Influence of Water Deficits on Flowering and Boll Retention

G. Guinn and J.R. Mauney


 
ABSTRACT

Excessive moisture has been reported to favor vegetative growth at the expense of fruiting. We conducted experiments to determine the effects of soil moisture deficits at different times of the year on flowering and boll retention. Delaying the first irrigation sometimes increase early flowering rate, but not always. Sweep counts indicated higher numbers of Lygus hesperus Knight (lygus bugs) in years when delaying the first irrigation increased early flowering. Further, we found that numbers of lygus bugs tended to remain low until stressed plots were irrigated, and then they increased. We postulate that water deficit does not directly stimulate flowering, but that occasions of increase flowering may result from decreased insect activity in moderately stressed plots.

A severe stress did not immediately affect flowering rate, but then caused a severe and prolonged decrease in flowering. Flowering rate did not start to recover until about 3 weeks after stress was relieved by irrigation. We interpret these results to indicate that moisture deficit affects development of squares at an early stage, lot has relatively little effect an older squares. Water deficit also decreased boll retention, but the results were confounded by a strong effect of boll load on boll retention. Because stressed plants produced fewer flowers and lost bolls during stress before irrigation they had a smaller boll load. Therefore, during the part of the season when boll load was a dominant factor in boll retention, water stressed plants fewer to compensate by retaining more bolls just after irrigation than control plants. This compensatory increase in boll retention partially counteracted the loss of bolls just before irrigation and caused the season-long average rate of boll retention to be almost as high as for control plants. Yield losses were mainly caused by decreased flower production.



Reprinted from Proceedings of the 1983 Beltwide Cotton Production Research Conference pg. 61
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified Sunday, Dec 6 1998