Nutrient management in organic crop husbandry F5
Fragstein, P. von1 and Piorr, A2
1) University of Kassel Department of Ecological Agriculture Nordbahnhofstr. 1a D-37213 Witzenhausen Germany; 2) Wilhelm-Pieck-str. 45 D-15377 Waldsieversdorf Germany
|The nutrient management in organic crop
husbandry depends on various indegenous and exogenous factors of a growing system, i.e.
quality and quantity of humus and minerals in the soil, exposition of the site to
atmospheric input, amendmends of organic and mineral sources for fertilization, crop
rotation and soil management techniques for the mineralisation and conservation of
nitrogen and other nutrients. Organic on-farm and off-farm sources are mainly used for the
reproduction of organic matter of the soil, including the transfer of nutrients.
Site-adapted crop rotations and green manuring techniques are factors for the
sustainability of systems with low or no stocking rate. N provision of the crops must
mainly be maintained by leguminous crops as intercrops, catch crops or annual to perennial
set-aside; an important aspect is the conservation of accumulated nitrogen by specific
catch crops and/or adapted soil management techniques. Composting and application
techniques of manure have to be optimized in order to guarantee a nutrient transfer to the
plants with minimum losses and adapted to the requirement of plants.
The application of fertilizers is clearly fixed by the regulations for ecological agriculture (IFOAM, EU, national organisations). Slowly wetherable minerals like rock phosphate or silicate rock dusts should be applied to systems of high internal transformation rate (high input of degradable organic residues in the soil or high biological activity during composting) in order to compensate the low rate of nutrient release. Organic fertilizers are side products of food processing, slaughter housesand other manufacturing procedures with agricultural products. Their properties are intersting for specialized cropping systems, i.e. vegetable or fruit growing. Examples will be presented for the provision of nutrients in an organic growing system, for the definition of inner and outer nutrient cycles and their application in ecological agriculture.