X射线衍射分析长期钾素盈亏对土壤含钾类矿物的影响

利用1991年—2013年国家紫色土肥力与肥料效益监测站长期定位试验的土壤样品，采用X射线衍射(XRD)光谱分析技术，研究了22年长期钾素投入亏缺和盈余处理中性紫色土壤钾素含量及含钾类矿物的演变特征。XRD图谱分析发现，长期钾素亏缺处理导致土壤云母、钾长石等含钾类原生矿物加速风化，表现为连续施肥22年<连续施肥12年<原始土壤，同时促进了蒙脱石的形成;长期钾素盈余处理土壤云母、钾长石等原生矿物风化程度虽得到有效缓解，但较原始土壤相比仍有明显风化。土壤含钾类粘土矿物的演变与原生矿物变化相似，长期钾素亏缺导致土壤粘粒中伊利石发生了明显崩解，且随着施肥年限的增加，粘粒中伊利石的含量随之减少，长期钾素盈余处理明显缓解了伊利石的风化进程;但是无论是钾素亏缺或盈余处理都出现土壤中伊利石的风化崩解，同时伴随蒙脱石等膨胀型矿物的形成，现有的钾素盈余水平也不能阻止土壤含钾类矿物的风化崩解。另外，长期钾素亏缺导致土壤中速效钾和缓效钾含量逐年降低，22年分别降低62.0%和37.4%;而钾素盈余处理提高了土壤速效钾含量，但缓效钾呈现下降趋势;土壤伊利石的风化程度和土壤缓效钾的演变趋势相吻合。表明中性紫色土壤中伊利石是土壤缓效钾的主要来源，长期钾素亏缺会造成土壤钾素枯竭和含钾类矿物的加速风化崩解，降低土壤供钾能力。

Effect of Long-Term Potassium Unbalanced Input on Clay Mineralogical Property of Purple Soil

In order to investigate the effect of long‐term (1991 — 2013) K fertilizer deficiency and surplus on potassium‐bearing mineral and K nutrition of purple soil ‐soil primary ,clay mineral composition and potassium (K) nutrition were determined on the long‐term experiment of fertility and fertilizer efficiency in neutral purple soil by using X‐ray diffraction (XRD) analysis tech‐nique .Five soil samples were selected from soil samples library for soil mineral analysis ,including original soil ,which preserved in 1991 before the experiment carrying out ;K deficient treatment for 12 years and 22 years ,which means no K fertilizer was ap‐plied during 1991 — 2003 and 1991 — 2013 ,respectively ;and K surplus treatment for 12 years and 22 years ,which means excess K fertilizer was applied during 1991 — 2003 and 1991 — 2013 ,separately .The result showed that ,soil potassium‐bearing primary mineral ,such as mica ,potassium feldspar ,had apparently weathered and slaked for the K deficient treatment and the weathered extent gradually aggravated following fertilization ages ,demonstrating fertilization for 22 years < 12years < original soil .Howev‐er ,for K surplus treatment ,the content of mica and potassium feldspar only had a little decline .As similar with primary miner‐al ,for soil clay potassium mineral ,the content of illite and mica was also seriously reduced for K deficient treatment and a slight ‐ly declined for K surplus treatment ,representing the disintegration of soil potassium mineral under rice‐wheat rotation system , and the deficient input of K fertilizer would obviously accelerate this weathering process .The two treatments all represented rai‐sing of vermiculite with the increasing of fertilization ages ,and it’s much higher on K surplus treatment than K deficient treat‐ment .In addition ,we found that the silica‐sequioxide ration of soil clay ,which indicated the degree of soil weathering ,decreased as the fertilization ages increasing ,and after 22 years K deficient input soil clay had the lowest silica‐sequioxide ration ,showing the greatest weathering extent of soil clay silicate minerals .To further research the changing of soil K nutrition ,we analyzed the content of soil available K ,slowly available K and total K .The result indicated that ,for K deficient treatment ,soil available K and slowly available K content all gradually declined with the increasing of fertilization ages ,about 62.0% and 37.4% down from 1991 to 2013 ,respectively .While there had a gain trend of soil available K content after long‐term K surplus input ,versus slightly dropping of slowly available K content .However ,we found that long‐term fertilization had no obvious effect on soil total K content .Therefore ,long‐term K deficiency could have negative effect on soil K ,exhausting soil K resource and accelerating soil mineral weathering .It seems to be difficult maintaining soil slowly available K and potassium‐bearing mineral content ,even excess applied K fertilizer .