The debate on the yield superiority of traditional crops over organic crops is set to continue as a recent study reveals that corn and soybeans were only minimally reduced when organic production practices were used instead of conventional production practices.
According to scientists at the University of Minnesota who carried out the research, after accounting for production costs, net returns between the two production strategies were equivalent.
More than 80 per cent of corn and soybeans produced in the United States is grown in the Midwest, the vast majority with conventional production practices in a corn-soybean rotation requiring annual synthetic fertiliser and pesticide application. This corn-soybean rotation is practiced on over 100 million acres.
Organic production practices, in compliance with standards defined by the United States Department of Agriculture's National Organic Program (NOP), offer an alternative production system to conventional practices.
The study was conducted at two Minnesota locations from 1989 to 1999. Scientists evaluated a two-year corn-soybean rotation and a four-year corn-soybean-oat/alfalfa-alfalfa rotation under conventional and organic management and production strategies. The analysis of yield data began in 1993, after the first complete cycle of the four-year rotation had occurred. From 1993 through 1999, yield of corn grown in the conventional two-year rotation averaged 143 and 139 bushels per acre at the two locations, while corn grown in the organic four-year rotation averaged 9 per cent and 7 per cent less, respectively.
During the same time frame, soybeans grown in the conventional two-year rotation averaged 43.1 and 40.7 bushels per acre, while organically produced soybeans averaged 19 per cent and 16 per cent less, respectively.
Not totally surprising, weed control was a major factor for the reduced yields in the organic production system, said Paul Porter, a university of Minnesota agronomist and co-author of the study. The larger yield reductions from organically produced soybeans relative to corn were associated with increased weed pressure in the soybean crop because of its placement in the rotation sequence.
Of particular interest is that while there was a reduction in both corn and soybean yields in the four-year organic strategy compared with the two-year conventional strategy, the organic strategy had lower production costs than the conventional strategy. Consequently, net returns for the two strategies were equivalent, without taking organic price premiums into account.
Conventionally produced soybeans were more responsive than conventionally produced corn to the expanded rotation length, added Porter.
Full findings of the study are published in the March-April 2003 issue of Agronomy Journal .