Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: September 1, 1995
Publication Date: N/A
Interpretive Summary: Most farm plans written to meet conservation compliance requirements specify minimum residue levels. Tillage systems are designed to meet these levels using specific residue retention factors for each implement in the tillage sequence. Residue has traditionally been measured in mass per unit area, but more recently as percent cover. In this paper we develop the relationship between residue retention by mass and by percent cover as influenced by residue quantity and characteristics. Conservation planners must be aware that in general, the same numeric values can not be used for mass and cover retention factors. Only when residue quantities are low and retention is high are the values similar.
Technical Abstract: The majority of farm plans written to meet conservation compliance requirements include surface residue as a major source of protection against excessive soil erosion. Expected residue levels at critical periods in the crop rotation are predicted by applying residue retention factor values associated with specific tillage implements. Frequently, values for retention by fraction of mass and by fraction of cover are used interchangeably. In this paper we developed a relationship between fraction of pretillage residue mass and fraction of pretillage residue cover retained as a function of residue characteristics and pretillage mass per unit area. It is shown that only under very limited conditions are cover and mass retention values similar. Conservationists and others designing farm plans must be aware of these differences and ensure that proper procedures are followed.