Pasture production and evaluation in a lowland and hill area in North Wales II. Methodology

Grassland responses to shelter — a review

“…In Wales, monocultures of perennial ryegrass and white clover were examined at 4 h in small sheltered enclosures and in exposed plots more than 20 h distant (Alcock 1973;Alcock et al 1976). On a hill site, ryegrass did not respond to shelter in a spring with minimal moisture stress, but in a second spring with "increasing soil moisture deficits" a yield increase of 30% was recorded in ApriVMay.…”

“…In the same spring, shelter did not affect clover growth on a lowland site where the canopy of clover leaves was much denser. Alcock et al (1976) also examined ryegrass monocultures at distances 3-4 h, 7-8 h, and more than 20 h from a porous plastic mesh barrier. In early season (May), there was no improvement with shelter, but with dry conditions in mid-season (JuneIJuly) large percentage increases (up to 80%) were measured in sheltered plots, although overall yields were less than 1 t DM/ha.…”

“…Also, the largest gains have been made when swards are in a vegetative rather than a reproductive phase of growth. Maximum increases with shelter have occurred with an exponential phase of sward growth, before the leaf canopy intercepted all incident light, and when pastures were under some moisture stress (Alcock et al 1976). Such conditions may exist in rotationally grazed pastures in New Zealand, even with irrigation.…”

“…Wind is a key element in our climate and in our agriculture (Coulter 1973(Coulter , 1975, with wind energy rated as high to very high compared to other countries (Cherry 1976). It is likely that much of our hill land is windier than sites in Wales and Scotland, where shelter has improved grass growth (Alcock et al 1976;Russell & Grace 1979a). The preceding review and discussion reveal that do respond favourably to shelter, and many New Zealand farmers in windv localities believe that wind shelter does improve grass growth.…”