Acidification and Soil Productivity of Allophanic Andosols Affected by Heavy Application of Fertilizers

Abstract

The acidification of allophanic Andosols by fertilizer application in relation to soil productivity was studied with special reference to the soil colloidal composition. Among the Japanese cultivated allophanic Andosols, in 95% of the samples, the exchange acidity y1 was < 6, while in 5% of the samples (30 soil samples) the exchange acidity y1 was ≧ 6. The strongly acidic allophanic Andosols (exchange acidity y1≧ 6) did not significantly differ from the weakly acidic allophanic Andosols in the contents of amorphous materials. However, the mean values of the strongly acidic allophanic Andosols for the soil pH and base saturation which were 4.5 ± 0.3 and 15 ± 9%, respectively, were relatively lower than those of weakly acidic allophanic Andosols. The content of KCl‐extractable Si in the strongly acidic allophanic Andosols dominated by allophane (exchange acidity y1≧ 6 and allophane/clay content ratio > 0.7) ranged from 51 to 141 mg kg−1, and the values increased with increasing concentrations of KCl‐extractable Al. KCl‐extractable Al in the cultivated allophanic Andosols was considered to be derived from both the allophane fraction and Al‐humus complexes. In the field studies of allophanic Andosols with successive application of fertilizers conducted at the Fujisaka Branch of Aomori Agricultural Experiment Station, the value of the exchange acidity y1 of the topsoil and subsoil exceeded 6 about 40 and 50 years after the start of the experiment, respectively. The yield of flint corn (Zea mays L. var. indurata Bailey. cv. Onoa) in the fertilizer plot decreased by the strong soil acidification. The amount of nitrogen mineralized in the soil of the fertilizer plot during a 280‐d incubation was 0.114 g kg−1 in the topsoil and 0.041 g kg−1 in the subsoil. These values were relatively low compared with those in the lime + fertilizer plot. Thus, we confirmed that the subsoil fertility of the fertilizer plot decreased by heavy application of fertilizers.

Broad Distribution of Diverse Anaerobic Ammonium-Oxidizing Bacteria in Chinese Agricultural Soils

“…Most of the collected samples had similar pH values (near neutral pH), ranging from 6.5 to 7.5. However, samples BH, CS, KM, NC, NJ, NN, and ZJ showed relatively lower pH values (4-6), a finding that may be related to the heavier application of nitrogen-rich fertilization at these sampling sites, which can directly and indirectly acidify the soil (38,39). The soil organic contents of most of the samples varied from 10 to 30 mg kg Ϫ1 , and all the soil samples showed relatively high TIN contents, ranging from 20 to 150 mg kg Ϫ1 .…”

Acid Soil Is Associated with Reduced Yield, Root Growth and Nutrient Uptake in Black Pepper (&lt;i&gt;Piper nigrum&lt;/i&gt; L.)

“…Furthermore, forms of applied N are usually urea-N, synthetic fertilizer-N (15-15-15) and manure-N, and, the percentage of inorganic-N is 77%. High rates of N fertilization can cause soil acidification both directly and indirectly [13] [14]. Consequently the decreasing soil pH may have affected pepper growth.…”

Biotechnological Solutions for Enhancing the Aluminium Resistance of Crop Plants

“…In Africa large tracts of the acid soil cannot be used for cultivation because they are sandy, nutrient-deprived and water-limited (Vonuexkull and Mutert 1995). Naturally acidic soils occupy about one third of Australia, but many agricultural soils in the intensive land-use regions have become more acidic as the result of removal of harvestable product, leaching of nitrate and calcium from nitrogen-producing pastures (Australia State of the Environment report, 2001), and high applications of nitrogen fertilizer (Juo et al 1995;Matsuyama et al 2005;Sirovy 1979). Rapid acidification associated with the overuse of nitrogen fertilizer is also an emerging problem in China (Guo et al 2010).…”