Articles
IMPORTANCE OF A WET SEASON COVER CROP TO NITRATE RECOVERY IN TROPICAL VEGETABLE PRODUCTION
Article number
958_11
Pages
105 – 111
Language
English
Abstract
The maintenance of adequate soil nutrient levels for vegetable production in the Northern Territory (NT), Australia is challenging due to low fertility soils and a tropical wet dry climate where approximately 2 m of rain falls each wet season.
Large scale vegetable cropping usually occurs over the dry season.
This study investigated the level of nitrate recovered by a forage sorghum (Sorghum bicolor) cover crop sown at the start of the wet season in December in comparison to plots of unmanaged weeds or herbicide fallow plots (with and without fertiliser). Soils were sampled over a four month period to a depth of 1.8 m at 30 cm intervals, and analysed for nitrate and ammonium nitrogen.
By the end of the wet season in late March, forage sorghum plots had the lowest nitrate-N concentrations (0.92 mg/kg) due to plant uptake.
The nitrate-N concentrations of deeper soil under unmanaged weeds indicated that the weeds were less efficient at recovering mineralized nitrate from a depth of about 1 m than forage sorghum at one month after establishment.
Fallow plots showed a significant increase in nitrate-N concentrations due to progressive mineralisation.
This information is useful for growers as it indicates the level of nitrate-N mineralisation over the wet season and the capability of an effective cover crop to recover this from depth for later use in vegetable production.
Large scale vegetable cropping usually occurs over the dry season.
This study investigated the level of nitrate recovered by a forage sorghum (Sorghum bicolor) cover crop sown at the start of the wet season in December in comparison to plots of unmanaged weeds or herbicide fallow plots (with and without fertiliser). Soils were sampled over a four month period to a depth of 1.8 m at 30 cm intervals, and analysed for nitrate and ammonium nitrogen.
By the end of the wet season in late March, forage sorghum plots had the lowest nitrate-N concentrations (0.92 mg/kg) due to plant uptake.
The nitrate-N concentrations of deeper soil under unmanaged weeds indicated that the weeds were less efficient at recovering mineralized nitrate from a depth of about 1 m than forage sorghum at one month after establishment.
Fallow plots showed a significant increase in nitrate-N concentrations due to progressive mineralisation.
This information is useful for growers as it indicates the level of nitrate-N mineralisation over the wet season and the capability of an effective cover crop to recover this from depth for later use in vegetable production.
Authors
S.L. Bithell, N. Hartley, C.C. Martin, M. Hearnden , S.H. Smith, G. Owens
Keywords
forage sorghum, Sorghum bicolor, nitrate nitrogen, ammonium nitrogen, mineralisation, leaching, catch crops
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