Here is a question for Owen and Neil.
Are there types of soil or kinds of terrain where keyline plowing is not suitable, or requires special adaptions?
I live in the Idaho Palouse. Our soil is a clay loam called loess. The land form is hilly dunes. The large scale farming is mostly dryland wheat. Hedgerows are now absent, and road edges are typically brush hogged and herbicided, so where occasional ponderosa pines, aspens, cottonwoods, and a praire steppe grass and shrub ecosystem once thrived, with wild rose, ocean spray, ninebark, snowberry, etc., now there is often not much. Even the poor cow parsley gets sprayed.
In late winter and early spring there typically appear slumps in the land, most often on the road edges, often where a field has been cultivated right to the brow of a hill above a road cut. A piece of ground will slide down the hill, often blocking the road, and sit there till the highway district hauls it away, or spreads it out along the downhill creek edge.
The topsoil (what remains after years of bad practices) and subsoil seem to slide slanty-sideways on seasonal springs of water which run out over the hard clay beneath. It''s like a layer cake with a too soft filling.
it seem obvious that one would never want to plow (or make a swale) on contour in these conditions, even if ones own location was better vegetated than average. Is keyline slowing still appropriate for our region? Should one make adjustments in the degree off contour one plows, or the depth of the cut, or the distance between cuts (or dug swales)? Other comments?