BACKGROUND
Aluminum (Al) toxicity caused by soil acidification is the main constraint for crop growth in tropical and subtropical areas of southern China. The critical values of soil solution Al3+ activity and pH for crops in acidic soils can provide useful reference for soil acidity amelioration.
RESULTS
A pot experiment in a greenhouse was conducted to investigate the critical values of soil solution Al3+ activity and pH for canola and maize in an Ultisol and an Alfisol. The critical values of soil solution Al3+ activity in Ultisol and Alfisol for canola were 1.5 and 10.0 μM, and 13.9 and 30.4 μM for maize, respectively. The Al-tolerance varied with soil types for the same variety of crop. There was more biomass of roots and shoots and higher plant height under the same Al3+ activity, and thus greater critical values of soil solution Al3+ activity for both crops in Alfisol than those in Ultisol, owing to higher Ca2+ /Al3+ , Mg2+ /Al3+ , and K+ /Al3+ ratios in soil solution caused by higher cation exchange capacity and exchangeable base cations in Alfisol, when compared with those in Ultisol. The critical values of soil solution pH for canola and maize in Ultisol were 5.09 and 4.72, respectively; while those in Alfisol were 4.87 and 4.54, respectively.
CONCLUSIONS
The critical values of Al3+ activity were higher for maize than for canola and the critical values for both crops were higher in Alfisol than in Ultisol. The critical soil pH for both crops showed opposite trends to soil Al3+ activity. This article is protected by copyright. All rights reserved.