-5- 



The root system of 13-year-old 'Coville' plants extended in 

 measurable amounts up to 4 feet firom the perimeter of the crown, and 

 a few roots were noted regularly at distances of up to 6 feet. 

 Roots were recorded at depths of 32 inches on most bushes. 



Overall, approximately 50^6 of the root system was located 



within 1 foot of the crown, while 84^ of the root system occurred 



within 2 feet of the crown, which was approximately the dripline 

 of the bushes. 



The root system of a typical 7-year-old 'Lateblue' plant is 

 usually located iv'ithin less than 2 feet from the crown perimeter. 

 In only 1 instance were roots detected at a 2 foot distance and 

 these were within 11 inches of the soil surface and comprised only 

 0.311 of the total root dry weight for that bush. Roots v\'ere 

 occasionally found at depths of 32 inches within the first 1 foot 

 from the crown perimeter. However, most or all of the root system 

 (88-100%) of individual plants was located in the upper 14 inches 

 of soil. Virtually 1001 of the root system of these plants was 

 located within the dripline. 



Discussion 



Ihe shallo^^.' root system may be in part responsible for the 

 blueberry's ability to survive in swampy locations. However, the 

 general depth of the mature system coincides with those reported 

 for other crops such as apple, peach, cherry, grape and olive. 

 Depths can be expected to vary, however, depending upon soil type 

 and aeration. For example, apple roots have been reported to 

 penetrate to depths in excess of 32 feet in a well-aerated Nebraska 

 soil, while the roots of similar trees growing in deep loam soils 

 in California were found to penetrate to only half that depth. 

 Presumably, the root system of the blueberry can also vary greatly 

 as soil conditions are changed. 



Use of mulches certainly modified blueberry root distribution. 

 Our finding of an absence of blueberry roots in the upper layers of 

 mulch is similar to a report on apple root distribution. In a study 

 of the effects of various m.ulches and fertilizers on yield and sur- 

 vival of blueberry plants, Kramer et. al , in Maryland found remark- 

 able differences in root distribution under peat mulch as compared 

 to no mulch. They reported that the roots of 2-year-old 'Pioneer' 

 and 'Concord' plants spread approximately 35 inches from the main 

 stem but were limited totally to the upper 3 inches of mulch, while 

 those of the control plant spread only 12 inches but penetrated to 

 a depth of 9 inches. They reported similar but less dramatic results 

 with other mulches, including pine needles, oak leaves, and straw. 



This experiment indicates that the cultivated highbush blue- 

 berry plant posseses a shallow, fibrous root system that is primarily 

 distributed within the area between the crown and the dripline of 

 the bush. Fertilizer should therefore be placed beneath the dripline 

 of the bush and cultivation, if practiced at all, must be very 

 shallow in this area. 



