The effects of cutting frequency on natural Glyceria maxima stands

Abstract

Reed sweetgrass, Glyceria maxima, (Hartm.) Holmb., is potentially suitable for concomitantly accomplishing wastewater nutrient removal and biomass production. In this study, the effects of two different harvest frequencies on shoot and rhizome growth during two consecutive years were investigated in two fertilized natural stands. Three plots (20 and 24 m 2) were used in each stand and were treated as follows; unharvested; two harvests per year; or three harvests per year. Harvesting two or three times per year affected the stands to about the same degree. The harvested biomass was significantly lower in Year 2 with 60 and 75% of that in the first year. In the harvested stands the rhizome biomass decreased significantly during the first year. There was a strong relationship between the amount of non-structural carbohydrates stored in the rhizomes in November of Year 1 and the number of shoots with basal diameter > 5 mm in June of Year 2. A lack of carbohydrates during shoot initiation seemed to result in thinner shoots. This effect may have been accentuated by a lack of N during late summer and autumn. During Year 1 the amount of N used for shoot growth was 40–80% higher than in the control plots, whereas in Year 2 the relationship was reversed. The results imply that harvesting G. maxima either two or three times per season will cause a decrease in shoot biomass even in highly productive stands. A sustained high biomass yield may be promoted by continuous application of nutrients, but this remains to be verified.