CULTURAL VARIATION AND MYCORRHIZAL STATUS OF BLUEBERRY PLANTS IN NW OREGON COMMERCIAL PRODUCTION FIELDS

Authors: Scagel, Carolyn; YANG, WEI - OREGON STATE UNIVERSITY

Submitted to: International Journal of Fruit Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2003
Publication Date: 3/1/2004
Citation: Scagel, C.F., Yang, W. 2005. Cultural Variation And Mycorrhizal Status Of Blueberry Plants In NW Oregon Commercial Production Fields. 5:85-111.

Interpretive Summary: Blueberry plants form symbiotic associations with specific soil fungi called ericoid mycorrhizal fungi (EMF). These fungi can help the plant with the uptake of nutrients from different sources. In August of 2001, we sampled 55 fields in Oregon to assess the mycorrhizal status of blueberry plants under production conditions and to determine whether any relationships exist between field characteristics, root distribution, soil factors and level of colonization by EMF. We found that root biomass was lower in the upper 15 cm of the soil compared to the 15-30 cm depth however roots in the upper 15 cm of the soil were longer and finer than roots lower in the soil profile. Variation in root biomass, root length, and root type occurred with cultivar, field age, bed type, irrigation and mulch. Root colonization by EMF ranged from 0.5 to 44% of total root length. Average colonization was 22% with higher colonization occurring in the upper 15 cm of the soil where the majority of finer roots were found. Variation in root colonization occurred with cultivar, field age, bed type, irrigation and mulch.Blueberry cultural practices in western Oregon are highly variable. With the possibility of new cultivar releases and the broadening cultural practices to extend the growing season of blueberry, optimal production systems for blueberry need to be defined with the potential to decrease production costs by decreasing inputs (e.g. increasing nutrient use efficiency). The level of blueberry root colonization by mycorrhizal fungi has implications to the efficiency of fertilizer uptake in both organic systems and conventional production systems, and is an important factor to consider when assessing optimal cultural and fertilization practices for blueberry production.

Technical Abstract: Ericoid mycorrhizal fungi (EMF) form symbiotic relationships with roots of blueberry plants providing increased access to nutrients from fertilizers and soil. In August of 2001, we sampled 55 fields in Oregon to assess the mycorrhizal status of blueberry plants under production conditions and to determine whether any relationships exist between field characteristics, root distribution, soil characteristics and level of colonization by EMF. Variation in the soil characteristics, root type, root distribution and EMF colonization occurred with cultivar, field age, bed type, annual rate of nitrogen (N) fertilization, irrigation type, and mulch. Root biomass was lower in the upper 15 cm of the soil compared to the 15-30 cm depth and distribution of root biomass varied significantly with field age, N fertilization rate, and the time of 50% harvest. Root length was greatest in the upper 15 cm of the soil where roots were finer and smaller than at the 15-30 cm depth. Root colonization by EMF ranged from 0.5 to 44% of total root length with higher colonization generally occurring in the upper 15 cm of the soil where the majority of smaller, finer roots were found. Colonization increased with increasing plant age with highest levels of colonization in roots from the upper 15 cm of soil in younger plants and at the 15-30 cm depth in older plants. Root colonization by EMF in the upper 15 cm of the soil decreased with increasing N fertilization rate while root colonization at the 15-30 cm depth changed little with rate of N fertilization. Roots on cultivars that fruited early in the season tended to have higher levels of colonization than cultivars that fruited later in the growing season.