Much less water, extra watermelon: Grafting may help growers yield extra


UC Cooperative Extension advisor exams historic method, new to California melons

As growers throughout California navigate extreme drought, supply-chain challenges, and rising inflation, decreasing inputs has developed into an existential necessity. And for watermelon growers, a brand new twist on a thousands-year-old application is exhibiting actual promise.

In the summer season of 2018, watermelon growers introduced an urgent drawback to Zheng Wang, who had not too long ago joined the University of California Cooperative Extension because the vegetable crops and irrigation advisor for Stanislaus, San Joaquin, and Merced counties.

Growers had been seeing a growing variety of their cartons rejected by supermarkets and different consumers due to the melons’ inconsistent high quality, and Wang was puzzled if the traditional strategy of grafting would assist the state’s melon growers, who plant about 10,000 acres of the crop every year.

Watermelons in a field

Growers plant about 10,000 acres of watermelon every year throughout California, making the state the No. 3 producer of the melon within 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 was comparatively little analysis on the melon throughout the state.

“Watermelons appear to have attracted not an excessive amount of consideration in comparison with different cucurbits, each Extension- and research-wise,” mentioned Wang.

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

But watermelon growers wanted to verify the added expense of utilizing grafted vegetation would repay. They had been in search of science-backed proof that the method may really scale back prices total, whereas sustaining or boosting productiveness.

“Sometimes as farmers, we need to take a look at a brand new cultural apply or crop product,” mentioned David Jarrett, discipline supervisor at Van Groningen & Sons, who grows watermelons within the San Joaquin Valley. “An individual like Zheng can arrange a significant experiment and he has the instruments for qualitative and quantitative evaluation; Zheng is aware of how you can measure a hunch and assign it a verifiable quantity measuring success.”

In his first trials in partnership with growers in 2019, Wang examined whether or not they may plant less watermelon vegetation, spaced at larger distances aside, whereas producing a steady yield of high-quality melons. The concept was that grafted vegetation, that is extra vigorous and develops bigger leaves and wider canopies, would produce persistently marketable melons that might be picked as much as seven or eight instances throughout a prolonged harvest season.

“That method we are able to make one plant equal ‘two,’” defined Wang, noting that non-grafted vegetation has a tendency to provide solely two or three picks of excellent melons, with high quality declining quickly afterward.

Grafting reveals numerous potentials for the long run

Comparison of more robust grafted watermelon plants versus non-grafted

The extra strong grafted watermelon vegetation (on the correct) presents bigger leaves and a wider cover, in comparison with their non-grafted counterparts (on the left). Photo by Zheng Wang

After two years of trials, the growers decided, with sturdy confidence, that watermelons planted 4-5 toes aside may produce a yield equal to – or surpassing – that of the vegetation 3 toes aside (the usual for his or her non-grafted counterparts).

According to Wang, growers reported that, on common, their efficiently grafted fields produced 15% to 25% extra watermelons than non-grafted fields per acre, whereas utilizing 30% less vegetation and an identical quantity of water and fertilizers.

With the potential for larger profitability, grafting might be a serious boon throughout a very difficult time for growers.

“California agriculture is pressured competing for finite sources similar to land, water, fertilizer, and different secure however efficient chemical instruments, however, the exterior of this realm we are able to enhance a few of our crops by grafting,” Jarrett defined. “Just as many tree crops are grafted, we’re studying that different crops may be efficiently grafted too; the aim is to create a heartier plant, which can develop higher in marginal soils with lowered inputs.”

Watermelon harvesting

Whereas non-grafted watermelon vegetation yields two or three picks of high-quality marketable melons, grafted vegetation may produce as many as seven or eight picks throughout a prolonged harvest season. Photo by Zheng Wang

Confidence in the method has led to a big enhancement within the planted acreage of grafted watermelon throughout California – from lower than 250 acres in 2018 to greater than 1,500 acres in 2021. At the identical time, growers have adopted 4 or 5 toes as the brand new “normal” spacing for their watermelon vegetation, enabling them to scale back their populations whereas sustaining or boosting yield.

“Using grafting has the type of opened a brand new channel within the watermelon world, and for all vegetable manufacturing in California,” Wang mentioned.

Next up for Wang is testing numerous mixtures of scions and rootstocks. During these 12 months, he started selection trials with rootstocks of varied cucurbit relations (like hybrid squashes, Citron, and bottle gourd), with hopes of manufacturing outcomes that watermelon growers may use to determine the perfect choices for their native circumstances.

“In sum, there are numerous unknowns – but additionally numerous potential for the long run,” he mentioned.