Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 13, 2006
Publication Date: August 3, 2006
Citation: Mikha, M.M., Rice, C.W., Benjamin, J.G. 2006. Estimating soil mineralizable Nitrogen under different management practices. Soil Science Society of America Journal.70:1522-1531. Interpretive Summary: Management practices that increase soil organic matter (SOM) and reduce nutrient losses are important for improving environmental quality. The ability to account for nitrogen (N) released from SOM decomposition is a difficult but important goal that scientist have tried to achieve for many years. Manure (M) is one of the N sources used in agricultural practices for crop production. Residual N from M application could improve soil N supplying capacity and sustain yield for a few years following the application. The combination of No-tillage (NT) and M are management practices that may increase SOM and improve soil N supplying capacity. The objectives of this study are to investigate (i) the effect of tillage in combination with two residual N periods from previous fertilizer and manure application on soil N supplying capacity and (ii) to evaluate the relationship between field measurements and laboratory estimation of N mineralization after adjusting the laboratory N to the field conditions. Residual N was studied one year after cessation of a 10-year N-application and 6-year after cessation of a 5-year N-application. Nitrogen sources used in this study consisted of manure (M) and ammonium nitrate fertilizer (F) managed under no-tillage (NT) and conventional tillage (CT). An analysis of our results suggest that a combination of NT and M improved mineralizable N even 6-year after discontinued N application to the same extent as one year after discontinued N application. A close relationship was observed between field and laboratory N mineralization with both residual periods. This suggests the possibility of estimating field N mineralization from laboratory data exists, but is not generalized to different soil types and environmental conditions. Over all, NT and M sustained soil N 6-year after discontinued N application and laboratory N mineralization could be used to forecast ranges of mineralizable N after adjusting it to the field conditions.
Technical Abstract: In the last few decades, there has been a great interest in predicting nitrogen (N) mineralization to improve environmental quality. This study investigated the effect of tillage and residual N on soil N supplying capacity and evaluated the relationship between measured and estimated mineralizable-N. The experiment was established on a moderately well drained Kennebec silt loam (Fine-silty, mixed, superactive mesic Cumulic Hapludoll) in 1990 with four replications of continuous corn (Zea mays L.). Residual N was studied one year after cessation of a 10 yr N-application (R1) and 6 yr after cessation of a 5 yr N-application (R6). Nitrogen types consisted of manure (M) and NH4NO3 fertilizer (F) under no-tillage (NT) and conventional tillage (CT). We measured N mineralization using in situ method (Nmin) and potential mineralizable N (No) under laboratory condition. In addition, we adjusted laboratory derived No with the field measured soil moisture and temperature using simple model (Nmodel) to compare modeled, Nmodel, to in situ, Nmin, measured N mineralization. Nitrogen mineralization was studied in situ by placing a shelter (90 x 90 cm) over a fallow area. Samples were collected from of 0- to 5, 5- to 15, and 15- to 30-cm depth. No-tillage and M significantly increased soil total N, Nmin, and No. The combination of NT and M significantly improved No with R6 to the same extends as R1. High correlation was observed between Nmin and Nmodel (r =0.79) for 0- to 5-cm and (r =0.77) for 0- to 30-cm depth. No-tillage and M sustained soil N 6 yr after discontinued N application and No could be used to forecast ranges of mineralizable-N after adjusting it to the field conditions.