Spanish research finds organic cereal more profitable

February 13, 2004, Fundazioa: University of Navarre, Spain researchers have designed a system for growing cereal crops that does not require fertilizer or weeding yet produced yields twice that of its conventional counterpart. The experiment, which took place on semiarid land, compared fields that used neither fertilizer nor weeding and instead implemented an alternating rotation of vetch and fallow, and a practice of returning the straw to the soil after harvest with conventionally managed fields using chemical fertilizers and herbicides.

In addition, researchers found that the higher yields of the ecological system could be turned into a profitability of four times that of the convention system when an organic market exists. The results were presented in a PhD thesis by Gabriel Pardo Sanclemente of the Public University of Navarre titled “The comparative study of fertilization and weeding of the ecological cultivation of cereals on semiarid land.”

The thesis is based on results from 26 tests carried out in various semiarid land zones in Spain in which barley was grown with vetch as a green manure and rotated with wheat and fallow. Experiments were carried out comparing chemical methods of fertilizer application and weeding with alternative organic methods.

The greatest profitability was obtained from the “ecological system,” with organic fertilizer application and the mechanical control of weeds. Following this was the “minimum system” without fertilizer application or mechanical control of weeds. Trailing behind and presenting the worst results in terms of profitability was the “conventional system”.

In the wheat tests, the average production rates from the fertilized and non-fertilized plots were practically the same. With barley, the chemically fertilized plots produced on average 400 kg/ha more than the organically fertilized ones, but this difference was not significant.

It was found that the high levels of soil organic material and initial phosphorus level were maintained after six years of testing, even in the non-fertilized plots, but the level of potassium dropped slightly. This suggests that the crop rotation used, together with the returning of the crop residues to the soil, was sufficient to maintain the initial levels of soil nutrients.

Regarding the weeding methods, both hoeing and the use of herbicides did not increase the crop yields in the test conditions. Weed density was, in general, poor on those cereal plots after the lying-in-fallow or buried vetch period. The least density of weeds achieved after any weeding treatment – mechanical or chemical – did not give rise to any significant increase in grain production when compared with the control.