Biological activity in soils treated with green manures of Lupinus spp. (Leguminosae) using the hydrolysis of fluorescein diacetate method (FDA) in Jalisco, Mexico

The incorporation of legumes as green manures modifies some physical and chemical properties of soil, but its effects on some biological properties have not been evaluated. The current study aimed to evaluate the potential microbial activity of soil freshly amended with green manures of wild Lupinus species using the hydrolysis of fluorescein diacetate (FDA) method. Two wild lupine species ( Lupinus exaltatus , L. rotundiflorus ) with green manure potential were added at the rate of 44 t ha -1 to two different agricultural soils from Jalisco, Mexico, and incubated for 14 days under laboratory conditions. A treatment with maize (control + ) as green manure and a treatment without addition of green manure (control – ) were also included in the experiment. The enzymatic activity in terms of the hydrolysis of FDA was quantified at 1, 3, 7, 10, and 14 days. The FDA hydrolysis values fluctuated from 0.51 to 0.82 mg fluorescein kg -1 h -1 in the treatments with green manure and from 0.10 to 0.13 mg fluorescein kg -1 h -1 in the soil without green manure. L. rotundiflorus and maize yielded higher values of FDA hydrolysis compared with L. exaltatus . The addition of the organic amendments increased microbial activity measured as FDA hydrolysis.