Composted Rabbit Manure as Organic Matrix for Manufacturing Horticultural Growing Media: Composting Process and Seedling Effects

This study investigated composted rabbit manure as an organic matrix to replace peat for manufacturing horticultural growing media, where three kinds of rabbit manures were composted with temperatures > 50 degrees C lasting > 7 days, with a germination index > 70%. The heavy metal contents in rabbit manure were far lower than the thresholds in Chinese standards for safe use as horticultural growing media. Then, different ratios of compost and peat were mixed with perlite and vermiculite to manufacture growing media, which were evaluated in a 28-day seedling experiment with cabbage. The manufactured growing media characteristics could satisfy the seedlings' requirements; air spaces in particular were improved from 15.7% to up to 28.7% by mixing composted manure. Seedling emergence percentages > 90% and good seedling qualities (including enhanced root length, seedling height, and chlorophyll content) indicated that composted rabbit manure could effectively replace peat to manufacture horticultural growing media. The best seedling performance was obtained with the following ratio of composted manure, peat, perlite, and vermiculite: 3:3:2:2. However, the mixing ratio could be further optimized, and other methods to reduce the salinity may be required for the different requirements of specific crops in further research.