Title page for ETD etd-01292001-111740


Type of Document Dissertation
Author Ogutu, Maurice Okendo
Author's Email Address maogutu@vt.edu
URN etd-01292001-111740
Title Developing methods of strip cropping cucumbers with rye/vetch
Degree PhD
Department Horticulture
Advisory Committee
Advisor Name Title
Caldwell, John S. Committee Chair
Morse, Ronald D. Committee Co-Chair
Kok, Loke T. Committee Member
McKenna, James R. Committee Member
Taylor, Daniel B. Committee Member
Keywords
  • no-till
  • soil moisture
  • cover crops
  • economic analysis
  • cucumber beetles
  • natural enemies
Date of Defense 2000-11-20
Availability restricted
Abstract
The purpose of this research carried out in 1998 and 1999 was to develop methods for strip

cropping of cucumbers with rye/vetch and black plastic mulch. Effects of planting methods,

weed control measures, and cover crop management techniques on pest and beneficial insects,

petiole sap nitrate-nitrogen, soil moisture, yields and economic viability were assessed. Four

treatments, namely cucumber direct seeded in black plastic mulch on tilled bare ground

(conventional); cucumber direct seeded in black plastic mulch laid over incorporated rye/vetch

residue; cucumber direct seeded into no-till rolled rye/vetch; and seedlings transplanted into no-

till rolled rye/vetch, were evaluated in a randomized complete block design. Weeds were

controlled in half the plot by critical manual weeding and pre-emergence herbicides applied in

the other half in all treatments except the conventional system. Three-week interval staggered

plantings of buckwheat to provide flowers for adult beneficial insects were also evaluated.

Results obtained indicate that rye/vetch habitat is more attractive to beneficial insects than

cucumber beetles before rolling or flail mowing. There were higher densities of adult Diptera (an

indicator for Tachinid parasitoids) in both years and of Pennsylvania leatherwings in 1999 in

plots with rye/vetch than in plots with rye only before planting. Preferential attraction to adult

Diptera was not found after planting with no differences in cumulative densities between no-till

and black plastic mulch plots after rolling or flail mowing. However, adult Diptera densities were

positively correlated with cucumber yield, higher densities of cucumber beetles occurred in black plastic mulch than in no-till plots in both years, and bacterial wilt, transmitted by cucumber

beetles, was reduced in no-till in 1999. Similarly, rye/vetch habitat plots had a higher diversity of

Carabidae species (in both habitat areas and crop rows) before rolling or flail mowing, and

higher densities of Carabidae (in habitat areas), Staphylinidae (in both habitat areas and crop

rows) and spiders (in crop rows) after rolling or flail mowing. Black plastic mulch plots with flail

mowed, incorporated rye/vetch residues had higher petiole sap nitrate-nitrogen and higher early

season cucumber plant dry weights than in conventional plots; later in the season, the highest

petiole sap nitrate-nitrogen occurred in no-till plots. No-till had higher marketable cucumber

yield than plastic systems. The profitability of these production systems depended more on

differences in marketable yield than on cost differences. The plastic with incorporated rye/vetch

and no-till transplant systems were more profitable during early harvests in late July, while no-

till direct seeded and transplant systems were more profitable from early August onwards. The

three-week interval staggered planting of buckwheat led to conservation of beneficial insects,

and the second and third seeded buckwheat flowering periods coincided with the period vetch

had lost flowers.

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