Iron Uptake by Two Citrus Rootstock Species in Relation to Soil Moisture and CaCO₃¹

Abstract

Pot cultures were used to study the effects of soil water suction, presence of CaCO3 in the soil, and two species of rootstock, Citrus Aurantium L. and Citrus sinensis (Linn.) Osbeck, on iron uptake and iron sufficiency. Iron concentration in standard leaf samples was used as the measure of iron sufficiency; total leaf iron per plant was used as the measure of uptake. Iron uptake was proportional to the weight of the root system (r = .92) when water suction was varied; this supports the hypothesis that iron uptake from aerated soils depends primarily on contacts between root surfaces and iron‐bearing soil particles. Differences in iron uptake not accounted for by root size are described in terms of “root efficiency”, expressed as µg of leaf iron per gram of roots. Addition of CaCO3 to the soil markedly reduced the efficiency of sweet orange roots but affected that of sour orange roots only slightly, which suggests that the transfer of iron from soil to root involves two or more mechanisms that are differentially sensitive to CaCO3. Sufficiency of iron supply to the plants was correlated with root: top ratio (r = .73 when water suction was varied; r = .72 when both soil CaCO3 and rootstocks were varied). It is concluded that physical dimensions of the iron source (roots) and sink (tops) are important plant factors that regulate iron sufficiency in the plant.

Diagnosis and Remediation of Nutrient Constraints in Citrus

“…Earlier studies (Cooper and Olson 1951;Cooper and Peynado 1954) showed that citrus rootstock exhibited varied degree of chlorosis under field conditions on calcareous soils. Later studies revealed that under certain conditions, sour orange was still prone to chlorosis (Wallihan and Garber 1968;Levy 1984) with 'Washington Navel' orange as the scion (Levy and Mendel 1982). Hamze and Nimah (1982) observed symptoms of lime-induced chlorosis on sour orange rootstock on a soil containing 88% CaCO 3 .…”

Accumulation of nitrate nitrogen and other mineral nutrients in sudangrass as affected by applied nitrogen and iron

“…He concluded that chlorosis of plants growing in a calcareous soil was a matter of iron activity within the plant rather than a failure of the plant to take up iron from the soil. Wallihan and Garber (1968) found that when the level of iron nutrition was the controlling variable, root to top ratios of orange and rice plants responded inversely to the level of iron supply and were inversely correlated with leaf-iron concentrations.…”

Soybean growth responses and soil chemical changes resulting from applications of pyrite recovered from Iowa coal

“…to obtain meaningful soil test levels (Soltanpour et al, 1976) A number of studies have shown that Fe chlorosis of plants has been associated with relatively moist soil conditions (Burtch et al, 1948;Elgala and Maier, 1964;Lindsay and Thome, 1954;Mortvedt, 1975;Mortvedt et al, 1977;Olomn and Racz, 1974;Wallace et al, 1976b;Wallihan and Garber, 1968) . Zinc chlorosis in beans growing in rela tively moist soils has been observed (Khan and Soltanpour, 1978).…”

“…However, excess water also causes poor soil aeration and results in a lack of oxygen to plants which inhibits active Fe uptake by the roots (Lucas and Knezek, 1972). Low oxygen tension of highmoisture soils reduced the root system of orange seedlings, thus reduc ing their Fe uptake (Wallihan, 1961;Wallihan and Garber, 1968).…”

“…species, can greatly differ in their ability to absorb Fe from soils(Brown et al, 1972). Soil and management factors can modify the nature and extent of root system and significantly affect the Fe uptake within the same cultivar(Wallihan and Garber, 1968).Further, temporary unfavorable soil conditions may induce the de velopment of Fe deficient plant tissues which can persist after the causative condition has disappeared. At best, chemical soil tests can estimate only a few of these parameters such as low supply of Fe in the soils or pH.…”