Establishing peach trees for organic production in Utah and the Intermountain West

- Weeds not soil fertility is associated with stunted tree growth in organic peach in Utah, US.
- Birdsfoot trefoil grown in the alleyway reduces the need for weed management in establishing peach orchards.
- Mulches, cover crops and compost are associated with improved soil properties in peach orchards.

Adequate weed control and nutrient supply are critical for successful establishment of fruit trees. This is of particular concern in organic orchard establishment. In order to determine the best approach for establishing peach trees (Prunus persica L.) organically in climates characterized by hot dry summers and cold winters such as the North American Intermountain West, seven organic and three integrated and conventional treatment combinations were established in two first leaf orchards at the USU Kaysville Research Farm, Utah, in 2008 and 2009. Treatments consisted of different tree-row and alleyway mulch and fertilizer combinations. Compost or conventional fertilizer (16-16-16 and urea) were applied at a baseline rate of 4.9, 9.6, 19 g and 114 g of available nitrogen (N) per 1st, 2nd, 3rd and 4th leaf tree respectively and adjusted up or down on a plot basis based on tree growth. Compost was supplemented with a feather meal 13-0-0 fertilizer starting in year three to avoid over application of phosphorus (P) and potassium (K). Organic experiment tree growth was initially slowed by living and straw mulches present in the tree-row. By 2011, 3rd leaf trees were largest in treatments with Birdsfoot trefoil alleyways, despite considerable tree-row weed/living mulch pressure. In the integrated experiment, trees were larger in the compost plus conventional herbicide compared to conventional fertilizer and herbicide treatment. Paper mulch depressed tree growth in combination with both compost and conventional N sources, but more so in combination with compost and organic herbicide where weed control was moderate. Weed pressure not lack of N was determined to limit organic tree growth in this study. A trefoil alleyway may alleviate the need for intensive weed control when establishing organic peach orchards.