Impact of mature dairy manure compost and water content on wettability and bulk density in peat moss-perlite root substrate
2013
Barnes, J. | Nelson, P. | Fonteno, W.C. | Whipker, B. | Jeong, Ka-Yeon
Addition of mature dairy manure compost (DMC) to peat-moss based root substrate adversely increases bulk density (Db) while enhancing water sorption of the substrate. Substrate manufacturers typically raise the weight-based water content of soilless root substrate to 50% to ensure adequate wettability during crop establishment. This study investigated the possibility of lowering the percentage of water in substrate containing DMC in order to reduce Db without adversely affecting wettability. DMC was incorporated into a 3 sphagnum peat moss : 1 perlite (v:v) formula as a partial substitution for peat moss at 0, 7.5, 15, 22.5, and 30% by volume of the substrate. The water content of each of the five formulations was adjusted to approximately 10, 20, 30, 40, and 50% by weight. Wettability curves were generated to assess the impact of DMC content and initial water content on substrate wettability. The wettability level in the 0% DMC substrate at the industry norm water content of 50% was achieved in 7.5, 15, 22.5, and 30% DMC substrates at water contents of 40, 30, 20, and 20%, respectively. Based on previous research, 15% DMC is a desirable level for plant growth. The Db of 0 and 15% DMC mixes at 50% water content are 130 and 232 g/L (a Db gain of 78%), respectively. However, our research indicated that only 30% water is required in the 15% DMC mix for it to equal the wettability in the 0% DMC-50% water mix. This reduction lowered the Db of the 15% DMC-30% H2O mix to 180 g/L (a 39% Db gain), which cuts the Db gain due to the DMC addition in half and lowers the handling and transportation costs of this mix; this scenario is best for the industry.
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