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Effects of Calcium Silicate on Yield and Nutrient Uptake and Mechanism of Silicon Transport in Plants
|Title:||Effects of Calcium Silicate on Yield and Nutrient Uptake and Mechanism of Silicon Transport in Plants|
|Abstract:||The effect of calcium silicate on yield and nutrient uptake by plants and the mechanism of Si uptake were studied in a series of three experiments. First, response to Si was measured on 22 plant species grown on two soils with four levels of calcium silicate in a greenhouse; second, corn was grown in the field to determine the magnitude of response to residual Si with variable P and pH levels; and third, five plant species were grown in culture solutions at varying transpiration rates to study the mechanism of Si uptake.|
Response to calcium silicate differed with species and the same species grown on different soils had variable amounts of Si and P depending on the Si contents of the soils. In general the 2.2 T Si/ha application produced maximum yields in both soils and in some species it produced yields comparable to those with 8.8 T Si/ha at lower cost. Silicon concentrations in different plant groups were in the following order: grains > grasses > vegetables and fruits > legumes except for those of the two Desmodiums in which concentrations were similar to those of grasses. Plant Ca concentrations generally increased whereas Mg, Mn, A1 and Fe concentrations generally decreased when calcium silicate was applied. Silicon concentration was greatest in papaya and pineapple leaves and in sugarcane sheaths and was lowest in stems.
Hawaiian Cement Corporation (HCC) and Tennessee Valley Authority (TVA) calcium silicates generally produced higher yields than Technical grade (TG) calcium silicate, especially at low rates and in the third and fourth harvests. Plant Si concentrations in both HCC and TG calcium silicate were generally higher than in the TVA material indicating greater Si availability in these two materials.
Ear corn yields in the field were significantly increased by P applications but were not significantly affected by residual Si or pH. Highest stover yields were obtained at pH 5.5 suggesting increased Si solubility at this pH may have increased stover yields by increasing mechanical strength and P availability. The application of 280 kg P/ha with Si produced yields nearly equal (98%) to those of 1120 kg P/ha without Si suggesting that comparable yields at lower cost may be obtained with the combination of high Si and low P, than with high P alone. Corn leaf Si values of 0.5 to 0.6% at silking appeared adequate for corn growth. Silicon taken up by the plant is more closely related to soil Si extracted with water than with sulphuric acid. Multiple regression analysis with yield and leaf nutrients indicated that Si, P and Fe are especially important for stover production while P, Ca, K, A1 and Fe are important for ear production.
A statistically significant increase in the amount of water transpired per gram of dry weight with decreasing relative humidity was found in all species except D. intortum in solution cultures, but no significant increase in Si transport was obtained with increasing transpiration in any species. This suggests that transport of Si in plants is not related to transpiration. In continuous dark, plants accumulated Si in the roots and only sugarcane translocated large amounts of Si to the tops suggesting that metabolic energy is required for Si transport. Additional evidence of active Si transport was provided by the transpiration stream concentration factor (TSCF) values which were above or below one. Silicon concentrations in xylem exudates of D. Intortum, corn and sugarcane were greater than those of external solutions suggesting Si movement by active transport rather than by mass flow. In tomato and alfalfa Si concentrations were lower in exudates than in external solutions suggesting a selectivity mechanism in the root. These experiments demonstrated that both Si and P transport require metabolic energy.
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Ph.D. - Agronomy and Soil Science|
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