Gladis M. Zinati

Distribution and fractionation of phosphorus, cadmium, nickel, and lead in calcareous soils amended with composts.

Abstract Composts improve organic carbon content and nutrients of calcareous soils but the accumulation and distribution of phosphorus and heavy metals among various fractions in soil may vary under the south Florida conditions. The accumulation of P, Cd, Ni, and Pb with depth and the distribution of water soluble, exchangeable, carbonate, Fe–Mn oxides, organic and residual forms of each element were investigated in soils amended with municipal solid waste (MSW) compost, co-compost and biosolids compost and inorganic fertilizer (as control). Total concentrations of P, Cd, Ni, and Pb were higher in the 0–22 cm soil layers and decreased considerably in the rock layers. These elements were in the decreasing order of P ≫ Pb > Ni > Cd. Amounts of water soluble and exchangeable forms of P, Cd, Ni and Pb were negligible at 0–22 cm soil depths except for Cd in the 10–22 cm depth. Amending calcareous soil with either organic or inorganic amendments rendered phosphorus, nickle and lead in the residual form followed by Fe–Mn oxides form in the 0–10 and 10–22 cm soil layers. Cadmium was predominantly in the Fe–Mn oxides fraction followed by the residual and carbonate forms in both soil layers. A significant positive correlation was found between various organic carbon fractions and organic forms of P, Cd and Pb in the surface soil layer. Soil amended with MSW compost had higher concentration of Cd in the organic fraction whereas, co-compost and MSW compost amended soil had higher concentrations of organic Ni fraction in the 0–10 cm soil layer.

Estimation of Field N Mineralization from Laboratory Incubation for Sugar Beet Production in Michigan

Abstract Optimum and economic sugar‐beet (Beta vulgaris L.) production requires an accurate prediction of the fertilizer nitrogen (N) required, and this in turn requires an accurate estimation of the quantity of N mineralized from soil organic matter. The objectives of this study were to 1) estimate cumulative net N mineralization (Nm) in a long‐term aerobic incubation study and 2) develop a model that predicts field cumulative net N mineralization (Nt) in Misteguay silty clay soil coupled with predictions of N lost in the 0- to 45‐cm depth. Laboratory data from soil incubations were fit to linear and one‐pool exponential models to predict field N mineralization. Rates of mineralization in linear and exponential models were adjusted for field air temperatures (T), and predicted cumulative net N mineralization (Nt) values were corrected for soil moisture content (W). Calculated field cumulative net N mineralization amounts were 93.5 N kg ha−1 and 84.1 N kg ha−1 in 1993 and 1994, respectively. Predicted amounts of N leached were 6.92 kg N ha−1 and 35.7 kg N ha−1 for 1993 and 1994 sugar‐beet growing seasons, respectively. The exponential model predicted Nt better than the linear model, and Nt values were 93 kg N ha−1 and 120 kg N ha−1 in 1993 and 1994, respectively. The results of this study provided information on the potential amounts of N, which mineralizes during the sugar‐beet growing season in Misteguay silty clay soil as well as the probable amounts of N leached from the 0- to 45‐cm soil layer. Thus, this model can be a valuable tool for use in the process of developing reliably good recommendations of fertilizer rates of N during wet or dry years needed to achieve economically optimum sugar‐beet production.