U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2002
Citation
Great Plains Soil Fertility Conference, March 5-6, 2002
Abstract
A routine soil testing procedure for soil N mineralization is needed that is rapid and precise. Not accounting for N mineralization can result in over application of N, especially in soils with a history of manure application. Our objectives were to compare results from a recently proposed rapid lab procedure with i) long-term N mineralization under standard laboratory conditions, ii) actual forage N uptake from soil receiving dairy cattle (Bas taurus) manure in a two-year field study and iii) yields of various crops throughout Texas and Oklahoma. The rapid procedure is based on the quantity of CO2-C evolved for 24 hours under optimum laboratory conditions following the rewetting of dried soil. Results of the one-day CO2 procedure were highly correlated with soil N mineralized from samples collected in March of 1995 and 1996 from a manure study and with forage N uptake both study years. Residual inorganic N in the same soil samples was much more poorly correlated with forage N uptake. Results of the rapid procedure were also highly related to yields of ryegrass, grain sorghum, corn, and wheat in 1996 - 1999.