Fig. 4

Nitrogen mineralized during 50-day period incubated at 15 (blue) and 30 °C (red). (a) Nitrogen mineralized from soils of Kaya on-farm trial fields. (b) Nitrogen mineralized from soils of Ishikawa on-farm trial fields. (c) Nitrogen mineralized from soils of Kaya on-farm trial fields mixed with Mamekko fertilizer. (d) Nitrogen mineralized from soils of Ishikawa on-farm trial fields mixed with Mamekko fertilizer. Each circle represents a measured value at the respective temperature. Dotted lines represent estimated values fitting to a first order reaction model, with rate constant k shown for each line. Values measured during the period between 0 and 10 days of incubation were excluded from the fitting due to significant changes in soil solution pH (see Supplementary Fig. 3).