Book of Abstracts
11th IFOAM
Scientific Conference
11-15 August 1996
Copenhagen, Denmark

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Humus and N Household in Organic Farming S21

Leithold, G.

Sächsische Landesanstalt für Landwirtschaft, Fachbereich Bodenkultur und Pflanzenbau, Referat Ökologischer Landbau, Gustaf-Kühn-Str. Nr. 8, D-04150 Leipzig

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In order to protect soil fertility it is necessary to call attention on the reproduction of humus in plough soils. Investigations with help of long-term experiments show a clear diversification of humus- and nitrogen content in soil and a strong connection between humus content and yield. Therefore, in organic farming, it should be strived for a humus content as high as possible achieving with acceptable economical expenditure. Aim in conventional farming is only a middling humus content. This point is one reason for a higher demand on manure and organic bounded nitrogen in organic farming than in conventional farming. A further reason is the fact that a higher humus level in soil is correlated with a higher content of nutritive humus, a higher content of microbiological biomass and a higher activity of its.

Long-term experiments show that under conditions of a higher humus content the nutritive humus is broken down quicker. Consequently, farmers are forced to supply the soil with more organic matter, in order to avoid higher losses of humus following mineralisation. Considering a better supply of organic matter to soil, a quicker microbiological breakdown of manure and plant residues must be taken into consideration too. Specific nitrogen balances of many cultures prove that in spite of lower yields in organic farming it consists a higher demand on organic bounded nitrogen and farmyard manure than in conventional farming. Another reasons for a higher demand on organic matter and organic bounded nitrogen are the renunciation of the positive direct and not-direct humus-forming effects of mineral nitrogen and a lower content of nutrients in animal excrements. Consequently, different coefficients for humus balancing are necessary in organic and conventional farming.