Combined application of chicken manure and biochar improves soil fertility and bamboo shoot yield and quality of Phyllostachys violascens ʻPrevernalisʼ forests

Objectives We investigated the effects of combined application of organic and chemical fertilizers with different doses of biochar on soil physicochemical properties, enzyme activities, and bamboo shoot yield and quality in Lei bamboo forests, in order to provide theoretical and technical support for scientific and efficient management of Phyllostachys violascens ʻPrevernalisʼ forests.

Methods The experiment was conducted in a Lei bamboo forest in Huzhou City, Zhejiang Province. Chicken manure-based organic fertilizer 22500 kg/hm² were only applied as the control plot (CK). Based on this, three biochar application gradients were set, 1500 kg/hm² (T₁), 3000 kg/hm² (T₂), and 4500 kg/hm² (T₃). Biochar was incorporated into the 20−25 cm soil layer during tillage in June 2022 and 2023. Soil samples were collected in February 2024 to analyze soil physicochemical properties and six enzyme activities related to carbon, nitrogen, and phosphorus cycling. Bamboo shoot yield was recorded, and protein and flavonoid contents in bamboo shoots were analyzed. Principal component analysis (PCA) was used to evaluate the contribution of soil properties to variations in bamboo shoot yield and quality, and comprehensive scores for different treatments were calculated.

Results Compared with the CK without biochar application, T₂ and T₃ significantly increased soil total porosity, aeration, pH, organic carbon (SOC), total phosphorus (TP), nitrate nitrogen (NO₃⁻-N), ammonium nitrogen (NH₄⁺-N), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents in the 0−20 cm soil layer. They also significantly enhanced acid phosphatase (ACP) activity in the 0−20 cm soil layer and catalase (CAT) and sucrase (SC) activities in the 0−40 cm soil layer. Furthermore, bamboo shoot yield increased by 17.76% and 67.87% in T₂ and T₃, respectively. Compared with CK, bamboo shoot protein content increased significantly by 7.42% to 7.79%, total flavonoid content increased by 10.12% to 20.13%, and cellulose content decreased by 3.6% to 11.23% in T₁, T₂, and T₃ treatments, which improved the nutritional quality and palatability of bamboo shoots. Correlation analysis showed that soil total porosity, pH and available phosphorus content had the most significant positive correlations with bamboo shoot yield and quality indicators. Soil aeration, catalase, urease, and acid phosphatase activities were also significantly correlated with yield and different quality indicators, serving as major factors influencing bamboo shoot yield, nutritional quality, and palatability. The comprehensive evaluation scores for the four treatments were CK (0.257) < T₁ (0.443) < T₂ (0.513) < T₃ (0.716).

Conclusions Annual application of 3000 to 4500 kg/hm² of biochar in combination with chicken manure-based organic fertilizer significantly improved soil total porosity, aeration, pH, and available nitrogen, phosphorus, and potassium nutrient contents in the 0−20 cm soil layer, as well as catalase and invertase activities, thereby significantly increasing bamboo shoot yield and nutritional quality and improving palatability. Considering soil quality, bamboo shoot yield and quality, and economic benefits in Phyllostachys violascens ʻPrevernalisʼ forests, the application of 4500 kg/hm² of biochar yielded the best results in terms of increasing yield and efficiency. However, the optimal continuous application rate of biochar requires further monitoring.