Hairy vetch becomes an alternative basal n fertilizer in low-input freshmarket tomato production in a plastic high tunnel

Abstract

In order to establish a low-input alternative production system based on cover crops, the effectiveness of hairy vetch (Vicia villosa Roth; HV) incorporated as a basal nitrogen fertilizer and its effects on soil carbon (C) and nitrogen (N) content in fresh-market tomato production in plastic high tunnel was investigated in Sapporo (snow cover region), Japan. The treatments consisted of HV seeding rates (HV2, 2 kg/10 a; HV5, 5 kg/10 a) and ammonium sulfate (AS10, 10 kg N/10 a) applied as basal N fertilizers, and the Non HV (control) with no HV and ammonium sulfate. In all plots, 15 kg N/10 a were added before tomato transplanting as a controlledrelease fertilizer (LPS100 41%−N) to maintain the tomato growth in the mid and late stages. HV aboveground biomass (dry weight) was 585 kg/10 a in HV2 and 719 kg/10 a in HV5. Nitrate in petiole sap was higher in HV2, HV5, and AS10 plots than in Non HV plots throughout the cultivation period with the exception of the first 2 weeks after transplanting (WAT). The Growth index (GI) was higher in HV2 (47971), HV5 (46285), and AS10 (43397) than in Non HV (39847) at 7 WAT, the beginning of the harvest. Higher marketable yields were found in tomatoes grown in HV2 (6.87 t/10 a), HV5 (6.91 t/10 a), and AS10 (6.08 t/10 a), compared with the Non HV (5.19 t/10 a). The HV plots had greater soil total and organic N than AS10 and Non HV, and slightly increased soil C after tomato production. From these results, the HV seeding rate of 2 kg/10 a will be enough to support the growth of tomatoes planted after HV production if HV grows steadily in a plastic high tunnel.