|Plant Part and Time:||Most recent mature leaves adjacent to fruit cluster taken in mid to late summer but before final swelling of fruit.|
|Element and Sufficiency Range||Interpretation and Recommendations|
If the leaf N is between 1.65 and 2.15%, continue the present N fertilization program. Generally, 80-100 pounds N per acre (50-60 pounds applied in the spring and 30 pounds applied after fruit set) will maintain the leaf N within the desired range. If the leaf N is below 1.65%, apply 60 pounds N per acre after fruit set. If the leaf N is in excess of 2.15%, reduce the normal application rate by one half.
Phosphorus levels are generally within the sufficiency range. If the P level is less than 0.12%, apply 100 pounds P2O5 per acre in next year's fertilization program. If the P level is between 0.12 and 0.16%, apply 40-50 pounds P2O5 per acre in next year's fertilization program. If the P level is 0.16% or higher, P2O5 can be omitted next year.
Leaf K levels below 0.80% generally indicate low soil K or a heavy fruit set. If the K level is below 0.80%, apply 100-125 pounds K2O per acre next year. If the K level is between 0.80 and 1.20%, apply 40-60 pounds K2O per acre next year. If the K level is greater than 1.20%, K2O may be omitted from next year's fertilization program.
Low Ca levels are usually corrected by application of limestone based on soil test recommendations. Maintaining the soil pH between 5.5 and 6.0 will generally supply sufficient Ca to keep the Ca level within the sufficiency range.
If the Mg level is below 0.15% and the pH is below 5.5, apply dolomitic limestone based on soil test recommendations. If the soil pH is between 5.5-6.0, apply a soluble source of magnesium such as potassium-magnesium sulfate or magnesium sulfate (Epsom salt) at a rate to supply the equivalent of 25 pounds Mg per acre.
Manganese is generally sufficient due to sprays with Mn based fungicides such as Maneb.
Iron levels are usually sufficient.
If the B level is less than 15 ppm, broadcast 1/2 pound B per acre (5 pounds Borax or 2 1/2 pounds Solubor per acre) every two years. (Note: This can be mixed with water and sprayed on the soil surface). The boron requirement can also be met by spraying the foliage with Solubor at the rate of 1 pound (0.2 pound B per acre) per acre just prior to bloom. Do not exceed the suggested rates.
Copper levels are usually sufficient.
Zinc levels are usually sufficient.