长期有机无机肥配施提高黑土磷含量和活化系数

【目的】长期不同施肥模式影响着耕层土壤磷库以及各形态磷的变化。研究不同施肥模式下黑土各磷素形态含量及有效性的变化，为黑土的肥力培育和合理施用磷肥提供理论依据。【方法】黑土长期定位施肥试验位于吉林省公主岭市，始于1990年，供试作物是连作玉米。肥料试验包括不施肥对照 (CK)、施氮、钾肥 (NK)、氮磷钾平衡施肥 (NPK)、氮磷钾 + 有机肥 (NPKM) 共4个处理。化肥处理施氮肥(N) 165 kg/hm2、磷肥(P) 36 kg/hm2、钾肥(K) 68 kg/hm2、猪粪21 t/hm2，NPKM处理的最终N?P?K养分投入量为165?75?145 kg/hm2。选取了1990、1995、2000、2005和2010年的土样，采用Hedley连续浸提法，分析了土壤全磷、有效磷及各有效磷形态含量，计算了土壤磷活化系数 (PAC)。【结果】与初始年份相比，NPKM处理土壤全磷、有效磷和磷活化系数，分别显著提高了88.47%、12.98倍和6.42倍。NPK处理对全磷含量影响较小，土壤有效磷含量和PAC值分别增加了1.65倍和2.67倍。CK和NK处理全磷含量降低了15.12%和32.67%，有效磷含量降低了33.47%和12.57%，土壤磷活化系数 (PAC) 分别降低了52.49%和2.55%。所有处理黑土磷库均以无机磷为主，占全磷的80.53%～90.43%。施磷肥处理的无机磷含量占全磷的比值显著高于不施磷处理，对有机磷含量影响不显著。不同处理均以中活性态磷含量最多，占全磷的50.37%～55.06%，活性态磷含量最少，占全磷的7.61%～19.02%。与不施磷处理相比，施磷处理显著提高了土壤活性态磷的比值，尤其是无机磷中的活性态磷的比值。CK、NK处理中Resin-P、NaHCO₃-Pi、NaOH-Pi、Conc.HCl-Pi、Residual-P无机磷形态均呈减少趋势；NPK处理中Resin-P、NaHCO₃-Pi、NaOH-Pi、Dil.HCl-Pi呈增加趋势，Conc.HCl-Pi和Residual-P呈减少趋势；NPKM处理中，各无机态磷含量均随施肥年限的增加呈增加趋势。相关分析结果表明有效磷含量的变化值与Resin-P、NaHCO₃-Pi、NaOH-Pi、Conc.HCl-Po变化值之间存在显著的相关性，其相关系数为0.972、0.665、0.860和0.605，说明活性较高的无机磷对有效磷效率的贡献最大。【结论】与施氮钾肥和氮磷钾肥相比，氮磷钾配合有机肥可显著提高土壤全磷、有效磷含量，显著提高土壤活性态无机磷的比例，进而提高土壤磷活化系数，提高磷素利用率。

Increment of soil phosphorus pool and activation coefficient through long-term combination of NPK fertilizers with manures in black soil

【Objectives】Long-term fertilization affects soil phosphorus (P) fraction and availability. The change of soil P and P fractions contents and the availability of soil P under long-term different fertilization were investigated, which will offer scientific support for P management in the black soil.【Methods】The used long-term fertilization experiment was started in 1990 on a black soil in Gongzhuling City, Jilin Province. The cropping system was continues mono maize. The selected four treatments included no fertilizer (CK), applying urea and potash sulfate (NK), applying urea, super-calcium phosphate and potash sulfate (NPK), and NPK plus pig manure (NPKM). For the three chemical fertilizer treatments, the corresponding inputs were N 165 kg/hm2, P 36 kg/hm2 and K 68 kg/hm2. The pig manure input was 21 t/hm2, and the N?P?K input were 165?75?145 kg/hm2. Soil samples were collected for every five years (1990, 1995, 2000, 2005 and 2010). Using the Hedley sequential extraction method, the total P and Olsen-P and P fraction contents were measured, and the soil P activation coefficient(PAC) was calculated.【Results】With the extension of the experimental years, the soil total P and Olsen-P contents and PAC in treatments of CK and NK displayed downward trends, while those in NPK and NPKM showed upward trends. Compared with the beginning samples, the soil total P and Olsen-P contents and PAC in NPKM treatment were respectively increased by 88.47%, 12.98 and 6.42 times; and those were decreased by 15.12% and 32.67%, 33.47% in CK and by 12.57%, 52.49% and 2.55% in NK treatment; and the Olsen-P contents and PAC were respectively increased by 1.65 and 2.67 times, and the total P contents were not significantly increased in NPK. The inorganic P was increased significantly in NPK and NPKM treatments, while the organic P was not. The inorganic P was the main fraction of soil P in black soil, accounting for 80.53%?90.43% of the total P. Mid-liable P was the main fraction in the P pool of black soil, and accounted for 50.37%?55.06% of the total P, while labile P fraction accounted for 7.61%?19.02%. The ratio of labile P fraction in total P, especially in inorganic P, was increased significantly in NPK and NPKM treatments. Resin-P, NaHCO₃-Pi, NaOH-Pi, Conc. HCl-Pi, Residual-P contents were decreased in CK and NK treatments, Resin-P, NaHCO₃-Pi, NaOH-Pi, Dil.HCl-Pi contents were increased and Conc. HCl-Pi, Residual-P contents were decreased in NPK treatment, all inorganic P fractions were increased in NPKM treatment. The variation of Olsen-P was significantly correlated with the contents of Resin-P, NaHCO₃-Pi, NaOH-Pi, Conc. HCl-Po, and the coefficient was 0.972, 0.665, 0.860 and 0.605 in turn.【Conclusions】Long-term combined application of NPK fertilizers plus manure not only has caused the significant increase of total P, Olsen-P contents, but also increased the ratio of labile P to inorganic P, and increased the availability of soil P. Therefore, the combined application of NPK and manure is recommended for the effective improvement of P fertility in black soil.