Carbon Sequestration During Sod Production Using Biosolids.

Wisconsin produces over 4,000 ha of sod annually at a value of nearly $10,000 ha^-1. Can we make sod production more sustainable by incorporating biosolids into soil, thereby conserving soil and providing an outlet for municipal biosolids disposal? The objectives of this study were to determine changes in Soil Organic Carbon (SOC) with biosolids additions to sod fields and estimate rates of CO₂ emissions when conventional fertilizers or biosolids are used as N sources. Kentucky bluegrass (Poa pratensis L.) was sown into sod production field plots amended with 0, 250, 500, or 1000 kg Plant Available N (PAN) ha^-1 biosolids. The experimental design was a randomized block design with four replications and two consecutive plantings were analyzed.  The non-amended plots received four applications of urea at 50 kg PAN ha^-1 during the growing season. CO₂ gas exchange data was collected monthly using an infrared gas analyzer and was not influenced by biosolids rate either year, but was influenced by collection date. Mid-summer Net Primary Productivity was statistically lower than spring values. Soil C values appear to have possibly increased over time, but any C gained is transported off site with the sod and additional data in the coming year from this study may support or refute this conclusion.