ARCHIVE: Set-aside and Environmental Benefits

Set-aside and Water Protection

Set-aside next to watercourses will help reduce the potential for accidental run-off or spray drift from agrochemical applications. They can also offer long-term solutions to LERAP regulations.

However, there is a danger that natural regeneration set-aside, through the lack of cultivation of the soil, may decrease soil infiltration, thereby increasing surface runoff, especially if heavy machinery has been used on the land. Nitrate levels in clay soils are decreased after development of a cover of natural regeneration, grassland or woodland. Nitrate leaching is greatest through bare soils in winter, so establishment of a good cover is required as soon as possible after harvest.

Riparian strips can be used to help protect water resources from contamination by nutrients and chemicals in agriculture (Cooper et al 1995, Peterjohn et al 1987). Poorly managed strips can have adverse effects on the quality of the water (e.g. shading out of the water channel by the growth of thick tree or shrub cover). Where as a well managed riparian buffer has been shown to act as an extremely effective filter for solutes and sediment entering the watercourse.

Long term effects of using a riparian zone as a filter are unknown. Although initially, the buffer vegetation acts as a sponge in removing nitrogen from the soil, rate of uptake must balance leaching rate in order for the filtering to remain effective in the long term. This method should be utilised in addition to, not instead of reductions in nitrate application on arable land. The biomass of the set-aside vegetation must be harvested regularly to ensure continued nitrogen uptake, and the riparian set-aside should be of sufficient width to absorb all the excess nutrients in the soil.

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