Brown leaf spot disease and fertilizer interaction in irrigated rice growing on different soil types
Studies have been undertaken in a 1000 ha area of irrigated rice (Oryzica sativa) at Caroni (1975) Limited to determine the effect of the fertilizer programme on the incidence of important diseases. Over a period of three years higher levels of brown leaf spot (Cochliobolus miyabeanus) on rice varieties Oryzica 1 and Oryzica 5 on three different soil types were associated with increasing levels of leaf P, from a low of 0.149% of dry matter (DM) to a high of 0.396% DM. On the Washington silty clay loam series (Inceptisol) brown leaf spot incidence was lowest when leaf P was between 0.135% and 0.149% of DM. However, disease incidence was higher when leaf P levels fell to 0.133% of DM or rose above 0.149%, under conditions where N was more than adequate. The moderate levels of the disease experienced over the period had no effect on yield, as grain infection was minimal. The results support the conclusion that the incidence of brown leaf spot on irrigated rice at Caroni is influenced by sub-optimal levels paticularly of P. Careful monitoring and managememt of P nutrition is seen as an important part in the overall strategy for controlling the disease.
Crop losses caused by rice brown spot disease in mangrove swamps of northwestern Sierra Leone.
Abstract The rice brown spot disease caused by Cochliobolus miyabeanus (Ito et Kurib.) Drechsl. ex Dast. = (Helminthosporium oryzae Breda da Haan) is a key disease in mangrove swamp rice ecosystem in Sierra Leone. On average, grain yield losses of 8.2–23.0% were caused by the pathogen in mangrove swamps of northwestern Sierra Leone in the 1983, 1984 and 1985 cropping seasons. Disease attack was closely linked with adverse soil conditions and favourable meteorological factors of long dew periods and moderate temperatures. However, attack by C. miyabeanus at the reproductive growth stage of rice caused the most damage because of direct effect on the grains.
Acid sulphate soils : a baseline for research and development
Acid sulphate soils :a baseline for research and development , Acid sulphate soils :a baseline for research and development , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی