Effectiveness of the GAEC cross compliance standard Rational management of set aside (weed control through mowing) in assuring a minimum level of habitats maintenance

The cross compliance standard Rational management of set aside (weeds control through mowing) regards sowable lands subject to the withdrawal from production (set-aside) or voluntarily withdrawn from the production. The aim of this standard is: i) to ensure a minimum level of maintenance of habitats; ii) to allow the maintenance of the productive potential and fertility of the soil; iii) to prevent the uncontrolled spread of weeds. Experimental data demonstrated that rational management of set aside according to GAEC standard 4.2 is very effective in increasing soil quality and stabilizing the edaphic animal community in terms of biodiversity. On the contrary minor improvement are made by the standard in the inland areas and high hills and mountain areas, where long crop rotations are adopted and soils are mainly used for long lasting natural or artificial meadow. The rule appears to be ineffective and even not suitable to prevent the spread of weeds, as the only one mowing or mulching of the natural vegetation, made mandatory by the standard, does not prevent the spreading of unwanted seeds to neighbouring cultivated fields. According to many authors, to leave a land uncultivated for a long period of time is not a good agricultural practice. Natural vegetation cover which persists for a long period during the year is detrimental to the subsequent crop, because of the abundant seed production and consequent spread of weeds. At least two or three cuttings per year are needed to effectively reduce the spread of weeds, particularly in the presence of perennial species. Moreover, in order to avoid the spread of a single biological group of weeds, it is necessary to use different types of mechanical work in the course the year. Furthermore, the cutting period should be carefully chosen. Another suggested weed control practice is the use of doses of systemic foliar-absorption herbicides lower than the minimum quantity recommended and approved. In fact, in set aside land it is not necessary to completely dry out weeds, but it is sufficient to control the plant development in order to prevent the production of seeds. Cover crops and green mulching (mowing without residue removal) are other techniques that have been proposed in order to reduce the input of herbicides in no-tillage cultivation, without compromising weed control. Crop rotation is also a factor considered crucial to control weed populations. Studies on floristic evolution under Minimum Tillage or No-Tillage demonstrated that, to observe macroscopic changes, tillage should be reduced for 2-3 years at least. In an experiment conducted in Fagna (Florence) regarding the micro arthropods in the soil it was observed that significant differences exist between the abundance of animal groups. In particular, mulched set aside has a greater abundance of life forms than not mulched set aside, while the lowest abundance was observed in the ploughed soil. The increased abundance and richness of life forms observed in the mulched set aside plots, also evidenced by some diversity indices, can be explained by the increased amount of organic matter fragments left on the soil surface that ameliorate the edaphic microcosm.