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Most of us are at least thinking about garden fresh tomatoes this time of the year. We all prefer to have delicious tomatoes from our garden. To attain the best tasting tomatoes it is important to focus on fertilizing your tomatoes to get delicious and quality fruits.

An article on "Fertilizing for Delicious Tomatoes," written by Dr. Rob Mikkelsen in Plant Nutrition Today, did a nice job of summarizing this topic. Below are some key points from his article that will be of use to our avid gardeners. Although it gets a little technical, you can catch the drift of what needs to be done.

"Managing soil fertility and application of plant nutrients, as per soil test recommendations, will influence the quality of the tomatoes and is essential to harvesting abundant, flavorful and nutritious tomatoes. A soil test provides an understanding of what nutrients are already present so the lab can provide the fertilizer and lime recommendations. Applying fertilizers without testing your soil, can cause imbalance of nutrients and will end up having plants that grow but doesn't produce any or much fruits. So remember, soil testing is the first step for growing quality tomatoes.

Tomato flavor preferences may differ depending on individuals. The intensity of flavor properties of tomato fruits is determined by the amount of sugar, organic acid content (citric, malic and total acidity) and the volatile compound composition. Normally, people find the best flavor to be associated with high soluble solids, high sugar and high acid content. Light has the most profound effects on fruit sugar concentration. This results in winter grown greenhouse tomatoes, having less sugar than field grown tomatoes produced in summer.

Effects of nitrogen (N), phosphorus (P) and potassium (K) on tomato quality: Research studies examining the effect of plant nutrients in tomatoes revealed tomatoes receiving enhanced NPK nutrition (150 percent) had fruits with better quality, color and market acceptability than the ones receiving standard NPK nutrition (100 percent). Many studies have shown P and K nutrition has positive effects on fruit sugar and acid content. High P application was shown to produce higher sugar content in tomatoes when compared to low P conditions. Supply of K has been found to increase acid content of tomatoes. Many studies have reported moderate N supply will improve tomato flavor, but excess N can harm the fruit favor. Heavy N and K fertilization can also have detrimental effects on fruit favor.

Research has shown when adequate K is supplied, tomatoes respond by producing more of the health promoting carotenoids and red lycopene which results in red color in tomatoes. Tomato variety selection, degree of ripeness, growing conditions and providing adequate plant nutrition are all important in producing tasty tomatoes with better flavor and appearance."

Supplementing tomatoes with nitrogen as the summer progresses is also important for keeping strong vigorous growth and dark green foliage, two traits making tomatoes leaves more resistant to foliar diseases. It will also help the plant to continue producing fruit, avoiding the August "swoon," which can often happen following stressful weather and a heavy fruit load. Fertilization should be made one to two weeks before first fruit ripening, two weeks after first fruit picking, and a month later. Many home gardeners won't supplement more than once; use of a time release fertilizer or a natural product like compost at first fruit picking is a good compromise.

Happy gardening!

Peter Sutter is a life-long gardening enthusiast and a participant in the MU Extension's Callaway County Master Gardener program. Gardening questions can be sent to [email protected]

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