Tomatoes require gardening soil that is full of nutrients.
If you haven’t had your soil tested in the past couple of years, there is a possibility that there may be a calcium deficiency in your garden soils. A deficiency can be corrected by adding gypsum to your soil. Lime is another good source of calcium, but not usually recommended for our area because of the normally high pH in our soils, unless soil tests indicate otherwise.
When should I test my soil?
- When you start a new tomato garden
- When tomatoes aren’t performing well
- When tomatoes, their stems, or their leaves exhibit unusual coloration
- When tomatoes demonstrate abnormal growth
- Every 3-5 years, even if plants are producing, to check for changes in soil composition
Best soil for tomatoes
Tomatoes like their soil pH around 6.0 to 6.8. Briefly, pH is a measure of soil acidity or alkalinity. On the pH scale, 7.0 is neutral; so the range which tomatoes prefer is slightly on the acid side. By the way, that’s the pH range at which most vegetables grow best.
If your soil pH is too low (too acid), you’ll need to add lime to the soil to bring the pH back into the proper range. Gardeners in western states (and some areas of the east) often have high pH or alkaline soils and may need to add sulfur to the soil to lower the pH. Although lime and sulfur can be added to the soil any time the ground isn’t frozen, fall is a convenient time for many gardeners and gives slow-acting lime a chance to take effect.
Testing with a do-it-yourself test kit. The advantage to a kit is convenience – you can test quickly on your own. Many manufacturers offer a variety of soil test kits. You can also use an electronic soil meter to get pH readings and water content. Some electronic meters also check nutrient levels. An electronic meter is a good investment if you’d like to check pH and water levels regularly throughout the season. MVG stocks a variety of Rapitest soil testing kits.
Testing through a soil testing lab. Use a local lab if possible, because they will be familiar with soil content in your area. Most charge a small fee to provide you with a soil analysis from your sample. Check with your local cooperative extension service to find out about their soil testing services, obtain a pre-paid soil sample mailer, and get instructions.
What will a test tell me?
Do-it-yourself kits test mostly for three major soil nutrients – nitrogen (N), phosphorus (P), and potassium (K) – and check the soil pH level.
Most lab tests provide three categories of information:
1. Samples major nutrients: nitrogen (N), phosphorus (P), and potassium (K)
2. Samples secondary nutrients (sulphur, calcium, magnesium) and minor nutrients (iron, manganese, copper, zinc, boron, molybdenum, aluminum)
How to amend with nutrients:
Nitrogen
Nitrogen helps your tomatoes maintain healthy, green leaves. Yellowed older leaves and slowed growth indicate nitrogen deficiency. But when you apply too much nitrogen before fruit is set, stems become quite large, leaves are deep green and soft, and there are few if any flowers. Tomatoes need about 1-3⁄4 pounds of nitrogen per 500 square feet. Incorporate nitrogen into soil just before planting.
Good organic fertilizer sources of nitrogen:
alfalfa meal
blood meal
compost
feather meal
fish meal
legumes
leaf mold
Good inorganic nitrogen sources:
ammonium nitrate
ammonium sulfate
anhydrous ammonia
calcium nitrate
potassium nitrate
sodium nitrate
urea
Phosphorus
Phosphorus helps your tomatoes develop strong root systems, build disease resistance, and cultivate fruit and seed formation. Slow, stunted growth and reddening stems and foliage indicate a phosphorus deficiency. Incorporate phosphorus-containing fertilizers into the soil before planting, rather than sprinkling them on the surface.
Good organic fertilizer sources of phosphorus
bone meal
compost
Good inorganic phosphorus sources
rock phosphate
super phosphate
Potassium
Potassium helps promote growth and disease resistance in your tomato plants. Weak plants and slow growth indicate a potassium deficiency. In more severe cases, leaf edges will brown. An easy way to amend the soil is to add wood ash, which is 5% potassium. Best rate is about 10-15 pounds to a 300 square foot bed. Work in wood ash in the fall or winter.
Good organic fertilizer sources of potassium
wood ash
granite dust (also called rock potash) – slow-releasing leaf mold
Good inorganic potassium sources
potassium sulfate
rock sand
Compost
Compost is broken-down organic matter. It’s not particularly high in nutrients but it’s a fantastic way to improve your soil. Compost improves soil structure, increases its cultivability, aids in nutrient retention, reduces compaction, attracts earthworms, increases microbes, and protects plants from disease. Adding compost is the singular most important step you can take to preparing your soil for planting tomatoes. You can save money and make your own compost when you start your own compost pile at any time of the year.
MVG - Growing Sustainably Since 1984.