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Effect of Soil Thickness on Nitrogen Distribution and Use by Crested Wheatgrass
Author(s) -
Power J. F.,
Merrill S. D.,
Smith S. J.
Publication year - 1985
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/sssaj1985.03615995004900060026x
Subject(s) - forage , agronomy , agropyron , nitrogen , fertilizer , soil horizon , zoology , environmental science , biology , chemistry , soil water , soil science , organic chemistry
Soil thickness can affect nitrogen (N) cycling and use in several ways, particularly if the solum contains materials restrictive to root growth. Microplots of 0.093 m 2 were established on a reconstructed mine soil composed of 0.2 m A horizon (Haploborolls) over 0.05, 0.30, 0.55, or 0.80 m of B and C horizon material spread over sodic (SAR 29.5) minespoil, giving soil thicknesses of 0.25, 0.50, 0.75, and 1.00 m, respectively. The area had previously been seeded to crested wheatgrass ( Agropyron desertorum var. Mandan) and fertilized annually with 55 kg N ha −1 . In spring 1978, the grass on eight microplots received enriched (27.5%) K 15 NO 3 at 48.6 kg N ha −1 . Grass on 16 other microplots harvested in 1979 and 1980 also received enriched 15 N fertilizer in late November 1978 and commercial ammonium nitrate (NH 4 NO 3 ) (50 kg N ha −1 ) in November 1979. After harvest in each of the 3 yr, soil in the eight microplots was excavated, and 15 N enrichment in forage, roots, and soil organic N was determined. Increased soil thickness greatly increased forage and root growth, but had much less effect on N concentration in plant material. Uptake of labeled N in neither forage nor roots was greatly influenced by soil thickness, either in the year of application or the following year. Uptake of labeled N in forage the 2nd yr was only 5 to 10% of that found the 1st yr. However, uptake of soil N in both forage and roots generally increased two‐ to threefold as soil thickness increased from 0.25 to 1.00 m. Soil inorganic N and forage N concentrations suggested that available N supply was not limiting. Thus, the increase in soil N uptake probably resulted from deeper and more effective root functioning with increased soil thickness. Approximately 35% of the labeled N applied was removed in harvested forage and 12% remained in roots, regardless of soil thickness. However, the quantity of labeled N immobilized as soil organic N varied from over 40% of that applied with 0.25‐m soil thickness to about 30% for 1.00‐m thickness. Because there was no runoff or leaching, this difference was probably due to gaseous losses, possibly by ammonia volatilization from plant material.