Length of rhizome and depth of burial affects the regeneration of bent grass (Agrostis castellana Boiss. et Reuter)

Abstract

Renovation of pastures dominated by bent grass (Agrostis castellana), by killing the vegetation with herbicides followed by cultivation and re-sowing, according to current recommendations, can kill up to 95% of the bent grass. To improve the success of killing bent grass and reducing the likelihood of regeneration from rhizomes after renovation, the behaviour of rhizomes after fragmentation was studied in pots. Rhizomes were cut into different lengths (15, 40, and 100 mm) to contain 1, 3, and 8 nodes per section and planted at depths of 25, 50, 75, 100, and 200 mm in cultivated soil, with or without competition from establishing seedlings of perennial ryegrass and white clover. The proportion of bent grass shoots developing from buried rhizomes was reduced to <10% when rhizomes were broken into sections containing only a single node and buried at or below 75 mm. Even after 3 months burial, an average of 0, 0·2, and 0·4 nodes in 1-node, 3-node, and 8-node sections, respectively, were still viable after fragmentation and could potentially develop, should conditions change, ensuring regeneration. The presence of newly sown pasture did not affect either the development of nodes or the vigour of shoots of bent grass during the 3-month measurement period. Pasture production, however, was reduced with increasing bent grass shoot production such that 8-node sections buried at 25 and 50 mm produced up to 3 times more dry matter per pot than other pasture components, giving bent grass a competitive advantage.