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UBC Theses and Dissertations

Seasonal distribution of herbage growth in the south coastal region of British Columbia in relation to management of grazing livestock Hunt, Derek Edward


The seasonal distribution of herbage growth has particular importance for the management of grazing animals since the major objective of most pasture utilization plans is to provide sufficient feed for continuous grazing for as great a portion of the year as possible. Providing a more even distribution of herbage production has obvious practical advantages. The main objective of this study was to examine the annual growth pattern of herbage in the South Coastal region of British Columbia as affected by cultivars, cutting management and fertilizer management, with the aim of extending herbage production in the fall and increasing herbage availability during the summer months. These investigations were conducted in plot trials at three different sites. Forage quality was also examined at two of these sites. In addition to these plot cutting trials an investigation into the accuracy of a height/density meter (disc meter) was conducted. The disc meter, and other similar non-destructive devices, have great potential as both research and farm management aids. The first plot cutting trial was conducted at Agassiz, B.C. and examined the productivity of two orchardgrass (Dactylis glomerata L.) cultivars, Prairial and Sumas and two perennial ryegrass (Lolium perenne L.) cultivars, Barlano and Norlea under two cutting regimes (low-infrequent and high-frequent). Annual yields averaged over the three years for low-infrequent (LI) cutting showed significant (P<0.05) differences between cultivars with the following ranking: Prairial (10,644) > Sumas (9,537) > Barlano (8,448) > Norlea (6,666 kg DM/ha). Annual yields averaged over two years for high-frequent (HF) cutting also showed significant (P<0.05) differences between the cultivars with the same ranking: Prairial (9,390) > Suinas (8,625) > Barlano (7,686) > Norlea (5,953 kg DM/ha). The same ranking of cultivars in terms of annual yield was obtained in each harvest year for both LI and HF cutting treatments. Annual herbage yields over the three years of the trial showed considerable variation in response to climatic factors. Average annual yields in 1984 (10,116) and 1986 (10,237 kg DM/ha) were not significantly different (P>0.05). However, yields in 1985 (5,916 kg DM/ha) were significantly (P<0.01) lower than 1984 and 1986 due to a wet, cool spring and exceptionally dry summer. Cutting regime did not have a significant effect on annual yields. There were no significant (P>0.05) differences between average annual yields under HF (7,914) and LI (8,824 kg DM/ha) cutting, nor were there any significant (P>0.05) differences in annual yields between cultivars due to cutting treatments. There was a tendency for LI cutting to produce higher yields than HF cutting for Prairial, Sumas and Barlano with the reverse being true for Norlea. Examination of productivity on a seasonal basis indicated differences in yield due to cutting regime, depending on the season. During the spring LI cutting produced greater yields than HF cutting due to the greater yields obtained from the longer regrowth period and lower cutting height (Reid and MacLusky, 1960; Bland, 1967; Anslow, 1967). However, during the dry summer months the reverse situation was observed with HF cutting producing higher yields than LI cutting. Sucli a reversal in yield is attributable to the dry conditions under which high cutting has been shown to produce more herbage than low culling (Janti and Kramer, 1956; Appadurai and Holmes, 1964). Under LI cutting orchard grass produced 34 and 46% of annual yield in the spring for 1984 and 1985 respectively and 52 and 40% of annual yield in the summer for the same two years. This distribution was changed under HF cutting with 21 and 36% of annual yield produced in the spring for 1984 and 1985 respectively and 65 and 50% of annual yield produced in the summer for the same two years. The situation was similar for perennial ryegrass. Under Ll cutting perennial ryegrass produced 53 and 58% of annual yield in the spring for 1984 and 1985 respectively and 25 and 30% in the summer for the same two years. Distribution of annual yield was more even under HF cutting with 28 and 35% of yield produced in the spring of 1984 and 1985 respectively and 63 and 50% produced in the summer of the same two years. Variation in the distribution of annual production was also evident between orchardgrass and perennial ryegrass. Both orchardgrass cultivars produced a greater portion of their yield during the summer, whereas both perennial ryegrasses produced a greater portion of yield during the spring and early summer. Growth curves were developed for each cultivar for both cutting treatments over all harvest years which indicate the variability in the seasonal distribution of annual yield attributable to climatic factors and which can be varied by cutting management and choice of cultivars. Another trial conducted at the U.B.C. Research Farm #2, Oyster River, examined the effect of split nitrogen (N) applications on annual and seasonal yields. Under regime I a total of 100 kg N/ha was applied in April. Regimes II, III and IV involved application of a total of 300 kg N/ha at varying times over the growing season. Application of 300 kg N/ha produced significantly (P<0.05) higher annual yields (mean, 10,228) than application of 100 kg N/ha (7,706 kg DM/ha). Annual yields produced under regimes II, III and IV were not significantly (P>0.05) different (10,248, 10,245 and 10,192 kg DM/ha respectively). The seasonal distribution of yield was affected by N application regime. Regime III produced a greater portion of annual yield during August (20.1%) compared to the other three regimes (mean, 13.4%) and application of 100 kg N/ha in August produced significantly (P<0.05) higher yields for regime IV (1,104) compared to the other three regimes (mean, 426 kg DM/ha). The August N application also produced significantly (p<0.05) higher yields in the following spring for regime IV (2,774) than yields obtained for regimes II and III (mean, 1,810) and regime I (1,341 kg DM/ha). Such yield improvements in the spring could have been due to improved root reserves and/or root mass produced from the August N application. Two other trials conducted at Abbotsford also examined cutting treatments and N application regimes. The cutting trial examined the yields produced by four cutting regimes examining: high-frequent (HF), high-infrequent (HI), low-frequent (LF) and low-infrequent (LI) cutting combinations. Annual yields were significantly (P<0.()5) lower for LF (6,721), HI (6,066) and HF (5,674) cutting regimes than the LI (8,207 kg DM/ha) regime. Low cutting (7,464) produced significantly (P<0.05) greater yields than high cutting (5,870 kg DM/ha) while there were no significant (P>0.05) differences between frequent (6,197) and infrequent cutting (7,137 kg DM/ha). Unlike the Agassiz trial, high cutting produced no yield advantage during the dry summer months due to the exceptionally dry period where growth stopped under all cutting regimes. The Abbotsford fertilizer trial examined split N application in a similar manner to the Oyster River trial. However, due to the dry summer there was little response to applied N throughout most of the summer and thus little variation in distribution of annual yield. Regimes II, III and IV involved application of a total of 300 kg N/ha and produced significantly (P<0.05) more herbage (mean, 5,584) than the application of 0 N under regime I (3,758 kg DM/ha). Annual yields did not differ significantly (P>0.05) between regimes II, III and IV. Results from the four cutting trials indicate that the annual and seasonal distribution of yield can be affected by management factors such as variety and cultivar selection, fertilization management and defoliation management. Forage quality was examined at both the Agassiz and Oyster River sites. Differences in forage quality were noted as a result of year, seasonal, cultivar, fertilization and cutting treatment effects. Investigations were also conducted to examine the use of a height/density disc meter to measure herbage yield. A significant relationship (P < 0.001) was found between herbage yield and disc height for vegetative growth but more mature growth, with stems and seed heads, yielded a poor relationship. The use and accuracy of the instrument is discussed.

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