外源钾铝对不同镁肥在砖红壤中淋溶的影响

Effect of Exogenous Potassium and Aluminum on Magnesium Leaching from Different Magnesium Fertilizers in Latosol

研究海南浅海沉积物发育砖红壤中高钾与高铝共存对不同镁肥淋洗的影响,可为该缺镁土壤上合理施用镁肥提供理论依据。采集浅海沉积物发育砖红壤,设置4个钾铝处理:不加钾铝(–K–Al)、高钾(+K)、高铝(+Al)、高钾高铝共存(+K+Al),通过室内土柱模拟试验研究了一水硫酸镁、白云石、氢氧化镁、氧化镁、钙镁磷肥的淋失特征。结果表明:不同处理第1次淋溶液中镁浓度最大(125.47~898.81 mg/L),第2次骤降(8.79~157.64 mg/L),第3次再骤降(0.51~29.28 mg/L),往后第4~11次趋于平稳(0.25~9.41mg/L);施用镁肥处理淋溶液中镁浓度均高于对照处理,其中一水硫酸镁处理最高(898.81 mg/L),而白云石处理最低(212.50 mg/L)。+K+Al条件下淋溶液中镁浓度显著高于其他条件,镁累积淋失量大致为+K+Al>+Al>+K>–K–Al;不同种类镁肥处理的镁累积淋失量为19.16~142.96 mg,+K+Al条件下镁累积淋失量由高到低顺序为:一水硫酸镁>钙镁磷肥>氢氧化镁>氧化镁>白云石,镁淋失率最低的是白云石处理(8.22%),最高是一水硫酸镁处理(82.54%)。11次淋洗结束,0~20 cm土层中,与对照处理相比,除一水硫酸镁处理外,施用镁肥处理均提高了土壤p H,土壤交换性镁含量大致为+K+Al<+Al<+K<–K–Al;同一钾铝条件下对照处理与一水硫酸镁、白云石处理的土壤交换性镁含量几乎没有显著差异,而且都显著低于氢氧化镁、氧化镁、钙镁磷肥处理。综上所述,施用镁肥后,应注意水分管理防止镁被大量淋洗;+Al处理对镁淋洗的影响大于+K处理,且+K+Al处理对镁淋洗有促进作用。在海南浅海沉积物发育的砖红壤上易淋洗的一水硫酸镁不宜作为基肥施用,尤其在钾铝共存条件下应少量多次施用,可选择镁肥淋失率较低的白云石做基肥。

In this paper,the effects of coexisting high potassium(K)and high aluminum(Al)on magnesium(Mg)leaching of different Mg fertilizers in latosol derived from the shallow sediments in Hainan was studied in order to provide a theoretical basis for the rational application of Mg fertilizers.Latosol derived from shallow sediments was collected and four treatments were designed,including non K and Al(–K–Al),high K(+K),Al toxicity(+Al),and coexistence of high K and high Al(+K+Al),and then the leaching characteristics of five Mg fertilizers,including magesium sulfate monohydrate(MgSO_(4)·H_(2)O),dolomite(CaMg(CO_(3))_(2)),Mg(OH)_(2),MgO,calcium magnesium phosphate fertilizer(CaMgP)were studied through simulated soil column experiments.The results showed that Mg concentration in the first leachate was the highest(125.47–898.81 mg/L),steeply decreased in the second and third leachates(8.79–157.64 mg/L and 0.51–29.28 mg/L,respectively),then tended to stable in the following leachates(0.25–9.41 mg/L).Mg concentrations in the leachates treated with Mg fertilizers were higher than that of CK,with MgSO_(4)·H_(2)O being the highest(898.81 mg/L)and CaMg(CO_(3))_(2)the lowest(212.50 mg/L).Mg concentrations in the leachates under+K+Al were significantly higher than those of other treatments,and the accumulated contents of leached Mg under different types of Mg fertilizers ranged from 19.16–142.96 mg,and were almost always in the order of+K+Al>+Al>+K>–K–Al.The accumulated contents of leached Mg under+K+Al treatment were in the order of MgSO_(4)·H_(2)O>CaMgP>(Mg(OH)_(2)>MgO>CaMg(CO_(3))_(2),with the lowest being CaMg(CO_(3))_(2)(8.22%)and the highest being MgSO_(4)·H_(2)O(82.54%).After 11 times leaching,compared with CK,in the 0–20 cm soil layer,except for MgSO_(4)·H_(2)O,Mg fertilizers increased soil pH,and soil exchangeable Mg contents were almost all in the order of+K+Al<+Al<+K<–K–Al.Under the same treatment,there was almost no significant difference in exchangeable Mg content between CK,MgSO_(4)·H_(2)O,and CaMg(CO_(3))_(2)treatments,but both were significantly lower than Mg(OH)_(2),MgO and CaMgP.Therefore,attention should be paid to water management after Mg fertilizer application to prevent excessive Mg leaching.+Al has a greater impact on Mg leaching than+K,and+K+Al can promote Mg leaching,then,MgSO_(4)·H_(2)O,prone to leaching,should not be used as a base fertilizer,especially under the coexistence of K and Al,it should be applied in small amount and multiple times.Comparatively,CaMg(CO_(3))_(2)with a low Mg leaching is recommended as the base fertilizer.