Reduction in nutrient leaching from sandy soils by Si-rich materials: Laboratory, greenhouse and filed studies

Abstract

Sandy soils usually have low nutrient retention capabilities. Leaching of macronutrients applied as fertilizers can initiate eutrophication of natural waters which puts the health of fish, birds, and humans at risk. Greenhouse tests that simulated intensive leaching from sandy Spodosol that is treated with traditional mineral fertilizers were conducted. Calcium (Ca)- and silicon (Si)-rich substances (lime, CaSiO3, SiO2 and two types of the slag from the metallurgical and phosphate industries) were applied at a rate of 1 g L−1. Barley was used as the cultivated plant. The application of Ca- or Si-rich materials reduced P, K, NO3- and NH4+ leaching by 21 to 78%. Silicon substances increased the total content of P by 26 to 104%; K - by 16 to 72%; and N - by 13 to 54% in the barley. In demonstration field test, Si-rich steel slag applied to a field with sorghum previously used as a cattle pasture provided the reductions in P concentrations in nearby rivers by 65 and 77%. There are several hypotheses which can explain this outcome: a) Si-rich materials applied to the soil enhance nutrient adsorption; b) additional plant Si nutrition accelerates nutrient uptake; c) newly formed monosilicic acid increases the sorption capacity of the soil.