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WORKSHEET 2 EXAMPLE CALCULATION FOR AVAILABLE MINERALIZED ORGANIC NITROGEN The organic nitrogen in sewage sludge continues to decompose and release mineral nitrogen through the mineralization process for several years following its initial application. This residual nitrogen from the previously applied sewage sludge must be accounted for as part of the overall nutrient budget when determining the agronomic rate for sewage sludge. Residual nitrogen can be determined through soil analysis or calculated using the following procedure. These calculations must be done for each yearly sewage sludge application unless soil analysis is performed prior to land application(see example calculations). Instructions: Complete a separate table for each year sewage sludge was land applied. Note that most do not calculate beyond the third year because the values become negligible. Sum the values of mineralized Org-N (Column d) from each table for the particular calendar year you're trying to determine Org-N available. (See example below.) i b 5taiting ori N� cMinet ahzahond. Mineralized Org-N' a Osg N a. ear, „(kg(ha) Rate,(Exhibit,E=3)_ (kglha) Remaining (kglha) 0-1 (year sewage sludge 139 0.2 28 111 was a lied 1-2 (1st year after) 111 0.1 11 100 2-3 (2nd year after) 100 0.05 5 95 Begin with year sewage sludge is applied,and continue for 2 more years. Z In the first year,this equals the amount of Org-N initially applied. In subsequent years,it represents the amount of org-N remaining from the previous year(i.e.column e). 3 The org-N content of the initially applied sewage sludge continues to be mineralized,at decreasing rates,for years after initial application. See Exhibit E-3 for mineralization values. °Multiply column b and column c. 5 Subtract column d from column b. Example Assume that anaerobically digested sewage sludge with a 3%org-N content(dry weight basis)was applied to the site at a rate of 5 mt/ha in 1986. The following year, 1987,3 mt/ha of sewage sludge(same org-N content as in 1986)was applied to the same site. It is now 1988,and you want to calculate the available nitrogen from previous sewage sludge applications. In 1986,the org-N in the sewage sludge applied = (0.03)(5 mt/ha)(1,000 kg/mt)= 150 kg/ha. In 1987,the org-N in the sewage sludge applied = (0.03)(3 mt/ha)((1,000 kg/mt)=90 kg/ha. Calculate the available nitrogen from 1986 and 1987 in the following manner(assume anaerobically digested sewage sludge). a Year* b.'Starting org-N c Minerahzahan d., Mineralized Org-N e Org;- ha)- ktate(Exh&t ?;2) a),, Rematnm � ha)- ._ 1986 Sewage Sludge.; 0-1 (first application-1986) 150 0.2 30 120 1-2(1987) 120 0.1 12 108 2-3(1988) 108 0.05 5.40 102.6 1987 Sewage Sludge 0-1 (first application-1987) 90 0.2 18 72 1-2(1988) 72 0.1 7.2 64.80 2-3(1989) 64.8 0.05 3.24 61.56 To determine the total mineralized organic nitrogen available in 1988 from the sewage applied in 1986 and 1987, add the mineralized Org-N value in the 1988 row of column d of the table for the 1986 sewage sludge to the mineralized Org-N value in the 1988 row of column d of the table for the 1987 sewage sludge (i.e., 5.40+ 7.2 = 12.6 kg/ha). Total mineralized Org-N available in 1988 from previous sewage sludge 12.6 kg/ha. E-8 *Facsimile page from EPA Land Application of Sewage Sludgy