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Title: OAT PLANT EFFECTS ON NET NITROGEN MINERALIZATION

Author
item Parkin, Timothy
item Kaspar, Thomas
item Cambardella, Cynthia

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2002
Publication Date: 6/1/2002
Citation: PARKIN, T.B., KASPAR, T.C., CAMBARDELLA, C.A. OAT PLANT EFFECTS ON NET NITROGEN MINERALIZATION. PLANT AND SOIL JOURNAL. 2002. V. 243. P. 187-195.

Interpretive Summary: Nitrogen in agricultural soils is an essential plant nutrient, yet nitrogen can leave agricultural fields and pollute ground- and surface waters. This study was conducted to learn more about how nitrogen behaves in soil so that strategies can be developed to provide plants the nitrogen they need and reduce the environmental problems. When the organic matter in soil is decomposed by bacteria and fungi the nitrogen trapped in the organic matter is released. This process of nitrogen release from organic matter is called nitrogen mineralization. The nitrogen that is released can be taken up by plants. Many things influence nitrogen mineralization in soils, including plants themselves. It is thought that living plants may excrete compounds from their roots in order to stimulate the soil bacteria and fungi and thus stimulate nitrogen mineralization. This study was conducted to determine the influence of living oat plants on nitrogen mineralization in soil. In the laboratory, oat seeds were planted in plastic cylinders containing soil. After 28 and 42 days, the amounts of nitrogen contained in the plants and the soil were measured. We found that plants stimulated nitrogen mineralization by as much as 81%; however, the amount of this stimulation was influenced by the past cropping history of the soil. It appears that there may be a special fraction of organic matter in soil that is especially susceptible to this plant stimulation effect. This information will aid farmers, scientists and extension agents in refining fertilizer recommendations to reduce water pollution.

Technical Abstract: Living plants have been reported to stimulate, inhibit, or have no effect on net nitrogen mineralization in soil. A series of experiments were conducted to evaluate the influence of living oat plants Avena sativa on new N mineralization. Oat plants were grown in plastic cylinders containing soil, and new N mineralization was assessed by determining the N balance in these microcosms. Measured N inputs included N contained in the oat seeds and N2 fixation. Nitrogen losses by NH3 volatilization and denitrification were also measured. We observed that in some soils net N mineralization was stimulated by as much as 81%, but in other soils there was no effect of living oat plants on net N mineralization. N mineralization responses are related to past cropping histories of the soils.