Coloniza o micorr赤zica e fertilidade do solo submetido a fontes e doses de aduba o nitrogenada em Brachiaria brizantha = Mycorrhizal colonization and soil fertility under different sources and levels of nitrogen fertilization on Brachiaria brizantha

作者：Flavia Cristina Delbem; Marcia Helena Scabora; Cecilio Viega Soares Filho; Reges Heinrichs

来源：Acta Scientiarum - Agronomy, 2010.

• sulfato de am nio
• ureia
• pastagem
• ajifer
• ammonium sulfate
• urea
• pasture

A viabiliza o e aumento da produ o de novas cultivares podem ser obtidos com a pr芍tica da aduba o nitrogenada. O objetivo desse trabalho foi verificar o efeito de fontes e doses de aduba o nitrogenada, em profundidades, na coloniza o micorr赤zica e na fertilidade do solo com Brachiaria brizantha cv. Xara谷s. O delineamento experimental em blocos casualizados e os tratamentos em esquema fatorial 3 x 4, envolvendo tr那s fontes de nitrog那nio (ureia, sulfato de am nio e ajifer-L40), quatro doses (0, 100, 200 e 400 kg ha-1) estudadas em duas profundidades (0-0,10 e 0,10-0,20 m), com tr那s repeti es. Por parcela, as amostras compostas, por cincoamostras simples de solo, foram coletadas, peneiradas, homogeneizadas e destinadas 角s an芍lises. O uso do ajifer e da ureia proporcionou maior produtividade de massa seca da parte a谷rea de B. brizantha cv. Xara谷s. Em contrapartida, esta sofre redu o 角 medida que as doses se elevaram. A melhor dose de aduba o foi a aplica o de 100 kg ha-1 de N. As doses mais elevadas de N, na camada 0 a 0,10 m de profundidade, determinam acidifica o do solo e reduzem os valores de MO, K+, Ca2+, Mg2+, SB e V%. A esporula o, mas n o coloniza o micorr赤zica, 谷 sensivelmente estimulada em elevadas doses. The feasibility and increase in the production of new cultivars can be obtained with the practice of nitrogen fertilization. The objective of this study was to verify the effect of sources andlevels of nitrogen fertilization, concerning the depths, on the percentage of mycorrhizal colonization and soil fertility when covered by Brachiaria brizantha cv. Xara谷s. A randomized blocks design was used and the treatments were under a 3 x 4 factorial scheme, regarding three nitrogen sources (urea, ammonium sulfate, and ajifer-L40) and 4 nitrogen levels (0, 100, 200 and 400 kg ha-1), studied at 2 different depths (0-0.10 and 0.10-0.20 m), with 3 replications. In each plot, the soil samples, composed of 5 simple samples, were collected, sieved, homogenized and sent for analysis. The use of ajifer and urea promoted higher production of shoot dry matter of B. brizantha cv. Xara谷s. On the other hand, this dry matter showed reduction with the increase of N doses. The best fertilization dose was 100 kg ha-1 of N. The increasing doses of N employed, on the depth of 0-0.10 m, resulted in soil acidification and decreased thelevels of MO, K+, Ca2+, Mg2+, SB and V%. Sporulation, but not mycorrhizal colonization, was stimulated by higher applied dosages.