June 5, 2008

 

Organic farmers gain higher yields from crop rotation
   

  

Organic grain farmers are at a disadvantage to their conventional counterparts when it comes to yields, but research on using complex crop rotations suggests these farmers can significantly raise production.

 

By utilizing a four-year rotation of corn, soy, wheat and hay, organic corn yields were increased by 30 percent compared to a simple organic corn-soybean rotation, according to research done by the USDA's Beltsville Agricultural Research Center in Maryland.

 

"It (the study) will help organic farmers recognize the impact of the crop rotation they select on yields and also on economic returns," said Michel Cavigelli, a soil scientist at the USDA's Agricultural Research Service and lead author of the study.

 

Cavigelli's research is one of the first to tackle the effects of crop rotation on organic farm yields.

 

The USDA study collected data on crop yields, nitrogen inputs and weed densities from the Beltsville Farming Systems Project, a long-term cropping systems trial with two conventional and three organic systems. The three organic systems used in the study each had differing crop rotations.

 

On the first organic system, a two-year rotation of corn and soy was implemented. The second organic system implemented a three-year rotation of corn, soy and wheat. The third organic system, which produced the highest yields, used a four-year rotation of corn, soy, wheat and hay.

 

Data was collected for 10 years on each of the organic systems, but the purported increase in corn yields was derived exclusively from 2000 to 2005.

 

The average corn yields during this six-year period were 75 bushels per acre on the two-year corn and soybean rotation, compared to 88 bushels per acre on the three-year rotation.

 

The four-year rotation saw 98 bushels per acre.

 

Adding alfalfa to the rotation boosted nitrogen, which is key to higher corn yields.

 

Still, these yields come up short compared with that from conventional agriculture, which yields 151 bushels per acre on national average. 

 

Traditionally, the natural animal manures and legume crops used as fertilizer on organic farms do not provide as much nitrogen as fertilizers used in conventional farming practices.

 

Since organic farming do not use pesticides, there is the problem of weed growth.

 

However, using lengthier and more complex crop rotations was found to cut down on such weed growth, said Cavigelli.

 

However, the variety of crops grown makes it harder for such growers to market their produce.

 

"There is more responsibility on the grower to find a market," said Jim Stordahl, extension educator and assistant professor at the University of Minnesota. "It's less of a reliable market, especially for those who tend to jump in and out."

 

Still, this means less exposure to price fluctuations. The more diverse the crop rotation, the less vulnerable farmers are to fluctuations, Cavigelli said.