Citrus. Soil applications of chelated iron give promise that lime- 
induced iron chlorosis maybe reduced to a minor problem in the propaga- 
tion of young grapefruit trees on calcareous soils in the Rio Grande Valley 
in Texas. Some desirable rootstocks on which Texas grapefruit can be 
developed have demonstrated weak resistance to iron chlorosis on these 
soils. 
In these experiments, cooperative with the Texas Agricultural Experi- 
ment Station, soil-applied iron compounded with either DTPA or HEEDTA 
has benefited young grapefruit trees growing on Cleopatra rootstock. 
Young trees on sweet orange rootstock responded best to irén compounded 
with one of the newer chelates, EDDHA. The work is.preliminary. Cost 
of chelate treatments has not been determined. 
In the Coachella Valley in California, ARS scientists are comparing 
iron chelate treatments with iron sulfate, soil applied, as chlorosis pro- 
tection for citrus. The trifoliate orange is being used as a test plant be- 
cause it is particularly susceptible to iron chlorosis in calcareous soils of 
this area. These experiments indicate that the effective life of some che- 
lated iron compounds ina calcareous soil may be as long as a year and a 
half, whereas zinc sulfate may be effective as long as 3 years. Thus far, 
iron sulfate has given more overall benefit inlastingness and effectiveness 
than the chelates tried. However, as new chelates are being developed, a 
chelated iron treatment may yet be found advantageous for citrus in this 
type of soil. 
Blueberries. Preliminary experiments with blueberries indicate that 
these acid-loving plants can be grown successfully in mildly acid or even 
neutral soils, if chelated iron is applied to enable the bushes to get ade- 
quate water-soluble iron. 
Pecans. ARS scientists are making comparative tests of zinc chelate 
and zinc sulfate treatments for zinc-deficient pecan trees in Louisiana 
and Texas. Both types of treatment have corrected the deficiency symp- 
toms in one orchard for a period of 3 years and may prove even more last- 
ing. Zinc deficiency is responsible for the malnutrition disease known as 
pecan rosette, which weakens pecan trees and reduces their yields. From 
10 to 30 pounds of zinc sulfate per tree in acid soil areas, and 100 to 200 
pounds per tree in heavy alkaline or neutral soils may be required to cor- 
rect rosette. A chelated metal treatment might be advantageous if cheaper 
initially or more lasting. Rough figuring has indicated that a pound of 
chelated metal might have to do the work of 20 pounds of zinc sulfate to 
keep the initial price of one treatment comparable. 
For comparative tests,zinec chelate has been appliedto the soil around 
selected trees as water solutions at rates of 1/2 to 8 pounds of chemical 
per tree, while other trees have been given 20 pounds of zinc sulfate. 
In acid soils, some nearly neutral, 1/2 to 2 pounds of the chelated 
zinc have corrected the zinc deficiency in some young pecan trees upto 
os (OE 
