Binderless board made from composted rice straw as substrate for rice seedlings

A binderless board was produced from mechanically dissociated compost straw via suction filtration. The binderless board was applied to replace the topsoil that is currently used predominantly as the substrate for rice seedlings in China. The binderless board showed the highest tensile strength when the rice straw had been composted for 20 days. The bulk density, aeration, and total porosity of the binderless board showed an increasing trend with composting time, due to the increased decomposition of rice straw. The examination of the growth parameters and root morphology of the rice seedlings showed that electrical conductivity (EC), pH, and nutrient content of the binderless board made from rice straw composted for 10 days were conducive to the growth of seedlings. Polyphenols inhibited rice seedling height and shoot weight and promoted the rice seedling stem diameter and root weight. Considering the quality loss, growth index, and the strength of the binderless board, 10 days of composting is the optimal condition. These results indicate that binderless board can replace top soil and peat when used as the substrate for rice seedling.