Fertilizers are associated with many of the biggest environmental issues for agriculture because of the challenges in supplying all a crop needs without leading to movement of those nutrients into surface or ground water or to emissions of the highly potent greenhouse gas, nitrous oxide. The best practice is to “spoon feed” the nutrients through the irrigation system at levels designed to closely track the changing demands of the crop throughout the season.

Drip Irrigated and Fertilized Grapes



This requires water-soluble forms of the nutrients and that is very expensive to do for the natural fertilizer sources allowed in organic. Since the plants absorb those nutrients in exactly the same molecular forms regardless of source, this cost barrier is a non-scientific impediment to doing the best thing from an environmental point of view. Organic fertilizers like composts or manures are also much less practical for variable rate application, an environmentally beneficial option for rain-fed crops in which different amounts of fertilizer are applied to different parts of the field based on geo-referenced soil and yield mapping data. Finally, the organic avoidance of "synthetic fertilizers" would mean that these growers would not be able to use what appear to be promising small-scale, carbon-neutral, renewable energy-driven systems for making nitrogen fertilizers.