Initial Substrate Moisture Content Affects Chemical Properties of Bagged Substrates Containing Controlled Release Fertilizer at Two Different Temperatures

摘要

Bagged potting mixes can be stored for weeks or months before being used by consumers. Some bagged potting mixes are amended with controlled release fertilizers (CRFs). The objective of this research was to determine how initial substrate moisture content and storage temperature affect the chemical properties of bagged potting mix with CRF incorporated and stored for up to 180 days. The base substrate composed of 60 sphagnum peat: 30 bark : 10 perlite (by vol.) amended with 5.5 g center dot L-1 dolomitic limestone and 0.5 g center dot L-1 granular wetting agent. This base substrate was either not amended with additional fertilizer (control) or amended with 0.59 kg center dot m(-3) N of a CRF (Osmocote 18N-1.3P- 5K) that was either ground (CRF-G) or whole prills (CRF-P). Substrates had initial moisture contents (IMCs) of 25%, 45%, or 65% andwere stored at temperatures of either 20 or 40 degrees C. IMC and fertilizer type affected pH, electrical conductivity (EC), and nutrient release. Substrate pH increased with increasing IMC due to greater lime reactivity. About 25% of N from CRF-G treatments was immobilized between 2 and 14 days of storage. Low moisture content of bags, due to low IMC or storage at 40 degrees C, reduced the rate of N release from CRF-P treatments. Substrate P was rapidly immobilized by microbial communities.