Saturday, 15 July 2006

Effect of Foliar Application of Iron and Sulphur in Alleviation of Iron Chlorosis in Acid lime (Citrus aurantifolia, Swingle).

Pravinchandra C. Patel, Main Forage Research Station, Anand Agricultural Univ, Anand-388110(Gujarat State), At and Post. Khetiwadi, Anand, India

Iron chlorosis of plant is essentially prevalent on alkaline soils in arid and semi-arid areas as some sandy soils having low organic matter (Mortvedt, 1991). Iron chlorosis could be controlled by foliar spray of ferrous sulphate or iron chelates. Citrus (Citrus aurantifolia, Swingle) is an important commercial fruit crop of India. For alleviation of iron chlorosis and improving health and productivity of citrus plants various investigators (Barney et al., 1984, Levy & Horesh., 1984 and Fernandez-Lopez et al., 1993) have suggested soil/foliar application of organic and inorganic compounds. Synthetic chelates are generally most effective Fe sources for soil and foliar applications (Mortvedt et al., 1991). Several S products are reported to lower soil pH and act as reducing agents to convert ferric iron to more readily available ferrous form (Tisdale et al.,1990).S products significantly increases leaf chlorophyll and active iron content of leaves and created a balanced nutritional environment and kept iron physiologically active for chlorophyll synthesis (Sahu and Singh.,1987).Iron chlorosis occurs in acid lime orchards grown in sandy soils of North Gujarat of India and many orchards failed due to iron chlorosis if proper preventive measures would not be taken up timely. Therefore, a field trial was conducted to understand the causes of Fe-chlorosis and to find out the effective foliar spray for immediate recovery of Fe-chlorotic plants. Forty trees of 16 years old acid lime of uniform growth and vigor having equal incidence of iron chlorosis were selected for the study. There were total 20 treatments including control. The treatment of Fe included different sources whereas S was taken from CaSO4. In case of iron, 4 levels of Fe (0.05, 0.10, 0.15 0.20 % Fe as FeSO4) were kept without neutralization (IS1 to IS4) and the other set of treatments with similar concentrations were also taken with neutralization by Ca (OH)2, (IS1N to IS4N). Additional two treatments of Fe with 0.05 and 0.10 % Fe as FeSO4 mixed with 0.025 and 0.05 % citric acid, respectively were included (i.e., IS1C & IS2C).The chelated forms of Fe from two different salts were used with 0.05 and 0.10 % Fe (IE1A and IE2 A for NH4 salt of FeEDTA and IE1S and IE2S for Na salt of FeEDTA). FeCl2 was the third source of Fe in which two concentrations of 0.05 and 0.10 % Fe as FeCl2 were included (i.e., IC1 & IC2 ). In case of S, only two levels viz., 0.05 and 0.10 % as S as CaSO4 (CS1 & CS2) were kept. These treatments were compared with two controls i.e., distilled water spray (DWS) and no spray control (NSC) in randomized block design. The foliar sprays were applied thrice at an interval of ten days. The soils were loamy sand (Typic Ustipasmments) and soils have pH 7.6-7.9, EC 0.14- 0.16 dS m-1, CaCO3 2.7- 4.8 g Kg-1, 7.2-7.4 mg Kg-1 of Ca (H2PO4)2 (P-0.5 g L-1) extractable S, P2O5 24.3- 25.4 kg ha-1 and DTPA extractable Fe, Mn , Zn and Cu were 5.4-6.2, 18.4-24.0, 0.7-1.1 and 0.4-1.0 mg Kg-1 soil, respectively. The irrigation water contained 342 mg L-1 HCO3- ions. Fresh leaves were collected on 8, 18 and 60 days after the first spray. Active iron from the fresh leaf samples was extracted by the standard method. The treatment of 0.5 % FeSO4 with 0.05 % citric acid significantly increased fruit yield by about two times and increased significantly active iron, total Fe and S contents of the leaves by about one and half to three times over the control. It decreased significantly leaf sap pH. These treatments could effectively control the chlorosis. Citrate is a natural carrier of iron in xylem transport and citric acid mixed with iron sulphate and dissolved in water might have caused higher efficacy of IS1C and IS2C treatments. It also helps in translocation of iron from roots to shoots. Fruit yield was closely associated with the decrease in chlorosis (r =0.939**). Several reports indicate the positive effect on fruit yield in citrus due to foliar application of iron (El-Kassas, 1984). Similarly, positive effect on fruit yield of citrus due to S application was also reported by Malavolta et al. (1987). The chlorosis of acid lime grown on loamy sand soils due to high soil pH, lower concentration of active iron, total Fe and S in the chlorotic leaves, S deficiency in soil and frequent utilization of high HCO3- containing irrigation water. It could be cured by foliar spray of soluble salts of iron and sulphur. Further, results indicated that total iron content in leaves increased due to foliar application of iron which recovered iron chlorosis .The results are in agreement with those reported for citrus (Fernandez-Lopez et al., 1993).It is the fact that the Fe treatments increased the contents of total Fe by 3 to 4 times more than that of control suggesting a decrease in total Fe content in leaves as a possible cause for chlorosis. The results suggest that the spray of 0.1 per cent iron as ferrous sulphate in 0.05 per cent citric acid solution proved more effective compared to other treatments in controlling these iron chlorosis. Also, IS1C treatment, having ferrous sulphate (0.25 %) and citric acid (0.025 %), foliar spray can control the chlorosis of the citrus trees. Key words: Foliar spray, Fe and S sources, alleviation of chlorosis in acid lime, fruit yield.

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