RESIDUE INCORPORATION BY TILLAGE - INTERACTION OF MASS AND COVER

The majority of farm plans written to meet conservation compliance req uirements include surface residue as a major source of protection agai nst excessive soil erosion. Expected residue levels at critical period s in the crop rotation are predicted by applying residue retention fac tor values associated with specific tillage implements. Frequently val ues for retention by fraction of mass and by fraction of cover are use d interchangeably. A relationship between fraction of pretillage resid ue mass and fraction of pretillage residue cover retained as a functio n of a single area to mars residue characteristic and pretillage mass per unit area is developed in this paper cover and mass fraction reten tion values are similar only under very limited conditions. Conservati onists and others designing farm plans must be aware of these differen ces in cover and mass fraction retention values and ensure that consis tent procedures are followed in estimating the residue levels expected at critical erosive periods.