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ROOT SYSTEM DISTRIBUTION OF HIGHBUSH BLUEBERRY 

 UNDER A SAWDUST MULCH 



R.E. Gough 

 Department of Plant and Soil Sciences 

 University of Rhode Island 

 Kingston, RI 



Even though vegetative and reproductive growth of plants is 

 very dependent on a functioning root system, relatively little 

 attention has been given to root system development in fruit 

 crops. This is certainly true of the highbush blueberry. Several 

 studies show that the root system of mature plants is shallow and 

 fibrous, but no one has studied its distribution in the soil. 

 Therefore, in 1979, at the University of Rhode Island we undertook 

 a study to determine the root distribution and general shape of the 

 root system of young and mature bushes of cultivated highbush blue- 

 berries. 



Six 13-year-old Coville and five 7-year-old Lateblue bushes 

 were growing on a Bridgehampton fine sandy loam soil at a pH of 

 4.8. Bushes were spaced 6 feet x 10 feet and the entire area 

 within and betxveen rows was maintained under at least 6 inches of 

 sawdust mulch for the entire life of the bushes. The sawdust was 

 a mixture of hardwood and softwood and was approximately 1-year- 

 old prior to annual application. The water table was at least 5 

 feet below the soil surface. Bushes generally were not irrigated. 

 Each bush received an annual application of 2 pounds of 5-10-10 

 fertilizer. 



Core samples containing roots were taken at different locations 

 around each bush and a trench was excavated completely beneath the 

 center and half way around 1 bush to determine the extent of vertical 

 root penetration and the regularity and the relative density with 

 which roots radiated from the crown. 



The dripline of all bushes was located approximately 2 feet 

 from the crown. In all cases, the bush crown, considered to be 

 that area from which new canes arose, was about 16 inches in dia- 

 meter. 



Findings 



The root systems were primarly composed of fine, fibrous roots 

 less than 0.1 inch in diameter. They were shalloiv and formed an 

 inverted cone of from 11 to 33.5 cubic feet in volume. Roots tended 

 to be primarily oriented parallel to the soil surface with very few 

 noticeable vertical roots. In no case were roots found in the unde- 

 composed layer of mulch. Fine, fibrous roots, intermingled with larger 

 roots, first appeared in the upper layers of partially decomposed 

 mulch. 



