In former times, farmers used to rotate their crops, so that a field would have different crops grown in it each year over three of four years until the cycle started again. Often, in mixed farms, one year’s ‘crop’ would be the livestock allowed to feed on the field, resting the soil and replenishing it with their manure.
The rationale for this was that different plants used different nutrients and attracted different pests and diseases. By moving the crops around, farmers could avoid depleting the soil of key nutrients and prevent the build-up of parasites.
Then modern farming vastly reduced crop rotation, which provided a more efficient use of the soil and higher yields. Except that it didn’t.
The US Department of Agriculture, University of Minnesota and Iowa State University joined forces in 2003 to investigate the effects of longer crop rotations on yield, profits, herbicide and fertiliser use, and labor inputs. This week PLOS One published the results of the trial. The findings showed that crop rotation increased yields and profits, and reduced the need for herbicide and fertiliser applications. Freshwater toxicity in the longest rotation of four years was reduced by 200%.
The researchers also found that labor input was greater the longer the rotation.
A return to working on the land?