Gardening Articles: Care :: Soil, Water, & Fertilizer
The Tomato-Vetch Connection (page 2 of 4)
by Jack Ruttle
Vetch Better than Plastic-plus-Fertilizer
Both systems provide plenty of nitrogen for a tomato crop, and both mulches keep the soil moist and eliminate weeds. But the vetch mulch, combined with less tilling, steadily improves the soil structure and the number of microbes, worms and other soil organisms at work. The thick mulch also keeps the soil evenly moist and cool, so roots can explore it thoroughly in their search for nutrients. The healthier root systems are better able to make use of available water and minerals so yields are much higher.
Vetch produce plenty of nitrogen for tomatoes, between 150 and 200 pounds per acre. About half of that is available to the tomato crop the first year; the other half remains bound up in organic matter and is used by the crops that follow. The nitrogen in decaying organic matter becomes available slowly and steadily through the season, more when it's warm and less when it's cool, down to about 50° F.
Adding chemical fertilizers, on the other hand, doesn't improve the soil. Once rain or irrigation leaches them away, they're gone for good. With the plastic-mulch test plots (and on the bare-ground plots, too), nitrogen is applied once a week through drip lines buried two inches deep. That's a more efficient way to apply fertilizer than spreading it before planting, but even so, nutrients are delivered only in the zone that is wetted by the emitters. With the vetch-mulch system, the organic matter supplying minerals to the roots becomes part of the topsoil of the entire bed.