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Effects of defoliation management on the productivity and clover content of irrigated perennial pastures

K.B. Kelly and A.R. Lawson

Department of Agriculture, Kyabram Research Institute PMB 3010, Kyabram VIC 3620

Perennial pastures in the irrigated region of northern Victoria generally are low in white clover (Trifolium repens) content despite clover being more advantageous for milk production than the normal companion grasses perennial ryegrass (Lolium perene) and paspalum (Paspalum dilatatum). This paper considers the effects of winter management on clover content and yield of irrigated pastures.


Defoliation strategies imposed were dependent on pasture type. In experiment 1, a paspalum dominant pasture last grazed in mid April 1990 was then either not defoliated (nil) or defoliated in late May, June, July or August to a 50 mm residual. All treatments were harvested at intervals from 16-40 days from mid September until April 1991, with composition and yield measured. In experiment 2, two frequencies of both winter (14 and 42 days) and spring defoliation (10 and 20 days) were imposed on small plots of white clover and perennial ryegrass, with structure, composition and yield measured until December.

Results and discussion

Winter defoliation increased clover content of paspalum dominant pasture in spring with no effect on pasture yield and no effect of the time when pasture was defoliated on either parameter (Table 1). However, after mid November all treatments had similar clover content, indicating that defoliation interval in spring-summer may need to be altered to maintain the increased clover content that can result from winter defoliation.

In ryegrass-white clover pasture, frequent winter defoliation increased the density of vegetative white clover buds (30% increase) and had no effect on ryegrass tiller density. Frequent defoliation significantly reduced DM production in both winter (35%) and spring (23%), with non significant trend towards increased clover content which was the main objective of this study. It is apparent from these preliminary experiments that winter/early spring is the time of year with most potential to influence clover content but the success of management strategies will be determined to a large extent by competition for light.

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