Thursday, November 16, 2006 - 11:10 AM

Nitrogen Management During Establishment of Organic Peaches.

Roland D. Meyer1, Janine Hasey2, Karen Klonsky3, Pete Livingston4, and Anil Shrestha2. (1) University of California-LAWR Dept., One Shields Ave., Davis, CA 95616-8627, (2) University of California Cooperative Extension, Yuba City, CA 95991, (3) University of California Agricultural Ecomonics, One Shields Ave., Davis, CA 95616, (4) University of California Agcultural Ecomonics, One Shields Ave., Davis, CA 95616

The demand for organically grown fruit crops is increasing but supplying adequate nitrogen is challenging. Five double row-middle nutritional treatments were established in a 2001 planting of cling peach (Prunus persica (L.) Batsch cv. Klamt) orchard transitioning to organic production: subclover; soft chess + 45 kg N compost; subclover + soft chess; resident vegetation + 45 kg N compost; and resident vegetation + 90 kg N ha-1 compost. The compost was variable in nutrient (low N in 2003) and moisture (high in 2005) content and had a chicken manure base in 2002-03 and yard waste in 2004-05. Subclover and soft chess populations remained stable without reseeding while burclover populations peaked in 2004 in the treatments receiving compost. Only the May 13, 2002 soil nitrate-N concentrations were reflected in the July 30 leaf N levels. Subclover treatments showed a trend for higher cover crop dry matter yield and nitrogen content which resulted in tree leaf N levels at 26.7 g kg-1 or higher during the 4 year study. All compost treatments received sodium nitrate in 2004 and 2005 when leaf analysis showed borderline N deficiency (<25 g kg-1) in several plots. The subclover and the 90 kg N ha-1 compost treatments had the most rapidly growing trees: 94.4 and 90.0 cm2 in 2004 and 116.1 and 114.5 cm2 in 2005 respectively. There were no significant differences in yields, fruit size or firmness in 2004-2005; however, more brown rot damage was seen in the treatment receiving the most compost and sodium nitrate. Annualized cost per hectare for double row-middle nutritional treatments ranked from lowest to highest was: subclover + soft chess - $50; subclover - $53, resident vegetation + 45 kg N - $134, soft chess + 45 kg N - $138, and resident vegetation + 90 kg N - $204.