Studies on Iron Chlorosis of Sugar Cane (Saccharum officinarum L.) at Metahara, Ethiopia: Soil and Plant Characterisation and Efficiency of Different Iron Sources

摘要

AbstractIn order to understand the nature and causes of chlorosis at Metahara Sugar Estate (8°53′N and 39°52′E) in Ethiopia, soil profile samples were collected from a ratoon field that exhibited chlorosis. From the same site, the first ratoon sugar cane leaf blades (+ 3) were sampled on the basis of the degree of chlorosis, and thus categorised into green, medium green, medium yellow and yellow. Soil sample analysis indicated that DTPA‐extractable Fe, Mn and Cu were adequate for normal plant growth in spite of an increase in CaCO3content. Moreover, the chlorotic leaves contained higher iron content than the green ones. Consequently, it is concluded that iron chlorosis of sugar cane at Metahara could be due to physiological inactivation of iron in soils and the plant.A field experiment was also conducted using sugar cane variety CO‐449 in order to select the most effective iron source to control iron chlorosis of the plant. The plots received the treatments of FeSO4, EDDHA and DTPA at three different levels each as foliar sprays. The untreated plots were used as control. The chemicals were applied on the first ratoon 3 weeks after harvest, and repeated a week after the first spray. Twenty millable canes from the middle two rows were sampled at 12 months for yield and juice quality determinations. Iron sulphate spray at 15 kg ha‐1increased cane length and commercial cane sugar by 33 and 44 over the control, respectively. The highest cane yield was secured by spraying DTPA at 1.80 kg ha‐1even though its recoverable sugar percentage was low. Not all sources of iron improved juice quality.Since FeSO4at 15 kg ha‐1was equally effective as the 30 kg ha‐1FeSO4, applications, the need to consider other than the currently used rate in the Estate is timely and