Mar 10, 2017

Agronomy & physiology WCRC Agro-physio-East-Austral-Africa WCRC1
Abstract                                                                         Back to Table of contents

Regular droughts in southern Africa reduce the available water for irrigation of agricultural crops.  Cotton in South Africa is mainly irrigated by centre pivot or other sprinkler type system whose efficiency in water distribution is poor under adverse conditions.  The aim of this study was to evaluate the response of cotton to drip irrigation and intensive management practices.  Three dripper line positions were compared in combination with two irrigation frequencies.  The third factor was method of nitrogen and potassium applications. This factorial trial was conducted annually from 1987 to 1992 on a red clay soil which contained 54% clay and 450 mm m-1 total water at field capacity.  Excessive vegetative growth was controlled with mepiquat chloride.  Irrigation requirements were determined by daily monitoring of the soil water content with a neutron moisture probe.

The means for seed cotton yield varied from 7569 to 8781 kg ha-1 over seasons compared to a best commercial yield of 4500 kg ha-1.  The daily irrigated plots received 800 to 900 mm water over the growing season and those irrigated at five day intervals, 650 to 700 mm.   There were no significant differences in yield with different placings of the dripper lines.  Good lateral water movement was obtained and a single dripper line could supply water to two adjacent rows on the soil type used. The cotton roots withdrew water to a depth of 1200 mm.  The fertilization practice had no significant effect on yield.  However, fertigation with either nitrogen, potassium or phosphorus proved to be easy, accurate and labour saving.


Cotton responded very well under drip irrigation and yield was 24-65% higher than sprinkler irrigated cotton at the same site.  The management inputs required for success were however also high.

On soils with similar lateral water movement characteristics as this clay soil, one dripper line can provide water for two cotton rows, and thus reduce the cost of the irrigation system by 40%.  Due to the high water holding capacity of the trial site, irrigation at intervals of a pentade yielded the same as daily irrigated cotton.   Fertigation of cotton was slightly inferior to the conventional fertilisation program.  However fertigation with either nitrogen, potassium and phosphorus proved to be easy, accurate and labour saving.  The affect of the applied treatments on fibre properties was small and over shadowed by seasonal effects.

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