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White clover seed production in British Columbia

University of British Columbia

In the Creston valley in southeastern B.C., intermediate white clover is grown for seed and is a useful crop in farm field rotations. For several years seed yields have been declining, and despite good prices and markets, hectarage to white clover is declining. In 1976, work was initiated to determine some of the factors responsible for the decline in seed yield and hectarage. At the same time, an exploratory study of the genetic variation in the seed stocks of the valley was instituted in the hope that a Creston strain might be characterized or selected. In 1977, in the Creston valley, a series of replicated plots in six fields, representative of the edaphic, climatic and management regimes, were established to measure seed and forage yields and losses from multiple sources. At the University of B.C., four hundred individual plants representative of twenty sources, including some Creston sources, and encompassing substantial genetic diversity, were established from seed in replicated uniform nurseries. In an adjacent nursery one hundred and eighty Creston clones were established. Observation and measurement of a number of characters were taken on all plants several times during the growing season. Average clean seed yields on the Creston experimental plots ranged from 468-972 kgs. per hectare (418-868 lbs per acre). Farm yields of clean seed, by contrast, ranged from 262-491 kgs per hectare (240 to 450 lbs per acre). It was estimated that of the loss in seed threshed (dockage) , but not cleaned, 3-10% was insect damaged; loss attributable to farm harvesting procedures was estimated to reach 50%. Losses in the developing crop are difficult to assess quantitatively but appeared to be very serious. To offset these losses, in recent years, producers have been reducing the length of white clover ley and are now in most cases obtaining one seed crop only in the year after establishment; this practice, if carried on without counter selection, might result in a biennial habit. Three species of weevil appeared to be the most serious pests, viz. the clover root curculio (Sitona hispidula Fab.), and the clover seed weevil (Miccotrogus picirostris (F)) and the lesser clover leaf weevil (Hypera nigrirostris Fab.). The population peaks of the adults apparently occur at different times in the season. Currently only one aerial application of malathion is applied in June to control the clover seed weevil. Almost all roots examined bore signs of larval feeding, doubtless due to the clover root curculio; root nodules, abundant in spring, diminished rapidly as the season progressed. Measurements of nitrogen fixation, using the acetylene reduction technique and the Kjeldahl N-determination, were incomplete. Flower frequency and development, flower colour, leaf area, petiole length, leaf markings, plant height and weight, and prussic acid levels were some of the characters measured and observed on the individual plants, established in the U.B.C. nurseries from Creston and other sources. Not unexpectedly, the Creston stocks possessed a measure of distinction from most other stocks of intermediate white clover; nonetheless, there appeared to be ample variability in the Creston stocks within which to select strains to meet at least two needs of the region - viz. a) plants useful in the revegetation of ranges and of unstable soils, and b) plants well adapted to the arable long ley pastures of the humid and sub-humid areas.

Text

2010-03-02

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http://hdl.handle.net/2429/21376

Forestry

University of British Columbia

Graduate