Ten Comments on Vegetable Nutritional Quality

Published: November 1, 2010

A recent article in the Vegetable Grower News reviewed some work by two researchers on the nutritional quality of vegetables. (Gene Lester with the USDA-ARS and Don Davis, retired from the University of Texas) It gave 10 rules of thumb for getting the most out of vegetables. One reason buyers want local produce is it is perceived as higher quality, and this is an important factor. They were as follows:

• There can be big differences between cultivars or varieties. Unfortunately, nutritional quality is not normally indicated or rated in seed catalogs.
• Produce grown on clay soil is usually higher in nutrients than produce grown on sand.
• Higher yields achieved by high rates of nitrogen fertilizer, irrigation (especially close to harvest) or choice of variety can result in produce with lower levels of nutrients or poorer quality protein, an effect known as dilution.
• Crops grown in the fall are nutritionally better than those grown in the spring.
• Foliar fertilization with calcium and potassium during fruit growth produces firmer, more flavorful fruits and vegetables.
• Over-fertilization with nitrogen is generally detrimental to produce quality.
• Color intensity is a good indicator of nutritional value.
• Riper is better.
• The larger the fruit or vegetable, the more nutritious it is in general, perhaps because it is more mature.
• Harvest time affects nutrition. Cooler morning hours provide a more nutritious fruit or vegetable.

For the potassium spray, application was made starting at fruit set until harvest. A solution of 800 ppm or 0.08% potassium (as potassium chloride) applied with the regular fungicide and/or insecticide applications was a minor product expense and no additional application cost.