Effect of organic soil amendments on the incidence of stalk rot of maize caused by Macrophominaphaseolina and Fusarium moniliformeFive organic materials, Cnlopogonium sp., rice straw, wood sawdust, fresh guinea grass and poultry manure, were added to soil in a field with a recent history of high stalk rot in maize caused by Macrophoniiw~ phnstdinn and F~s o r i i m uwni/i/oww, The two stalk rot organisms reacted difrerently to the organic amendments. All the amendments significantly reduced the incidence of Fu'uscirium stalk rot disease. Amendment of soil with fresh Cdopo~oniufl? leaves had almost no effect in controlling the incidence of Muc,ro/,/rorifina / J / I O . S~W /~J W , Organic amendment with poultry manure stimulated the disease. The other amendments appeared to be cyually cffective in checking the disease. Suppression of the disease appeared to be related in increased microbial activities.
Optimal growth and extracellular protease production by Aspergillus clavatus Des. was recorded at 30 degrees C and between days 5 and 7 of the 8-day incubation period. Purification of this enzyme was achieved by a combination of ultrafiltration, alcoholic precipitation and fractionation on DEAE-cellulose and Sephadex-G.200. A single peak of an alkaline protease was subsequently obtained with a 9-fold increase in specific activity and a final recovery value of 26.2%. The enzyme had optimal activity at 37 degrees C and a pH of 7.8. The enzyme did not degrade leucine amide, hippurylphenylalanine and hippurylarginine indicating lack of exo-protease activity. However, endo-protease activity led to a rapid hydrolysis of gelatin with optimal activity at 40 degrees C and pH 7.8. The high incidence of A. clavatus on Nigerian poultry feeds vis-a-vis the potential health risks posed to farm animals is discussed.
Six organic materials were added to the soil in a field recently showing a high incidence of brown spot disease in maize caused by Physoderma maydis. All the amendments lowered significantly the occurrence of the disease in comparison to the unamended control. However, the ability to suppress the disease differed substantially among the amendments. Rice bran and rice straw were most effective in this respect. The suppression of the disease appeared to be related to an increased microbial activity in the soil.
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