Aluminum, despite being present in large amounts, is pretty stable and its mobility /uptake is not really an issue. It only becomes a problem in very acidic conditions. Correcting soil acidity (e.g. liming) should resolve the problem.

I don't have the exact numbers with me now, but less than 50% ice-free land areas are arable, and of this, more than 50% are acidic (soil pH < 5.0), with aluminum (Al) exchangeable saturation (m%) higher than 50%. Consequently, these soils are poor in bases (K, Ca and Mg). These soils are generally in the tropics, but some are in the US. Liming is a "solution", but it costs +/- US$200 - US$300 per hectare per year, depending on the country. Therefore, there is a lot to research in this field if we want to overcome the Al toxicity in agriculture.

The question is what can be considered "sustainable". If you mean without any amendment, that would be a though question. I remember a speech by a Mexican research back in the 1990's in Purdue University about how his team was trying to genetically increase the exudation of citric and other Al-complexing acids by the roots (in maize, I think). Another strategy is to use crops with deep roots to "mine" nutrients from deep soil horizons. However, it is nice to remember that once there is an output of elements from soils by cropping, there would be a point in time were some elements have to be replaced. In BRazil , the use of ROck powder is being legalized, which can be a low cost (although slow) source of plant nutrients.

@ Antonio Azevedo.  By sustainable, I mean that the costs can be supported by the yields  during more than a favorable conjuncture cycle.

Salut Luc,

I have a great deal of managing Aluminium in Agriculture and Horticulture I have a paper under my profile that discusses Aluminium toxicity with Blueberries (normally tolerant) on soils of mixed Peat and Volcanic ash. Have a look at the article and if you wish to discuss this further send me an email. Cordialment Philip

Thank you Mr. Bortoluzi, but the oxisol in your experiment is not "allic" after the table 1.

Thank you also Mr. Barlow, but it is not established that your soils were allic oxisols (Soil Taxonomy) or allic soils (WRB). In fact they seem not! 

Dear Luc,

Your request is challenging indeed.

As already proposed, liming can address issues pertaining to acidity and aluminium toxicity  as well as improving Ca content of the soil a moderator in soil physical and chemical properties. But I believe that on top organic amendment  (dung, sludge, plant litter to mention only these 'low cost' material mix with the lime will prove more effective and I expect that their combination can reduce the requirement per se.

On top of above, deep furrowing will improve root penetration tapping nutrient and water at greater depth.

Soil cropping with tolerant species and varieties are avenues, but what is feared is that soil management practices such as regular liming will be left in abeyance that unfortunately may not prove sustainable in the long term.

Good luck with your work.

Jean Pierre's reply has good merit, but before using the deep furrow method make sure of the difference in topsoil pH and (KCl extractable) free aluminium levels. If the subsoil has lower Free aluminium the yes go for the deep furrow method and use Lean Pierre's other organic additions also. If subsoil Free aluminium is higher that that of the topsoil then use shallow or minimal tillage.

Acidity, Al toxicity and lime requirement in Red Ferruginous soils of humid tropical climates of India

The following commentary is based on a Review Paper (Pal et al., 2014.Catena 121:260-278) and may be of some  value to similar soils elsewhere.

         Soil acidity is a major constraint to crop production. Contribution of Al 3+ ions to exchangeable acidity is significant in the soils of humid tropical (HT) climate. Liming is generally recommended for strong to moderately acid soils of tropical India. But in some moderately acidic Alfisols of the Western Ghats, crop response to liming is not observed, because of the presence of Ca-zeolites in these soils. Aluminium toxicity to plants is a constraint in Oxisols, Ultisols and Dystropepts; and this is also associated with an overall low nutrient reserves. Ultisols and  Dystropepts of Kerala, Goa, Tamil Nadu, Karnataka and north-eastern hills (NEH) are strongly to moderately acidic, and liming is often recommended to correct soil acidity and improve nutrient availability.

        Liming is done to bring exchangeable aluminium level in the soil to < 1mg kg −1 for maintaining sustained productivity as a result of general improved nutrient availability. However, reports on Al toxicity to crops in Indian acidic soils are scarce. The KCl extractable aluminium is used for liming tropical acidic pH soils. It is intriguing that despite equally strongly acidic, Ultisols and Dystropepts of NEH, Ultisols of Kerala, and Alfisols of Goa have varying KCl exchange acidity. It is less than 1 cmol (p+)kg−1for the Ultisols of Kerala and Meghalaya, and Alfisols of Goa whereas in the Ultisols of Arunachal Pradesh, Assam, Mizoram, Nagaland, Tripura and Dystrochrepts of Manipur, it ranges from 3 to 6 cmol (p+) kg−1. The lime requirement (LR) of these acidic soils also varies widely. Lime requirement is around 1 t lime ha−1for Ultisols of Meghalaya, and for Dystrochrepts and Ultisols of other states of NEH, it ranges from 4 to 12 t ha −1. Such a low LR (

Thank you, Mr. Paul and Mr. Barlow for your advices. In Burundi highlands, I found large areas of allic oxisols in semi-natural pasture land where "100xAl/ECEC (m%)" was greater in the toposoil. But it was also more than 60% at 60 cm depth and even below.

Under such conditions I think also that regular liming and use of  NPK fertilizers may not be sustainable but I had to leave the country and so I could not achieve long term trials. Similar soils are largely represented in brazilian Cerrado or in the Amazon forest where commercial corn/soja  systems seem to have succeeded for more than 10 years. Their success may be due to favorable prices of soja on the int'l markets.  I hope to find some significant publications of trials that could confirm or not these ideas.

Thank you, Mr. Pal for your precise summary and review of Aluminium behavior in humid tropical soils of India. Al(OH)n amorphous polymers are also present in clays of Burundi highlands. In moderately acid soils there is no response to lime because Al stimulate growth at low concentrations. It seems to be related with the absorption of Al-P complexes by roots. But above a certain critical level,f Al toxic effects can appear. However some species as tea continue to absorb Al-P complexes without suffering of Al toxicity: tea is an accumulator of Al.