Hairy Vetch Derived-N Uptake by Tomato Grown in a Pot Containing Fast- and Slow-release N Fertilizer

In order to improve the use efficiency of a cover crop, hairy vetch (Vicia villosa R., HV), and supplemental chemical N fertilizer, N release and uptake patterns from HV, fast-release N fertilizer (Fast), and slow-release N fertilizer (Slow) in fresh market tomato (Solanum lycopersicum L.) production were investigated using the 15N-labeling method. In the incubation of soil-added N at two mix rates, 20% Fast + 80% Slow (FS) and 100% Slow (S), a large amount of inorganic N, mainly NH4-N, was released by FS in 4 weeks. Tomato ‘House momotaro’ was grown in 1/2000 a Wagner pots incorporating such N fertilizer and 15N-labeled HV residue (30 g DW/pot, about 200 kg N·ha-1). Plant biomass in tomato grown with HV was larger than that grown without HV. HV-derived N (Ndfhv) was taken up by the tomatoes mainly until 4 weeks after transplant (WAT). The uptake amount of Ndfhv was the same in the pot with HV-FS and HV-S. The rate of N uptake derived from HV to total N uptake in tomato plants (%Ndfhv) was 43% in HV-S, higher than that in HV-FS (34%) in 4 WAT; however, such a difference disappeared after 4 WAT. N uptake by tomato plants continued until 12 WAT. Based on these results, HV acted as a fast-release fertilizer. There was competition in N uptake between chemical fertilizer N and HV-released N in the early stage of tomato cultivation. A large amount of chemical fertilizer tended to suppress the uptake of Ndfhv. N uptake by tomato plant continued until the late stage. These results can be applied to establish a suitable combination of HV and chemical fertilizer for tomato production.