Adding nutrients to soil requires caution

Angela O'Callaghan

Thursday, Sept. 11, 2008 | 2:18 p.m.

Since there are at least three distinct planting seasons in Southern Nevada — early spring, late spring and early fall — now is certainly a good time to get started on planting the autumn crops. These would be those requiring fewer hours of sunlight, such as lettuce, spinach and other leafy vegetables. This is also the time to improve the nutrient levels in the soil, often by incorporating compost.

Compost, that terrific soil amendment, is what remains when dead plant tissue or animal manure has been broken down by microscopic organisms into what looks like fabulously rich soil. Because of its origin in living matter, compost is a fine source of nutrients for growing plants. Improving their nutritional level will help them to withstand many of the stresses they encounter, such as disease organisms, high temperatures and competition. In fact, some experts recommend adding compost to actually control plant diseases.

People who are not invested in gardening organically will often use fertilizers from a bag, bottle or box. These are perfectly good, and sometimes soluble fertilizers can provide a rapid boost to a needy landscape or garden. In general, however, I recommend using slow release fertilizers that offer a slower, steadier dose of nutrients.

The fertilizer, whether it is “organic” (compost) or “conventional,” should contain the major minerals, nitrogen, phosphorus and potassium. The package will have information on the concentrations of each, but there is no fixed amount or ratio for them. If a package says the contents are “all purpose” or “general purpose,” it means that the product is not formulated specifically for a certain kind of plant. There are fertilizers specifically designed for roses, tomatoes, turf grass and many more plants. Even among these, the formulations can vary wildly.

At times, however, adding a nutritional supplement like compost or fertilizer can actually cause problems for a plant. This occurs when two circumstances collide: the environment around the plant contains a high enough level of a disease organism and there is a sudden addition of nutrients. The same nutrients that are essential for healthy plant growth can be hijacked by disease organisms, to the detriment of the desirable plants, which then do not have the benefit of the fertilizer and have fewer resources to fight off disease pests.

Unpleasant as this scenario is, it is not an inevitable disaster. An avid, or even a somewhat blasé, gardener can take fairly easy steps to prevent this catastrophe. First, when preparing the planting area, make sure to remove all plant debris from the previous growing season. Too often, old dead materials are the sources of disease. Second, install only healthy plants. Finally, use dilute fertilizer solutions or compost tea, or small incorporations of new compost. Plants will tend to respond better than when they experience rapid peaks of fertilizer followed by long periods of limited or no fertility.

­Angela O’Callaghan is the area specialist in social horticulture for the University of Nevada Cooperative Extension. She can be reached c/o the Home News, 2360 Corporate Circle, Third Floor, Henderson, NV 89074, or [email protected].