Austria
July 8, 2019
Quelle: Saatbau Linz
Manuel BÖHM, editorial office LANDWIRT Bio
Catch crops should be sown on all fields where their cultivation is possible and sensible. The decision to plant catch crops should be taken for the benefit of a healthy soil and not because it is subsidised.
No main crops in catch crop mixtures
Cultivars grown as main crops are not suitable as catch crops. Ideally, you should sow cultivars that are not related with the main crop, i.e. before sowing legumes as a main crop, the catch crop mixture grown on the relevant field should not contain any legumes. When using clover but also other legumes, make sure you change varieties. Experience has shown that variation can avoid ‘legume fatigue’ (leading to poor growth and reduced yields) almost as effectively as a total cultivation break. Cruciferae are ideal catch crops because they are hardly ever used as main crops. Also graminae such as bristle oat (avena strigosa), forage rye, Sudangrass (sorghum drummondi) but also grasses used as undergrown crops have become more and more popular.
Mixtures to be preferred
Considering the fact, that even in organic farming, monocultures are standard for main crops, one should at least strive to break the monotony when it comes to sowing catch crops. In order to increase diversity in organic farming, we thus recommend using mixtures.
Diversity brings security
Mixtures have numerous advantages. The cultivation risk is reduced because the different plants will mutually protect and support each other and can more easily take advantage of climatic conditions. Any vegetation gaps will quickly be covered. At the same time, the emerging plant community is attractive for all kinds of beneficial organisms helping the farmer cope with pests. This biodiversity significantly increases the biological stability of the cropping system.
The fundamental advantage of mixtures though is the diversity of root types that their use will develop in the soil, yielding a densely and deeply rooted topsoil. This root diversity maintains and fosters the biodiversity of soil life.
Catch crops bring life into your field
The task of a root is not only to supply a plant with nutrients and water from the soil. Its other decisive function is to provide the entire soil life with vital energy through root excretion and dying-off fine roots. Natural soil fertility can only develop and persist through the continuous exchange between roots and soil life: Billions of soil organisms in just a handful of soil ensure the crumbly structure of soil.
Solar energy through year-round vegetation
The decisive factor for successful catch and main crop cultivation is not the nitrogen content as such but the soil bacteria that are active all year round and make for strong soils. These bacteria need sugar from living roots, not just until the first frost but throughout the winter and especially in the spring. It is thus a regrettable omission not to benefit from the efficient vegetation period in March and April by leaving the soils bare, prepared for seeding and simply waiting for cultivation. This problem is exacerbated when, in organic farming, maize, soybeans, pumpkin or hemp are sown as late as in May and soils remain uncovered until then. Solar energy stored underground as sugars, has extremely beneficial effects on yields by means of the bacteria feeding on these sugars. Bacteria constitute highly effective nitrogenous protein compounds – living nitrogen, literally! Catch crops that are hardy and active in early spring thus ensure a great shape of the following main crop. A reasonable compromise is to mix hardy components (grasses, crimson clover (trifolium incarnatum), white clover (trifolium repens) hop clover (medicago lupulina), forage rye, winter vetch (vicia villosa), winter peas, brassica rapa or rape) with non-hardy mixtures.
Manuel BÖHM, editorial office LANDWIRT Bio
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