‘Less Water, More Watermelon: Grafting Can Help Growers Yield More’

This is a press release from UC ANR News:

Vegetable crops and irrigation advisor Zheng Wang (crouching) shares with growers the results of his grafted watermelon trials during a UC Cooperative Extension Field Day. Photo by Adrian Yepez

As growers across California navigate severe drought, supply-chain challenges and rising inflation, reducing inputs has become an existential necessity. And for watermelon growers, a new twist on a thousands-year-old practice is showing real promise.

In the summer of 2018, watermelon growers brought a pressing problem to Zheng Wang, who had recently joined University of California Cooperative Extension as the vegetable crops and irrigation advisor for Stanislaus, San Joaquin and Merced counties.

Growers were seeing an increasing number of their cartons rejected by supermarkets and other buyers because of the melons’ inconsistent quality, and Wang wondered if the ancient technique of grafting would help the state’s melon growers, who plant about 10,000 acres of the crop each year.

Growers plant about 10,000 acres of watermelon each year across California, making the state the No. 3 producer of the melon in the U.S., behind Florida and Georgia. Photo by Zheng Wang

Although California is the No. 3 watermelon-producing state in the U.S. (behind Florida and Georgia), there has been relatively little research on the melon across the state.

“Watermelons seem to have attracted not too much attention compared to other cucurbits, both Extension- and research-wise,” said Wang.

Fresh from his postdoctoral work at The Ohio State University on grafting fresh market tomatoes, Wang knew that vegetable growers understood the theoretical benefits of grafting, which combines a scion (the above-ground part of a plant) with the sturdy rootstock of a related plant.

But watermelon growers needed to make sure the added expense of using grafted plants would pay off. They were looking for science-backed evidence that the technique could actually reduce costs overall, while maintaining or boosting productivity.

“Sometimes as farmers we want to test a new cultural practice or crop product,” said David Jarrett, field manager at Van Groningen & Sons, who grows watermelons in the San Joaquin Valley. “A person like Zheng can set up a meaningful experiment and he has the tools for qualitative and quantitative analysis; Zheng knows how to measure a hunch and assign it a verifiable number measuring success.”

In his first trials in partnership with growers in 2019, Wang tested whether they could plant fewer watermelon plants, spaced at greater distances apart, while producing a stable yield of high-quality melons. The idea was that grafted plants, which are more vigorous and grow larger leaves and wider canopies, would produce consistently marketable melons that could be picked up to seven or eight times during an extended harvest season.

“That way we can make one plant equal ‘two,’” explained Wang, noting that non-grafted plants tend to produce only two or three picks of good melons, with quality declining rapidly afterward.

Grafting shows ‘a lot of potential for the future’

The more robust grafted watermelon plants (on the right) show larger leaves and a wider canopy, compared to their non-grafted counterparts (on the left). Photo by Zheng Wang

After two years of trials, the growers determined, with strong confidence, that watermelons planted 4-5 feet apart could produce a yield equal to – or surpassing – that of plants 3 feet apart (the standard for their non-grafted counterparts).

According to Wang, growers reported that, on average, their successfully grafted fields produced 15% to 25% more watermelons than non-grafted fields per acre, while using 30% fewer plants and the same amount of water and fertilizers.

With the potential for greater profitability, grafting could be a major boon during a particularly challenging time for growers.

“California agriculture is stressed competing for finite resources such as land, water, fertilizer and other safe but effective chemical tools, but outside of this realm we can improve some of our crops by grafting,” Jarrett explained. “Just as many tree crops are grafted, we are learning that other crops can be successfully grafted too; the goal is to create a heartier plant, which may grow better in marginal soils with reduced inputs.”

Whereas non-grafted watermelon plants yield two or three picks of high-quality marketable melons, the grafted plants could produce up to seven or eight picks during an extended harvest season. Photo by Zheng Wang

Confidence in the technique has led to a significant increase in the planted acreage of grafted watermelon across California – from less than 250 acres in 2018 to more than 1,500 acres in 2021. At the same time, growers have adopted 4 or 5 feet as the new “standard” spacing for their watermelon plants, enabling them to reduce their populations while maintaining or boosting yield.

“Using grafting has kind of opened a new channel in the watermelon world, and for all vegetable production in California,” Wang said.

Next up for Wang is testing various combinations of scions and rootstocks. This year, he began variety trials with rootstocks of various cucurbit family members (like hybrid squashes, Citron and bottle gourd), with hopes of producing results that watermelon growers could use to decide the best options for their local conditions.

“In sum, there are a lot of unknowns – but also a lot of potential for the future,” he said.

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Not Blind
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Not Blind
1 year ago

Seems like an interesting experiment, but probably not commercially viable. What farmer is going to be grafting acres of melons versus direct seeding and where do they store all the juvenile plants while they are being grafted?

Barry Bassboat
Guest
Barry Bassboat
1 year ago
Reply to  Not Blind

Kinda like cloning.. done in the nursery. I’ve heard of this being done in Texas. Actually talked to a farmer who came through Humboldt looking for property. He grew the highest per acre yield of pumpkins in the US. He did this with melons too. First I’d heard about it. He was not interested in growing weed. He talked to Martin Black in County code enforcement after noticing the abated properties around, and was shocked at how much that guy seemed to hate it here and everyone who lives here. It made such an impression he pointed it out to his USDA buddies.

Not Blind
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Not Blind
1 year ago
Reply to  Barry Bassboat

What’s the cost of starts? $3 per plant (guessing) vs $0.25 for seed? I think I’d over seed and keep the money. Also might be difficult to transplant on acreage. Just speculating, not trying to criticize. BTW, are you of the Clear lake Bassboat tribe or from the Ruth lake Bassboats? I think my cousin went to highschool with you…

Barry Bassboat
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Barry Bassboat
1 year ago
Reply to  Not Blind

Started out with the Bank-fisher tribe of lake Chabot. Joined the Canoes of Southern Ontario. I’ve been known to migrate between Ruth and Clear lake now. Easy though. First I need to figure out how monetize the search for Barry Bassboat’s identity.
At $1.00/comment, I owe the RHHB something like 4 million dollars.

Barry Bassboat
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Barry Bassboat
1 year ago
Reply to  Not Blind

…and tell your cousin it was not them. It was me I just wasn’t ready to commit yet. I left a wake of unrequited love behind me. You don’t want to get mixed up with a guy like me. I’m a loner Not Blind. A rebel.

thatguyinarcata
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thatguyinarcata
1 year ago
Reply to  Not Blind

It’s already standard practice for large scale hot house tomatoes. With a valuable enough crop, strict buyer standards, and sufficient nursery scale grafted plants pay for themselves in a number of ag settings. I wouldn’t be surprised if grafted cannabis became commonplace in the next decade. Mechanized transplanting is pretty well advanced at this point so its often more economical than overfeeding and thinning

Mr. BearD
Member
Mr. Bear
1 year ago
Reply to  Not Blind

If they are really getting 15%-25% greater yield it could be very viable to do the extra labor

Two Dogs
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Two Dogs
1 year ago
Reply to  Not Blind

It worked well in politics.

Mark
Guest
1 year ago
Reply to  Not Blind

Tri-Hishtil Nursery specializes in grafted plants. They do the work!

susan boyd
Guest
susan boyd
1 year ago

So We’re Wounding If We Have No Water ! ? Then We’ve Got No Life !? So Id Rather Have Water Too Grow Foods That’s More Important Too Us ! We Pray For Us ALL !

Ernie Branscomb
Guest
1 year ago
Reply to  susan boyd

I pray for clear communication.

Bug on a Windshield
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Bug on a Windshield
1 year ago

Good luck. Only your god can do that and when was the last time that communication happened without being in parable or riddle form? As long as faty foingers, caPs lOck Keys, punc,tu’ation; negligence;! in accurate spoil chuck, and social media forums exist, it might not ever never not get achieved.

Cetan Bluesky
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Cetan Bluesky
1 year ago

Time and farmers costs have to be considered.. although tractor planting less plants into same space is not a problem.. That research is all well and good but doesn’t change water use issues. Although dry farming melons does work under specific conditions anyone who has done it will tell you it’s not exactly viable for commercial applications. Just don’t get the same yield.

Mr. BearD
Member
Mr. Bear
1 year ago
Reply to  Cetan Bluesky

The article referenced a 15%-25% increase in yield with no additional water use. Seems like that would change the water use issues

Dano
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Dano
1 year ago
Reply to  Mr. Bear

Yes, it does because they grow fewer plants to get similar similar/more yield.

thatguyinarcata
Guest
thatguyinarcata
1 year ago
Reply to  Cetan Bluesky

I’m fairly certain we have a couple of dry farmed melon operations in the Eel River basin. Not sure if anyone is doing it in blue lake, but down south of Scotia there are definitely dry land commercial melons

Seldom Seen
Guest
Seldom Seen
1 year ago

Dry farming in Freshwater Bottoms. Been done there for years. That is where they grew potatoes for Lays, as in the commercial potatoe chips.

farfromputin
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farfromputin
1 year ago

Great article, REDHEAD. Davis is where it’s at!