Mineral contents of organically and conventionally grown spinach (Spinacea oleracea L.) during two successive seasons.

Spinach (Spinacea oleracea L.) plants were grown organically and conventionally during two successive seasons (late autumn and early winter) in order to examine the nutrient content of the plants. In a series of 17 organic applications including chicken manure (CM), farmyard manure (FM), blood meal (BM), and one mineral fertilizer treatment and one control, collectively 19 treatments, were used at each season. The optimum doses to be recommended should be divided into groups depending on the mineral nutrients and also the seasons as follows: 1.7 CM+7.5 FM in the late autumn season and 2.5 CM + 4.0 FM in the early winter season for N, P, K content; 5.0 FM + 1.2 CM + 0.4 BM in the late autumn; and 2.5 CM + 4.0 FM in the early winter season for Ca and Mg. Regarding the micro nutrients, the group divisions should be as follows: 10.0 FM + 0.4 BM in the late autumn season and 5.0 FM + 2.5 CM in the early winter season for Fe and Cu, and 3.5 CM in the late autumn season and 10.0 FM + 1.2 CM in the early winter season for Mn and Zn content. High rates of farmyard manure (FM) and chicken manure (CM) can be successfully used in organic production, and high rates of these manures may substitute for mineral fertilizer, especially in the late autumn season.