A comparison of nutrient removal by harvested reed canarygrass (Phalaris arundinacea) and ryegrass-clover in plots irrigated with treated sewage effluent

Abstract

Harvested plots of reed canarygrass (Phalaris arundinacea) surface-irrigated at 3-weekly intervals over 12 months with treated sewage effluent, produced similar dry matter yields, and removed similar quantities of nutrients, as plots of ryegrasswhite clover. The higher spring production of reed canarygrass was offset by much lower production in autumn and winter. Nevertheless, the reed canary grass maintained low NO₃-N levels ( < 3 mg/I) in the drainage water throughout the year, whereas levels under ryegrass-clover increased to as high as 18 mg/l in winter. The high levels under ryegrass-clover were caused by a continuation of mineralisation of soil N, and nitrification of the effluent NH4-N, at soil temperatures too low for herbage growth (< 5°c). It was concluded that reed canarygrass maintained low NO₃-N levels in winter by a continuing uptake of N by the plant's rhizome system. A corresponding decrease in CI in drainage under reed canarygrass suggested that N uptake during this period took place as NH₄-N rather than as NO₃-N.