Degree

Doctor of Philosophy (PhD)

Department

School of Plant, Environmental Management and Soil Sciences

Document Type

Dissertation

Abstract

Studies were conducted to evaluate the impact of silicon (Si) fertilization on the uptake of harmful trace elements in Louisiana rice production system, and document the effect of silicate slag granular size on its ability to supply Si in wheat. The influence of silicate slag and lime on the uptake and translocation of harmful trace elements in rice grain was determined. Results showed that both slag and lime had similar effects on pH at five of the nine sites investigated. Soil Si was significantly (P <0.001) increased with application of silicate slag at all sites. Lime and silicate slag had no effect on the concentration of trace elements in soil. However, increasing Si rates were negatively correlated with arsenic (As) and cadmium (Cd) concentration in rice grain. The release pattern of monosilicic acid (H4SiO4) from wollastonite and silicate slag was compared in a wheat greenhouse study. Maximum release of Si from these materials were observed within the first 30 days after application and thereafter remained steady until 120 day after treatment application when a decline in soil Si became evident. Silicon extracted from soils treated with fine and ungraded silicate slag showed the greatest increases in soil Si when compared to wollastonite and the coarse and pellet slag materials. Wheat Si uptake was also higher for the fine silicate slag followed by ungraded silicate slag and wollastonite. But wheat yields were higher in the wollastonite treatments compared to silicate slag treatments. Among the different granular sizes of silicate slag, fine and ungraded materials resulted in higher wheat grain yield than coarse and pellet. In a field study, different granular sizes of silicate slag were applied at increasing rates to establish optimum Si application rate for wheat in Louisiana. The application of 1.8 and 3.6 Mg ha-1 of fine material was sufficient to increase wheat grain yield in three out of four sites studied. It is likely that application of Si in Louisiana agriculture has the potential to improve rice grain safety, by x limiting uptake of harmful trace elements and also improve grain yield in wheat cultivated on Si deficient soils.

Committee Chair

Tubana, Brenda

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