Starter Fertilizer

Many vegetable growers use starter fertilizers in their transplant water to give the plants a better start in the field. There are many factors that influence the response to starter fertilizers. Growers also need to consider the potential for salt injury to the transplant from the fertilizer.

The key nutrient in a transplant starter is phosphorus. In cool soils, it is difficult for the plant to take up sufficient phosphorus. We often explain this by saying that phosphorus is less available in cool soils, but a key reason for this is slow root growth, limiting the amount of phosphorus the plant can reach.

Nitrogen is of secondary importance in a starter fertilizer. A bit of ammonium nitrogen helps the plant take up phosphorus better, but too much ammonium can injure the young plants. A small amount of nitrogen in the starter can also improve early vigour.

Potassium is not an important nutrient in a starter fertilizer. A benefit could only be expected in soils with very low potassium levels. Potassium salts, like nitrogen, can cause fertilizer burn.

When comparing starter fertilizers, be sure to make your comparisons based on delivering equal phosphorus levels. It is also wise to invest in a handheld or inline EC meter. Keep track of the EC, or electrical conductivity, of your starter solutions through the day. Typically, the manufacturer's recommendations on starter concentrations should be followed, but half rates are generally used on very light soils with low organic matter, when the soil is dry, or when soil temperatures are above 18 degrees Celcius or 64 degrees Fahrenheit.

For those looking for more information, Ridgetown Campus is conducting a set of starter fertilizer research trials in tomatoes this season, on campus and at grower sites. You'll be able to learn more at the Ridgetown vegetable research open house later in the summer. The date will be announced later.

This has been Janice LeBoeuf, Vegetable Crop Specialist in Ridgetown, reporting for the Ontario Ministry of Agriculture, Food, and Rural Affairs.