Articles | Volume 8, issue 1
https://doi.org/10.5194/se-8-149-2017
https://doi.org/10.5194/se-8-149-2017
Research article
 | 
09 Feb 2017
Research article |  | 09 Feb 2017

Determination of critical pH and Al concentration of acidic Ultisols for wheat and canola crops

M. Abdulaha-Al Baquy, Jiu-Yu Li, Chen-Yang Xu, Khalid Mehmood, and Ren-Kou Xu

Abstract. Soil acidity has become a principal constraint in dry land crop production systems of acidic Ultisols in tropical and subtropical regions of southern China, where winter wheat and canola are cultivated as important rotational crops. There is little information on the determination of critical soil pH as well as aluminium (Al) concentration for wheat and canola crops. The objective of this study is to determine the critical soil pH and exchangeable aluminium concentration (AlKCl) for wheat and canola production. Two pot cultures with two Ultisols from Hunan and Anhui (SE China) were conducted for wheat and canola crops in a controlled growth chamber. Aluminium sulfate (Al2(SO4)3) and hydrated lime (Ca(OH)2) were used to obtain the target soil pH levels from 3.7 (Hunan) and 3.97 (Anhui) to 6.5. Plant height, shoot dry weight, root dry weight, and chlorophyll content (SPAD value) of wheat and canola were adversely affected by soil acidity in both locations. The critical soil pH and AlKCl of the Ultisol from Hunan for wheat were 5.29 and 0.56 cmol kg−1, respectively. At Anhui, the threshold soil pH and AlKCl for wheat were 4.66 and 1.72 cmol kg−1, respectively. On the other hand, the critical soil pH for canola was 5.65 and 4.87 for the Ultisols from Hunan and Anhui, respectively. The critical soil exchangeable Al for canola cannot be determined from the experiment of this study. The results suggested that the critical soil pH and AlKCl varied between different locations for the same variety of crop, due to the different soil types and their other soil chemical properties. The critical soil pH for canola was higher than that for wheat for both Ultisols, and thus canola was more sensitive to soil acidity. Therefore, we recommend that liming should be undertaken to increase soil pH if it falls below these critical soil pH levels for wheat and canola production.

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Short summary
Al toxicity to plants and soil infertility in acidic soils are the main limiting factors for crop growth. To establish which acid soils need to be ameliorated for plant growth, the parameters of critical soil pH and soil Al concentration must be determined. The critical soil pH and exchangeable aluminium of two Ultisols for wheat and canola production were determined in this study. The results obtained will provide useful references for the utilization and management of acid soils.