Undersown
Undersowing refers to the sowing of seeds of a second fruit together with the seeds of the main crop in the field . Undersown crops can be sown at the same time as the main crop or later into the existing main crop (or vice versa, see picture on the left). Only after the main crop (also known as the cover crop ) has been harvested does the undersowing grow, green the harvested field and counteract soil erosion by rooting . Due to the growing undersown crops, the topsoil , i.e. the most fertile and agriculturally most important part of the field, is less exposed to wind erosion ( deflation ) and water erosion ( denudation ).
Undersowing also refers to the sowing of seeds for the purposes of green manure or the production of animal feed under wooded areas, in tree nurseries, when growing vegetables or in viticulture.
Undersown crops are used in agriculture , agro-forestry and horticulture . The topsoil does not lie fallow due to undersown and the soil life ( Edaphon ) is promoted by plant exudation .
Effects
Due to the germination and growth of the undersown crops, active erosion protection can be achieved through soil cover (closed plant cover), especially in the case of woody plants that do not cover the ground due to wide row spacing (e.g. in viticulture ) or, accordingly, in the early stages of development, the main crops (e.g. maize ), but also in closer crops such as grain . At the same time , the groundwater is protected by binding nutrients that are difficult to adsorb from the soil (e.g. nitrogen from nitrate ). Furthermore, root penetration and cover through the undersowing effect an improvement of the soil structure through higher quantities of fine roots and thus also the bearing capacity of the soil , maintenance or improvement of soil fertility as well as displacement and suppression of weeds . Furthermore, the soil's humus balance can be improved by the decomposition of the residues of the undersown crops . It can also have positive effects on the local climate . The effects mentioned are also known from some mixed cultures .
The fact that the use of legumes results in a direct nitrogen supply to the accompanying main crop has not been proven as a rule. Rather, it is often a question of crop rotation effects of previously grown plants (previous crop ).
When cultivating forage plants as undersown crops, there is a developmental advantage over catch crops sown as stubble due to the earlier sowing time . Furthermore, in this case, work is relieved during the harvest time due to the omission of the work for sowing the catch crop.
material
In view of the competition with the cover crop, undersowing must be suitable for undersown crops, i.e. it must not deprive the cover crop of nutrients or soil moisture it needs or displace them, but also not be displaced by the cover crop. In part, the undersowing suitability is therefore also a breeding goal, e.g. B. Low growth of flat peas for undersown use in viticulture.
The selection of the plants to be cultivated as undersown thus depends specifically on the existing site conditions, the main crop (see there under the individual species) and the classification in the crop rotation . It must also be taken into account to what extent there are restrictions on the use of pesticides on the main crop in order to protect the undersown crops , or whether undersown crops can lead to harvesting problems for the main crop. In the case of grain, for example, undersown ryegrasses or clover have proven to be suitable, which, if the crop is managed correctly, do not lead to a loss of grain yield.
use
If the undersown crops are grown as green manure, they are usually chopped up after the main crop has been harvested and worked into the soil. If the undersown crops are used as feed, they are harvested at the appropriate time after the main crop has been harvested.
Mixed culture
As far as plants or their fruits from different "floors" are all to be harvested in a targeted and equivalent manner ( floor cultures ), see further under mixed cultures .
swell
- Bodo Frahm: BGJ Agricultural Economics . 4th edition, Ulmer, Stuttgart 1980/1991, ISBN 3-8001-1049-0 , p. 156
- Gerhardt Preuschen: Agriculture according to ecological laws . 2nd edition, Ecology and Agriculture Foundation - Verlag CF Müller, Heidelberg 1991/1994, ISBN 3-7880-9873-2
- Klaus-Ulrich Heyland (editor): Special crop production . 7th edition, Ulmer, Stuttgart 1952/1996, ISBN 3-8001-1080-6 , p. 74 ff.