A farmer proves that men can quilt just as well as their wives in new children's book; Sam Johnson and the Blue Ribbon Quilt, by Lisa Campbell Ernst. New York: Lothrop, Lee & Shepard. 32 pp. $11. Ages 5-8.

Sam Johnson is a farmer with a healthy disdain for conventions. One evening, while his wife is away, Sam sets out to mend a tear in the pigpen awning. ''At first, just running the needle in and out of the fabric was hard work, but as the evening wore on, Sam became more expert. Soon he was having a fine time choosing patches of different shapes and colors.''

Sam's enthusiasm for his new craft leads him to join his wife's quilting club. To his surprise, his overture is rebuffed by the ladies. Sewing, it seems, is women's work. Undaunted, Sam rounds up the men of the county to form their own quilting club. Both clubs set to work to outdo one another, sewing quilts for the county fair contest.

Lisa Campbell Ernst, an experienced quilter with a university degree in design, has packed the pages of this four-color picture book with verve, perky characters, and cozy, turn-of-the-century detail. The pictures are enclosed in decorative borders that use authentic quilt patterns as their motifs. The story, although contrived, brings men and women to a happy, united conclusion, in one quilt and one quilting club for all.