SCIENCE CORNER
Every month, we will feature here a new science paper and a ‘classic paper’ that represents an important milestone in the science of plant nutrition. Many discoveries were made in the past +200 years that influenced our current knowledge about nutrients, their forms and behavior in soils, plants or the wider environment. Some discoveries had immediate value, while others only later turned out to be of great significance for farming. Where possible, we provide a web link to openly accessible papers.
News
January 2023
How understanding soil chemistry can lead to better phosphate fertilizer practice: a 68 year journey (so far). Plant Soil 476: 117-131.
Barrow, N.J. 2022.
Summary by Dobermann, A.
This paper is one of those rare gems that provide you with decades of scientific knowledge distilled into a very readable and inspiring format. Jim Barrow started doing research at the interface between soil chemistry and plant nutrition in 1954 when, as a new graduate, he was employed by CSIRO in Australia. Here he summarizes what he has learned about phosphorus (P), and why some of our views on it are outdated. He addresses two main questions: (1) Why do farmers reapply phosphate? The short answer is that phosphate effectiveness decreases with time and it is therefore necessary; (2) Why does P effectiveness decrease with time? The major reason for the decline in effectiveness with time is penetration of phosphate ions by diffusion into the reacting soil surfaces, which changes their properties. Readers will also learn a lot about terminology and methodology used in studying the fate of P in soils and how the process of knowledge generation took place over decades, leading to more comprehensive hypotheses and models.
This work has implications for some of the most widely held theories in soil science. These theories are largely based on the notion that soil phosphate exists in discrete compounds with iron, aluminium and calcium. The work summarised here indicates, however, that such compounds do not exist under most common soil conditions. Barrow suggests that long-term fertilized soils no longer lock up or fix applied P. It is then only necessary to feed the plants, not the soil, i.e. annual doses (if they are needed at all) should be much smaller. Failure to appreciate this is the cause of P losses from farmland and consequent pollution of water bodies. He also suggests that for long-term fertilized soils, current soil tests do not give information on two important characteristics: the decrease in P buffering and the slowing of the penetration. This paper provides much food for critical and innovative thinking. Enjoy it.
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.