Nutrient Budgets and Internal Cycling of N, P, K, Ca, and Mg in Conventional Tillage, No‐Tillage, and Old‐Field Ecosystems on the Georgia Piedmont

Abstract

Nutrient budgets (N, P, K, Ca, and Mg) were developed for conventional—tillage, no—tillage, and old—field systems. Data for the budgets were collected over a 2—yr period, with grain sorghum as a main season crop followed by a cover crop of winter rye. Nutrient uptake by crops, weeds, and old—field plants was the largest flow in each system. Leaching losses were small compared to input from fertilizer (except for Ca). Leaching losses of N and Ca was greatest in conventional—tillage, followed by no—tillage systems, and least in the old field. No significant differences were observed between conventional— and no—tillage systems for leaching losses of P, K, and Mg, although leaching of P and K was significantly less in the old field than in either crop system. No—tillage and old—field systems maintained a larger litter component on the soil surface compared to conventional—tillage systems. Decomposition of litter and subsequent mineralization of nutrients appeared to be more rapid in conventional—tillage systems than in either no—tillage or old—field systems. Insect consumers mobilized a small portion of total nutrient flux within each system. In all three systems, nutrients were retained in litter and plant biomass, not lost through leaching.

Calculation of nitrogen mineralization in soil food webs

“…) showed that the simulated rates were close to the observed rates (Table 4). Comparison of the simulated N mineralization rates in the HSB webs with estimates of N mineralization rates obtained from N budget analyses (Stinner et al, 1984) showed that the simulated N mineralization rates were higher than the rates obtained from the N budgets. It must however be noted that the estimates obtained from the N budgets differed strongly between years (Table 4), and that the data used for the present simulation were from different years (1983)(1984) than the data used for the N budgets (1978)(1979)(1980).…”

“…a Obtained from in situ measurements (Bloem et al, 1994). b Obtained from a N budget for 1978/1979 (Stinner et al, 1984). c Obtained from a N budget for 1979/1980 (Stinner et al, 1984).…”

Molecular and Culture-Based Analyses of Prokaryotic Communities from an Agricultural Soil and the Burrows and Casts of the EarthwormLumbricus rubellus

“…This site is located on a river floodplain on Hiwassee series soil (fine loamy, siliceous, thermic, and Rhodic Kanhapludult). Clover and rye have been the winter cover crops in the plots since 1978 (3,30,31,72). Maize (Zea mays L.) was the summer crop in 1996 and 1997.…”

Soil‐atmosphere exchange of methane in adjacent cultivated and floodplain forest soils

“…The HSB site is about 14 ha in area and is surrounded on three sides by a meander loop of the North Oconee River. Except for the cropped areas and perimeter, which is forested, much of the site is in successional old field vegetation [Stinner et al, 1984]. The soil is a well-drained sandy-clay loam (66% sand, 13% silt, and 21% clay in the row crops area [Groffman et al, 1986]) with moderately high fertility relative to the southern Piedmont [Stinner et al, 1984].…”

“…Except for the cropped areas and perimeter, which is forested, much of the site is in successional old field vegetation [Stinner et al, 1984]. The soil is a well-drained sandy-clay loam (66% sand, 13% silt, and 21% clay in the row crops area [Groffman et al, 1986]) with moderately high fertility relative to the southern Piedmont [Stinner et al, 1984]. The climate of the region is humid subtropical, with a mean annual temperature over the last 30 years of 16.3øC (25.5øC in summer and 6.7øC in winter [Hendrix, 1997]).…”