It's still early for tomato harvest in most North Coast gardens, but it isn't too early for a second round of fertilizer. Savvy gardeners prepared soil weeks ago by digging in ample compost up to a foot deep before planting to get vegetable crops off to a good start. But as roots reached out beneath ground, they've already taken in a good deal of those nutrients. Now, they're ready for more.
Tomatoes are considered heavy feeders, one of a group of crops that produce most abundantly when provided with additional nutrients as fruit development begins.
Good fertility in the root zone is critical for flowering and fruiting plants since most mineral compounds do not move freely through the soil. They need to be below the surface where plant roots can access them.
Certain nitrogen compounds are an exception. Some — mostly those applied in liquid inorganic form — move with water and reach roots easily, but the downside is that over-fertilizing simply allows this nutrient to leach away.
The advantage of organic fertilizers is that nitrogen is held in compounds that stay in place until soil microbes slowly break them down for take-up by root systems.
Spreading compost as mulch around plants helps hold moisture in the soil, but most of the nutrients don't move very far underground. All it takes is a few probes with a trowel to work in the loose material followed by a thorough watering. Plants respond quickly, within a few days.
If you use granular or powdered fertilizers or liquid fish emulsion, they, too, are most effective in boosting production when worked into soil. Spread as a side dressing and cultivate 6 to 12 inches away from stems or in furrows between rows. Always follow directions on label when using packaged materials.
Other warm-season crops whose developing fruits respond with gusto after a second round of fertilizing include peppers, eggplants, corn, onions, and all types of squash family plants — squash and pumpkins, cantaloupe and other melons, and cucumbers.
Note that potatoes aren't as demanding as their tomato family relatives and are sustained by initial soil preparations without the need for a second application of fertilizer.
Anyone who has ever grown zucchini and other summer squash has learned that despite its appetite, withholding second helpings of nutrients reduces over-productivity, a legendary concern with zuchs.