『Abstract
We studied the impact of heating on minerals in a lateritic podzolic
soil from Bakers Hill, Western Australia and consequent effects
on phosphate availability and plant growth. This forest soil was
heated at 250, 350 and 500℃, which are temperatures attained by
topsoil during bushfires. Heating soil caused kaolinite, gibbsite
and goethite to dehydroxalate and to partly alter into metakaolinite,
amorphous alumina and hematite respectively. Heating increased
soil pH, from 4.63 for unheated soil to 4.67, 5.40 and 5.45 for
soil heated at 250, 350 and 500℃ respectively. Electrical conductivity
(EC) values also increased on heating to 250℃, although EC then
relatively decreased for 350℃ and 500℃ heating. A glasshouse study
determined the effect of heating soils on their pH and EC values
after cropping and on P uptake by ryegrass. Yield of ryegrass
decreased with increasing temperature of heating for unfertilized
soil and for heated soils supplied with phosphate (P) fertilizer.
The P concentration in ryegrass for each of three harvests ranged
from 0.03% to 0.3% and decreased in the same sequence as for yield
(i.r. unheated soil>250℃>350℃>500℃ heated soil). Clearly heating
of soil by bushfires may reduce the availability to plants of
native and added phosphate.
Keywords: Heated soil; Synchrotron XRD; Phosphorus; Dehydroxylation;
Rehydroxylation』
1. Introduction
2. Material and methods
2.1. Soil and glasshouse experiment
2.2. Soil and plant analysis techniques
3. Results and discussions
3.1. XRD and SEM
3.2. Heating impacts on chemical properties
3.3. Forms of Fe, Al and Si in the heated soils
3.4. Plant dry matter
3.5. Plant analysis
4. Conclusions
Acknowledgments
References