Nitrogen management in organic agriculture is discussed focussing on s
trategies maximizing nitrogen input (source: N-2-fixation) and minimiz
ing nitrate losses on-site (field losses) and off-site (losses from ma
nure heaps). Due to a strong relationship between grain yield/amount o
f N in grains and N-2-fixation in pulse-crops or total dry matter yiel
d and N-2-fixation in fodder legumes, e.g. grass/clover mixtures, nitr
ogen fixation can be maximized by selecting the best site-adapted (bes
t yielding) species, varieties or mixtures, respectively. Strategies t
o reduce nitrate losses are based on N-sinks, that is, plants taking u
p soil-borne and residual nitrogen during or after growth of legumes e
fficiently, e.g, brassica-underseeds in faba beans, catch crops, or fo
llowing crops with great sink capacity for nitrogen. In order to keep
pre-winter mineralization as low as possible (minimizing N-source) tur
n over of grass/clover can be postponed or tillage intensity can be re
duced in depth or frequency. Gaseous losses of NH3 from manure heaps c
an be reduced by shorter duration of storage, by covering heaps with c
lay or stone meal having a high base exchange capacity, and by coverin
g heaps with an additional layer of organic residues of high carbon co
ntent. Field losses of ammonia can be reduced by injecting liquid manu
res directly to the soil. Generally manures have to be turned under im
mediately after distribution.