Potentially mineralizable nitrogen is soils green manured with biocidal crops

Kurzfassung

Biofumigant crops used as green manure, in addition to producing a biocidal effect on some soil-borne pathogens and pests, could represent a source of N for crop nutrition. In two laboratory experiments we compared i) the potentially mineralizable N (PMN) of a silty clay soil after incorporation of glucosinolate-containing (GLS+) and non-containing (GLS–) plants, or after incorporation of metam sodium; and ii) the mineralization rate of different types of soils (silty clay, loam and loamy sand) after green manuring with GLS+ crops. After a 3-month incubation, the PMN of the silty clay soil amended with the GLS+ Brassica juncea was significantly higher than the unamended control and the soil amended with Triticum aestivum and Eruca sativa. Metham sodium, while showing a remarkable nitrification inhibition activity, gave rise to amounts of inorganic N (mainly in the ammonium form) of the same level as B. juncea. Mineralization rate was higher in the loamy sand soil than in the loam and in the silty clay soils. Biofumigant crops used as green manure, by increasing N availability in soil, may represent an interesting source of N for the following crops in organic agriculture.