Assessment of the Mineral Nutritional Value of Vegetable Crops Grown in Organic or Conventional Systems of Farming

Experiments will be conducted in the greenhouse and in the field with leafy vegetables to investigate if the mineral nutrient content of these foods can be enriched through fertilization of the crops. This research will address investigations of mineral nutrients, suggested to include phosphorus, calcium, magnesium, potassium, iron, manganese, copper, and zinc, which the investigators have the capability of analyzing in their laboratories. The research will emphasize investigations with lettuce that can be cycled rapidly in greenhouse or field production. Lettuce will be grown until it is of marketable sizeVegetable crops will be provided with complete nutrition from fertilizers that are available commonly for organic or conventional fertilization of crops. Organic fertilizers will include seed meals, animal by-products (dried blood, farm manures, feather meal), and compost.          A complete chemical fertilizer will be a conventional fertilizer in the investigation. The elemental nutrient composition (Total and nitrate-N, P, K, Ca, Mg, and selected micronutrients) of the plants will be determined in edible parts the crops by Kjeldahl analysis, colorimetry, and plasma spectro-photometry.
Many growers are trying to produce crops in containers on the ground or hard surfaces, on decks, or on rooftops in urban areas.  Because of the costs of materials and labor for buying and handling media, media are being used for two or more crops in succession. Nutritional disorders are apparently limiting productivity in the second season particularly with organic production. A study will be conducted with peat-based medium that has been fertilized with organic fertilizers, such as seed meal, bloodmeal, and dehydrated farm manure for the first crop and grown in a greenhouse. The second crop will be grown in the same medium. Fertilization of the second crop will be with no additional fertilization or with fish emulsion or with water-soluble fertilizer (such as 20-10-20 Peat-lite Special) to provide organic and conventional fertilization. Radish (Raphanus sativus L.) or loose-leaf lettuce will be used. Radish is suggested because of the small amount of fibrous roots that will be residual in the containers. These crops will be assessed for productivity and composition of mineral elements.
A commercially available organic fertilizer that is acceptable for hydroponic production of lettuce will be compared with a conventional hydroponics solution. This study will be in containers filled with an inert medium that is fertilized repeatedly to simulate hydroponic production. Loose-leaf lettuce or romaine lettuce will be the test crop for greenhouse production. The medium will be a peat-based medium to which nutrition is supplied with the fertilizer solutions on a daily basis. The medium will supply no nutrients to the crop, but an unfertilized treatment will be included to assess nutrient supply from the medium. The lettuce will be assessed for productivity and composition.