Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Enviromental and Soil Sciences

First Advisor

Stephen A. Harrison

Abstract

Intensive cereal management (ICM) can optimize the yield and performance of winter wheat (Triticum aestivum L. emend. Thell.). Planting is often delayed beyond the optimum date along the Gulf Coast due to frequent precipitation. Field experiments were conducted at four locations in 1991 and two locations in 1992 to evaluate the effects of intensive management practices on performance of wheat planted at recommended and post-recommended dates. Seeding rates of 84 or 168 kg ha$\sp{-1}$ and topdress N rates of 90 or 90 + 45 kg ha$\sp{-1}$ were evaluated for an early and a late-maturing cultivar planted at a recommended date or 35 d later, with or without foliar fungicide application. Late planting resulted in significant yield loss even though more spikes m$\sp{-2}$ were produced. Yield loss for the late-planted crop was due to lighter and fewer kernels spike$\sp{-1}.$ Leaf area index (LAI) was unaffected by either planting date or seeding rate. Grain yield was not affected by seeding rate for the early-planted wheat. The seeding rate of 168 kg ha$\sp{-1}$ gave higher leaf rust (Puccinia recondita Rob. ex. Desm. f. sp. tritici) and Septoria leaf (Mycosphaerella graminicola (Fuckel) Schroeter) and glume (Leptosphaeria nodorum) blotch ratings, but increased grain yield when the crop was planted late by increasing spikes m$\sp{-2}.$ Additional spring N significantly increased yield of the crop planted at a recommended date by increasing grains spike$\sp{-1},$ but did not increase the yield for the late-planted crop. Additional spring N also increased LAI and absorption of photosynthetically active radiation by the crop planted at both dates. 'Traveler' gave higher grain yield by producing heavier and more kernels spike$\sp{-1}.$ 'Terral-101' produced higher LAI and spikes m$\sp{-2}.$ Fungicide application increased the yield of resistant and susceptible cultivar equally, despite the fact that the susceptible cultivar developed about three-times the severity of leaf rust as the resistant cultivar in the absence of fungicide. Bacterial streak (Xanthomonas campestris pv. translucens (Jones, Johnson, and (Reddy) Dye) was not affected by fungicide application, N, and seeding rate, while Septoria leaf blotch was only affected by cultivar.

Pages

101

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