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Tillage Effects on Legume Decomposition and Transformation of Legume and Fertilizer Nitrogen‐15
Author(s) -
Varco J. J.,
Frye W. W.,
Smith M. S.,
MacKown C. T.
Publication year - 1993
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1993.03615995005700030021x
Subject(s) - vicia villosa , agronomy , fertilizer , legume , tillage , cover crop , nitrogen , mulch , chemistry , residue (chemistry) , crop residue , green manure , mathematics , zoology , biology , agriculture , ecology , biochemistry , organic chemistry
The inclusion of legumes in cropping systems raises questions about their effectiveness as a N source. The objective of this study was to determine the effects of tillage on legume cover crop decomposition and transformation dynamics of legume and fertilizer 15 N. Nitrogen‐15‐labeled hairy vetch ( Vicia villosa Roth.) residue or fertilizer was added to soil cores contained in open‐ended Plexiglas tubes placed in the field. Vetch residues were either placed on the soil surface for notillage (NT), or mixed with the soil for conventional tillage (CT). In 1984, 15 NH 4 15 NO 3 was applied at rates of 0 and 100 kg N ha −1 and, in 1985, ( 15 NH 4 ) 2 SO 4 was applied at rates of 0 and 150 kg N ha −1 to both NT and CT cores with a history of winter fallow. Fertilizer 15 N was applied in solution to the soil surface. Within 30 d, 77% of the original vetch residue weight was lost with CT, compared with 45% with NT. Nitrogen lost from the residue by 30 d averaged 89% with CT and 60% with NT. At 15 d in 1985, soil inorganic 15 N recovery for fertilizer was 78% with CT and 57% with NT, and for vetch it was 47% with CT and 12% with NT. Vetch 15 N immobilization averaged 2.3 times greater than fertilizer 15 N with CT and 1.7 times greater with NT. The results indicate that N availability as measured by soil inorganic N is less from vetch residue than fertilizer due to both greater vetch N immobilization and the dependence of vetch N mineralization on decomposition rate.