Effect of silicon on low pH soil phosphorus sorption and on uptake and growth of maize

• Published in: Communications in soil science and plant analysis 2005-01, Vol.35 (15-16), p.2369-2378
• Main Authors: Owino-Gerroh, C, Gascho, G.J
• Format: Article
• Language: English
• Subjects: acid soils; Agronomy. Soil science and plant productions; Biological and medical sciences; corn; Fundamental and applied biological sciences. Psychology; nutrient availability; nutrient uptake; nutrient use efficiency; phosphorus; Phosphorus availability; Phosphorus sorption; plant growth; Silicate; silicates; silicon; Soil acidity; soil nutrients; soil pH; Soil science; soil treatment; sorption; Zea mays
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1081/LCSS-200030686

High soil sorption of phosphorus (P) in some P deficient low pH soils reduces the efficiency of P fertilizer use and crop yields. Silicon (Si) application has been reported to decrease P sorption and increase yields in such soils. The effect of silicate on P sorption and availability and on growth of maize (Zea mays L. cv. Golden Acres 7885) grown in a low pH Greenville soil from the Coastal Plain of Georgia was investigated in laboratory and pot experiments. Applied sodium (Na) silicate markedly reduced the soil's high P sorption. In a pot study in a greenhouse, both maize shoot and root dry weights were increased by applications of silicate, phosphate, and by applications of silicate together with phosphate. Dry weights of both shoot and root were increased by 3.92 mg Si/pot when Si was applied together with P. Silicon and P contents in the shoot and the root were increased by Si, but not by P application. The reduced P sorption when silicate was applied was adduced to the increase in the soil pH from the accompanying Na cation. The applied silicate ion converted to amorphous silicic acid (H3SiO4) in the soil. Amorphous H3SiO4 has less negative surface charge than the phosphate ion. Therefore, it should not replace P on soil binding sites or be preferentially absorbed when both are in the soil solution. Phosphorus was limiting in the soil and all applied P rates increased maize dry weight. The weight increase when Si was applied was attributed to the increase in the soil pH from the accompanying calcium (Ca++) and Si concentration in the soil solution, which improved the conditions for the growth of maize resulting in increased transpiration and therefore greater P uptake and utilization. The same reason is given for the increase in dry weight when both Si and P were applied. This is because greater dry weight was found at lower P rate (0.1 g P/pot) than the recommended rate (0.2 g P/pot). Greater P uptake and utilization was supported by increased P and Si contents in the shoot and root when Si was applied.