Sweet potato is often base fertilized with nitrogen and no further dressing nitrogen fertilizer is needed. It is important to develop and screen slow-releasing nitrogen fertilizers that could meet the nitrogen requirements of sweet potato at different growth stages in order to promote yield and reduce nitrogen rate. A greenhouse pot experiment using variety Sushu 16 was conducted to analyze the effects of different slow-releasing nitrogen fertilizers (urea formaldehyde, sulfur-coated urea, urea formaldehyde resin, urea combined with nitrification inhibitors) on leaf photosynthesis, above-ground and underground biomass and nitrogen content, nitrogen use efficiency, and soil mineral nitrogen (nitrate nitrogen and ammonium nitrogen) content at different growth stages of sweet potato (seedling stage, vine burying stage, bulking stage, and harvest stage). Compared with the control, the sulfur-coated urea and oxamide controlled-release nitrogen fertilizers increased the biomass of sweet potato roots by 96.79% and 103.59%, respectively, significantly higher than that of the urea-formaldehyde and urea combined with nitrification inhibitor treatments (P<0.05). In addition, the photosynthesis rate of sweet potato throughout the entire growth period was significantly higher in the sulfur-coated urea treatment than that of unfertilized control, which is beneficial to improving the biomass of sweet potato roots. The nitrogen releasing of sulfur-coated urea and oxamide was less in the seedling and closure period and more in the swelling period and harvest period. The sum of ammonium nitrogen and nitrate nitrogen was 1.24-1.60 times that of urea-formaldehyde and urea combined with nitrification inhibitor, and the nitrogen fertilizer utilization rate increased by 1.17-1.80 times. In conclusion, sulfur-coated urea and urea formaldehyde are more suitable for the one-time application of nitrogen fertilizer in sweet potato production. The study results could provide scientific basis for nutrient management and nitrogen fertilizer reduction and yield enhancement in sweet potato production.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |