The use of plastic mulch in vegetable production has become a standard. Plastic mulch has been adopted by most small roadside farms and large vegetable production operations because its’ use offers substantial gains in crop earliness and in total and marketable yields (5). Plastic mulches have been used in vegetable production to help reduce erosion, soil compaction, and weed establishment, retain soil moisture, and reduce soil-borne diseases. However, the use of plastic mulches have been shown to increase disease development in some crops and weed control is still necessary (9,10).

The use of organic mulches in vegetable production has gained attention in recent years (1,3,6,10). Organic mulches are sown in the fall in the same manner as green manures. However, unlike green manures, organic mulches are desiccated in the spring and left on the soil surface for the production season. Organic mulches offer the same benefits as green manures and plastic mulches. Unlike most plastic mulches, organic mulches can easily be tilled back into the soil after the growing season and can easily be implemented in most production operations without the use of specialized equipment (5). Research has shown that organic mulches can suppress early weed establishment (3), help retain soil moisture (1), increase soil tilth (1), and may be effective in reducing the spread of some soil-borne pathogens, like buckeye rot (6, Wyenandt et al, unpublished). The use of organic mulches have been shown to increase yield and may have an effect on increasing fruit quality (10, Wyenandt et al, unpublished).

Rational & Significance:

In the past few years there has been mounting pressure on the vegetable production industry to reduce the use of synthetic fertilizers and pesticides. IDM programs have been developed for many crops which attempt to reduce synthetic inputs. IDM programs incorporate the use resistant cultivars, good cultural practices, disease forecasting systems, and production methods that produce the highest quality crops while minimizing chemical inputs. Disease forecasting systems (DFS) have been developed for many crops which predict when disease outbreaks may occur and advise growers on when to make chemical applications. Disease forecasting systems for tomato production have been used by growers for the past 25 years. The most common DFS for tomatoes used by growers to date include FAST (8), CU-FAST (4), and TOM-CAST. These DFS have successfully reduced the amount of total season fungicide input without compromising yields (4). The TOM-CAST DFS measures leaf wetness and average temperature during leaf wetness hours and assigns a disease severity value (DSV). DSV’s accumulate over a given time period depending on the weather and once a critical threshold is reached fungicide applications are advised. TOM-CAST, for example, can save as much as 55 to 72% of total fungicide input without compromising yield which result in substantial savings for the grower (4,6). It has been shown that tomatoes cannot be grown commercially in the mid-west without the use of fungicides (2). Diseases such as anthracnose fruit rot (AFR) caused by the pathogen Colletotrichum coccodes must be controlled with fungicides. Though DFS help to control diseases such as AFR other systems still need to be incorporated into IDM programs for tomato production. Organic mulches (cover crops) may become valuable additions to IDM programs as restrictions and loss of registration of fungicides in vegetable production becomes more prevalent in the upcoming years.

Materials & Methods:

In the fall of 1996 a randomized split plot design with bed types as main plots (conventional, chemical kill and mechanical kill cover crop) and fungicide treatments (Bravo Ultrex 2.75 lbs/A & Benlate WP 1 lbs ai/A) as sub-plots (4 reps) was set up at the Waterman Horticulture Farm, Columbus, OH (Franklin Co.). A fall sown cover crop of Hairy Vetch (Vicia villosa) + Winter Rye (Secale cereale) was seeded at ~50 lbs/A each on raised beds. The cover crop was either chemically killed with an application of 2,4-D (2 pts/A) + Round-Up (4 pts/A) on 5/7/97 or mechanically killed with an undercutter (5/16/97). Single rows of tomato ‘Peto 696’ were transplanted into 5’ wide x 30’ long beds (5/27-30). Each plot consisted of 4 beds on 5’ centers with outer 2 beds serving as guard rows and center 2 beds as treatment rows. Sub-plots were randomly assigned one of the five treatments as follows: no spray, 7 day spray, Tom-Cast advised sprays at DSV intervals of 15, 18, and 25. Campbell Scientific equipment (CR-10) (Logan, Utah), was used to measure rainfall, leaf wetness, and air temperature. Two additional CR10’s were used to measure soil temperature and soil moisture at 5 & 15 cm. depths within each main plot (2 reps). DSV’s were calculated for the Tom-Cast advised sprays and all field data were downloaded daily from each of the three CR10 units. Spray treatments were applied using a single row tractor mounted CO-2 powered (60 psi) boom with 5 HC-12 nozzles. Weekly foliar disease ratings for Septoria Leaf Spot (Septoria lycopersici) were done for each plot and area under disease progression curve, (AUDPC's) for mechanically killed beds, AUDPC’s for conventional beds, and AUDPC’s for chemically killed beds, were calculated. Normal production practices were followed throughout the growing season. Harvest was on 8/30/97 for no spray treatments in conventional beds, 9/5/97 for no spray treatments in chemically and mechanically killed beds, and on 9/12-13/97 for all spray treatments when red fruit was 80-90%.

Results to date:

The results of the first year of the study indicate that the use of a killed cover crop mulch had a significant increase in yield (2x) when compared to tomatoes grown in conventional beds (Table 2). No spray/cover crop treatments yields were comparable to the 7 day spray/cover crop treatments (Table 2). There were no significant differences in yield of tomatoes grown in either a chemically killed or mechanically killed mulched bed (Table 2). There were no significant differences in yield within each main plot indicating that fungicide treatments did not have any effect on yield (Table 1). However, the use of the disease forecasting system, Tom-Cast, resulted in a reduced amount of fungicide input (55-72%) without a compromise in yield or quality when compared to the 7 day fungicide treatment. Incidence of ground rots were significantly lower in mulched beds when compared to conventional beds (Table 6). The use of the cover crop significantly reduced the percent of mold (anthracnose + ground rots) on fruit (table ). Percent mold as a percentage of total fruit harvested was lower in the mulched beds (>2%) when compared to conventional beds (<12%) (Table 3 ).