Increasing profitability of tomato production in high tunnels
Improving the quality of common hybrid tomatoes grown in high tunnels will increase farmers profits. Common hybrid varieties of tomatoes such as ‘Big Beef often suffer from ripening disorders when grown in high tunnels. Because of customer demand producers continue to grow these varieties in spite of loosing nearly 25% of their crop to ripening disorders such as yellow shoulders. Low levels of potassium are often associated with tomato ripening disorders such as yellow shoulders. Research with grafted heirloom varieties has shown to increase the potassium level. Our project will compare the fruit quality of grafted versus non-grafted hybrid tomatoes evaluating them based on marketability and yield for two growing seasons in 2016 and 2017.
The question to be answered by the project would be, “Can grafting common hybrid varieties and greenhouse varieties of tomatoes increase the quality of fruit produced in high tunnels”. The objectives of the project are to:
- Compare fruit quality and production between grafted versus non·grafted ‘Big Beef tomatoes using rootstocks that favor uptake of water and nutrients
- Compare fruit quality and production of grafted versus non-grafted greenhouse tomato varieties.
- Increase adoption of grafted tomato plants among high tunnel tomato producers
The research comparing grafted versus non-grafted ‘Big Beef’ was conducted on five farms in Garrett County, Maryland in six different high tunnels. Producers were provided with 50 ‘Big Beef’ tomato plants grafted on to ‘Maxifort’ root stock. The grafted plants were purchased from an experienced grower in Pennsylvania. The plants were received in 72 cell trays on March 25th and were transplanted into 4” round pots and grown in a greenhouse until being transplanted into the high tunnels between April 20th and May 5th. Growers planted two 25 plant blocks of grafted plants in their high tunnels in rows with ‘Big Beef’ non-grafted plants. Producers used their own production practices to raise the plants. Ten plants of both grafted and non-grafted plants in each of two locations were identified before the harvest season started for weighing and evaluation of YSD. Once the harvest began, producers harvested fruit on their typical harvest schedule. They weighed and counted the number of fruit from the twenty identified grafted plants and twenty non-grafted plants. The producers also evaluated each fruit for the YSD giving the fruit a rating of 0 (no evidence of YSD) to 4 (high degree of YSD) compared to a pictorial chart provided by the researcher.
In the comparison of grafted versus non-grafted commercial tomato varieties (“Geronimo” and “Big Dena”), the grower that was to graft the plants was unable to graft the plants so we had to contact another grower. They were able to produce the plants but by that time they were grafted and delivered they were three weeks behind the non-grafted plants. We had the non-grafted plants for a couple weeks to allow the grafted plants time to get up to size which resulted in a later planting date. Growers were asked to count and weigh the fruit yield from 20 plants each each high tunnels.
Grafted plants exceeded the yield of non-grafted plants in all six tunnels by an average of 5.15 pounds per plant which is a 26% increase in production. The variation in increased production ranged from 2.94 pounds per plant to 7.47 pounds per plant (Table 1). Due to large variations in increased yield, the difference between grafted and non-grafted plants was not statistically different.
When comparing the difference in YSD, the ratings were separated into fruit with a rating of 0, 1 & 2 which was considered marketable for fresh market tomatoes and a rating of 3 & 4 which was considered non-marketable as a fresh market tomato. Most producers sold the tomatoes rated as 3 or 4 as canning or juicing tomatoes. The results of the YSD was wide among both the grafted and non-grafted plants ranging from 98.7 % to 48.2% in the marketable category in grafted plant and 96.6% to 50.9% of marketable in the non-grafted plants. Five of the six high tunnels showed a higher percentage of marketable fruit in grafted plants. The average marketable fruit was 4.6% greater in the grafted versus non-grafted plants (Table 2).
With the commercial greenhouse varieties, in two of the three tunnels, non-grafted plants out produced the grafted plants.
Impacts and Contributions/Outcomes
The cost of using ‘Big Beef’ grafted plants is justified in additional yield and marketability of the fruit based on YSD. The additional cost of using grafted plants is based on the cost to purchase (including shipping) grafted plants. Grafted plants range in cost from just over $2.00 per plant to as much as nearly $4.00 per plant. Our plant cost was $2.25 per plant for the grafted plants and $.25 per plant for non-grafted plants. At a price of $1.50 per pound for marketable fruit, the grafted plants averaged a value of $29.38 per plant while the non-grafted plants averaged $20.96 per plant for an increase value of $8.41 per plant for grafted plants (Table 3).
Five of the six tunnels exceeded the additional cost of $2.00 per plant for the grafted plants. It is also noteworthy in this year’s research that the three tunnels with the highest production per plant had an average increased value of $10.90 per plant compared to the $5.93 for the three lower producing high tunnels. This might indicate that grafted tomato plants are profitable even at high production levels. Since the price of grafted tomato plants varies greatly among suppliers and the price of marketable tomatoes vary among producers, we looked at the profitability among six high tunnels with the price of grafted plants ranging from $4.00 to $1.50 per plant and the price of tomatoes ranging from $.75 per pound to $2.00 per pound. At the higher plant cost ($4.00 per plant) and the lowest marketable price ($.75) 4 of the 6 high tunnels showed increased profit from raising grafted tomato plants (Table 4).
If the price of tomatoes is raised to $1.00 per pound or the cost of the grafted tomato plant seedlings is reduced to $3.00 five of the six high tunnels showed a profit above the cost of the grafted seedlings. For the high tunnel exhibiting the lowest increase in yield a market price of $2.00 per pound of fruit and a cost of $2.00 or less for grafted seedlings would be required to have an increased profitability with grafted tomato plants in this research. This does indicate that even with low marketability and low production that if a producer purchases grafted plants for a reasonable cost and has a high value market that grafted plants can be profitable.
With the commercial greenhouse varieties (“Geronimo” and “Big Dena”), while in our first year we found no gain with grafted plants over non-grafted plants. This may have been due to the fact that the grafted plants were about three weeks behind the non-grafted plants. The age difference resulted in about a two week delay in fruiting on grafted plants. This indicates that to take advantage of the benefits of grafted plants the plants need to be planted as early as possible.
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