SCIENCE CORNER
New Science
June 2022
High probability of yield gain through conservation agriculture in dry regions for major staple crops. Scientific Reports 11: 3344.
Su, Y., Gabrielle, B., Beillouin, D., Makowski, D. 2021.
Summary by Dobermann, A.
Conservation agriculture has been promoted to mitigate climate change, reduce soil erosion, and provide a variety of ecosystem services. It usually includes three main practices: permanent soil coverage (e.g., residue retention), reduced or no tillage and diversified crop rotations. Its impacts on crop yields or soil carbon sequestration remain controversial because they also depend on climate and soil type. In this paper, the authors mapped the probability of yield gain when switching from conventional tillage systems to no-till farming or to full conservation agriculture practices. 4403 paired yield observations on 8 crop species were extracted from 413 publications and relative yield changes were estimated with machine learning. No-till or conservation agriculture practices generally performed better in regions where water stress prevails, whereas yield benefits under wetter conditions were less or non-significant. Due to extra yield benefits arising from residue retention and diversified crop rotations conservation agriculture had better productive performance than systems in which only tillage was reduced. The authors also investigated the role of fertilizers, irrigation and weed and pest control, showing that no-till or conservation agriculture benefits are highest with good agronomic management. Of particular value in this paper are the global maps showing where in the world conservation agriculture targeted at specific climatic regions and crop species may work best, or where it may have no or only little yield benefit.
Classic Plant Nutrition Paper
Plowman's folly. University of Oklahoma Press, Norman, OK 162 pages.
Faulkner, E.H. 1943.
Summary by Dobermann, A.
Plowing the soil was thought to be a fundamental crop husbandry practice ever since it emerged in Mesopotamia around 3000 BC, or even earlier in rice cultivation in China. Yet, in July 1943, Edward Faulkner published his book Plowman’s Folly, which Time magazine called “one of the most revolutionary ideas in agriculture history.” Faulkner worked as a county agent in Kentucky and Ohio, as a teacher of agriculture, and through observation and experimentation as a researcher. He saw first-hand the devastation caused by the Dust Bowl in the Midwestern U.S. during the 1930, which firmed up his view that soil impoverishment, erosion, decreasing crop yields, and other adverse effects could be traced to the practice of plowing. In Chapter 4 he states: “In all truth, the ultimate scientific reason for the use of the plow has yet to be advanced.” As a remedy, he advocates the use of the disk-harrow to cut and incorporate crop residues or green manures into the surface soil, claiming that this might increase crop yields five- or ten-fold. His thought was that this would emulate nature’s way of incorporating organic materials into the forest floor or in natural meadows, and that this would also help with preserving soil moisture and controlling weeds and pests. Faulkner’s book provoked a huge discussion in the United States. In 1947 he published a sequel, A Second Look, in which he answered his critics and re-examined his earlier theories. We now know that Faulkner’s were based on the where he worked, and that a more differentiated view is need. The disk plow is not a universal solution either, and in some environments plowing remains essential. Moreover, since no-till, direct sowing of crops became possible in the 1950s it has become a popular element of conservation agriculture worldwide. But Faulkner’s stimulating book can be considered as the birth of the conservation agriculture movement. Globally, conservation agriculture rose from less than 5 million ha in 1980 to about 200 million ha at present.