keith soils, fall 1973 c-15 1,210 I4 IS30 770 6 750 0.35 11.2 0.6 Ll.0 1.5 7 . 9 13.6 3&60 613 0.71 11.4 0.5 20.6 3.0 7.5 13.7 800 13 838 0.31 2. 22 6. 4 0. 6 2. 21 8. 2 1.7 7. 8 14. 9 0. 42