SOIL NITRATE LEVELS AS INFLUENCED BY APPLE ORCHARD FLOOR MANAGEMENT-SYSTEMS

Mulches are an alternative to herbicidal control of weeds in orchards. Mulches may affect soil nutrient levels and consequently alter tree g rowth, fruit yield, and quality. The objective of this study was to de termine the effects of cultivation, straw mulch, geotextile mulch, gra ss cover, a cover crop mixture of lupin and wild carrot, and manure co mpost mulch on extractable soil nutrients in two newly established dwa rf apple orchards in Quebec. In 1992, manure compost and straw mulches resulted in higher soil NO3--N and K relative to those levels under g round cover. Levels of soil NO3--N were related to soil water content under any particular mulch. Straw mulch resulted in high July NO3--N l evels and low September levels of soil NO3--N. Geotextile and cultivat ion treatments resulted in higher September NO3--N levels relative to July. Soil under manure compost tended to have higher P levels than so il under other treatments. There was little or no effect of mulch trea tments on extractable levels of soil NH4+-N, Ca, or Mg.