Rice hulls are the by-product of rice cultivation of food for humans and animals.
Rice hulls are used in three forms for plant cultivation: aged, composted, fresh and parboiled. Aged rice hulls are allowed to passively decompose until the hulls have oxidized to a brown color. Composted rice hulls are black or brown and have broken into smaller pieces and are used primarily for water holding capacity. Fresh rice hulls decompose very slowly and have shown to be inferior compared to other types of hulls for plant production. Parboiled rice hulls, or PBH, are yellow or tan colored and have been exposed to high temperature water to sterilize for pathogens. Parboiled hulls have been shown to be superior to other hulls as a media amendment.
Rice hulls are a by-product of food production and are readily available in the United States with most production coming from Louisiana, Texas, Arkansas, and California. Comparable to perlite in water holding capacity per weight, but has a higher air-porosity ratio than perlite which means it has greater potential for oxygen in the root zone. Bio-degradable, inert, and no dust like perlite.
Rice hulls seem to work best as a media amendment at about 25% volume/volume mixed with peat or coir, but don’t seem to perform as well when used as a standalone media. Also, has a low cation exchange capacity.