02910naa a2200301 a 450000100080000000500110000800800410001910000220006024500920008226000090017452020730018365000160225665000180227265000140229065000210230465000150232565000210234065300080236165300080236965300400237765300300241770000180244770000190246570000170248470000200250170000180252177300690253916246182003-10-24       2003    bl ---       0--  u    #d1 aRESENDE, A. S. de  aUse of green manures in increasing inputs of biologically fixed nitrogen to sugar cane.  c2003  aIn this study the contribution of biological N2 fixation (BNF) to several green manure crops used at planting of sugar cane, or in the inter-rows of the ratoon crop, was evaluated. The subsequent effects of these legumes on the N supply and yield of the sugar cane crop was also investigated. The experiment was conducted in an extremely sandy N-deficient soil over two consecutive years. In the first year the legumes were planted on the same day as the sugar cane and in the second year they were planted immediately after the harvesting of the cane. The treatments consisted of four legume species ( Crotalaria juncea, C. spectabilis, Canavalia ensiformis and Mucuna deeringiana), 100 kg N as urea fertiliser in a sp1it addition, and no ferti1iser N addition. The legumes were planted as two rows spaced 40 cm apart between each row of cane. Sorghum (Sorghum vulgare) and maize (Zea mays) were planted along the side of the experiment to act as non-N2-fixing reference p1ants for the application of the 15N natural abundance technique to quantify the BNF input to the legumes and the sugar cane. The soil cover, monitored using an overhead digital camera, showed that Crotalaria juncea was the quickest to establish and cover the soil. At 31 days after planting (DAP) it reached a height of over 60 cm, more than twice that of any of the other green manures, and covered 55% of the soil, 16% more than that of the second most vigorous legume, Canavalia ensiformis. Using the natural abundance 15N technique it was deduced that all of the legumes had obtained over 60% of their N from BNF .BNF inputs to some of the green-manure legumes were quite significant, ranging from 35 to 55 kg N ha-l for Canavalia ensiformis, Crotalaria juncea and Mucuna deeringiana at plant crop, whereas the effect of the presence of these legumes on final cane yield and dry matter and N accumulation was not significant. There was also considerable evidence of negative (allelopathic) effects on cane growth induced by the presence of some of the legumes, especially Crotalaria juncea.  aallelopathy  agreen manures  asugarcane  aAdubação Verde  aAlelopatia  aCana de Açúcar  aBNF  aFBN  aFixação biológica de nitrogênio  aNitrogen fixation biology1 aXAVIER, R. P.1 aQUESADA, D. M.1 aURQUIAGA, S.1 aALVES, B. J. R.1 aBODDEY, R. M.  tBiology and Fertility of Soils, Berlingv. 37, p. 215-220, 2003.