The use of carbon isotope ratios to evaluate legume contribution to soil enhancement in tropical pastures

brachiaria decumbens c3 plants c4 plants carbon carbone carbono colombia colombie ferralsol ferralsoles ferralsols fertilidad del suelo isotope isotopes mejora de pastizales mineralisation mineralization pastizales pasture improvement pastures plantas c3 plantas c4 plante en c3 plante en c4 pueraria phaseoloides soil fertility tropical zones zona tropical zone tropicale