Background and methodology
This study involved fruit from a 1.6-hectare commercial apple orchard (Malus domestica Borkh. cv. ‘Golden Delicious’) planted in 1994 in Washington state. The orchard consisted of four replicate plots of each of three production systems: organic, conventional and integrated. One objective of this study was to assess the long-term effects of these production systems on soil/plant mineral nutrient relations and fruit quality. Organic soil management practices included the addition of composted poultry manure and bark mulches, woven polypropylene fabric, and mechanical tillage for weed control. Conventional soil management practices included synthetic fertilizers and herbicides for weed control. The integrated treatment utilized a combination of organic and conventional practices.
After five years under these production systems, total topsoil nitrogen was significantly higher in the organic and integrated systems compared to the conventional system, although nitrate was lowest in the organic system. Even though these differences in available soil nitrogen have not led to differences in leaf nitrogen among the three systems, the lower available soil nitrogen in the organic system is associated with significantly lower fruit tissue nitrogen. Fruit calcium contents have consistently risen in all three production systems over the four cropping years. In addition, there were significant differences in fruit nutrient ratios among the three systems. These differences are discussed in terms of fruit quality under varying soil management practices inherent among organic, conventional and integrated apple production systems.
Andrews, P. K., Fellman, J. K., Glover, J. D., & Reganold, J.P. (2001). Soil and plant mineral nutrition and fruit quality under organic, conventional, and integrated apple production systems in Washington State, USA. Acta Horticulturae, 564, 291-298.