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Making Drip Irrigation Cost-effective

The Tomato Magazine
Feburary 2005

DELTA, Ohio - Looking for ways to make drip irrigating field tomatoes more cost-effective, Jim, Jerry and Chris McDonnall of McDonnall Farms have been experimenting with fertigation. The 2005 tomato crop will be their second year experimenting with the process.

The McDonnalls grow approximately 250 acres of processing tomatoes in the Delta, Ohio area each year, along with field corn and soybeans. The tomatoes are contracted with Red Gold, out of central Indiana.

Jim and Jerry are brothers; Chris is Jim's son.

Dealing with Low Rainfall Years
In an effort to protect their tomatoes against short-rainfall years, the McDonnalls are using supplemental irrigation. Seventy-five to 100 acres of their tomato crop is under drip, an experiment that began four or five years ago and has been a big help, especially during low-rainfall years. A traveling unit is available for use in other fields. The growers prefer the drip but have struggled to justify its cost-approximately $100 per acre.

"After going to the expense of putting down tape, if we do get adequate rain, it's hard to feel good about the added investment," Chris admits. "You may only use the tape two or three times and, under such circumstance, it is difficult to see any bottom line advantage."

Looking for ways to make the investment more cost-effective, the family turned to their local supplier who suggested fertigating their crop through their drip system. At the dealer's recommendation, they also used Rootfeed™ and Harvest More Urea Mate™, products from Stoller Chemical Company, Houston, Texas.

The 2004 tomato crop was the first test for the experiment, and, despite a learning curve, the McDonnalls are optimistic about future benefits.
The drip tape now plays an enhanced role in their production tool portfolio, even when there is adequate natural moisture. There is no need for additional trips through the field during the year to make sure the crop is adequately fertilized.

Had Weed Challenge
The cultural practice in the past has been to plant the crop, wait a few days, cultivate and then side dress with a fertilizer application, Chris says. When fertilizing with drip tape, the recommended practice has been to place the tape immediately after planting to ensure needed moisture. However, the growers soon discovered that, under their circumstances, there were good reasons to do things differently. The recommendations they were following were based on fertigating through drip lines placed under plastic mulches.

"Our hope was that we could use fertigation to replace the early fertilizer side dressing applied in the past," Chris says, "however, when the drip tape was put down immediately after planting, it became impossible to cultivate between the rows."

Traditionally, the McDonnalls plant two rows of tomatoes, 18 inches apart, on raised beds. They would then wait10 days and lay the tape, positioned above ground, between the rows.

"For weed control, we like to cultivate between the rows with a shovel, when the plants are still small," he explains. "Unfortunately, last year, when we positioned the tape immediately after planting, we discovered we were no longer able to cultivate between the rows. You can't go after the weeds with a hoe for fear of cutting the tape. It was just too early to place the tape. We ended up fighting weeds throughout the season.."
Despite that learning experience, Chris says the family is optimistic that this coming season they can tweak the system and make things work. The first tomato plantings begin between the first and tenth of May, when there is less danger of a serious frost. The balance are planted through June 15 to insure the processor will have a continuous supply over the six- to eight-week harvest season.

Having learned from their experiences in 2004, the McDonnalls currently plan on planting the crop, according to the accustomed schedule, only reverting back to side dressing the crop for its early fertilizer needs. Following that, they plan to wait three weeks and then place the tape. That way, they can take care of the early cultivation and fertigate the crop through the tape through the balance of the growing season.

"Last year was not a wet year, but we still ended up with plenty of moisture," Chris remembers. "While we did not have to use the tape to augment moisture levels like you would during a dry year, we were able to use it to fertigate the crop. We saw a definite increase in yields in the fields fertigated, anywhere from four tons per acre to as high as seven or eight tons."

Tomato yields on the farm also vary from field to field because of differences in the soil as well as varieties grown, the growers note.
The McDonnalls acknowledge that 2004 was the first year in their on-going trial with fertigation and the use of Rootfeed™ and Harvest More Urea Mate™. The coming year brings with a new opportunity to see if the gains hold up.

Always Some Rain
"Most years here, we are going to get some rain," Chris points out, "and you may go two or three weeks without turning the pump on at all. After that, it's important to add some fertilizer, so you turn the pump on just long enough to push the fertilizer through the tape. Under such conditions, we're not trying to saturate the ground. Other years, however, especially if the ground is dry, we'll be putting water on constantly. The system operates in zones, and you may finish covering all of your zones only to find it's time to begin all over again."

Because there was good moisture in 2004, the tape lines were not used for irrigation that frequently, but, when they were, they also were carrying nutrients to the plants, Chris says.

With the use of irrigation, the McDonnalls typically see their tomato yields in the high 30-ton range. With certain varieties, it is not uncommon to achieve yields in the 50- and 60-ton range, but the overall average is generally in the high 30s.

"Some of the varieties we plant are not big yielders," Chris points out. "Most often, these are special varieties for whole packing, where the tomatoes are harvested, peeled and then diced. While the yields on these are lower, the processor compensates offering growers a higher return per ton."

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