A comparison of methods to estimate N mineralization in soils amended with poultry litter

WYNGAARD, N.; CABRERA, M.L.

Long Beach, California

Conferencia; 2014 ASA, CSSA and SSSA international annual meetings; 2014

Thisstudy evaluated the change in total nitrogen (Nt) and N mineralizationpotential after long-term poultry litter (PL) amendments as compared toinorganic fertilization (IF) in soils with contrasting texture. It also assessedthe capacity of different methods to estimate this change in mineralizationpotential. To this end, samples from four soils (Delaware, Maryland, Iowa andGeorgia) fertilized with PL or IF for more than ten years were aerobicallyincubated for 24 weeks to determine the N mineralization potential (No),and were also used to estimate N mineralization by the Illinois soil testanalysis (ISNT), extraction with hot KCl, NaOH, phosphate-borate (PB), andanaerobic incubation (Nan). The PL application generated an increasein Nt compared to IF ranging from 0.08 to 0.63 g N kg-1,which was closely associated to the soil clay content, and resulted in anincrease in No ranging from 1.8 to 233.1 mg kg-1. Fromthe chemical methods to estimate No, PB presented a low correlation(R2=0.55), while ISNT and NaOH and KCl extraction were highlyassociated (R2>0.94) but resulted in separate models for IF andPL. The use of the IF model on PL amended plots would result in anunderestimation of No. On the other hand, the association between Nanand No resulted in one model for both IF and PL (R2=0.96).Due to its simplicity, biological basis and capacity to predict Noin PL and IF amended soils, we recommend the use of Nan as anestimator of N mineralization.