02278naa a2200325 a 450000100080000000500110000800800410001910000190006024500740007926000090015352014430016265000180160565000220162365000190164565000130166465000210167765000200169865000230171865000150174165000090175665000090176565300120177465300080178665300080179465300390180265300150184170000170185670000180187377300610189116208811996-09-17       1995    bl ---       0--  u    #d1 aDOBEREINER, J.  aAlternatives for nitrogen nutrition of crops in tropical agriculture.  c1995  aThe development of sustainable agricultural systems for the tropics requires among other technologies, alternatives for nitrogen fertilizers which are often limited in availability for financial reasons and also represent a major source of groundwater and air pollution. There are many new alternatives for the development of agricultural systems which make use of biological processes in soil. Biological nitrogen fixation (BNF), that is, the biological conversion of atmospheric dinitrogen into mineral N, is the most important alternative among them. Examples are given of the impact of various technologies used in Brazil. Soybean, introduced into the country 30 years ago, is now the second most important export crop, reaching 24 million tons annually with no N fertilizer application. Consequently, Brazil today is the country in the country in the world which uses the lowest amounts of nitrogen fertilizers in relation to phosphate. Alternatives for crop rotations and pastures are also discussed. Possibilities of expanding BNF to cereals and other non-legume crops are gaining new credibility due to the identification of endophytic associations with diazotrophic bacteria. The definite proof of substantial BNF in sugar cane with N balance and 15N methods in certain genotypes selected under low N fertilizer applications opens up new alternatives for sustainable agriculture and will be the key to viable bio-fuel programmes.  agreen manures  anitrogen fixation  aorganic matter  asoybeans  aAdubação Verde  aBiocombustível  aMatéria Orgânica  aProdução  aSoja  aSolo  aBiofuel  aBNF  aFBN  aFixação biologica de nitrogênio  aProduction1 aURQUIAGA, S.1 aBODDEY, R. M.  tFertilizer Research, Dordrechtgv. 42, p. 339-346, 1995.