从高效施肥角度出发，采用田间试验，研究施氮量对木薯干物质积累、养分吸收及土壤有效养分含量的影响。结果表明：随施氮量的增加，茎、叶干物质积累量显著增加，但块根干物质积累量先增后降，以施氮 130 kg/hm² 的最高，比不施氮增加 18.13%。增加施氮量，木薯各器官磷、钾积累量及茎、叶氮积累量明显增加，块根氮积累量则先增加后下降。氮肥农学利用率、生理利用率及偏生产力随施氮量的增加而显著下降，氮肥吸收利用率以施氮 130 kg/hm² 的最高，比其他处理提高 11.37% ~ 25.12%。木薯收获后，随施氮量的增加，土壤碱解氮明显增加，有效磷及速效钾不同程度下降，但各处理有效磷、速效钾及施氮 195 kg/hm² 处理的有效氮明显盈余。综合分析认为，本研究条件下木薯施氮 130 kg/hm² 较为适宜。

From the viewpoint of efficient fertilization, a field experiment was conducted to investigate the effects of nitrogen (N) application rates on dry matter accumulation and nutrient absorption of cassava and the contents of soil available nutrients. The results showed that the dry matter accumulation of stems and leaves increased significantly with the increase of N application rates, while the yield of root tubers increased with N application rates firstly, reached the maximum value at N 130 kg/hm² and then decreased with the further increase in N application rates. The maximum yield of cassava was increased by 18.13% compared to control with no nitrogen fertilizer applied. The increase in N application rates led to the accumulation of phosphorus and potassium in cassava organs and nitrogen accumulation in stems and leaves of cassava. However, nitrogen accumulation in root tubers increased firstly, reached the maximum value and then decreased with the further increase in N application rates. The agronomic and physiological use efficiency and partial factor productivity of applied nitrogen decreased significantly with the increase in N application rates. Nitrogen recovery efficiency reached the maximal value at 130 kg/hm², and was increased by 11.37% to 25.12% compared with other treatments. After cassava harvest, the alkali-hydrolyzed nitrogen content increased obviously with increasing nitrogen application, but available phosphorus and potassium contents decreased. The available phosphorus and potassium nutrients in the soil of all treatments, as well as the available nitrogen in the soil of the treatment with N 195 kg/hm² were obviously surplus. In conclusion, the optimum application amount of nitrogen for cassava was 130 kg/hm².

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广西自然科学基金项目(2013GXNSFBA019050)、广西教育厅广西高等学校科研立项项目(LX2014673)和广西科技大学鹿山学院科学基金项目(2013LSZK03)资助。