Collected Evidence: Collected Evidence: Use mixed pastureWeeds: Two of two studies (both randomised, replicated trials, one also controlled) from the USA found reduced weeds in mixed compared to monoculture pasture. Pests: Five studies from North America measured pests including four randomised, replicated, controlled tests. One study found fewer pests and two studies found reductions in some pest groups or in some pasture mixes. One study found no effect and another found more pests, although the effect was potentially inseparable from grazing treatments. Crop mortality: One randomised, replicated study from the USA found no effect on forage crop mortality caused by nematodes.Yield: Two of five studies (including two randomised, replicated, controlled tests) from North America found increased forage crop yields and two studies found mixed effects depending on the crop type and year. One study found no effect. Crops studied were alfalfa, bird’s-foot trefoil, chicory, cicer milkvetch, clovers, fescues, oats, ryegrass, other grasses, other legumes, rapeseed and turnip.Collected, 30 May 2013 11:59:00 +0100Collected Evidence: Collected Evidence: Grow plants that compete with damaging weedsWeed weight and cover: Nine studies from Australia, Slovakia, the UK and the USA tested the effects of planting species to compete with weeds. All (including four replicated, randomised, controlled trials) found reduced weed plant weight or ground cover, although two found this only in some years or conditions. Weed reproduction and survival: Five studies (including three replicated, randomised, controlled trials) also found that competition reduced weed reproduction, survival or both. One of these found an effect only in one year only. Crops studied were clovers, fescues, ryegrass, other grasses and turnip.Collected, 30 May 2013 12:00:17 +0100Collected Evidence: Collected Evidence: Delay mowing or first grazing date on pasture or grasslandNatural enemy abundance: One replicated, randomised, controlled study found fewer predatory spiders with delayed cutting. Three studies from the UK (two of them replicated, randomised and controlled) found no change in insect predator numbers and one replicated study from Sweden found mixed effects between different predator groups. Natural enemy diversity: One replicated study from Sweden found a decrease in ant diversity with delayed cutting and one replicated, randomised, controlled study from the UK found no effect on spider and beetle diversity. Pests: One of two replicated, randomised, controlled studies from the UK and USA found more pest insects in late-cut plots and one found no effect. Insects in general: Four replicated, randomised, controlled studies measured the abundance of insect groups without classifying them as pests or natural enemies. One UK study found lower numbers in late-cut plots, while two found effects varied between groups. Two studies from the UK and USA found no effect on insect numbers. Crops studied were barley, bird’s-foot trefoil, clovers, fescues, rapeseed, ryegrass, other grasses and wheat.Collected, 30 May 2013 13:34:12 +0100Collected Evidence: Collected Evidence: Use grazing instead of cutting for pasture or grassland managementNatural enemies: Two studies (one before-and-after and one replicated trial) from Australia and the UK found grazing instead of cutting had mixed effects on natural enemies, with some species and groups affected on some dates but not others. One replicated study from New Zealand found no effect. Pests and diseases: One of five studies (including three replicated trials) from Australia, New Zealand, the UK and the USA found more pests, and two studies found effects varied between pest groups and sampling dates. Two studies found no effect on pests. One study found no effect on disease when grazing was used in addition to cutting. Pasture damage and plant survival: One randomised study found more ryegrass shoots were attacked by pests. One study found lower survival of alfalfa plants but another found no effect. Yield: One of four randomised, replicated studies (one also controlled) found lower yields and two found no effect. One study found lower ryegrass and higher clover yields, but no difference between clover varieties. Another randomised study found more ryegrass shoots. Crops studied were alfalfa, cock’s-foot, perennial ryegrass, other grasses and white clover.Collected, 18 Sep 2013 15:54:32 +0100
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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