Comparison of nutritional quality of the crops grown in an organic and conventional fertilized soil

Organic farming is growing rapidly in its potential for producing healthy foods and has been adopted in a wide range of climate and soil types. The perception among consumers is that organically produced crops possess higher nutritional quality. However, there are many factors that can affect the nutritional quality of crops, and few studies have been able to account for these differences. A comparative long-term study of organic versus mineral fertilisation has been conducted for nine years in a calcareous loamy soil classified as Xerofluvent in the Guadalquivir River Valley, near Seville, Spain. The macronutrient concentration, dry matter and nitrate content in the edible part of the plants over the last five years of the experiment were examined. We found that the nitrate concentration in the edible parts was significantly lower in crops grown in organically fertilised plots. We also found a tendency for lower N and higher P content in organic crops cultivated in same crop cycle. However, the results also showed variability in the nutritional parameters for the same crop but cultivated in different years. We conclude that it is not possible to assert a higher nutritional quality of organic crops according only to the criteria of fertiliser type; other factors, such as fertiliser characteristics and management in each particular crop cycle, exert a higher influence on the nutrient content of crops. (C) 2011 Elsevier B.V. All rights reserved.