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The Effect of Quantity of Plant Material Added to Soil on its Rate of Decomposition
Author(s) -
Broadbent F. E.,
Bartholomew W. V.
Publication year - 1949
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/sssaj1949.036159950013000c0048x
Subject(s) - citation , decomposition , soil water , library science , computer science , information retrieval , environmental science , chemistry , soil science , organic chemistry
NORMAL additions of plant residues and manures to soils seldom exceed 2 tons dry matter per acre. In general the quantity of plant residues annually returned per acre of soil under ordinary farming systems is much less. In laboratory experiments on decomposition, however, it is often necessary to add proportionately larger quantities in order to be able to measure accurately the influence of the organic residues, their decomposition products, or the reactions attending decomposition on soil properties and soil processes. The question then arises whether such differences in concentration of biological substrate result in atypical rates of decomposition or abnormal patterns of nutrient mineralization. The studies reported here have been concerned with an evaluation of the influence of plant residue concentration in soil on the rates of residue and humus decomposition. Rates of decomposition have been relatively slow in some laboratory investigations and sizeable fractions of the plant residues have remained undecomposed after long periods of time. For example, Waksman and Diehm (4) reported 40% of fresh horse manure remaining after 290 days decomposition at room temperature. Waksman and Gerretson (5) found a 70.1% reduction in the dry weight of oat straw after 273 days decomposition at room temperature in earthen pots. In both of the studies just cited, decomposition was carried out in the absence of soil. Peevy and Norman (3) found that after 833 days decomposition of variously treated straws in soil appreciable fractions of the added carbon still remained. Even where dextrose was added, 2.75% of the added carbon remained at the end of this period. In this latter work the organic materials were added in 10% amounts or the equivalent of 100 tons per acre. With rates of addition of organic residues to soil on the order of 1 to 2% Broadbent (1) found carbon losses approximately equal to the carbon additions in decomposition experiments carried out for the relatively short time periods of 30 to 90 days. In field experiments where plant residue additions of 5 to 10 tons per acre are made frequently, the soil organic matter seldom is increased. This suggests a proportionately higher rate of decomposition at the lower rates of addition of plant residues.