Survey of Compost Use by South Florida Vegetable Growers

Abstract

The success of long-term vegetable production and maintenance of environmental quality is dependent on soil quality. Indicators of soil quality include cation exchange capacity (CEC), organic matter (OM), carbon (C), pH, and the number and community structure of soil organisms. The use of appropriate compost has been shown to improve soil quality and enhance the response to fertilizer, therefore improving growth and yield of vegetable crops. The objective of this study was to evaluate changes in the chemical and biological properties of soil in response to compost use in conventional vegetables production systems. A survey was conducted on 5 farms (three in Immokalee, and one each in Delray Beach, and Clewiston) growing tomato, pepper, and specialty vegetables. Most of the farms were applying composted yard trimming waste alone or in combination with biosolids or horse manure at application rates of between 7 to 112 Mg·ha-1 once a year. Soil samples were taken from composted and non-composted areas in each farm during Feb. and Mar. 2002. Soil pH, OM, C, K, Ca, Mg, Cu, Fe, MN and Zn were higher in the composted areas compared with the non-composted areas for each farm. CEC values in composted areas were double those in non-composted areas. Most importantly, application of compost enhanced the overall soil microbial activity as determined by total microorganism number, SRD (species richness diversity), and TSRD (total species richness diversity) of six functional groups including heterotrophic aerobic bacteria, anaerobic bacteria, fungi, actinomycetes, pseudomonads, and nitrogen-fixing bacteria, in all the participating farms. The greatest soil quality improvement was seen in soils receiving the highest rates of compost for the longest time.