Objectives   Effects of applying organic manure on the growth and photosynthesis of plants cultivated on acid red soil contaminated by aluminum were studied.

  Methods   In a pot experiment, aluminum-laden acid red soil was used as control (CK) or blended with either pig manure at the rate of 10 g·kg⁻¹ (P10), 30 g·kg⁻¹ (P30), or 50 g·kg⁻¹ (P50), chicken manure at 10 g·kg⁻¹ (C10), 30 g·kg⁻¹ (C30), or 50 g·kg⁻¹ (C50), or pig and chicken manures at 15 g·kg⁻¹ each (PC15). Biomass and photosynthetic properties including chlorophyll fluorescence indexes of Brassica napus L. seedlings grown in the pots were determined.

  Results   Application of the organic manure in the soil significant improved the aboveground biomass, photosynthetic pigment content, and chlorophyll fluorescence indexes of the seedlings over CK (P＜0.05). In 80 d after the treatments, these indicators were higher than CK indicating the heavy metal toxicity in the soil had been gradually alleviated by chelation. At a same application rate, chicken manure rendered a greater effect than pig manure on the increases of aboveground biomass and photosynthetic pigment but less on the photosynthetic parameters, F_v/F_m and qP, while the combination of chicken and pig manures performed superior to either chicken or pig manure alone on the photosynthetic pigment content, T_r, G_s, C_i, and qN (P＜0.05). It appeared that the alkaline chicken manure benefited the growth more and that the nutrient-rich pig manure did the photosynthesis more for the seedlings.

  Conclusions  To effectively mitigate the aluminum stress on B. napus L. seedlings grown in an acid red soil, an application of pig manure at 50 g·kg⁻¹, and chicken manure at 30 g·kg⁻¹ with appropriate adjustments according to the actual field conditions was recommended.