AMELIORATING ACID SOILS WITH ORGANIC MATERIALS - EFFECTS OF AMENDMENTS DERIVED FROM COAL ON YIELD AND COMPOSITION OF YOUNG WHEAT PLANTS GROWN ON AN ACID RED PODZOL
Ad. Noble et Pj. Randall, AMELIORATING ACID SOILS WITH ORGANIC MATERIALS - EFFECTS OF AMENDMENTS DERIVED FROM COAL ON YIELD AND COMPOSITION OF YOUNG WHEAT PLANTS GROWN ON AN ACID RED PODZOL, Communications in soil science and plant analysis, 29(19-20), 1998, pp. 3023-3043
Acidity in surface and subsurface soil horizons limits crop and pastur
e production over considerable areas of the world, and lime is the tra
ditional amendment used to neutralize surface soil acidity. Earlier re
ports have indicated that calcium (Ca)-saturated organic materials, pr
oduced by the oxidation of coal, may be of value as ameliorants for su
bsurface acidity. Two of them (OXPR and OXFU) were evaluated and compa
red with lime in pot studies with wheat (Triticum aestivum). In the fi
rst experiment; lime, OXPR and OXFU, each at four rates, were applied
to an acid red podzolic soil, high in extractable aluminum (Al) and we
re compared for their ability to improve seedling root growth. an the
second experiment, the three amendments were applied to the same soil
and shoot yields and mineral content were measured after five weeks gr
owth. The three amendments raised soil pH, lowered extractable Al and
increased root elongation. OXFU at the highest rate (25 t ha(-1)) inhi
bited root growth possibly due to the high concentration of solutes as
indicated by high electrical conductivity of the soil solution. In th
e second experiment the three amendments improved shoot yields, with s
ignificant increases up to 0.8 t Ca ha(-1) application. Yields were in
general higher with lime than with OXPR and OXFU at equivalent rates
of added Ca. However, a significant asymptotic relationship was observ
ed between yield and calcium carbonate (CaCO3) equivalence of each of
the applied amendments. Yield was highly correlated with measures of s
oil Al {r(2) for [Al] in 0.01M calcium chloride (CaCl2), 0.915; [Al] i
n 0.1M barium chloride (BaCl2)/ammonium chloride (NH4Cl), 0.873; [Al]
in water, 0.779; [Al] in water/EC, 0.904}. Plant manganese (Mn) concen
trations were decreased by lime and OXPR and there were linear correla
tions between plant Mn concentration and soil Mn extractable in 0.01M
CaCl2. With OXFU, which has a high concentration of water soluble Mn,
plant Mn was decreased below the unamended controls only at the higher
rates of application. Leaf tissue zinc (Zn) concentrations were high
in treatments receiving the two coal-derived amendments. In an effort
to determine the role of ion complexation in the remediation process,
a third study evaluating the Al complexing ability of the two coal der
ived products was compared to that of a water-soluble fraction extract
ed from chestnut (Castanea sativa) litter which is known to have a hig
h affinity for Al. The two coal derived materials had considerably low
er affinities for Al than the chestnut extract supporting the thesis t
hat complexing reactions were of minor importance in the observed resp
onses. The results indicate that field testing of these products is wa
rranted particularly at sites where plant growth is constrained by sub
surface soil acidity.