Growth of wild rice, Zizania aquatica L., in flocculent sediments

Abstract

The objectives of this research were to classify sediments from wild rice lakes, and to examine, in detail, one type of sediment that is not suitable for commercial production of wild rice. Based on physical and chemical differences, cluster and discriminant analysis classified sediments from 39 potential and existing wild rice lakes into clay, organic, flocculent, organic-flocculent, organic-clay, and organic over clay (organic/clay) types. The major differences among the six sediment types were the percent loss on ignition, bulk density, phosphorus and cation content, and pH values. Wild rice production was best in organic, organic over clay, and organic-clay sediments. Flocculent, clay, and organic-flocculent sediments produced the lowest dry weights of individual plants. Organic-flocculent and organic/clay sediments were examined for further physical and chemical differences, as well as seasonal nutrient trends and wild rice production. Organic-flocculent and organic/clay sediments were found to have C:N>10, and similar inorganic biogenic composition, mineral content, pH, and redox values. Major differences in nutrient values were found to exist between the sediments. Lower nutrient values (except N) in organic-flocculent sediment appear to be closely linked to the origin, type, and degree of decomposition of the organic material within the sediment. A comparison of seasonal nutrient trends between organic-flocculent and organic/clay sediments showed no nutrient depletion during the exponential growth of wild rice. Fertilizer trials and foliar nutrient deficiency symptoms determined which nutrients were limiting production in organic-flocculent sediments. Phosphorus was found to be the main limiting nutrient; nitrogen deficiency played a secondary role. Plants grown in unfertilized organic-flocculent sediments displayed the purple leaves and slower maturation rate characteristic of phosphorus deficiency.