Interaction between silicon cycling and straw decomposition in a silicon deficient rice production system

Rice plants (Oryza sativa L.) contain large quantities of silicon (Si) in form of phytoliths, which increase their resistance to abiotic and biotic stresses. The Si cycle through rice fields is hardly studied. We tested how increasing Si availability affects rice growth and the decomposability of the straw. Secondly we tested the role of straw recycling for Si availability. In a field experiment, we applied three levels of silica gel during one rice cropping season. In a follow-up laboratory experiment, we used straw produced in the field experiment, having different Si concentrations, and studied straw decomposition, straw Si release, and Si uptake by plants. Silicon fertilization increased Si contents, biomass production, and grain yield of rice plants. Increased Si uptake by rice decreased concentrations of C and some essential nutrients (N, P, K, Ca, and Mg) in the straw, and increased straw decomposability and Si release. Fertilization with silica gel is an option to improve Si supply to rice plants growing on weathered soils with low levels of plant-available Si. Phytoliths from fresh rice straw dissolve fast in soil, thus, recycling of rice straw is an important source of plant-available Si.