HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Board, J. E. Articles by Boethel, D. J. Search for Related Content PubMed Articles by Board, J. E. Articles by Boethel, D. J. Agricola Articles by Board, J. E. Articles by Boethel, D. J.

Soybean Yield Reductions Caused by Defoliation during Mid to Late Seed Filling

Dep. of Agronomy

Alan T. Wier and David J. Boethel

Dep. of Entomology, Louisiana Agric. Exp. Stn., LSU Agric. Ctr., Baton Rouge, LA 70803

^* Corresponding author.

Little is known about soybean [Glycine max (L.) Merr.] yield response to defoliation during the last half of the seed-filling period (R6.3 to R7) and how it is affected by source/sink ratio. Because defoliating insect pests in the southeastern USA frequently attack soybean during this period, greater knowledge of yield responses to defoliation at this time would aid in making management decisions. Therefore, the objectives of this field study were to (i) determine yield losses to total defoliation near the temporal midpoint (R6.3) and three-quarter point (R6.6) the seed-filling period; (ii) determine if alterations in source/sink ratio affect this response; and (iii) determine yield component mechanisms responsible for the yield reduction. ‘Centennial’ soybean was planted in 1991 and 1992 near St. Gabriel, LA. Treatments were no defoliation (control), 100% defoliation at R6.3, and 100% defoliation at R6.6 arranged as split plots within high, normal, and low source/sink ratios during seed filling (main plots). Defoliation at R6.3 resulted in 40% yield reduction, whereas defoliation at R6.6 caused a 20% yield loss. Lower yield resulted from reduced seed size. Source/sink ratio did not affect this response. Smaller seed size in both defoliation treatments resulted partly from reduced seed-filling rate (28% less than control). Shorter effective filling period also contributed to smaller seed size, but this effect was influenced by treatments and years. In conclusion, 100% defoliation during R6.3 to R6.6 must be avoided to maintain optimum yield.

Received for publication January 20, 1994.

This article has been cited by other articles:

				J. E. Board, V. Maka, R. Price, D. Knight, and M. E. Baur Development of Vegetation Indices for Identifying Insect Infestations in Soybean Agron. J., April 4, 2007; 99(3): 650 - 656. [Abstract] [Full Text] [PDF]

				J. Timsina, K. J. Boote, and S. Duffield Evaluating the CROPGRO Soybean Model for Predicting Impacts of Insect Defoliation and Depodding Agron. J., January 1, 2007; 99(1): 148 - 157. [Abstract] [Full Text] [PDF]

				J. E. Board Soybean Cultivar Differences on Light Interception and Leaf Area Index during Seed Filling Agron. J., January 1, 2004; 96(1): 305 - 310. [Abstract] [Full Text] [PDF]