Green manure refers to the targeted cultivation of plants to improve the soil in arable , fruit , viticulture and horticulture . Unlike useful plants , the plants are usually not harvested, but mulched or plowed in .
Effects of green manure
The cultivation of plants for green manure compensates for temperature fluctuations through the shading of the soil. At the same time, the impact of the raindrops is reduced, which counteracts silting up and crusting of the soil surface. The resulting improvement in the living conditions of the soil organisms improves the fermentation state of the soil and the growth conditions of the useful plants. Intensive rooting of the soil by the green manure plants and the promotion of the soil organisms that build up the crumbs improve and stabilize the soil structure; By cultivating deep-rooted plants such as lupins or sunflowers , even compaction in the subsoil can be combated. In particular in sugar beet cultivation of serving mustard or radish of the green manure also suitable for controlling in the form of nematodes ( Rübenälchen ) by biofumigation .
Green manure has only a few disadvantages, such as the additional costs due to the fact that the seeds usually fall during peak work times and possible problems when later incorporating the plant residues.
Green manure supports the formation of humus and counteracts soil erosion and the leaching of plant nutrients from the soil. Through the use of fast-growing plants can unwanted weeds and volunteer cereals are suppressed, an important function in connection with the no-till farming method direct seeding . When legumes such as peas , field beans , clover , vetches or lupins are grown , the soil is also enriched with nitrogen (the next crop to be cultivated has an additional 30-40 kg of nitrogen per hectare). Since fertilization with mineral nitrogen fertilizers ( artificial fertilizers ) is not allowed in organic farming , legume cultivation is an important source of nitrogen there. A study showed that in very dry soils, 30% more nitrogen can be absorbed by the plants in organic farming than in the conventional agriculture . This is because the soil organisms in organic farming can deal with drought stress better than the soil organisms in conventional agriculture.
In livestock farms, green manure crops can also be used as an additional source of fodder. The cultivation of clover is particularly suitable here due to the high protein content, which is essential in beef cattle husbandry. In addition, clover (a legume ) also contributes to nitrogen input into the soil.
Green manure crops and crops
For green manure, the following plant species are mainly used individually or in mixtures (e.g. Landsberger Gemenge ): cruciferous vegetables such as white mustard , rape or oil radish , legumes such as lupins , vetch or clover , grasses such as Italian ryegrass and other species such as sunflowers or phacelia . When choosing green manure plants, the intended crop rotation must be observed; the sowing of cruciferous vegetables, for example before the cultivation of cabbage, is not advisable because it encourages the spread of typical diseases such as cabbage hernia .
If the green manure plants such as Phacelia collapse during the winter cold period, i.e. freeze off, the plant residues can either remain as a layer of mulch on the soil surface after the winter or be worked under. In the case of hardy species, on the other hand, it is common to work under them before the onset of the cold period or at least to shred them with a mulcher, for example , so that the green manure plants are prevented from growing in the next crop in the coming vegetation period.
The cultivation of green manure can be used as main crop undersown or time between the actual main crops as intercrop done. However, cultivation as the main crop, i.e. without an actual harvest in the year of cultivation, is only common for new soils to be cultivated ( e.g. recultivation areas ).
- Schlipf: Handbuch der Landwirtschaft , 32nd edition, Paul Parey, Hannover 1958, p. 81.
- Nadine Baumgartner: Organic soils suffer less from drought stress. In: bauernzeitung.ch. November 21, 2018. Retrieved November 21, 2018 .
- Annie Francé-Harrar : The last chance - for a future without need , new edition 2007, page 565 ff.
- Bodo Frahm: BGJ Agrarwirtschaft , 4th edition, Ulmer, Stuttgart 1980, 1991, ISBN 3-8001-1049-0 , p. 154 ff.
- Gerhardt Preuschen: Agriculture according to ecological laws , 2nd edition, Ecology and Agriculture Foundation - Verlag CF Müller, Heidelberg 1994, ISBN 3-7880-9873-2 , p. 146 ff.