School of Agriculture, Food and Ecosystem Sciences - Theses

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End date: 2005 × Start date: 2005 × Type: Masters Research thesis × Subject: Bhutan ×

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    Species composition of improved dairy pastures in Bumthang, Bhutan
    Wangchuk, Kesang ( 2005)
    Multilocation studies of forage mixtures since 1970s identified white clover, cocksfoot, tall fescue and Italian ryegrass as appropriate pasture mixture for Bhutanese temperate environments. To date, there has been limited evidence on the long-term sustainability of these mixtures in farmer managed environments. Forty-one grazed pastures and fifty cut pastures were sampled in the elevation range of 2500-3500 m asl. Species composition was expressed in terms of tiller/growing point density of grass and legume species. Tiller core technique was used to measure plant densities. Soil samples were collected from depth profile of 5- 15cm. The dried soil samples were analysed for P, K, pH and texture. Dairy farmers were interviewed to obtain paddock histories and information on defoliation management. The tiller density of cocksfoot was higher in cut pastures though cocksfoot was negatively associated with cutting frequency. Cocksfoot was negatively associated with white clover and Italian ryegrass for both cut and grazed pastures. Soil pH was negatively associated with pasture age. Negative associations between K and pasture age was observed for both cut and grazed pastures. White clover was positively associated with P in grazed pastures. Italian ryegrass was positively associated with P, soil pH and moisture in grazed pastures. Available P was negatively associated with elevation. Cocksfoot abundance in cut pastures has been attributed to cocksfoot being a well adapted hay type species. The lower tiller density of cocksfoot in grazed pastures may be the consequence of continuous grazing without adequate rest period. White clover is positively associated with available P due to white clover being a well known plant that requires adequate levels of available P. The positive association between Italian ryegrass and pH has been explained by the greater availability of P with increasing pH. A decline in the levels of available K in older pastures was related to repeated defoliation without K inputs to replace the losses.
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