SHORT-TERM NITROGEN DYNAMICS IN SOIL AMENDED WITH FRESH AND COMPOSTED CATTLE MANURES

The amount of available nitrogen in fresh and composted manures is required to adjust inorganic fertilizer applications for crops when using manures and composts. Com (Zea mays L.) plants were grown for 8 wk at temperatures of 17-27-degrees-C and 12-18-degrees-C in soil amended with two rates of fresh and composted solid beef cattle manure. Apparent N uptake of com grown in soil amended with fresh solid beef cattle manure, composted beef cattle manure and (NH4)2SO4 at the higher temperature was 2, 8, and 36%, respectively, during this 8-wk period. Nitrogen uptake by com in fresh solid beef cattle manure-amended soil at low temperature was affected by factors other than N availability. A 12-wk laboratory experiment was performed in which (NH4+)-N-15 was added to fresh and composted manure-amended soil to determine the fate of the inorganic N in the manure and to measure N mineralization rates. Net immobilization of inorganic N occurred with all manures; however, after 3 wk, net mineralization occurred with the solid and composted beef cattle manure. Immobilization of N-15 continued with all manure amendments as a result of mineralization-immobilization turnover. The amount of unrecovered N-15 after 12 wk was 10.5, 2 and 1% of the added N-15 in soil amended with solid beef cattle manure, composted beef cattle manure and manure composted with bark, respectively.