2016 Volume 85 Issue 3 Pages 217-223
Utilization of cover crops helps the establishment of environmentally friendly agriculture due to their nutrition supplying ability mainly in the current year of application, but cover crop-derived N also remains until the following year. In the present study, the nutritional effect of a cover crop on tomato production in a greenhouse in the following year was investigated using the 15N-labeling method. Hairy vetch (Vicia villosa R., HV) was used as a cover crop. 15N-labeled HV (1319 mg N/pot) was applied to a 1/2000 a Wagner pot, and a fresh market tomato (Solanum lycopersicum L.), ‘House Momotaro’ was cultivated in it at 0, 80, and 240 kg·ha−1 of N application in 2011 (N0HV, N80HV, and N240HV). After the tomato cultivation in 2011, the soil was stored in a greenhouse (the temperature varied from −4.1°C to 26.5°C) without any water or fertilizer. Tomatoes were cultivated again in the Wagner pots containing the soil used in 2011, to which was added the same rate of N fertilizer (0, 80, and 240 kg·ha−1 of N) and unlabeled HV (935 mg N/pot) in 2012. Total N uptake of tomato plants was higher in N240HV (2377 mg/plant), followed by N80HV (1760 mg/plant), N0HV (1498 mg/plant). On the other hand, the uptake of N derived from HV applied in 2011 (HV2011, 1319 mg N/pot) was not different among the treatments (57.7 mg/plant on average); thus, nitrogen use efficiency derived from HV2011 in 2012 was 4.4% on average. This value was much lower than that in 2011 (47.1% on average), but HV2011-N also remained in the soil after the tomato cultivation in 2012 (500 mg N/pot). The distribution ratios of HV2011-N to the fruit in 1st and 2nd fruit clusters that developed in the early growth period were higher than those of N derived from soil, fertilizer, and HV applied in 2012. These results showed that although the N supplying effect of HV was small, HV could be available not only as short-term N source, but also long-term N source, and HV-derived N applied in the previous year was absorbed by tomato plants during a relatively early growth period in the following year.