Mineralization in Soils Amended With Manure as Affected by Environmental Conditions

Abstract

Concerns for environmental quality have prompted interest in recent years to develop agricultural practices that mitigate nutrient loss to the environment. It is imperative that management practices are developed that maximize the use of plant nutrients while minimizing environmental degradation. Thus, the main aim of this dissertation was to evaluate the impact that manure application to soil from different environmental conditions, soil types, and management practices have on nutrient cycling. This dissertation consists of four parts: (1) Residual effects of long-term tillage and manure application on carbon and nitrogen mineralization, (2) Mineralization of N in soils amended with dairy manure as affected by wetting/drying cycles, (3) A seasonal nitrogen mineralization study as influenced by soil properties and landscape position, (4) Soil microbial community dynamics as influenced by soil properties and landscape position. In the first study, C and N cycling was evaluated in the laboratory using soil from long-term tillage and manure (poultry litter) plots. No-tillage (NT) with litter contained the highest total organic carbon (TOC) in the 0-5 cm depths, which corresponded to significantly higher C and N mineralization rates. Carbon and N mineralization was higher in the 0-5 cm depthsfor NT, while conventional tillage (CT) was higher in 10-20 cm depths. In the second study, influence of manure addition on N mineralization was most evident at higher soil temperatures. The rate of N mineralization was mainly attributed to soil series, Catlin (silt loam)> Goldsboro (loam)> Bama (sandy loam). No significant differences were observed between constant and cycling moisture regimens. In the third study, dairy compost manure was mainly influenced by season with summer months mineralizing the most N. Landscape and soil texture also influenced N mineralization; during the winter months soil with the greatest percentage of sand located in a low lying area lost most of the added manure N, while the loam soil with the greatest soil moisture mineralized the most N during the summer. In the fourth study, dairy compost manure caused a shift in microbial dynamics, which was most evident during summer compared to winter months. Landscape and soil type also changed microbial properties. A loam soil located in a depressed area produced the highest microbial biomass and microbial activity. Canonical discriminate analysis using phospholipid ester-linked fatty acid (PLFA) profiles confirmed these changes in microbial properties by indicating a shift in lipid composition had occurred between season, manure application, and soil landscape. The knowledge acquired from this dissertation study has improved our understanding of nutrient cycling and could aid in the development of better management practices that increases the N use efficiency of litter.