Effects of cutting height and nitrogen nutrition on growth pattern of turfgrasses
- W. A. Adams,
- P.J. Bryan and
- G. E. Walker
The effect of nitrogen supply level within the range 1 mM to 10 mM and cutting height within the range 1.25 cm to 7.5 cm on the growth of tops, yield of roots, tillering, and verdure were examined on cultivars of Lolium perenne L. and Poa pratensis L. Three dimensional graphs were used to illustrate the effect of the two cultural variables on the four parameters of turf grass development. Top growth was found to increase with increase in cutting height and nitrogen supply, except at the lowest nitrogen level where growth of both species was greatest at the lowest cutting height. This was interpreted as being due to a higher requirement for basal nitrogen turnover at higher heights of cut and indicates that the two cultural variables interact.
Root yields increased with cutting height but decreased with increase in nitrogen supply; the latter being opposite to the behavior of top growth. In both species, tillering was stimulated by increasing nitrogen supply between 1 mM and 4 mM at all but the lowest height of cut in Lolium perenne ‘S.23’ where it was depressed. Above 4 mM nitrogen there was either very little stimulation or a depression of tillering. No stimulation of tillering was recorded because of closer cutting except at the 1 mM nitrogen level in Lolium perenne S.23 where reducing the cutting height from 2.5 cm to 1.25 cm resulted in increased tiller numbers.
Examination of the total nonstructural carbohydrates (TNC) of Lolium perenne S.23 confirmed that stem bases are the main sites for fructosan storage. At higher nitrogen levels there was a more rapid turnover of carbohydrate for growth and therefore less TNC stored compared with low nitrogen levels where shortage of nitrogen prohibited carbohydrate utilization for top growth. Stored TNC was rapidly utilized for regrowth provided nitrogen was adequate. Even when large quantities were stored, substantial depletion was found to occur after 14 days regrowth in the dark.
On the basis of the experimental observations, two hypotheses were made to explain the growth responses of turfgrasses to nitrogen supply level and cutting height.
Top growth takes precedence over root growth when nitrogen is nonlimiting.
At low nitrogen supply levels, roots are relatively less nitrogen deficient than the tops to which little nitrogen is translocated. This is expressed in a change in root/shoot growth pattern. Additional index words: Total nonstructural carbohydrate, Basal nitrogen turnover, Verdure, Lolium perenne L., Poa pratensis L.
Copyright © 1974. . Copyright 1974 by the American Society of Agronomy, Inc. and the Crop Science Society of America, Inc., 5585 Guilford Rd., Madison, WI 53711 USA