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Tomato nutrition and grey wall – Is there a connection?

Is there a connection?

April 1, 2008  By Marg Land

The incidence of green core and grey wall were high in fresh field tomato production during 2005.

The incidence of green core and grey wall were high in fresh field tomato production during 2005.

According to various vegetable research findings, grey wall, which is described as a disorder that “results in irregular ripening, yellowing or internal browning of fruit” (Cornell University), is connected to increased cloudy and wet weather during the growing season. Because of this, the fruit does not ripen properly and vascular bundles form on the interior walls of the fruit, which then develop areas that always remain dark green and never ripen.


Dr. Ron Goldy 

There are also some vegetable researchers who believe high nitrogen and low potassium may also play a role in the development of grey wall.

Dr. Ron Goldy, a vegetable researcher with Michigan State University at the Southwest Michigan Research & Extension Center, Benton Harbor, decided to investigate different tomato nutrition regimes during the 2005 season and observe if there was any connection between the nitrogen and potassium rates and the incidence of grey wall and/or green core.

Plots were established, all of which were fumigated with 350 lbs. per acre of methyl bromide/Chloropicrin (67/33) and received preplant fertilizer applications of (per acre) 125 lbs. of 33-0-0, 250 lbs. of 0-0-60, 100 lbs. of Cal-fortified, which contains calcium plus micronutrients, 25 lbs. of sulphur and 10 lbs. of Solubar, a formulation of sodium borate.

The Mountain Spring transplants were set out in the field May 27 into black plastic with 5.5 feet between the rows and 1.5 feet between plants for a density of about 5,200 plants per acre.

The plots were subjected to varying nitrogen/potassium ratios of 1:1, 1:2, 1:3, and 1:4 at a rate of 0.5 lbs. and 1.0 lb. of nitrogen per acre. All treatments were applied on a per acre per day basis through the drip irrigation system from June 20 to September 12. Foliar CaNO3 was also applied four times during the season (July 28, August 4, 11, and 18) at a rate of 10 lbs. per acre.

Harvest was conducted seven times starting August 9 and ending September 26. Fruit was graded and incidences of grey wall and green core were evaluated randomly by selecting eight fruit from six harvests and examining them internally. Leaf nutrient analysis was performed at both nitrogen rates.

“Little significance was noted in yield or quality in Mountain Spring at either nitrogen rate,” reported Dr. Goldy, although he did add that a ratio of 1:3 and 1:4 at 1.0 lb. nitrogen did result in higher yields.

The experiment was also performed under a high tunnel management situation with similar results.

“This was the situation regardless of whether they were grown in or outside of the tunnels,” said Dr. Goldy. “Lack of differences may have resulted from lack of extreme nutrient levels, consistent moisture and lack of cool, wet, cloudy conditions during the growing season, all of which are reported to contribute to symptom expression.”

While he stressed a comparison between inside and outside of the raised tunnels was “not statistically possible,” Dr. Goldy provided the data anyway, showing that incidences of grey wall and green core were more plentiful when the tomatoes were grown in a raised tunnel environment. Higher yield, increased average fruit weight and a larger amount of Number One fruit were also recorded in the raised tunnel system.

“It was disappointing that little differences were noted in the incidence of green core or grey wall, or in the levels of nitrogen and potassium in the leaves,” said Dr. Goldy.

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