Iron requirement studies of navel orange trees in solution cultures

Abstract

Difficulties in controlling the supply of iron to citrus trees when grown in soil led the authors to use of nutrient solutions for this study. Twenty-four nucellar navel orange trees were grown for eleven years in individual tanks of nutrient solutions, out of doors. Eight of them were maintained at high-iron levels by regular additions of iron sulfate to the nutrient solutions. The remaining trees became iron deficient at various rates. Analyses of standard leaves, picked in the early fall season, provided a measure of the changing level of iron nutrition for each tree from year to year. The results show that, when the concentration of iron in standard leaves was 30 ppm or less for two consecutive years, the rate of tree growth and the numbers of fruit produced diminished. Fruit sizes were unaffected, except that in some years, fruit on irondeficient trees were somewhat larger than those on trees supplied with iron. Chemical differences in the fruit were slight except for iron concentrations. Fruits were lighter colored in iron-deficient trees. Iron deficit was also accompanied by loss of leaves and dieback of twigs. This obvious symptom may provide a useful measure of the severity of iron deficit.

Iron content during lime‐induced chlorosis with two citrus rootstocks

“…In certain conditions, the iron content in chlorotic leaves decreased to around 60 ppm, yet this retains within the optimum range (Chapman et al, 1940;Smith et al, 1950;Wallihan et al, 1967;and Errfoleton et al, 1978) and still superior to the value reported by many authors for chlorotic citrus plants. Thus Chapman (1939) reported an iron content of 20 ppm in chlorotic lemon (Eureka), and Wallihan (1955) found an iron content of 16-33 and 24-68 ppm in cases of extreme and moderate chlorosis, respectively, and a 42-137 ppm in healthy leaves of orange, laron and grapefruit.…”