The chemistry of aluminium in strongly acidified sandy soil in Poland

Abstract

Organically-bound A1 in acidic, base-poor sandy soils seems to be a major contributor to dissolved Al. This hypothesis has been tested under field conditions at two intensely acidified sites. The research was conducted at the agricultural trial fields at Lyczyn, Poland, which have been fertilized continuously for 30 yr with 130 kg ha-' a-' N (as NH4N03 or urea). The effect of depletion of Al on its solubility was also studied.Field data confirmed that mobilized Al originates largely in the organically bound fraction of soil Al. Depletion of this fraction resulted in a considerable decrease in the mobility of Al such that, at pH = 3.0 and reaction times of a few weeks, small amounts of Al were mobilized. Apparently, the rate at which A1 is dissolved from structural silicates, which are abundant in the soil investigated, is small. This suggests that at sites in Poland most exposed to acid deposition, where the rates of soil acidification and depletion of organically-bound Al are greatest, both the concentration of Al and the soil solution pH are expected to decline with time.

Interrelationship of Organic Acids and Aluminum Concentrations in Rhizosphere and Nonrhizosphere Soil Solution of Rice in Acidic Soil

“…The lower concentration of Al in the rhizosphere are attributed to the formation of Al organic complexes as the rhizosphere contains a wide range of low-molecular-weight organic acids produced by metabolic activities of plant roots and microorganisms. This is in conformity with the findings of Porebska and Mulder (1996), who tested this hypothesis under field conditions and reported that mobilized Al originates largely from the organically found fraction of soil Al.…”

“…A negative relationship of solution Al concentration with tartaric acid indicates more acid excretion by roots under Al-stress condition in acidic soil. Chemical equilibria model predictions indicated that under acidic conditions, addition of citrate was sufficient to reduce free solution Al by about 85%, while a reduction of 73% was found in case of malate (Porebska and Mulder 1996). Jones and Darrah (1994) reported that 18% of the citrate added to an acidic soil was complexed with Al and the degree of Al-citrate complexation was highly dependent on the pH of the soil solution.…”

Comparison of water-soluble and exchangeable forms of Al in acid forest soils

“…[21]) most often [20,[22][23][24][25][26][27][28][29][30][31]. A number of researchers [10,20,[32][33][34][35] also recommend water with the intention to closely simulate Al speciation in real soil solution.…”