AG 001 Lecture Notes - Lecture 21: Fenthion, Ammonium Nitrate, Hectare
8 Oct 2020
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Document Summary
It is carried out only in the crop that has been directly planted so as to achieve spacing of 8cm between two plants within the row. The thinned plants referred to as spring onions are used as vegetables in salads. Calcium ammonium nitrate at the rate of 250kg per hectare is recommended for topdressing onions. This is done 3 months after planting. These cause silvering and withering of leaves from the tips downwards. They are controlled by spraying with appropriate insecticides such as diazinon or fenthion. Characterized by oval greyish lesions with purple centres on leaves. Characterized by brown spores covering the leaves leading to death of the whole. The two diseases are effectively controlled by crop rotation and application of. Onions are ready for harvesting 5 months after planting. When leaves start drying the tops are broken or bent at the neck. This hastens the withering of the stems.
