Vegetable Garden: Nitrogen "Side Dressing"

CSU Extension Master Gardeners Notes 711 explains what is Nitrogen "side dressing" and how to use it in your garden. This information is provided to our readers for information purposes and we strongly suggest that you consult your master gardener or CSU Extension Services before application for best results.


 

Plant need for nitrogen varies. Beans, peas, tomatoes, and vine crops (cucumbers, squash, pumpkins, and melons) are examples of vegetables with a lower need for nitrogen. High nitrogen promotes excessive growth of the plant at the expense of fruiting.
Crops such as potatoes, corn, and cole crops (broccoli, cauliflower, cabbage, and kale) use large amounts of nitrogen and need supplemental applications during the growing season (referred to as side dressing). For example, home garden potatoes often show nitrogen deficiency from August into fall. Symptoms start as a yellowing of lower leaves and progress into a general browning and dieback of the vine. When nitrogen stress hits, potatoes become more susceptible to diseases, including early blight and verticillium wilt. [Table 3]
Table 3. Nitrogen Side Dressing of Vegetable Crops
Vegetable
Timing
Application Rate
(Based on rate of 0.1 lbs. actual N per 100 square feet)
Ammonium sulfate
21-0-0
Ammonium nitrate
34-0-0
Water soluble
fertilizers
Asparagus
1) early spring
2) at end of harvestseason
0.5 lbs. fertilizer per 100 sq. ft. (approximately 1 cup)
Sprinkle over soil and water in, OR place in furrow to side of plant. CAUTION: an over application will burn roots, stunting or killing plants.
0.3 lbs. fertilizer per 100 sq. ft. (approximately 2/3 cup)
Sprinkle over soil and water in, OR place in furrow to side of plant. CAUTION: an over application will burn roots, stunting or killing plants.
See label of specific product.
Water soil with fertilizer added to water. Low burn potential, but significantly more expensive.
Sweet Corn
1) 12” tall
2) one month later
Leafy green vegetables
3-4 weeks after emergence
Onions
3-4 weeks after emergence
Potatoes
Late-July to early-August
Tomatoes, peppers, and eggplants
First fruits 1” diameter
Cole crops (broccoli, cabbage, cauliflower)
1) 2-3 weeks after
transplanting
2) 4-5 weeks after
transplanting
See label for
specific
product.

 

Fertilizers commonly used in the home garden for side dressing include ammonium sulfate, ammonium nitrate, and water-soluble fertilizers such as MiracleGro, Peters, etc. Phosphate and potash fertilizers are best added in the spring or fall, when they can be cultivated into the soil.

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