Management options for increasing white clover contents of swards, without resowing

Abstract

Two field experiments were carried out at North Wyke, Devon in 1985 (Experiment A) and 1986 (Experiment B) to investigate the effectiveness of either cutting or rotational sheep‐grazing managements for raising the clover content of clover‐depleted swards. Subplots were pretreated in March with (a) propyzamide at 0·4kg a.i. ha‐1, (b) chlorpyrifos at 0·72 kg a.i. ha‐1 and methiocarb at 0·22 kg a.i. ha‐1, (c) carbofuran at 1·3 kg a.i. ha‐1, or (d) not so treated, in order to reduce grass tiller density, control insect and mollusk pests, or control all invertebrate pests respectively (a‐c), Carbofuran was not applied to swards that were to be grazed subsequently. The propyzamide pretreatment (a) significantly reduced the quantity of herbage dry matter (DM) grazed and the silage DM yields in both years, but raised the numbers of active clover buds, and clover stolon density and its weight in 1986, though not in 1985, The pesticide package (b) raised the quantity of herbage DM grazed in both years, and the silage DM yield in 1986, Carbofuran (c) raised silage yields in 1985. Neither pretreatment (b) nor (c) significantly affected clover performance. In comparison with sheep grazing, cutting showed a trend to higher DM yields, and significantly raised clover stolon density and weight in both years, and active bud numbers in 1986. The periodic sheep grazing management included recovery intervals of 14 d and 35 d. In 1986 (but not 1985) the longer recovery interval raised herbage DM consumption, but had no effect on clover development. The cutting management included nitrogen inputs of either 100 kg ha‐1 in March, or none. N input raised annual DM yields in 1986 (but not 1985) but did not affect clover DM yields or performance in either year. The experiments at North Wyke were supported by on‐farm experiments using exclosure cages at ten sites in 1985 and nine in 1986, in Yorkshire, Wales, the Midlands and Devon. In both years, application of propyzamide as in treatment (a) reduced DM yields (P<0.001) and raised the proportion of clover (P<0.001) in May harvests. The density of active clover buds (P<0.05), stolon density (P<0.001) and stolon weight (P<0.001) were increased by October. A combined carbofuran and methiocarb treatment significantly (P<0.001) increased herbage yields, but did not affect measures of clover performance. Unlike the main experiments, a comparison of grazing (outside the cages) and cutting management (within the cages) showed no effect on clover development. It was concluded that cutting, or rotational sheep grazing with a long recovery interval, would promote clover development in the clover depleted sward. Though successful in the overall assessment, application of propyzamide gave highly variable results on different sites and was not sufficiently reliable.

Long-term effects of pastoral fallowing on the distribution and performance of white clover (Trifolium repens L.) in a hill country pasture

“…Wilman and Acuna-P (1993) have shown that swards should be cut or grazed closely and regularly to promote branch development in order to encourage white clover competition with grass and raise the content of white clover in the pasture. By contrast, however, other studies of the effects of alternating grazing and/or cutting management on improving the growth and content of white clover in mixed swards found that, when longer recovery intervals (over six weeks) between defoliations was imposed in white clover-depleted swards, the clover content was raised without the expense of either reseeding or oversowing (Curll & Wilkins 1985;Sheldrick et al 1993). These conflicting conclusions may reflect the roles of different growth components, i.e.…”

Mixed Grazing and Climatic Determinants of White Clover (Trifolium repens L.) Content in a Permanent Pasture

“…The persistence of sward clover depends upon the effects of companion grass species (Chestnutt and Lowe, 1970; high position in the canopy from where it can intercept irradiation, and that resting for too long, or a wrongly timed rest period, can have deleterious effects due to shading by the grass component (Newton and Davies, 1987;Orr et al, 1990;Grant and Barthram, 1991;Sheldrick et al, 1993; Barthram and Grant, 1995). Curll and Wilkins (1985) found that timing of the rest period had no effect at low stocking rates, but at high stocking rates mid-or late-season rests were most beneficial.…”

Influence of the timing and duration of pastoral fallowing and nitrogen fertiliser on pasture and white clover (Trifolium repens) growth in hill country

“…However, the increase in main stolon growth by internode elongation can not compensate for the loss of secondary stolons, resulting in lower total stolon density (Nie et al 1996). Altering clover stolon growth behaviour and increasing stolon dispersion through pasture management such as fallowing or rotational grazing with a long recovery interval resulted in improved production and content of white clover in grass-white clover swards (Sheldrick et al 1993;Nie et al 1996Nie et al , 1997b. In this experiment, there was a trend for stolon density to decline in all fallowed treatments, but these treatments did not differ significantly from the grazed control at the end of fallowing (Fig.…”