Wilson, Katherine Susan Louise (2011) Sorghum ratooning as an approach to manage covered kernel smut and the stem borer Chilo Partellus. PhD thesis, University of Greenwich.

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Abstract

A three-year study on the practice of ratooning of sorghum was conducted in Eastern Kenya (1999 to 2002), with emphasis on the stem borer (Chilo partellus) and covered kernel smut (Sporisorium sorghi Ehrenberg Link). Ratooning is the practice of stimulating tillering by cutting the old straw after harvest (Doggett, 1988). A six season on-station experiment in Machakos District showed the practice of ratooning short duration sorghum increased the reliability and yields in comparison to a direct sown with yield ranges of 1630-1778kg/ha and 0-148kg/ha, respectively. The higher number of heads and stems per unit area meant the ratooned crop had higher level of stem borers per unit area than the direct sown crop and when infected with covered kernel smut was a greater source of inoculum. Unlike the incidence of CKS, the number of stem borers had little correlation with the numbers in the previous season’s crop; there was no upward trend to the number of stem borers per stem during the experiment suggesting factors other than the presence of a sorghum crop have a stronger influence on the population. Yield loss was an interaction between cultivar*incidence of stem borers * stage of infestation * rain quantity and distribution, but rain was the most important factor. An on-station trial in Kitui (2001-2) found the ratooned crop outperformed the direct sown crop in yield by a factor of three and non-cutting of stems produced a similar yield to cutting back stems after harvest. The different ‘ratoon’ methods did not significantly affect the incidence of covered kernel smut or level of stem borers.

On-farm trials in Mwingi District (2000-2) showed that short duration sorghum ratooned outperformed direct sown sorghum. The timing of the cutting back of the stems had an effect on plant survival and yield; cutting back stems at harvest produced higher yields than cutting the stems at the on-set of rains, however cutting the stems at the onset of rains increased plant survival when the stems were dry at harvest. A decision tree was produced outlining the decisions a farmer needs to make when deciding whether or not to practice ratooning. Four factors were identified as important for varieties to perform well under the practice of ratooning: drought tolerance, stem strength, non-senescence and the ability to produce tillers during growth stage 3.

Item Type:	Thesis (PhD)
Additional Information:	uk.bl.ethos.549134
Uncontrolled Keywords:	sorghum ratooning, crops, agriculture
Subjects:	S Agriculture > SB Plant culture
Pre-2014 Departments:	School of Science > Natural Resources Institute
Last Modified:	13 Apr 2017 15:39
URI:	http://gala.gre.ac.uk/id/eprint/8053

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