Comparison of root‐ and shoot‐acting growth retardants on a grass/clover sward

Abstract

SummaryThe effects of six grass growth retardants, maleic hydrazide (±2,4‐D), mefluidide, paclobutrazol, EL500 and a mixture of mefluidide with paclobutrazol on a grass/clover sward were compared over a 3‐year period. Maleic hydrazide, which is the most commonly used retardant, gave poor levels of growth control except when used with 2,4‐D. Greatest growth suppression, a 38% reduction in dry matter production from May to July, was obtained from a mixture of mefluidide and paclobutrazol. Differences were observed between the effects of the shoot‐acting retardants, maleic hydrazide and mefluidide and the root‐acting retardants, paclobutrazol and EL500. Shoot‐acting retardants were less effective in wet weather and lasted for a shorter period than root‐acting retardants. They also increased compensatory growth after a period of growth suppression, and increased the proportion of clover in the sward.