Contribution of N derived from a hairy vetch incorporated in the previous year to tomato N uptake under hairy vetch-tomato rotational cropping system

Abstract

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 the15N-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.