Allelopathic effects of white clover 2. Field investigations in tussock grasslands

Abstract

Abstract Seed of white clover, alsike clover, cocksfoot, and perennial ryegrass was sown, and seedlings of white clover were transplanted into dry, intermediate, and moist sites in the presence of 0, 0.5, 1, 2, and 4 t/ha of air‐dried white clover shoot material, 0 or 50 kg/ha of Nand 0 or 3 g of PVPP per row metre. Four patterns of growth response were observed in relation to the addition of white clover shoot material: at an early stage a linear allelopathic depression; a late linear promotory stage presumably due to mineralisation; and a combination of 2 intermediate stages of promotion at lower rates and depression at higher rates, or depression up to intermediate rates followed by increase at higher rates. The relationship between the patterns is discussed. The autoallelopathic effect was the most depressive system found.