Increasing profitability of tomato production in high tunnels

Final report for ONE16-266

Project Type: Partnership
Funds awarded in 2016: $14,800.00
Projected End Date: 04/15/2018
Grant Recipient: University of Maryland Extension
Region: Northeast
State: Maryland
Project Leader:
Willie Lantz
University of Maryland Extension
Expand All

Project Information

Summary:

Improving the quality of common hybrid tomatoes grown in high tunnels will increase farmers profits.  This project compared using grafted hybrid tomato plants to increase quality and yield in high tunnels.

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 compared 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.  During both growing seasons the grafted ‘Big Beef’ tomatoes had increase of 5.15 and 4.1 lbs salable tomatoes per plant compared to the non-grafted plants (p-value ≤ .0284).  The only additional cost to use the grafted plants is the cost of the grafted transplant over the cost of the non-grafted transplant which is typically around $1.50/plant.  For farmers with 500 plants in a typical high tunnel receiving around $1.25 per pound for tomatoes they can realize a profit exceeding $2,000 per tunnel. 

Research was also conducted using typical greenhouse varieties of ‘Gerinimo’ and ‘Big Denna’.  Both of these varieties claim to have good resistance against soil diseases.   Grafted and non-grafted plants were compared in soils with and without know soil diseases.  Where the soil disease (Fusarium oxysporum) was present a yield increase of 26% or over 5 pounds per plant was realized on grafted plants.  When grown in soils not known to have a soil disease problem, only a slight difference of .66 pounds per plant increase was observed in the research.  

The educator conducted two on farm demonstrations, made seven presentations at local and regional fruit and vegetable meetings and has presented the information in the form of a poster at four state and national meetings.  

 

Introduction:

High tunnels have allowed producers to extend the growing season and increase the production of tomatoes for fresh market sales.  Many high tunnel producers utilize common varieties of tomatoes used in field or garden production.  These varieties often have problems with fruit quality when grown in tunnels compared to greenhouse varieties.  However, producers continue to prefer to use these varieties because of customer demand.  The variety, ‘Big Beef’ is popular with fresh market and auction producers.  ‘Big Beef’ produces an early large fruit that has excellent flavor.  Customers often ask for the variety by name and pay more for the variety at the produce auction.  The major problem with the variety ‘Big Beef’ is that it often develops yellow shoulders disorder (YSD) during the mid-part of the growing season. 

YDS is a ripening disorder in which the top of the fruit remains green or turns yellow.  The underlying tissue of the tomato is white, hard and poor tasting.  The larger the yellowing on the top of the tomato indicates more severe damage to the fruit.  Fruits with even moderate amounts of YSD cannot be sold for fresh market or packed at #1 or #2 fruit at the produce auction. 

YSD is complex and while not completely understood the factors that are typically found in plants that have fruit with YSD is lower potassium levels in the plant.  Lower plant potassium can be caused by high temperatures in the root zone which reduces potassium uptake.  Increasing amounts of YSD can also be made worse by plants that have heavy fruit loads, plant disease, insects and too little water. 

Grafting tomatoes and other fruiting vegetables has been practiced for several years around the world.  The majority of the grafting has been to reduce soil disease problems on production.  Only recently have researchers looked at the benefits of nutrient uptake on yield and fruit quality of plants grown in non-disease soil conditions.  In 2007 and 2008, a group of researchers from North Carolina State University compared yields and nutrient uptake of grafted versus non-grafted indeterminate tomato plants grown in high tunnels.  The nutrient content of leaf tissue was higher in grafted plants including potassium.  In 2014, Jerry Brust, University of Maryland Vegetable Extension Specialist, conducted research on the heirloom variety ‘Cherokee Purple’ to compare the increased yield and quality in a non-diseased high tunnel.  In his study he found that grafted plants had an average of 18% greater leaf tissue nutrient concentrations of nitrogen and potassium.  Yields were increased by 25%, with 30% greater marketable fruit on grafted plants. 

Increasing the quality of tomatoes by reducing yellow shoulders could greatly affect the profitability of producing high tunnel tomatoes.  If grafted ‘Big Beef’ tomatoes can increase the marketability the in similar ways that was reported by Jerry Brust with ‘Cherokee Purple’ (25% increase in yield and 30% increase in marketability), could increase the profitability by $5 to $10 per plant.  With 500 plants in a standard high tunnel (30′ X 96′), the increase in profitability per tunnel could be as much as $5,000.  

Little research as been conducted with grafted greenhouse type tomato varieties such as ‘Geronimo’ and ‘Big Dena’.  These varieties are reported to have resistance to soil diseases, however, the researcher has first hand experience with drastically reduced yields in a high tunnel with these varieties caused by Fusarium oxysporum which causes Fusarium Wilt.  Farmers with soil disease such as Fusarium Wilt are often forced to relocate tunnels which is a costly process.  Some growers also have limited land to relocated tunnels.   If grafted greenhouse type tomatoes can increase yields to nearly the same as plants grown in non-diseased soils and be much greater than non-grafted plants, this may save the farmer the work and time to relocate tunnels.  

We also plan to compare grafted to non-grafted greenhouse varieties in tunnels with no know soil diseases.  Again little to no research is available on this type of comparison.  If farmers can increase yield beyond the additional cost of grafted plants with no additional time and labor, that additional income will be profit.  

 

Project Objectives:

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:

  1. Compare fruit quality and production between grafted versus non·grafted ‘Big Beef tomatoes using rootstocks that favor uptake of water and nutrients
  2. Compare fruit quality and production of grafted versus non-grafted greenhouse tomato varieties.
  3. Increase adoption of grafted tomato plants among high tunnel tomato producers

 

Cooperators

Click linked name(s) to expand
  • Dan Fiscus
  • Faye Harvey
  • Fred Petersheim
  • Noah Yoder

Research

Materials and methods:

The research was conducted in 2016 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 Yellow Shoulder Disorder (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 2017, three farms in Garrett County compared yields and quality of tomatoes between grafted and non-grafted plants of the variety ‘Big Beef’.  The research design was changed in 2017 to have a row of grafted plants and a row of non-grafted plants planted beside each other in the high tunnel.  Three ten plant plots of grafted plants and three ten plant plots of non-grafted were selected from each row at the same location along the length of each row.   The grafted ‘Big Beef’ tomato plants where grafted on to ‘Maxifort’ root stock.  The grafted plants were purchased from an experienced grower.  The plants were grown and harvested in the same manner as in 2016.  Plant tissue samples were also collected at the three farms from May 16th to August 24th.  A sample was collected from grafted and non-grafted plants every two weeks.  The samples were sent to a certified lab for analysis. 

In 2016 and 2017,  the variety ‘Geronimo’ was grown in a tunnel with a know disease problem, Fusarium oxysporum.  The ‘Geronimo’ plants were grafted on ‘Arnold’ rootstock by Plug Connection in California.  The plants were received in mid March and transplanted to four inch pots and grown in the greenhouse.  The plants were transplanted into the high tunnel in late April.  Three ten plant plots of grafted and non-grafted plants were planted in the same row.  The plants were grown by pruning to a single stem and trellised with string to the purlins of the high tunnel.  Once harvest began the fruit was counted and weighed weekly.  The same method was used to compare the greenhouse varieties in two tunnels with no know soil disease with the exception that in 2017, the plants were planted in two different rows and three ten plant samples were taken from each row at the same place along each row.

 

Research results and discussion:

‘Big Beef’ Comparison of Grafted and Non-Grafted Plants

In 2016, 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).

Table 1  Increased Yield Per Plant

High Tunnel

Grafted lbs/plant

Non-Grafted lbs/plant

Increase lbs/plant

% Increase per plant

NY1

31.70

24.23

7.47

24%

NY2

29.58

23.59

5.99

20%

0LH

29.75

24.39

5.36

18%

FP

18.33

12.75

5.58

30%

MH

9.70

6.75

2.94

30%

LL

11.68

8.09

3.59

31%

AVG

5.15

26%

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).  

Table 2 – Quality Difference Per High Tunnel

 

High Tunnel

% of Marketable Fruit Grafted Plants

% of Marketable Fruit Non-Grafted Plants

Difference

 
 

NY1

98.7%

96.6%

2.1%

 

NY2

98.8%

94.5%

4.2%

 

LH

79.7%

68.4%

11.3%

 

FP

97.3%

93.5%

3.8%

 

MH

48.2%

50.9%

-2.6%

 

LL

92.6%

75.5%

17.1%

 

Average

89.5%

84.9%

4.6%

 

Again due to large variations of the percent of fruit in the marketable category, the difference between grafted and non-grafted plants was not statistically different. 

In 2017 with 9 plots in three different high tunnels, the average production on grafted ‘Big Beef’ was 19.3 pounds and the yield on non-grafted was 15.8 lbs per plant.  The yield advantage for grafted plants was 3.5 pounds per plant.  The grafted plants also averaged 85% of the fruit scoring from 0 to 2 (salable fruit) on the yellow shoulders evaluation.  The non-grafted plants averaged 78% of the fruit being salable.  This results in an increase of 7% salable  fruit for grafted plants.  With the average yield of 19.3 lbs of fruit and an increase of 7% salable fruit, the grafted plants had an advantage of 4.1 lbs of salable fruit per plant. One farm recorded an average (3 plots) of 28.9 lbs of fruit and 78% salable on grafted plants and 24.2 lbs of fruit and 64% salable on non-grafted which was an increase of 7.2 pounds of salable fruit per plant.  The grafted compared to the non-grafted were significantly statistically different with a p-value of .0284.  

The results of the 2017 tissue tests are reported in Table 3 based on the average % of the nutrient on a dry matter basis.  While the average nutrient level for Nitrogen, Phosphorus and Potassium was higher in grafted plants it was not higher in every sample.  Nitrogen was higher in grafted plants in 17 of the 19 samples while phosphorus and potassium were higher in 15 of the 19 samples.  For Magnesium and Calcium, the non-grafted plants had higher average levels than the grafted plants.  Magnesium was higher in 15 of the 19 samples of non-grafted plants, however the average and the majority of the samples for both grafted and non-grafted were below the sufficiency range suggested by the lab.  While the average calcium level was slightly lower (.03%) in grafted plants, the calcium % of grafted plants was higher in 14 of the 19 samples and the average for both grafted and non-grafted was in the sufficiency range.  

Table 3 – Percent Plant Nutrient in Tissue Samples

Nutrient

Grafted

Non-Grafted

Sufficiency Ranges*

Nitrogen

4.86%

4.66%

4.2-4.8%

Phosphorus

0.47%

0.42%

.50-.80%

Potassium

3.04%

2.70%

2.8 – 4.25%

Magnesium

0.31%

0.34%

.40 – 1.00%

Calcium

2.40%

2.43%

1.00-3.00%

*According to Waypoint Analytical, Leola, PA         

Grafted Plant versus Non-Grafted Greenhouse Hybrid Tomatoes in High Tunnels with Know Disease Problem

In 2016 and 2017, Grafted tomato plants out yielded non-grafted by over 5 pounds per plant (table 4).  The data has not been evaluated for statistical significance.

Table 4

 

 

Lbs Per Plant

Average

    2016

2017

Two Year Avg.

 Yield Difference

Geronimo Grafted

 

14.9 lbs/plant

14.36 lbs/plant

14.68 lbs/plant

5.38 lbs/plant

Geronimo Non-Grafted

9.6 lbs/plant

9.01 lbs/plant

9.3 lbs/plant

 

  • The combined results of 2016 and 2017 were significantly different with a p-value of 0.024.  

Grafted Plant versus Non-Grafted Greenhouse Hybrid Tomatoes in High Tunnels with  No Know Disease Problem

In 2017, on 5 side by side 10 plant plots, grafted tomato plants out yielded non-grafted plants in 4 out of the 5 plots.  The grafted yield was .66 pounds per plant greater than the non-grafted plants. 

Research conclusions:

‘Big Beef’ Comparison of Grafted and Non-Grafted Plants

In 2016, the cost of using grafted plants was justified by additional yield and marketability of the fruit based on YSD (see table 5).  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 5  Value of Marketable Fruit

 

Grafted/plant

Grafted/plant

Change in Value

NY1

 $ 46.92

 $ 35.12

 $ 11.80

NY2

 $  43.82

 $  33.45

 $ 10.37

LH

 $  35.57

 $  25.04

 $ 10.53

FP

 $ 26.75

 $ 17.89

 $ 8.86

MH

 $  7.02

 $  5.15

 $ 1.86

LL

 $ 16.22

 $  9.17

 $ 7.05

Average

 $  29.38

 $ 20.97

 $ 8.41

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 indicates 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 6)

Table 6 – Profit per Plant at Various Market Prices and Cost of Grafted Seedling

High Tunnel

Pounds Marketable Fruit per Plant – Grafted

Market price of Tomatoes/lb

Cost of Grafted Seedlings per plant

 $                0.75

 Pounds Marketable Fruit Per Plant – Non-Grafted

 $     4.00

 $    3.00

 $    2.00

 $    1.50

 Profit Per Plant

NY1

31.28

23.41

 $     1.90

 $    2.90

 $    3.90

 $    4.40

NY2

29.21

22.30

 $     1.18

 $    2.18

 $    3.18

 $    3.68

LH

23.72

16.69

 $     1.27

 $    2.27

 $    3.27

 $    3.77

FP

17.83

11.92

 $     0.43

 $    1.43

 $    2.43

 $    2.93

MH

4.68

3.44

 $  (3.07)

 $ (2.07)

 $ (1.07)

 $ (0.57)

LL

10.81

6.11

 $  (0.47)

 $    0.53

 $    1.53

 $    2.03

               

  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. 

In 2017, grafted ‘Big Beef” tomatoes had an increase of 4.1 pounds of salable fruit and an increase of 7% salable fruit.  Table 7 shows the additional profit per plant at different costs of grafted plants and price of tomatoes.  The table shows that only when the additional cost of grafter tomato plants is at $2.50 and the price of tomatoes is at $.50 per pound that grafted tomatoes are not profitable.  With typical additional cost between $1.50 and $2.00 per plant and tomato prices between $1.00 and $1.50 per pound, the profit per plant ranges between $2.10 and $4.65.  For farmers with high tunnels with 500 plants the additional profit from utilizing grafted plants is $1050 to $2325.

Table 7 – Profit per plant of ‘Big Beef’ tomatoes at various levels of plant cost and tomato prices*

 

Price of Tomatoes per Pound

$.50

$.75

$1.00

$1.50

$2.00

Additional Plant Costs

$1.00

$1.05

$2.08

$3.10

$5.15

$7.20

$1.50

$.55

$1.58

$2.60

$4.65

$6.70

$2.00

$.05

$1.08

$2.10

$4.15

$6.20

$2.50

-$.45

$  .58

$1.60

$3.65

$5.70

*based on the 2017 research reported in this document of 4.1 lbs of increased saleable fruit/plant

Grafted Plant versus Non-Grafted Greenhouse Hybrid Tomatoes in High Tunnels with Know Disease Problem

For farmers with soil disease problems our research shows that using grafted tomatoes even with greenhouse varieties that are resistant to soil diseases, produced a higher yield by over five pounds per plant.  Depending on the price of tomatoes, the additional yield would result in additional profits of between $2,000 and $5,000 per high tunnel (500 plants per tunnel).  While this research showed positive results, the disease levels in the tunnel are unknown and the level of production for other varieties may vary.  

Participation Summary
7 Farmers participating in research

Education & Outreach Activities and Participation Summary

8 Consultations
2 On-farm demonstrations
2 Published press articles, newsletters
7 Webinars / talks / presentations
3 Posters presented at state and national meetings

Participation Summary

293 Farmers
170 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

The educator has conducted two on farm workshops for local farmers in 2017 during the growing to share the results of the 2016 plots and to allow farmers to view the plants and fruit.  The educator also has presented information on grafted tomatoes and data from the project at seven regional and state vegetable workshops including Future Harvest in College Park, MD; the Mid Atlantic Fruit and Vegetable Conference in Hershey, PA; and the West Virginia Small Farms Conference in Morgantown, WV.  The Mid Atlantic Fruit and Vegetable Conference published an article in the 2017 Mid Atlantic Fruit and Vegetable Conference Proceedings.  The educator presented the research to the University of Maryland new employee tour.  The educator also presented a poster at the 2017 University of Maryland Extension Summit.  The educator published an article in the University of Maryland Fruit and Vegetable News newsletter presenting the 2017 project data.   

The educator has also presented a poster at the “Our Farms, Our Future” 2018 National SARE Conference.  A poster was also submit for the 2018 NACAA Annual Meeting and Professional Improvement Conference.  The poster was accepted and will be judged for consideration of a national award.    

Learning Outcomes

5 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Five or more farmers learned that using grafted tomatoes on good root stock can increase marketable yield and profit over the increased cost of grafting.

Project Outcomes

9 Farmers changed or adopted a practice
Project outcomes:

Five of the seven (two stopped growing tomatoes due to reasons not associated with profitability or the project) cooperating farmers have continued using grafted tomatoes in high tunnels in 2018.  Four additional farmers are trying grafted tomato plants for the first time in 2018.  A total of over 2,000 grafted plants were planted in 2018.  Four farms are trying grafted tomato plants with additional hybrids.  Two farmers received training on grafting tomato plants and plan to offer grafted tomato plants locally for farmers.  

Assessment of Project Approach and Areas of Further Study:

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. 

Table 3 Value of Marketable Fruit

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.  

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.