Cooling Off With Compost, Ctd

A reader says the case for no-till farming is more complicated than it seems:

While the evaporation argument made by the Ars Technica article is valid, I don’t see the benefit from the change in albedo - the amount of sunlight reflected from the Earth’s surface. During most of the hot and sunny portion of the summer, for example, the crops we grow on our family farm in Missouri will have grown tall (corn) or canopied (soybeans) so that the residue is in shadow. Other crops like winter wheat are planted and harvested on a different cycle, so there might be more benefits from the effect on albedo.

Regarding carbon affects, there are drawbacks to no-till systems. Typically, more herbicide is required to kill weeds, and more nitrogen (which is produced with fossil energy) is required for fertilizer. Farmers argue about the comparative yields, but generally, flat land farmers still use conventional tillage. A recent USDA analysis shows that 35.5 percent of US cropland was planted with no tillage in 2009. No-till use has increased a great deal since it began to be adopted in the 1980s, but even in the US it’s still used on a minority of farms. There’s research under way at the Economic Research Service of the USDA on the potential of various methods to mitigate carbon dioxide additions to the atmosphere. Here‘s an example of their analysis [partly illustrated in the above graph].

Overall, higher temperatures and the greater risks and uncertainty of more extreme weather conditions are driving forecasts for 15- to 20-percent reductions in crop yields over the next 25 to 50 years. The implications of those forecasts are sobering.