It's ideal to change planting sites so that tomatoes return to a growing location only once every three years. Cool temperatures slow growth, as will shorter days. Tight spacing increases the incidence of disease and may reduce yields. Cultivate the soil, testing it for adequate calcium, phosphorus and nitrogen. Adequate soil calcium helps to prevent blossom end rot.
Adequate phosphorus ensures healthy flowers and fruit development.
Too much nitrogen causes abundant leaf growth at the expense of flowering and fruit formation. Overfertilizing can also cause a buildup of salts in the soil, interfering with normal nutrient uptake. With tomatoes, it's best to fertilize at planting and then at midseason with low analysis fertilizer containing 5 or 10 percent nitrogen. Avoid high nitrogen fertilizers that promote excessive top growth at the expense of fruit development. Make sure the soil receives annual additions of compost.