ROOT DEVELOPMENT OF PERENNIAL GRASSES AND ITS RELATION TO SOIL CONDITIONS

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Abstract
Blocks of soil 7X1 in. were taken to a depth of 12 in. to determine abundance and rate of development of roots of pasture and turf grasses on a typical podzolic soil of the gray-brown forest soil group in New Jersey. The block of soil was transferred to a wooden form, trimmed, and the soil washed away. Kentucky bluegrass began root growth 2 weeks earlier than bent grass; new roots formed intermittently in bent grass during 40 days after it had ceased in blue-grass. Maximum weight of bluegrass roots occurred in May and that of bent grass about 2 weeks later. About 1/2 of the new root system is newly generated each spring. Practically all of the grass roots were found in the upper 9 inches of soil. Total weight of roots gave a high correlation with root weight below the layer of rhizomes, thus eliminating the necessity of separating roots and rhizomes in the first inch of soil. Hard fescue was the only one of 6 spp. of grasses that extended its roots below the depth of the furrow slice. The roots of all spp. declined rapidly in abundance between the 1st and 6th inch soil layers. Reduced root development below 6 in. was associated with greater soil acidity, lower available P, and lower C content, but this relation was apparently not one of cause and effect. Mowing twice weekly at 1/4-inch height greatly restricted root development of 3 bent grasses, the effect being most pronounced below the 3rd inch. The ratio of roots to tops was considerably lower than when mowed at 7/8-in. height. Under similar treatment, hard fescue eventually died. Cutting blue grass at 7/8-in. height twice weekly had no harmful effect upon the roots, but roots of red top were reduced. The root development of creeping bent grass cut at 1/4-in. length with 12 different systems of fertilization indicated that the residual effect of fertilizers on the soil is of great importance. Root weights were several times as great on plots with pH below 5.5 as on those with pH 5.8 or above, due, probably, to the accumulation of roots of previous years, the soil reaction not being favorable for their decay. The vigor of tops was inversely correlated with root abundance. Available P, organic C content, or abundance of lime could not be correlated with root development. Slowly available nitrogenous fertilizers permitted somewhat greater root development than soluble fertilizers supplying equal amounts of total N.

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