AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Winter 2002, No. 1
Productive farms export nutrients. Producing food and feed removes nutrients from the soil. Nutrients removed must be replaced. Opportunities to recycle include use of animal manures and incorporating crop residues in the soil, but recycling is never one hundred percent efficient. Continued export is not sustainable.
Standards for organic farming make it more difficult to replace exported nutrients. Their rules require nutrients to be chiefly from organic sources, such as green manures and animal manures. Preferably, these manures are generated on-farm. The major certifying bodies exclude use of the synthetic and soluble forms of nitrogen and phosphate that contribute greatly to today’s productive agriculture. They differ on allowable forms of potash. Overall, these rules constrain the replacement of nutrients on the farm.
As a small proportion of the total farm population, organic crop producers benefit from the nutrients provided from synthetic fertilizers. Use of phosphorus and potassium fertilizers has built up soil fertility—today about 45 percent of North American soils test medium or less, compared to more than 70 percent 30 years ago. Even though it may take decades for the soils to be depleted of their reserves, nutrient imbalance will put a limit on the sustainability of organic cropping.
Commercial fertilizers of all kinds contribute to the production of organic materials. The nutrients turn up in animal manures and crop residues. Through various paths, the surplus nutrients of conventional farms make their way to organic farms.
Productivity is the other constraint limiting the sustainability of organic cropping. Because of lower yields, widespread adoption of organic cropping would push production onto marginal land—land more susceptible to erosion and nutrient loss. And less would be left over for wildlife habitat.
Progressive producers recognize the need to improve crop yield and quality while reducing environmental impact. They recognize that sediment and nutrient losses are sometimes higher than many desire. They could benefit by espousing some of the positive ideals of organic farming. For example, green ground cover. The corn-soybean rotation, highly productive though it is, has a huge gap in green ground cover. Especially in the spring, there’s a big opportunity to capture more of the sunshine that falls wasted and convert it to green organic material for the soil. Cover cropping could go a long way to enhancing sustainability, and preventing nutrient losses—but it must work within a nutrient-balanced, high-yield system.
Healthy soils need actively growing crops that contribute organic matter and support life. Healthy plants need nutrients, water, air, and support from the soil. And healthy people need quality food, produced without contaminating water and air.
Today’s producers need to recognize the reasons why consumers choose organic. They share the goals. They will demonstrate that nutrient-balanced production practices based on science are the ones that produce healthy soils, healthy plants, and healthy people.