Burning of alfalfa stubble for insect control as it affects soil chemical properties

Abstract

Southern Alberta growers often burn fields of seed alfalfa (Medicago sp.) prior to initiation of growth in the spring as a part of an Integrated Pest Management Programme. An 8-yr study compared the effects of (a) fall-burned every year, (b) spring-burned, prior to growth, every year, (c) spring-burned, prior to growth, every other year, and (d) zero burned, on various chemical properties of the upper 50 mm of soil. Burning led to highly significant increases in carbohydrates, total N, NO3-N, and extractable K over the 8 yr. Increases were also highly significant for NH4-N under the fall-burned every year regime. Spring-burning, prior to growth, every other year, led to the least accumulations of measured parameters. Although pest insects were controlled and pedigreed alfalfa seed production was increased under the various burn treatments examined within the conditions of the experiment, changes in certain soil chemical properties identified the need to monitor subsequent crop behavior once the alfalfa fields have been ploughed. Key words: Fire, prescribed burning, pest management, seed alfalfa