Slot‐seeding investigations. 5 The effects of simulated delayed emergence and propyzamide on the spread and growth of white clover in permanent pasture

Abstract The effects of delayed emergence of white clover (cv. Grasslands Huia) seedlings, following slot‐seeding during spring and early summer 1983, were simulated by sowing seeds at intervals into slots cut in turves of permanent grassland in soil‐filled tanks or in the field. The resulting spread and growth of the species were assessed during the following 15–18 months. The effects of propyzamide, a grass‐suppressing herbicide (at 0·2 kg ha‐1), were also investigated in the field. A delay of 10 or 18 days in the sowing of seeds in turves in the tanks reduced clover dry weight yield from 23 to 11 during 1983 and from 118 to 96 g (0·12 m)‐2 during 1984. Spread of stolons from the slots was also greatly delayed and effects persisted for at least a year. Increased clover growth on the earliest sown treatment more than compensated for a slightly smaller yield of grass. In the field, yields of clover from late summer 1983 until spring 1984 closely reflected the order of emergence. Afterwards, differences were less clear‐cut but the cumulative yield of clover until August 1984 of the earliest‐sown treatment was twice that of a treatment sown 20 d later. Effects of delayed sowing in summer 1983 were more pronounced on stolons than on foliage growth when measured in September 1984, with significant reductions in many stolon attributes even with 8 d delay in sowing. Application of propyzamide in autumn 1983 increased clover yield during 1984 from 1·7 to 3·0 and total herbage yield from 7·1 to 8·6 t ha‐1. The results demonstrated some of the benefits of rapid seedling emergence and of the use of a grass‐suppressing herbicide, but did not indicate any interaction between the two factors.