Uptake and Distribution of Nitrogen Derived from Hairy Vetch Used as a Cover Crop by Tomato Plant

One of the ways to reduce chemical fertilizer application is the use of cover crops, which improve soil properties and supply nutrition to subsequent crops. The application effect of a legume cover crop, hairy vetch (Vicia villosa R., HV), on N dynamics in fresh market tomatoes (Solanum lycopersicum L.), 'House Momotaro,' was investigated using the N-15-labeling method. Tomato seedlings were transplanted into a 1/2000 a Wagner pot at 0, 80, and 240 kg.ha(-1) of N application (N0HV, N80HV, and N240HV) on June 9, 2011. Before transplanting, the labeled HV and chemical fertilizers were incorporated into the soil. Five tomato plants were collected 6 times in each treatment and then separated into leaves, stems, and roots. Fruits were harvested at maturity. HV-derived N uptake was recognized mainly in the first 4 weeks after transplant (WAT). Especially in N240HV, HV-derived N uptake ceased at 4 WAT. The uptake amounts of HV-derived N at 10 WAT were 587, 657, and 729 mg.plant(-1) in N240HV, N80HV, and N0HV, respectively, and were increased by decreasing N fertilizer application. The rate of N uptake derived from HV to total N uptake in tomato plants (%N-dfhv) was the highest at 2 WAT, and %N-dfhv in N80HV (52.1%) and N0HV (51.5%) were significantly higher than in N240HV (43.6%). After 2 WAT, %N-dfhv, decreased gradually in all N rates as tomatoes grew and decreased to 24.8%, 34.4%, and 37.1% in N240HV, N80HV, and N0HV, respectively, until 12 WAT. Nitrogen use efficiency (NUE) from HV-derived N was the highest at 10 WAT, and N0HV (55.3%) was significantly higher than N240HV (44.5%) and N80HV (49.8%). The partition rate of HV-derived N into fruits was 63.9%, and 39.7% of HV-derived N was distributed into 1st and 2nd fruit clusters. From these results, it was clarified that HV can be expected to be an alternative N fertilizer because HV-derived N was absorbed effectively with a small amount of N fertilizer. Further research on fertilizer management in tomato's early stage will be needed for an N-reduction system because HV-derived N was mainly absorbed for 4 WAT.