Because Texas has such variability in its soil types, a single broad fertilizer recommendation is not applicable in all cases. The best means of determining your individual soil need is to have a soil test done by the Texas Agricultural Extension Service's Soil Testing Laboratory. Information on sampling techniques and prices is available from your county Extension office. Where soil tests are unavailable and a general recommendation is needed, use the following guidelines. Acceptable rates are 1 pound per inch of trunk diameter per year of age for trees up to 10 years old and 1 pound per 10 feet of row for blackberries and grapes.
Iron deficiencies are common on most of the alkaline soils in Central, South and West Texas.
Generally foliar iron sprays do not work well to correct iron deficiencies in fruit crops. Where iron deficiencies are a problem, do not use fertilizers containing phosphorus, as they usually make the problem worse. Do not spray other plants with zinc at the rates used on pecans since leaf burn and defoliation may occur. Zinc nitrate is least likely to cause burn to other plants in the landscape. When zinc deficiency is a problem on other crops, it can usually be corrected by soil applications of zinc sulfate.