SOIL APPLICATION OF AGRICULTURAL WASTE TO IMPROVE CROP PRODUCTION SYSTEMS AND ENVIRONMENTAL QUALITY
Location: National Soil Dynamics Laboratory
Title: Soil Property and Landscape Position Effects on Seasonal Nitrogen Mineralization of Composted Dairy Manure
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 6, 2009
Publication Date: January 27, 2010
Citation: Watts, D.B., Torbert III, H.A., Prior, S.A. 2010. Soil property and landscape position effects on seasonal nitrogen mineralization of composted dairy manure. Soil Science. 175(1):27-35.
Interpretive Summary: Information on the availability of N from manure applied to agricultural fields that contain different landscapes is need. This information would be helpful developing management practices that better utilize this plant nutrient. Thus, a study was conducted to evaluate N availability from soils located at different slopes receiving manure during winter and summer months. Soils with the added manure generated more plant available N than soils without the added manure. More N was released during the summer months compared to the winter months. This was probably due to the climatic conditions with more N being released as a result of higher temperatures. The slope and difference in soil-type also contributed to N release. During winter months the sandiest soil located at the bottom of the slope produced the most N. However, this soil was more susceptible to N loss due to the high leaching potential. During summer months the soil with an even mixture of sand, silt and clay under the best field conditions produced the most plant available N. The soil with the greatest compaction, although produced the least amount of plant available N, retained the most N. In essence, the soil with greatest compaction had the least amount of leaching. Hence, these results show that in order to supply the plants with greatest plant available N from manure landscape and soil-types must be taken into consideration.
To develop better management practices that optimize the amount of N derived from manure, more information is needed regarding the mineralization and dynamics of N under normal field conditions. Thus, an in situ field study, using three different soil types located in close proximity, was conducted to evaluate N mineralization patterns during the summer and winter months. The three Coastal Plain soils investigated were Bama (Ultisol), Lynchburg (Ultisol), and Goldsboro (Ultisol). Dairy composted manure was incorporated into in situ soil cores, at a rate of 350 kg N ha-1, and compared to an unamended control. Addition of dairy composted manure greatly increased the mineralization of N. This was most evident during summer months, suggesting seasonal timing of application will influence mineralization. The seasonal patterns of N mineralization were affected mostly by temperature; N mineralization was minimal during the winter when temperature was low (~ 10° C), but was greater during the summer due to higher temperatures (25-30°C). Landscape and soil texture played an additional role in mineralization. During the winter months, the soil-type with the greatest percentage of sand located, in a low lying area, lost more of the added N from dairy compost compared to the other soils. During the summer, however, the loam soil with the greatest field capacity mineralized the most N. Additionally, the soil with the highest bulk density was more effective in retaining N in the soil compartment of the in situ core. These results show that soil variability, temperature and landscapes needs to be taken into account when applying manure to agricultural fields.