“双季稻-鸭”共生生态系统稻作季节氮循环

“稻鸭共生”是对我国传统农业稻田养鸭的继承与发展.2010年5-10月在长江流域双季稻主产区湖南布置了稻田养鸭田间试验，以常规稻作为对照，研究了早、晚稻两季“稻鸭共生”生态系统氮(N)循环特征.结果表明：“早稻-鸭”共生系统N输出是239.5 kg·hm^-2，其中鸭产品N是12.77 kg·hm^-2.“晚稻-鸭”共生系统N输出是338.7 kg·hm^-2，其中鸭产品N是23.35 kg·hm^-2.在早、晚稻两季，“稻鸭共生”系统在目前的N养分投入水平下，土壤均存在N亏缺；鸭子系统N输入主要来自系统外投入的饲料N；鸭粪N作为系统内被循环利用的养分，早、晚稻两季循环率分别为2.5%和3.5%.两季稻作后，土壤截存的N量是178.6 kg·hm^-2.

Nitrogen cycling in rice-duck mutual ecosystem during double cropping rice growth season.

Raising duck in paddy rice field is an evolution of Chinese traditional agriculture.In May-October 2010, a field experiment was conducted in a double cropping rice region of Hunan Province, South-central China to study the nitrogen (N) cycling in rice-duck mutual ecosystem during early rice and late rice growth periods, taking a conventional paddy rice field as the control. Input-output analysis method was adopted. The N output in the early rice-duck mutual ecosystem was 239.5 kg·hm-2, in which, 12.77 kg·hm-2 were from ducks, and the N output in the late rice-duck mutual ecosystem was 338.7 kg·hm-2, in which, 23.35 kg·hm-2 were from ducks. At the present N input level, there existed soil N deficit during the growth seasons of both early rice and late rice. The N input from duck sub-system was mainly from the feed N, and the cycling rate of the duck feces N recycled within the system was 2.5% during early rice growth season and 3.5% during late rice growth season. After late rice harvested, the soil N sequestration was 178.6 kg·hm-2.