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Net mineralization, net nitrification and potentially available nitrogen in the subsoil beneath a cultivated crop and a permanent pasture
Author(s) -
WEIER K. L.,
MAcRAE I. C.
Publication year - 1993
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1993.tb00467.x
Subject(s) - subsoil , mineralization (soil science) , pasture , agronomy , nitrate , panicum , soil water , nitrogen cycle , leaching (pedology) , nitrogen , environmental science , topsoil , chemistry , biology , soil science , ecology , organic chemistry
SUMMARY The brigalow clay soils of central Queensland in eastern Australia contain large quantities of nitrate‐N in the subsoil beneath shallow rooting cultivated crops. A laboratory incubation study was conducted to determine whether nitrate accumulation at depth beneath these crops was due to in situ nitrogen mineralization. Intact soil cores, 5 cm long and 5 cm diameter, were obtained at four depths to 120 cm beneath cultivated black gram ( Vigna mungo ) and green panic ( Panicum maximum var trichoglume ) permanent pasture and incubated for 12 weeks at 60% water‐filled pore space and 25°C. Net mineralization of organic N occurred in all soil cores obtained from under black gram with values ranging from 4.3 to 9 mg N kg −1 soil at 12 weeks. Beneath the pasture, net mineralization had not commenced by the end of 12 weeks. Potentially available nitrogen ( N a ) ranged from 1.2 to 62.7 kg N ha −1 under black gram, and from 10.2 to 136.9 kg N ha −1 under pasture. A significant relationship was observed between N a and total N beneath both crops, and between N a and total C under the pasture. Leaching of N mineralized in the surface layers of soil appears to be the main avenue of nitrate build‐up in the subsoil beneath black gram, with subsoil mineralization making only a partial contribution to the accumulated nitrate pool.