Environmental impacts and consumer preference for sustainably cultivated Japanese mustard spinach, komatsuna

Sustainable agriculture is spreading in Japan in response to growing concerns about the environmental burden of the agriculture sector, but less than 1% of the total crop area for each vegetable in Japan is grown sustainably. Environmentally friendly agricultural products are produced by using organic and low-input farming techniques; low-input farming aims to reduce chemical inputs, such as fertilizers, pesticides, and herbicides, by half. Here, we used komatsuna (Japanese mustard spinach, Brassica rapa var. perviridis) as a model vegetable to study the environmental impact of low-input farming and ways to promote the purchase of organically and low-input farmed vegetables. We first assessed greenhouse gas emissions resulting from organic, low-input, and conventional farming of komatsuna. We also evaluated the effectiveness of providing consumers with detailed farm management and seasonality information to market organically and low-input farmed vegetables. We estimated marginal willingness-to-pay (MWTP) using choice-based conjoint analysis, based on attributes of price, fertilizer use, pesticide use, and region of origin. For seasonality, the questionnaire incorporating these attributes was conducted twice: once assuming purchasing in season, the other out of season. The greenhouse gas emissions of organic farming per area (196.7 kg CO₂-eq/10 a/year) and per yield (72.3 kg CO₂-eq/t/year) were less than those of low-input (322.6 kg CO₂-eq/10 a/year, 120.7 kg CO₂-eq/t/year) and conventional (594.0 kg CO₂-eq/10 a/year, 220.7 kg CO₂-eq/t/year) farming. MWTPs were highest for pesticide-free komatsuna (76.9 yen out of season, 66.2 yen in season), followed by full organic fertilizer (66.0 yen out of season, 63.4 yen in season), half organic fertilizer (35.8 yen out of season, 19.8 yen in season), and half pesticide (29.2 yen out of season, 21.0 yen in season). Consumers showed greater preference for organically and low-input farmed komatsuna out of season than in season. Consumers were more interested in pesticide information than in fertilizer and region of origin information. Our findings suggest that providing detailed cultivation and seasonality information would be a beneficial consumer communication tool to increase the market for sustainable agricultural products.