Abstract: In order to optimize the fertilization technology of rice in rice and frog co-cropping mode, a field experiment was conducted with 4 densities of Pelophylax nigromaculatus, and the effects of different densities of Pelophylax nigromaculatus on rice yields and soil fertility in paddy fields were analyzed. The results showed that the effective panicles per unit area increased significantly with the increase of the density of Pelophylax nigromaculatus in the paddy field. Rice yield, soil pH, organic matter and nutrient contents also showed an upward trend as the increase of the density of Pelophylax nigromaculatus. Compared to before the test, soil pH, organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen and available phosphorus at the end of one season increased by 2.3%~89.0%, while total potassium and available potassium decreased by 6.9%~24.4%. Therefore, it does not apply nitrogen and phosphorus fertilizer to rice production, but only apply appropriate amount of potassium fertilizer in rice and frog co-cropping mode.

Key words: paddy field, Pelophylax nigromaculatus, rice（Oryza sativa L.）, yields, soil fertility