Effects of conventional and organic fertilization on spinach (Spinacea oleracea L.) growth, yield, vitamin C and nitrate concentration during two successive seasons

Current experiment was laid out in order to compare different kinds of organic manure and chemical fertilizer application in growing spinach under the open-field conditions in two successive seasons. Matador type spinach (Spinacea oleracea L.) was cultivated organically and conventionally and spinach growth, yield, vitamin C and nitrate concentrations were checked throughout two successive seasons (autumn and winter). Commercial chemical fertilizer was used as conventional application, and chicken manure (CM), farmyard manure (FM) and blood meal (BM) were used as organic manure applications as a single and as mixtures at different quantities by aiming to receive 150 kg N ha−1 for each, totally 19 applications. In general, autumn season gave the better results in terms of spinach growth, yield and resulted in lower nitrate concentration, whereas the vitamin C concentration was found to be higher in winter season. Reasonable applications to be recommended should be as follows with regard to the seasons; 3.5 ton ha−1 CM and 0.6 ton ha−1 BM + 0.85 ton ha−1 CM + 4.0 ton ha−1 FM for spinach growth; 3.5 ton ha−1 CM and 5.0 FM + 1.2 CM + 0.4 BM applications for spinach yield; 5.0 ton ha−1 FM + 2.5 ton ha−1 CM and 15.0 ton ha−1 FM for vitamin C and nitrate concentration in the autumn and the winter season, respectively. In conclusion, FM and CM can be used effectively in growing organic spinach especially in the autumn season and can be transferred successfully into an asset.

Research highlights▶ Organically grown spinach contains lower amounts of nitrate and higher amounts of vitamin C. ▶ Plant growth in single application of CM is as high as in mineral fertilizer. ▶ FM and CM are superior to BM application. ▶ Organic applications respond well in the autumn season than that of the winter.