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Utilization of Anhydrous Ammonia Fixed by Clay Minerals and Soil Organic Matter
Author(s) -
Norman R. J.,
Gilmour J. T.
Publication year - 1987
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/sssaj1987.03615995005100040025x
Subject(s) - anhydrous , chemistry , dry matter , organic matter , fertilizer , agronomy , soil water , nitrogen fixation , nitrogen , leaching (pedology) , lolium multiflorum , zoology , biology , environmental science , soil science , organic chemistry
A portion of anhydrous NH 3 fertilizer applied to soil can be rendered nonexchangeable through fixation by clay minerals and soil organic matter. The plant availability of anhydrous NH 3 fixed by these two soil fractions can be important agronomically if such fixation limits plant uptake of the fertilizer N. In this study, three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf) with clay and organic C contents ranging from 120 to 310 and 7.8 to 30.1 g kg −1 , respectively, were injected with 15 N‐labeled (2 atom % 15 N) liquid anhydrous NH 3 at a rate equivalent to 245 kg N ha −1 . Soluble and exchangeable N were removed by leaching and the soil was cropped to ryegrass ( Lolium multiflorum Lam.) in pots. Soils were analyzed before and after cropping for clay fixed N and organic matter fixed N. Four cuttings (harvests) were made at 3‐ to 4‐week intervals and roots were collected at the termination of the experiment. Aboveground dry matter, total N uptake, and fertilizer‐derived fixed N uptake (mg N pot −1 ) increased from the first to the second harvest and declined thereafter. Nitrogen recovered in the roots accounted for <11% of the total N and <7% of the fixed N utilized, and root dry matter accounted for 13 to 14% of the total dry matter produced. The ratio of fertilizer‐derived fixed N uptake to total N uptake declined with harvest suggesting that the fixed N became less available to the ryegrass with time. Fertilizer‐derived fixed N recovered in the ryegrass ranged from 19 to 26% of that originally fixed by the soil. The percentages of fertilizer‐derived clay fixed N removed from the soils during cropping (35–72%) were much larger than those of the fertilizer‐derived organic matter fixed N (<12%) suggesting that a majority of the plant uptake of fixed N originated in the clay fraction. Overall, fertilizer‐derived fixed N removal from the soils (21–30%) agreed well with plant uptake data.