Synergistic Regulation of Fertilization and Standing Culm Density on Productivity of Phyllostachys makinoi and Optimization of High-Yield Cultivation Techniques

To address the issues of low fertilizer efficiency, imbalanced standing culm density, constrained yield, and poor economic returns in traditional extensive management of Taiwan Makino Bamboo (Phyllostachys makinoi Hayata), this study aimed to develop a standardized high-yield protocol through synergistic optimization of cultivation techniques. A three-year field trial was conducted in Xikou Village, Zhangping City, Fujian Province (fertilization experiment) and Guanling Village, Pingnan County, Fujian Province (density experiment). Experimental treatments were established as follows: (1) Fertilization experiment: Comparing split fertilization (T1: 750 kg·hm⁻² urea in spring early shoot emergence stage, 975 kg·hm⁻² PK fertilizer 375 kg·hm⁻² urea + 225 kg·hm⁻² potassium sulfate (K₂O≥50%) + 750 kg·hm⁻² calcium superphosphate (P₂O₅≥12%) in summer culm elongation stage, and 4.5t·hm⁻² commercial organic fertilizer organic matter≥45%, N+P₂O₅+K₂O≥5% in autumn rhizome bud differentiation and nutrient accumulation stage) with traditional single application (CK: 900 kg·hm⁻² NPK compound fertilizer N:P₂O₅:K₂O=15:15:15 applied once in autumn); (2) Density experiment: Gradient treatments of 4500, 6000, 7500, and 10000 culms·hm⁻². Shoot yield, timber (culm) yield, new culm survival rate, and economic benefits were measured. The results demonstrated that: (1) T1 significantly enhanced productivity compared to CK: Shoot yield reached 23.95 ± 0.25 t·hm⁻² (235% increase, p<0.01), timber yield was 4.94 ± 0.09 t·hm⁻² (35% increase), and economic benefit was 1.37 ± 0.06 × 10⁴ CNY·hm⁻² (3.26 times higher); (2) The optimal standing culm density was 7500 culms·hm⁻²: Peak shoot yield of 24.96 ± 0.29 t·hm⁻² was achieved, representing increases of 7.0% and 14.9% compared to lower (4500 culms·hm⁻²) and higher (10000 culms·hm⁻²) densities, respectively (p<0.05), with a new culm survival rate of 96.67 ± 3.34%; (3) Following technology integration, the annual net income was 0.685 × 10⁴ CNY·hm⁻², while soil organic matter (38.7 ± 1.5 g·kg⁻¹) and available phosphorus/potassium levels remained stable. The synergistic model of "spring N-summer PK-autumn organic" split fertilization combined with a standing culm density of 7500 culms·hm⁻² effectively overcomes traditional productivity bottlenecks and provides core parameters for the formulation of the Cultivation Technical Code for Shoot-Timber Dual-Purpose Forests of P. makinoi.