Application of silk waste to planting of bulbous plants in construction byproduct.

Abstract

The fertilizer efficiency of silk waste for planting of bulbous plants in construction byproduct as a planting ground were examined and compared with two commercial controlled release fertilizers, isobutylidene diurea (IBDU) and polyolefin-coated fertilizer. Silk waste mainly consists of silk proteins, which has high N content and is decomposed slowly in soil. Five species of bulbous plant, Narcissus tazetta var. chinensis, Lycoris albiflora, Allium chinense, Muscari armeniacum and Oxalis variabilis, were planted with each of the three fertilizers. No maintenance was carried out, except for weeding once during the experimental period. The silk waste was decomposed continuously for about 400 days, which indicated that the silk waste had fertilizer efficiency for not less than 400 days under the conditions used in this study. In the second growing season after planting, all plants grown with the silk waste or IBDU were larger than those grown without any fertilizers, except for 0. variabilis, which was hardly viable until the second season. In the case of A. chinense and M. armeniacum, no or little effects of fertilizer were seen on growth with polyolefin-coated fertilizer. Regardless of the type of fertilizer or the degree of plant growth, the ratios of green coverage, determined by image analysis, were equally increased relative to those without fertilizer, except for A. chinense and M. armeniacum with polyolefin-coated fertilizer. N. tazetta var. chinensis with IBDU had many thin leaves of daughter bulbs, which indicated that the division of bulbs occurred during the first growing season due to the excess N released from IBDU. The weight of M. armeniacum with IBDU was smaller than that with the silk waste, which suggested that salt damage occurred in the first growing season resulting in the depression of fertilizer efficiency or that the fertilizer efficiency of the silk waste was higher than that of IBDU in the second growing season. These results suggested that silk waste was an efficacious fertilizer in planting under these conditions.