Soil Carbon Fractionation Under Perennial Forage.

Crop management practices can improve soil quality. Forage type and N-sources might also affect soil organic matter, especially soil carbon fractionation. The objective of this study is to evaluate the impact of legume inter-planting and compost application on soil C pools under a perennial grass mix. Parameters were determined in soil collected from plots representing different forages and various N-sources. The treatments in this study are laid out in a Randomized Complete Block Design with two factors and three replications. The first factor is the variety of perennial forage: Hybrid Wheatgrass-Tall Fescue-Hybrid Brome (HWG-TF-HB), Tall Fescue (TF), and Orchardgrass-Meadow Brome-Smooth Brome (OG-MB-SB). N-sources are the second factor: Sainfoin, dairy compost (24.71 Mg ha^-1), Alfalfa, and Alfalfa+dairy compost (24.71 Mg ha^-1). Data were analyzed by Analysis of Variance with a 95% level of confidence, and when there was a significant difference, data were further analyzed using Least Significant Differences. HWG-TF-HB had the greatest total carbon (2.16%) and recalcitrant carbon (0.78%) levels among the forage mixes tested. Alfalfa+dairy compost resulted in the greatest total C levels (2.16%) as compared to other N-sources. The shallow depth (0-5 cm) had greater total and recalcitrant C levels, i.e. 2.21 and 0.78%, respectively, than the 5-10 cm depth. N-sources affected total C but not recalcitrant C levels at 0-5 cm. The alfalfa+dairy compost (2.34% C) had significantly higher total C in the 0-5 cm depth than sainfoin (2.14%) or alfalfa (2.14%). The grass mix and N-sources had no significant effect on total and recalcitrant C in the deeper sampling depth (5-10 cm).       
Key words: carbon pools, perennial forage, N-sources