Possibility of Introducing Winter Legumes, Hairy Vetch and Faba Bean, as Green Manures to Turmeric Cropping in Temperate Region

A field experiment was conducted to examine the possibility of introducing winter legumes, hairy vetch and faba bean, as green manures to turmeric cropping in a temperate region. Hairy vetch shoots were incorporated to determine the effect of N and P added as green manure. Higher values in plant height and number of leaves of turmeric were observed in the treatment with incorporation of hairy vetch than in that without incorporation (no-incorporation) throughout the growth periods. The differences in total amounts of N and P of turmeric between incorporation and no-incorporation treatments were the highest on 15 October, when the amount was increased by 8.0 g N and 1.1 g P m–2 compared with the no-incorporation treatment. From September to October, curcumin content rapidly increased with rhizome thickening, and gradually increased. We also quantified the N and P contribution from faba bean residues to the succeeding turmeric. The total amounts of N and P in turmeric cultivated after incorporating shoot and root residues into previously cultivated faba bean field were 2.5 g N and 1.0 g P m–2, respectively, larger than incorporating only roots. In previously fallow field, the incorporation of the shoot increased the total amount of N and P in tumeric by 4.5 g and 1.9 g m–2, respectively, compared with that without incorporation. In the second year after incorporation, growth and nutrient uptake of the turmeric crop did not significantly differ from those without incorporation. In the temperate region, these winter legumes would be used as basal organic matters for turmeric production.