Bogash demos how to achieve quality in fresh market tomatoes

By DOROTHY NOBLE
AFP Correspondent

LANCASTER, Pa. ─ During Ralph Cramer’s latest Haygrove owners conference, Penn State regional horticulture educator Steve Bogash presented research on maximizing the quality of fresh market tomatoes.
“The single most important technique in growing great fruit is careful water management in the root zone,” Bogash reported.
Significantly, Bogash pointed out that defects including fruit cracks, shoulder checks, radial cracking and blossom-end rot result in serious losses in the number of marketable fruit.
However, properly balanced nutrients, mulches, irrigation management and high tunnels can decrease losses.
By reducing rain splash, high tunnels boost fruit quality. Also, the avoidance of spreading spores practically eliminates bacterial and fungal diseases.
But spider mites, whiteflies and powdery mildew still challenge fruits grown in tunnels.
Bogash said that erratic water applications causes more numerous cracked and split fruits. He noted that tomatoes can use up to two inches of water per week during fruit fill. A medium flow drip tape at 0.5 gallon per minute per 100 feet should run for about nine hours per week to apply one inch of water.
At both the flowering and fruit fill stages, Bogash said the potassium/nitrogen ratio (K/N) becomes critical. Pointing to a Southwest Michigan experiment, he found that a 2K to 1N ratio is necessary to produce quality fruit during fruit filling. That ratio will enhance fruit firmness plus reduce yellow shoulder as well.
Michigan researchers also found that one foliar application of boron at 25 pounds per acre reduced shoulder cracking; and in some, but not all, cases foliar calcium was also beneficial.
However, Bogash urged using caution when applying these micronutrients because excessive amounts cause fruit damage.
Mulches too can reduce fruit cracking due to better moisture control and less temperature variation between daytime and nighttime. Both organic and plastic mulches are effective.
Bogash emphasized that soil and plant nutrient analysis is essential for high quality fruit. He recommends preseason soil testing, followed by testing as the plants transition to flowering and fruiting.
“Keeping better records of irrigation running time as well as some type of soil moisture monitoring will also increase packout of top quality fruit,” he advised.
In his tests of yellow shoulder, Bogash counseled, “For most growers the best practices to prevent yellow shoulder will be to intensively leaf test tomatoes from first flower cluster for Ca, K+ and Mg levels.”
He pointed out the causes of yellow shoulder has baffled scientists for the last 30 years. He added that many believe that the interaction of temperatures above 90 degrees Fahrenheit, nutrition, genotype and virus may cause the disorder.
Also, cultivar susceptibility has not been conclusively researched.
Bogash concludes that tissue analysis can best determine deficiencies plus indicate corrective action to produce high quality fresh market tomatoes.