5) Nutritional Sprays
Florida and California lead in the application of nutritional sprays on citrus and other fruit[7]. Vegetables, too, respond remarkably thereto[8]. I see no reason why nut trees likewise should not benefit from them, especially when other spray materials are used. Copper sulphate, zinc sulphate, manganese sulphate, magnesium sulphate, iron sulphate, cobalt sulphate and borax are all compatible with each other and with most other spray materials. Combination sprays seem to perform better, anyway, than single sprays, and the only objection would seem to be that some element is applied that is not deficient. It can be taken for granted, however, that nothing is wasted, even though the benefits may be invisible. Soils benefit in the long run from sprays. One element, even though not noticeably needed, may make another available or it may antidote toxicity of some element present to excess. Indirect results in all likelihood are always obtained.
In Florida, recommendations for spray applications to citrus are made annually[9]. They can be obtained from the Florida Citrus Commission, Lakeland, Fla. A typical formulae is as follows:
3-5 lbs. zinc sulphate |
3-5 lbs. manganese sulphate | per 100 gallons of water or
2-5 lbs. copper sulphate with | other spray material
equal amounts of lime. |
1 gallon of lime sulphur or 1-1/2 lbs. of lime is used for every 3 lbs. of sulphate of manganese or zinc.
Cherries, apples, plums are quite responsive to such applications, and I have seen the defoliation of prune trees in New York State corrected with a mixture containing:
Manganese 10% | All as metallic, in the form of hydrated oxides,
Copper 10% | and applied at the rate of 4 lbs, for the combination
Zinc 5% | material per 100 gallons.
Boron 1% | The addition of 2 lbs. lime is optional.
In California a manganese deficiency has been observed on English Walnuts[10], and 5-15 lbs. commercial manganese sulphate was used per 100 gallons of water during late May, through June, to correct this.
Sprays should be applied at ten day intervals until the deficiency symptoms no longer persist.
Plausible reasons for the somewhat quicker action of sprays than fertilizers may be furnished by two prominent authorities: