Nitrogen fixation by nodulated soybean under tropical field conditions estimated by the 15N isotope dilution technique |
| |
| Authors: | Robert M Boddey Phillip M Chalk Reynaldo L Victoria |
| |
| Institution: | EMBRAPA, Programa Nacional de Pesquisa em Biologia do Solo, Km 47, Seropédica, 23460, Rio de Janeiro, Brazil;Centro de Energia Nuclear na Agricultura, Caixa Postal 96, Piracicaba, 13400, São Paulo, Brazil |
| |
| Abstract: | The contribution of biological N2 fixation to the N nutrition of nodulated soybean was estimated using the 15N isotope dilution technique and a non-nodulating soybean isoline as a non-fixing control plant. The plants were grown in the field in concrete cylinders (60 cm dia) and harvested at seven stages of plant growth. Labelled N was added to the soil either as labelled organic matter before planting or in seven small additions (2kg N ha?1) of (NH4)2SO4 during the growing period.There was good agreement between isotope dilution estimates of nitrogen fixation for the two labelling methods. Acetylene reduction assays on intact root systems greatly underestimated N2 fixing activity. The difference in total N between nodulated and non-nodulated plants generally gave higher estimates compared with the isotope technique. The data indicate that this was because nodulated plants recovered more N from the soil than the non-nodulated plants. After 92 days of growth, the soybean derived approximately 250kg N ha?1 from biological N2 fixation. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
