The new code replaces a Scottish code of good agricultural practice issued in 1985, and has a greater legal significance than its predecessor.
In the past, a farmer charged with a water pollution offence could not be convicted if he could demonstrate that he had complied with good agricultural practice. This statutory defence was removed by the Water Act 1989, under which a breach of a statutory code is not itself an offence but may be taken into account in legal proceedings.
The code has a double significance in that the Scottish river purification authorities (RPAs) are now obliged by section 51 of the Control of Pollution Act 1974, as amended by the 1989 Act, to take into account whether there has been or is likely to be a contravention of a statutory code in determining whether to exercise powers conferred on them by section 31.
Regulations were made last year under section 31 to introduce minimum standards for slurry, silage and agricultural fuel oil stores. In general, these apply only to new installations, but where an RPA considers that an existing store poses a significant pollution risk then it may order a farmer to upgrade it to the standards set for new installations (ENDS Report 193, pp 35-6).
In England and Wales, a code on water pollution from farms was given legal force last July. The same step has now been taken in Scotland, and the new code has statutory backing from 27 March.
However, only those features of the code dealing with water pollution have a statutory status. Other sections dealing with air pollution and soil protection are purely recommendatory. These issues are to be dealt with in separate codes south of the border.
A draft code dealing with air pollution from agriculture in England and Wales was published last summer. It dealt with issues such as odours and smoke pollution and ammonia emissions from livestock housing and slurry spreading. The section dealing with ammonia - a major cause of environmental acidification - appeared unlikely to be effective because it treated the gas as a cause of odour nuisance rather than one which required abatement even when no odour complaints occurred (ENDS Report 199, pp 33-4).
The Scottish code recognises this as an issue, advising farmers to take steps to minimise ammonia emissions even in remoter locations where odours associated with slurry spreading are unlikely to attract public complaint. However, in the absence of any statutory controls, it must still be open to doubt whether farmers will feel impelled to introduce ammonia abatement measures when the environmental damage caused by the gas is insidious, long term and dispersed.
The code's advice on soil protection is confined to three pages dealing with water and wind erosion, flooding, contamination by sewage sludge and other materials, acidification, and soil organic matter and nutrient status. It remains to be seen whether the separate code for England and Wales will address these issues in greater depth.
The Scottish code differs from its counterpart south of the border in that it takes account of the recently agreed EC Directive on nitrate in water (ENDS Report 205, p 35 ). This obliges Member States to draw up codes of good agricultural practice recommending practices which will protect waters against nitrate pollution, and the Scottish Office says that this has been done via its new code. However, additional measures may be needed in "vulnerable zones" liable to be affected by nitrate pollution if any are identified in Scotland.