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 (N_m) in a long‐term aerobic incubation study and 2) develop a model that predicts field cumulative net N mineralization (N_t) 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 (N_t) 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 N_t better than the linear model, and N_t 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.

Keywords:

• Mineralization
• nitrogen
• sugar beet

Acknowledgment

Financial support of this work provided by Michigan Sugar Company and by the Monitor Sugar Company is gratefully acknowledged. Also, the authors thank Clavin E. Bricker and Lee F. Siler for assistance with the field studies.