Issue link: http://read.uberflip.com/i/1073364
WWW.POTATOGROWER.COM 59 2354-41ViveCropProtection12h.indd 1 1/3/19 4:08 PM farmer for fertilizer. The organic farmer benefits from the manure nutrients at the expense of the farmer who produced the grain, unless all of the manure is returned to the original field (and nutrient losses will still occur as the chickens grow). When manure and compost is used to build soil organic matter and nutrient availability, it does so at the expense of other fields. Transfer of manure to organic farms also deprives other farmers from the use of the organic manure and its nutrients. The application of manure can improve soil properties, regardless of the farming system. Manure and compost are not "new" nutrients, but a valuable and scarce resource that can benefit all farmers. High-yielding organically grown crops rely on large inputs of organic matter, often from intensive animal operations. These organic materials are made available at considerable investment of time, land, water and nutrient inputs. These basic requirements are too often overlooked in the quest for using "organic nutrient sources." The true cost of producing these materials and building soil organic matter needs to be considered. The continued transfer of nutrients and organic matter from a large area to smaller farms is only maintained by replacing harvested nutrients with fertilizers to rebuild the lost fertility… and this does not account for the nutrients transported through food exports to cities and are then only partially returned to non-organic fields as biosolids. All sustainable cropping systems must eventually replace the nutrients removed in harvested materials. This replacement should be carefully managed to close the nutrient cycles as much as possible, produce healthy and nutritious crops, protect the soil, and minimize adverse environmental impact. Accomplishing these goals simultaneously is not a simple matter! Byproducts of the meat industry such as dried blood, feather meal, fish emulsion and ground bone are freely used as organic fertilizer without much thought of where their inherent nutrients came from. The animal byproducts only contain nutrients obtained from the soil where the feed or forage was grown. Similarly, products such as worm castings merely concentrate and transform soil nutrients, while making it convenient to transfer to another location. Cover crops and green manures will make valuable additions to the nutrient supply of the following crop, especially when N2-fixing crops are grown. But even legumes (such as alfalfa) require an abundant supply of phosphate and potassium in the soil for vigorous nitrogen fixation and vegetative growth. If harvested, an average-yielding alfalfa crop (3 tons per acre) will remove 45 pounds of phosphate and 180 pounds potash per acre from the soil. Additionally, during the time the field is being used for green manure production, a cash-producing crop is not being grown. There are clearly many benefits of using organic materials as sources of plant nutrition. The addition of organic matter to soil can stimulate soil biology, enhance soil porosity and structure, aid water and air infiltration, reduce soil density and benefit root health. However, let's be clear about where the nutrients in these organic materials come from. Recognize that accumulating organic materials from a wide area to fertilize a few fields is sustainable only by replacing the harvested nutrients to avoid gradual soil degradation.