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Wheat Root Growth Responses to Enhanced Ammonium Supply
Author(s) -
Gao S.,
Pan W. L.,
Koenig R. T.
Publication year - 1998
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/sssaj1998.03615995006200060035x
Subject(s) - nitrification , subsoil , loam , ammonium , chemistry , agronomy , soil horizon , greenhouse , urea , mollisol , nitrogen , horticulture , zoology , soil water , environmental science , biology , soil science , organic chemistry
Slowing nitrification with a nitrification inhibitor (NI) provides an enhanced NH 4 supply (EAS), which has improved N uptake efficiency and crop yield. A physiological response to EAS has been demonstrated in container experiments with restricted rooting volumes and uniform N distribution, but less is known about root responses to EAS when distributions of N forms are not uniform. Greenhouse and 2‐yr field experiments were conducted to determine how the root system of wheat ( Triticum aestivum L.) responds to EAS. Three N sources: (i) calcium nitrate (NO 3 ); (ii) urea with a nitrification inhibitor, nitrapyrin (NH 4 + NI); and (iii) 50% NO 3 + 50% NH 4 + NI were uniformly incorporated in the field into the top 20 cm of a Shano silt loam soil (Coarse‐silty, mixed, superactive, mesic Xeric Haplocambid). Urea with a NI increased NH 4 in the top 30 cm of soil and increased root surface area densities in this soil layer at the boot stage in both years. Rooting was either decreased or not affected by NH 4 + NI relative to NO 3 in the 30‐ to 90‐cm subsoil. In a greenhouse experiment, NO 3 , NH 4 + NI, or NH 4 + NI + CaCl 2 were uniformly mixed into the top 20 cm of soil (diffused) or banded at the 20‐cm depth in rooting‐boxes (5 by 17 by 70 cm). Nodal root density at boot stage increased in the fertilized zones with NH 4 + NI, mostly in the presence of CaCl 2 , compared with NO 3 , while seminal roots in the fertilized zones were only enhanced by banded NO 3 . Wheat root types responded differentially to N forms and the associated differences in vertical distribution.