Jim E. Wyatt, Craig H. Canaday, Donald D. Tyler, and Gary L. Lentz

Early yields tended to be higher in plots without cover crops while late season yields were higher in plots with either hairy vetch or wheat stubble. Total tomato yields were not significantly different due to tillage system. ‘Sunsation’ produced higher early yields than ‘Mt. Fresh’ but in the later part of the season this trend was reversed. Highest late season yields in the test were on ‘Mt. Fresh’ grown in a cover crop of wheat stubble. Number of cull fruit or mean fruit size were not affected by tillage treatment. ‘Sunsation’ had more culls and slightly larger fruit size than ‘Mt. Fresh’.

Tomatoes in Tennessee are often grown on land with moderate to excessive slopes and this frequently results in severe soil losses due to erosion. Significant acreages of all agronomic crops are grown in no-till culture with a great deal of success and at a great savings of topsoil resources. Previous studies have shown that staked tomatoes for fresh market can be grown in no-till culture starting in the spring and utilizing killed wheat which had been planted the previous fall.

Objectives of this study were to investigate cover crops for fall-grown tomatoes which would produce no-till yields equal to or better than conventional tillage culture and to identify tomato hybrids which may have some tolerance to heat during the summer months and produce higher yields in the fall when tomato prices are rising due to continued demand and reduced supply.

In the fall of 1999, hairy vetch and wheat were planted in plots to be used for no-till tomatoes during the summer of 2000. The study was to include another no-till treatment of foxtail millet to be planted in mid-April; this crop did not germinate and establish a sufficient ground cover to be used as a no-till plot so it was included as an uncultivated plot. A conventional, cultivated plot was included as a control.

Two tomato hybrids were seeded on May 16 in the greenhouse. ‘Mountain Fresh’ is a hybrid which is grown commercially in the area and ‘Sunsation’ is a putative heat-tolerant hybrid which was identified as horticulturally acceptable in a previous study. In early June, mature wheat was harvested with a combine and the hairy vetch and the uncultivated plots were sprayed with a contact herbicide. Conventional plots were disked and harrowed to loosen the soil and destroy weeds. All plots received 400 lbs/acre of 15-15-15 fertilizer and tomatoes were transplanted on 14 June.

Plants were staked and tied using the "Florida weave" support system. Supplemental water was applied as needed with a drip irrigation system. Diseases and insects were controlled by applying appropriate pesticides registered for use on tomatoes.

Fruit were harvested at the mature green or breaker stage of maturity. Fruit from each plot were sized on a commercial grading machine into small, medium, large and extra large sizes and fruit from each category were counted and weighed. Fruit were classified as culls if they did not meet standards required for U. S. No. 2 grade. Harvest distribution for the season was divided into early (8/14-8/24), midseason (8/28-9/8) and late (9/11-9/22) harvest periods. Mean fruit weights for each period were calculated from fruit number and weight data. Data were analyzed by size and harvest period by appropriate statistical methods. Data presented are of large and extra large fruit classes since these are fruit with the highest value. Similar results were found with small and medium fruit.

No-till treatments had the overall effect of decreasing early season yields and increasing late season yields (Table 1). Although the differences were not always significant, the highest early yields were produced on plots without cover crops (conventional and uncultivated) while highest late yields were on plots with cover crops (hairy vetch and wheat stubble). In the spring, these differences could probably be attributed to differences in soil temperatures with colder soils being found in plots with cover crops. However, this test developed fruit during the hottest part of the summer and cover crops probably did not have a large moderating effect on soil temperatures. The yield effects were probably due to plant nutrition since nutrients may have been tied up in the organic matter or breakdown products of the cover crops early in the season and released for the crop to utilize later in the season. Total yields of all tomatoes were not significant due to tillage system, which confirms earlier work in this area.

Table 1. Early, late and total yields of two tomato hybrids grown in four tillage systems at the West Tennessee Experiment Station in summer/fall of 2000.