2010 Annual Report for OS10-054
Evaluating compost and lime effects on soil organic matter, soil microbial communities and the control of Fusarium wilt in commercial tomato grown in Florida's sandy soils
Summary
Application of composts and lime may reduce the incidence of Fusarium wilt and improve soil conditions during commercial tomato production. The effect of compost and lime on soil properties and incidence and severity of Fusarium wilt was studied. Compost and lime treatments had no effect on soil chemical properties or the incidence of Fusarium wilt. Soils amended with 20-30 ton/A compost supported statistically higher numbers of culturable bacteria and lower numbers of culturable fungi during mid-season; these effects were diminished by the end of the season. To date the grower has received little benefit from compost and lime additions.
Objectives/Performance Targets
The objective of this study is to determine the effect of compost and lime on soil organic matter, the soil microbial community, including Fusarium spp., and the incidence and severity of diseases caused by soil borne pathogens, such as Fol. Specifically, the proposed treatments will directly evaluate the effect of compost and lime amendments on the severity of Fusarium wilt, soil microbial community structure and soil organic matter.
In addition, we will evaluate the effect of compost amendments on soil organic matter under Florida’s humid sub-tropical climate. Increases in soil organic matter can improve nutrient cycling, increasing water holding capacity and sequester carbon. We will also determine the effect of the proposed treatments on the availability of essential plant nutrients, especially Ca and Mg. Both Ca and Mg can form complexes with dissolved organic carbon and be leached from the soil when composts are applied. Losses of Ca and Mg from soils can lead to abnormal fruit development (blossom end rot) and large yield losses.
Results from this study will give Pacific Tomato Growers and the greater grower community guidance in the use of soil amendments and soil pH management. The information collected as part of this project will be invaluable to Mr. Whiddon and other organic growers in the southeastern U.S., where few options for the management of soilborne disease and pest problems are available. This research is part of a long-term effort by both UF investigators to identify cost-effective cultural practices that reduce the need for chemical pesticides and fertilizers by improving soil conditions that enhance soil microbial populations and activity. Such practices are sustainable, environmentally benign and have practical applications for conventional and organic crop production in Florida and other southeastern states.
Accomplishments/Milestones
Field trials conducted spring 2010 (February – June) and in the fall 2010 (August – December) production cycles at the growers site located in Manatee County, Florida have been completed. The completed tasks associated with the two field trials include:
1. Collection of pre-treatment composite soil samples.
2. Chemical and soil microbial (total bacteria and fungi) analysis of pre-treatment soil samples.
3. Application of organic amendments and lime (see below for rate information).
4. Analysis of compost samples.
5. Collection and analysis of composite soil samples at flowering, fruit set, and final harvest.
6. Soil microbial in periodic composite samples using standard dilution plating techniques.
7. Disease ratings on a periodic basis over the course of tomato production.
8. Statistical analysis of all data collected during seasons 1 and 2.
The following soil treatments consisting of compost (municipal yard waste) and lime amendments alone and in combination were applied to field trials in season 1 (spring 2010) to manipulate soil organic matter and pH:
1) Compost, low rate (5 tons/A)
2) Compost, high rate (10 tons/A)
3) Dolomitic lime, final soil pH 7.0 (rate will vary)
4) Dolomitic lime, final soil pH 7.0, and Compost, low rate (5 tons/A)
5) Unamended control
The following soil treatments consisting of compost and lime amendments alone and in combination were applied to field trials in season 2 (spring 2010) to manipulate soil organic matter and pH:
1) Compost, low rate (10 tons/A)
2) Compost, medium rate (20 tons/A)
3) Compost, high rate (30 tons/A)
3) Dolomitic lime, final soil pH 7.0 (rate will vary)
4) Dolomitic lime, final soil pH 7.0, and Compost, low rate (5 tons/A)
6) Unamended control
The entire experiment will be repeated for an additional fall growing season in 2011.
Impacts and Contributions/Outcomes
Compost and/or lime treatments had no effect on pH, EC, organic matter content, soil temperature. Similarly, compost and/or lime treatments also had no effect on phosphorus, potassium, calcium or magnesium content of soil as measured by the Mehlich-3 test. Soil CO2 flux data did not suggest a soil treatment effect in either season. Compost and/or lime treatments had no effect on the incidence of Fusarium wilt throughout the growing seasons. In fall 2010, soils amended with the 20 and 30 ton rates of compost supported statistically higher numbers of culturable bacteria and statistically lower numbers of culturable fungi on the mid-season sampling date of 7-Oct, although no statistical differences were observed following planting on16-Sep and after first harvest on 19-Nov. No differences in the culturable levels of fluorsescent pseudomonads or Fusarium oxysporum were observed among treated soils either.
To date, our results suggest that the grower is seeing little benefit from applications of composted yard waste to sandy soils prior to planting. Although the 30 ton rate used in the fall 2010 is 3 times the typical rate applied by the grower, it appears that application of compost may have no treatment effect on the incidence of fusarium wilt. It is possible that growers may benefit from longer-term applications of composted material; however, this cannot be assessed in our study. It should be noted that variability in microbial population and soil chemical characteristics was very high in plots receiving the 20 – 30 ton/A applications of compost. It is possible that treatment effects were masked due to high variability. The study will be completed again in Fall 2011 to obtain data from two fall growing seasons.