Masters Theses

Julie A. Hale

Date of Award

6-1987

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Carl E. Sams

Abstract

A spacing study utilizing broccoli (Brassica oleracea var. italica) was conducted at two locations in the spring and fall of 1984 and 1985. Rectangular and square spatial arrangements were evaluated using a central composite experimental design. Spacings ranged from 15 x 15 cm to 122 x 122 cm at 15 cm intervals. As spacing decreased, total yields increased, with maximum yields of 18,000 kg/ha predicted at the closest spacing tested. However, a high proportion of commercially undesirable heads (i.e., culls) were produced at the very closest spacings. Increases in spacing resulted in increased leaf number and size, sideshoot quantity and size and whole-plant size. However, leaf area index decreased as spacing distance increased. Plants grown at wide spacings also had larger heads, greater incidence of hollow-stem and a higher crude fiber content than those grown at narrow or intermediate spacings. The general conformation of plants was altered in response to changes in spacing. The narrowest spacings produced slender plants with elongated stalks, while plants grown at wide spacings were stocky and robust. No correlation was detected between plant spacing and mineral composition of leaf tissue, and no nutrient deficiencies were detected at any spacing tested. Soil moisture content was greatest at the wider spacings while leaf stomatal conductance was highest at the narrower spacings. At the wider spacings, leaf area per plant was ten times greater than at the narrowest spacings, while head size was only three times larger, indicating a lower horticultural production efficiency of heads per unit leaf area.

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