CHEMICAL PROPERTIES OF SOIL AS AFFECTED BY A SINGLE BURN OF ALFALFA STUBBLE TO CONTROL INSECTS
Southern Alberta growers often burn fields of seed alfalfa (Medicago sp.) prior to initiation of growth in the spring as apart of an Integrated Pest Management Program. The present study examined the effect of a single burn of the standing dead growth and debris of a 4-yr-old alfalfa crop in early spring, late spring, or autumn on various chemical properties of the upper 50 mm of soil. Burning led to small but significant increases in organic matter, NO3-N, NH4-N, available P, extractable K, EC, and pH levels immediately after the fire. The only measurable impact 1 year later was slightly higher (P < 0.05) organic matter, but after 2 years there were no differences in these levels. Even though this study portrayed a single burn event, thereby precluding predictions of the long-term effects of different fire regimes, the changes observed were only measurable for less than 1 year. If the burning of the alfalfa stubble is done every third year it is unlikely that this practice would be detrimental to the soil characteristics examined. Key words: Fire, pest management, organic matter, prescribed burning