磷素吸附特性演变及其与土壤磷素形态、土壤有机碳含量的关系

在黄土旱塬区长期试验(1985-1997年)中,选取对照(不施肥,CK)、磷肥(P2O5.60.kg/hm2,P)、氮肥(N.120kg／hm2,N)、氮磷(N,120.kg／hm2,P2O5,60.kg/hm2,NP)、氮磷有机肥(N.120.kg/hm2,P2O560.kg/hm2,有机肥75.t／hm2,NPM),种植方式为冬小麦连作的5种有代表性的施肥处理,研究了石灰性土壤磷素吸附特性的演变及其与土壤磷素形态、土壤有机碳(SOC)含量的关系。结果表明,P素的最大吸附量(Qm),1997年对照(CK)、N处理比1985年分别提高了18％和14％;而P、NP和NPM处理分别降低了26％、13％和24％。吸附能常数(k值)随时间延长,对照和N处理相对稳定,P和NP处理呈升高趋势,而NPM处理有降低趋势。土壤磷素吸附饱和度(DPS)和零净吸附磷浓度(EPC0)对照和N处理随时间延长呈降低趋势,P、NP和NPM处理呈升高趋势。Qm与Ca8-P、Al-P存在极显著相关关系(P0.001),与Ca2-P、Pe-P存在显著相关关系(P0.05)。Ca2-P、有机磷含量变化与土壤DPS的相关性达到显著水平(P0.05)。EPC0只与有机磷间存在显著的相关关系(P0.05)。Qm、DPS和EPC0变化与SOC存在显著或极显著的线性相关关系(P0.001)。

Changes in characterization of phosphorus sorption in relation to its forms and soil organic carbon

Phosphorus (P) sorption in soil evidently affects phosphate fertilizer use efficiency. Changes in P sorption and its relation to P forms and soil properties under long-term fertilization (1985-1997) were investigated in continuous winter wheat ( Triticum aestivum L. ) systems on loamy soil ( Ustic Isohumisols) of the Loess Plateau. The treatments consisted of unfertilized (CK), nitrogen (N), phosphorus (P), nitrogen and phosphorus (NP), and nitrogen, phosphorus and farmyard manure (NPM) . The application rate of N, P₂O₅, M was 120, 60 kg/ hm², and 75 t/ hm², respectively. Using the soil samples collected in 1985, 1993, and 1997, soil total P, Ca₂-P, Ca₈-P, Al-P, Fe-P, O-P, and Ca10-P were measured, respectively. Phosphorus sorption isotherms were constructed for the collected soil samples, too. Organic P level, maximum P sorption capacity (Q_m) , degree of P saturation ( DPS ) and EPC0(equilibrium P concentration at zero sorption) were estimated. The results showed that; 1) Q_m of CK and N treatment in 1997 was increased by 18% and 14% , compared with that in 1985. In 1997, Q_m in P, NP and NPM treatments were reduced by 26% , 13% and 26% , respectively, compared with that in 1985. The affinity constant of P in soil (k) was stable in CKand N treatments, increased in P, NP treatments, and decreased in NPM treatment with increasing of time. DPS and EPC0 in CK and N treatment decreased , however, increased in P, NP, and NPM treatments with increasing of time. There was highly significant correlation between Q_m and Ca₈-P or A1-P( P≤0.001)and significant correlation between Q_m and Ca₂-P or Fe-P ( P≤0.05) . DPS was highly related to Ca₂-P and organic P form ( P≤0.05). There was significant relationship between SOC and Q_m, DPS and EPC0 .