Performance Study On Application Of Steam-exploded Rice Straw For Growing Substrate

With steam-exploded rice straw used as materials, the effect of composition and structure properties as growing substrate is investigated. The main results are listed as follows.1. By the treatment of steam-explosion, the content of hemicellulose in rice straw decreased greatly. The content of lignin and ash changed little. C/N ratios and pH value got lower, but EC value was higher. Steam explosion pulp was abundant in nutrient elements and without heavy metal pollutants.2. The physical properties of rice straw changed significantly after steam explosion treatment. With milling treatment bulk density and total porosity improved, but airspace and ratio of large and small pores decreased. Through utilizing steam-exploded rice straw to amend sandy soil, the bulk density, porosity and water holding capacity showed a good linear relationship with the content of steam-exploded rice straw.3. Bok choy (Brassica chinensis) was used to investigate the effects of the dissolved substrate of steam-exploded rice straw on seeds germination. A positive effect can be observed on promoting germination potential and germination rate. The total fresh and dry weight increase under suitable concentration. The releasing substance from steam-exploded rice straw is also beneficial to vegetable root/stem.4. According to the ion analysis of dissolved substance from steam-exploded rice straw, K⁺, Ca²⁺, Mg²⁺ and NH₄⁺ were detected, in which K+ was the highest, and NH₄⁺ was the lowest. Milling and refining had a positive effect on mineral substances releasing. Nutrient liquid being added, the increase of Ca²⁺ and Mg²⁺ lowers the adsorption efficiency of K⁺ and NH₄⁺. The adsorption ability of Ca²⁺ was stronger than Mg²⁺, and even part of the adsorption point of Mg²⁺ is replaced by Ca²⁺. The anions adsorption of steam-exploded pulp is not stable. The dissolved organic matter with negative charge decreases the quantity of anions adsorption.