No abstract

No abstract

Present studies show that nitrate accumulation is the major factor influencing the water uptake by vegetables, but there is lack of knowledge on how the relationship between nitrate and water concentrations in different vegetable tissues. We determined nitrate accumulation and water content in vegetables of rape, Chinese cabbage, and spinach under different nitrogen levels (experiment I), 29 spinach cultivars (experiment II), and 27 rape cultivars (experiment III). The results from experiments I-III showed a highly linear relationship between nitrate accumulation and water content, and the levels thereof in different organs of the vegetables revealed that the petiole exhibited the best correlation between them compared with the root and leaf blade. These suggest that (1) vegetables with high water content have high nitrate content, (2) water content in the petiole can be used to screen cultivars with low levels of nitrate accumulation, and (3) increasing soil water content in agronomic practice is essential to decreasing nitrate accumulation in vegetables.

No abstract

Purpose Nitrous oxide emissions from pasture soils account for one third of total agricultural greenhouse gas emissions in New Zealand. The aim of this study was to determine nitrous oxide (N 2 O) emissions from animal urine patches under summer (with irrigation) and winter conditions as affected by dicyandiamide (DCD) in grazed grassland in New Zealand. Materials and methods Sixteen monolith lysimeters were collected from an established perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture on a Templeton fine sandy loam (Udic Ustochrept) located near Lincoln University on the Canterbury plains of New Zealand to study the N 2 O emissions from animal urine as affected by season and a nitrification inhibitor dicyandiamide. The experiment was conducted in the summer of 2008-2009 and the winter of 2009 with four treatments (control, control+DCD (10 kg ha −1 ), urine (1,000 kg N ha −1 ), urine+DCD) for both seasons. N 2 O fluxes from the pasture were measured in summer and winter. Results and discussionResults showed that the application of urine significantly increased N 2 O emissions and the application of nitrification inhibitor, DCD, to pasture soil was very effective in reducing N 2 O emissions both in summer and winter. Total N emissions from urine-N applied at 1,000 kg N ha −1 were 7.8 kg N 2 O-N ha −1 in the summer season and this was much lower than the 12.7 kg N 2 O-N ha −1 emitted during the winter season. The application of DCD reduced summer N 2 O-N emissions to 4.8 kg N 2 O-N ha −1 and winter N 2 O-N emissions to 3.9 kg N 2 O-N ha −1 , representing 40% and 69% reductions in the summer and winter seasons, respectively. Conclusions The results demonstrate that N 2 O emissions from animal urine-N in grazed pastures were much higher in the winter season than in the summer season with irrigation and that DCD was more effective in reducing N 2 O emissions in the high-emitting winter season.