The effects of integrated Azolla-duck-rice farming system on weeding, pest control and the behaviour of ducks

摘要

The present study was conducted to examine the effect of integration of aquatic fern Azolla and the Aigamo ducks on weeding, pest control, and behaviour of the Aigamo ducks in paddy fields. The paddy fields were allocated into 5 treatments, named: agrochemical (standard fertilizer, herbicides and pesticides were used), control, Aigamo ducks, Azolla and Azolla-Aigamo ducks plots. The experiments were carried out during 1996-1997. Azolla was inoculated into the paddy fields the day after rice transplanting at the rate of 70g/m~2 in 1996 and 25g/m~2 in 1997. After the Azolla was grown for 6-7 weeks, the biomass was plowed into the soil or submerged due to the stirring behaviour of the Aigamo ducks. Aigamo ducks (6ducks/3a) of 1 week of age were introduced into the paddy fields 1 week after rice transplanting, and then they were free-ranged for 2 months until the rice was in ear. In August and September of 1996, the emergence of weeds in the Azolla-Aigamo ducks and the Aigamo ducks plots was significantly less than that of control. In August of 1997, the emergence of weeds in the Azolla-Aigamo ducks plot was significantly less compared with the other plots, except for the agrochemical plot. Echinochloa crusgalli was effectively suppressed by a thick Azolla mat, Cyperus difformis, L. perocumbens and R. indica var. uliginosa were foraged by the Aigamo ducks. It was suggested that the weeding effect in Azolla-Aigamo ducks plot was due to the integration of Azolla and the Aigamo ducks. In the early period of the rice culture, the infestation of Sogatella furcifera in plots with the Aigamo ducks was significantly smaller when compared to the plots without the Aigamo ducks but the infestation of Nilaparvata lugens in plots with Azolla was higher than the Aigamo ducks plot in the late period of the rice culture. There was no significant effect on the control of Nephotettiz cincticeps by the Aigamo ducks. It was indicated that the infestation of pest in the late period of the rice culture was dependent on the time of plowing the Azolla. The Aigamo ducks in the Aigamo ducks plot engaged in foraging at night, whereas those in the Azolla-Aigamo ducks plot did so during the daytime. Comparing the Aigamo ducks plot, the Aigamo ducks in the Azolla-Aigamo ducks plot spent distinctly less time on foraging and moving behaviour for 24 hours, however, it was observed that ducks in this plot spent more time on resting behaviour.