Direct calorimetric analysis of turf grass sod for storage life assessment

Heating of stacked turfgrass sod post-harvest, causes rapid plant tissue deterioration and is a major factor for stacking arrangement, storage time and the geographic distance that sod can be shipped. Direct calorimeters were designed, built, and tested to measure heat production and heat transfer rates through material with known thermal properties. They were calibrated using electrical resistance heating and analyzed as steady-state systems. Kentucky bluegrass (Poa pratensis L.) sod sections with moisture contents ranging from 6 to 30% were placed in calorimeters throughout the summer and fall of 2002 to determine the influence of moisture content on heat production. Energy production had a positive linear relationship with moisture content. Transient temperatures cycles were found to be small. The rate of increase was 0.0032 W kg^-1 dry weight for each percent sod moisture content between 6 and 30%. This suggests that lower moisture content is more desirable for generating less heat, but sod must be irrigated prior to harvest to provide adequate handling properties. Further research needs to be conducted to determine the minimum sod moisture content to reduce heating, while maintaining handling properties. Controlling sod heat production could expand the shipping area for sod producers.