By spreading sand one can make a soil less fertile. In the winter period a small quantity of sand, i. e. 1-3 m3 per 1,000 m2, is sprinkled over the meadow, very finely distributed, creating a thin film of sand on its surface. After a few years of doing so, the sod will become less fertile. If this method is consistently applied, a very poor turf may be created, with a relatively open sod. Moderately rich to richer soils may thus be made less fertile without creating disturbances. It also makes the turf more able to be trafficked when wet, which is advantageous for maintenance work.
Manuring
On poor soils, where older meadows have been maintained for a long time with the methods for making the turf less fertile, a point may be reached when the fertility becomes so low as to result in less free-flowering vegetation. Uncommon and even rare species with less conspicuous flowers enter the scene. On wet peaty soils, for instance, one will see an increase of Agrostis canina, Viola palustris, Ranunculus flammula and Carex nigra, which will start to form the main aspect. This will be at the expense of Lychnis flos-cuculi, Succisa pratensis, Ranunculus acris, Centaurea jacea, Lotus uliginosus, Briza media, Anthoxanthum odoratum and Rhinanthus angustifolius. Although this shift may be very interesting in a botanical sense, leading up to the development of unusual vegetation of high ecological or curiosity value, the manager has to take other aspects into account as well. Public green space is there for the public and should therefore be attractive, especially in residential areas. At the same time, the natural values being as high as possible are appreciated. A differentiated type of management may be the solution here. If the free-flowering aspect diminishes, it is time to reduce the measures taken to decrease fertility, and it may even be necessary to start fertilisation. It may sound strange to vegetation experts, yet this is nothing new, farmers used to do this all the time. Since one is striving for differentiation, one will manure carefully chosen spots, at the same time refraining from manuring other spots that have been chosen with the same carefulness. The method of manuring should have a limited effect, adding only a small quantity of fertilising material. A good method is the application of mud from an adjacent pond or ditch. This is applied in a thin layer, allowing the plants to push through easily. The layer should be a few centimetres thick, measured when wet and applied before winter. In many cases, however, one will use well-decomposed farmyard manure. The quantity to be applied depends on the local situation, but one should stay on the safe side and start with a small dose, 0.25-0.5 m3 per 100 m2. The manure is thoroughly shaken loose and distributed over the selected spots as evenly as possible.
Manuring may be repeated periodically, for example once every few years. The vegetation will indicate when it is required. That is why one should monitor the results closely in order to be able to plan the next step deliberately: continuing manuring or not, finding the right dose and the correct frequency There may be other circumstances inducing one to increase mowing frequency, for example in the case of flowery road verges. Exhaust fumes, litter and water ‘spray’ from the road may contribute to soil fertility considerably. Even on poor soils the quantity of nutrients available to the vegetation may reach such levels as to increase biomass production. This may lead one to bring the moment of mowing forward or even to increase its frequency. The November to December mowing round is brought forward to September, causing a greater reduction of soil fertility. Alternatively, one may change the single mowing round in September to two, one in July and one in October.
