长期施肥及石灰后效对不同生育期玉米根际钾素的影响

依托祁阳红壤旱地定位施肥试验(始于1990年),选取施氮磷(NP)、氮磷+石灰(NPCa)、氮磷钾(NPK)、氮磷钾+石灰(NPKCa)、氮磷钾配施秸秆(NPKS)、氮磷钾配施秸秆+石灰(NPKSCa)6个处理,采集玉米不同生育期根际与非根际土壤,测定其钾、钙、镁、铝含量和p H。结果表明:与NP处理相比,施钾处理(NPK和NPKS)根际和非根际土壤速效钾含量显著提高。NP、NPK和NPKS处理根际速效钾在拔节期和灌浆期均处于亏缺状态,亏缺率分别平均为18.2%、34.2%和26.4%。与对应不施石灰处理相比,NPKCa和NPKSCa处理根际土壤速效钾含量在苗期分别降低46.0 mg kg~(-1)和26.5 mg kg~(-1),非根际分别降低68.5 mg kg~(-1)和56.0 mg kg~(-1);从拔节期至收获期,根际速效钾含量平均升高25.2 mg kg~(-1)和33.7 mg kg~(-1),非根际略微降低。NPCa、NPKCa和NPKSCa处理根际土壤速效钾盈亏率与不施石灰相比,整个生育期分别平均提高8.6%、33.2%和19.3%。根际和非根际土壤速效钾含量与相对应缓效钾含量、钾饱和度、K+/(Ca2++Mg2+)和K+/Al3+呈极显著正相关关系。缓效钾和钾饱和度相对变化率(交换性钙镁相对变化率)与速效钾相对变化率呈极显著正(负)相关关系。长期施氮磷钾肥基础上施石灰(NPKCa和NPKSCa)4年以后,根际土壤速效钾、缓效钾含量及钾饱和度均提高(苗期除外),根际土壤交换性钙镁含量提高幅度低于非根际,最终缓解根际土壤钾素的亏缺。

Effect of Long-Term Fertilization and Residual Effect of Liming on Potassium in Rhizosphere of Maize Relative to Growth Stage of the Crop

Objective]In attempt to provide a theoretical basis for amelioration of acidified red soil through liming and build-up of potassium(K)pool,efforts have been made to explore residual effect of liming on K in rhizosphere and bulk soil in maize field at different maize growth stages in acidified red soil. Method]From a long-term fertilization experiment(Started in 1990),designed to have six treatments, including chemical nitrogen and phosphorus(NP),NP plus lime(NPCa),NPK,NPK plus lime (NPKCa),NPK plus straw(NPKS),and NPKS plus lime(NPKSCa)and conducted on a tract of upland maize field of red soil in Qiyang,Hunan Province,samples of rhizosphere and bulk soils were collected in the maize field at the seedling stage,jointing stage,filling stage and harvesting stage of the crop in 2014 for analysis of contents of different forms of K,pH and contents of exchangeable calcium and magnesium (Ca2++Mg2+),and exchangeable aluminum(Al3+).Result]Results show that 1)compared with Treatment NP,Treatments NPK and NPKS were obviously or 120.4 mg kg-1 and 149.6 mg kg-1,respectively,higher in readily available K(RAK)content in both rhizosphere and bulk soils,however,Treatments NP, NPK and NPKS,all suffered K deficiency in rhizosphere at the jointing and filling stages,with deficit being 18.2%,34.2% and 26.4%,respectively;2)comparison of Treatments NPKCa and NPKSCa with Treatments NPK and Treatment NPKS,respectively,shows that liming lowered RAK content,respectively,by 46.0 mg kg-1 and 26.5 mg kg-1 in rhizosphere soil and respectively,by 68.5 mg kg-1 and 56.0 mg kg-1 in bulk soil at the seedling stage,and increased RAK content in rhizosphere by 25.2 mg kg-1 and 33.7mg kg-1, respectively,but reduced the content slightly in bulk soil during the period from jointing to harvesting;comparison of Treatments NPCa,NPKCa and NPKSCa with their corresponding non-liming treatments shows that liming increased soil RAK gain and loss rate in rhizosphere soil by 8.6%,33.2% and 19.3%, respectively,over the whole growing season;3)soil RAK content in both rhizosphere and bulk soil was significantly and positively related to the corresponding slowly AK(SAK),potassium saturation(KS), K+/(Ca2++Mg2+)and K+/Al3+,and SAK was in ultra-significantly positive relationship and KS in ultra-significantly negative relationship with RAK in relative variation rate.Conclusion]Four years after liming in the farmland,under long-term N,P and K fertilization,it is found that liming has increased the contents of RAK and SAK and KS in rhizosphere soil(except at the seedling stage)and the content of(Ca2++Mg2+) in rhizospheresoil,but not so significantly as in bulk soil,thus eventually alleviating RAK deficiency in rhizosphere soil.