玉米种植制度对红壤磷素形态及其有效性的影响

以攀西地区抛荒地、玉米连作、西葫芦-玉米轮作、豌豆-玉米轮作下红壤耕层(0～20 cm)和亚耕层(20～40 cm)土壤为研究对象,探讨玉米种植制度对红壤磷素形态及其有效性的影响。结果表明: 耕层土壤全磷、有效磷含量和磷素活化系数均高于亚耕层,以豌豆-玉米轮作土壤最高。4种种植制度下红壤磷素均以有机磷为主,在耕层中占全磷的57.8%～81.1%,在亚耕层中占74.3%～85.5%。除豌豆-玉米轮作外,其余3种种植制度下土壤磷组分均以氢氧化钠提取态磷(NaOH-P)为主;而有效性较高的水溶性磷(H₂O-P)和碳酸氢钠提取态磷(NaHCO₃-P)含量较低,在耕层中仅占全磷的0.3%～2.1%、在亚耕层中仅占1.7%～10.0%;两层土壤的盐酸提取态磷(HCl-P)含量均以豌豆-玉米轮作最高,与其他3种种植制度差异显著。相关分析表明,两层土壤的有效磷、碳酸氢钠提取态有机磷(NaHCO₃-P_o)、氢氧化钠提取态有机磷(NaOH-P_o)、盐酸提取态无机磷(HCl-P_i)含量与土壤pH、阳离子交换量、铁氧化物、铝氧化物和土壤质地呈显著相关关系。说明攀西地区豌豆-玉米轮作是提高红壤磷素有效性的最优种植制度。

Effects of corn-based cropping systems on phosphorus fractions and availability in red soil

To clarify the effects of corn-based cropping systems on phosphorus (P) fractions and availability in red soil, we measured P fractions and availability of topsoil (0-20 cm) and subsoil (20-40 cm) in abandoned farmland (control) and three corn-based cropping systems (corn continuous cropping, zucchini-corn rotation and pea-corn rotation), respectively. The results showed that total P, available P contents and P activation coefficient in topsoil were higher than those in subsoil. The value of relative P parameters in topsoil of pea-corn rotation was the highest among all cropping systems. Organic P was the main P fraction in red soil, accounting for 57.8%-81.1% (topsoil) and 74.3%-85.5% (subsoil) of total P. Except for pea-corn rotation soil, sodium hydroxide extractable P (NaOH-P) was the main P fraction in other cropping systems. The contents of water-soluble P (H₂O-P) and sodium bicarbonate extractable P (NaHCO₃-P) with high availability were lower than other P fractions, only accounting for 0.3%-2.1% (topsoil) and 1.7%-10.0% (subsoil) of total P. The pea-corn rotation soil had the highest hydrochloric acid extractable P (HCl-P) content in topsoil and subsoil, and significantly differed from other cropping systems. The contents of available P, sodium bicarbonate extractable organic P (NaHCO₃-P_o), sodium hydroxide extractable organic P (NaOH-P_o) and hydrochloric acid extractable inorganic P (HCl-P_i) were significantly correlated with pH, cation exchange capacity, iron-aluminum oxides and soil texture. In conclusion, pea-corn rotation was the most suitable system to improve P availability of red soil in Panxi area.