R. Kolli et A. Kanal, HUMUS STATUS OF ARABLE PODZOLUVISOLS AND THE ROLE OF ANNUAL LITTERFALL IN ITS FORMATION, Zeitschrift fur Pflanzenernahrung und Bodenkunde, 158(3), 1995, pp. 235-241
In this work comparative research of the quantitative characteristics
of the humus status (HS) of Estonian arable Podzoluvisols (PD) and som
e very closely related soils were carried out. This study was conducte
d to determine soil humus cover (HC) and subsoil humus content (percen
tage and pool) and to analyse the role of plant residues in their form
ation. The specific objective was to discuss the ecological factors an
d mechanisms which influence the flux of soil organic matter (SOM) thr
ough soils and to evaluate its contemporary status. For this purpose d
ifferent databases (DB) were used: (1) DB of large-scale soil mapping
(1958-78), (2) DB PEDON of pedoecological researches (1967-85), (3) DB
of HS research transecis (1986-91) and (4) data from two long-term fi
eld trials (1985-92). In the conditions of regular agricultural practi
ce the mean SOM percentage in the HC of arable PD is within the range
of 1.8-2.1%, which is 0.1-0.3 units (%) the below optimal level and is
in a critical state. Impoverishment is caused mainly by deep plowing.
The dependence of humus retaining capacity (presumed to be a good cri
terion for evaluating the current HS of soils) on the mode and intensi
ty of tillage, soil water regime, carbonate content and textural class
was discussed. Mean annual inflow of organic matter into HC (4-5 Mg h
a(-1) yr(-1)) forms an average 5.5-6.7% from its pool in soil. Applica
tion of manures increases this percentage to 12-13. It may be conclude
d that the HC might be shallower, but must be richer in humus. The ann
ual balance of SOM reflects better than annual balance of humus, the i
nfluence of fresh SOM on the soil current year productivity.