ABSTRACT

To assess the effect of long-term rice cultivation and aquic conditions on the physicochemical properties and different forms of iron and manganese and also to make a comparison with non-paddy and adjoining uncultivated soils in calcareous soils of southern Iran. The soil samples were taken from the paddy and non-paddy soils with similar parent materials and landforms. The results showed that in the paddy fields, the amounts of available (extracted by DTPA), total (extracted by nitric acid), and poorly crystalline iron and manganese oxides (extracted by ammonium oxalate) were higher than those in the non-paddy soils and show the highest amount in the surface horizons of paddy fields. In general, the paddy land use increases the iron and manganese oxides with poorly crystalline form, Fe_o/Fe_d and Mn_o/Mn_d ratios by 1.84, 1.57, 2 and 3.2, respectively. It also reduces the amount of pedogenic iron and manganese oxides and their crystalline forms relative to the adjacent uncultivated soils. Finally, a significant positive relationship was found between the amounts of poorly crystalline iron and manganese oxides and total form and the amount of organic matter and clay in the soils under study. Also, by changing the land use from the non-paddy to paddy field, the amount of smectite increased and, in contrast, the amounts of illite and chlorite decreased. Therefore, it seems that the significant amount of organic matter introduced and their burial caused by the plowing operation and, on the other hand, their slow decomposition due to the inactivation of aerobic activities in the reduction conditions is among the factors affecting the variations of chemical properties in paddy soils and, generally, wet land soils.

摘要

评估长期水稻种植和含水条件对理化性质和不同形式的铁和锰的影响，并与伊朗南部钙质土壤中的非稻田和毗邻的未开垦土壤进行比较。土壤样品取自具有相似母质和地貌的稻田和非稻田土壤。结果表明，稻田有效（DTPA提取）、总量（硝酸提取）和低结晶铁锰氧化物（草酸铵提取）量均高于非稻田并在稻田地表中显示出最高的数量。一般来说，稻田利用增加了结晶较差的铁锰氧化物，Fe _o /Fe _d和 Mn _o /Mn _d比率分别为 1.84、1.57、2 和 3.2。相对于相邻的未开垦土壤，它还减少了成土的铁和锰氧化物及其结晶形式的数量。最后，在所研究的土壤中，低结晶铁和锰氧化物的数量和总形态与有机物质和粘土的数量之间存在显着的正相关关系。此外，通过将土地利用从非稻田改为稻田，蒙脱石的量增加，相反，伊利石和绿泥石的量减少。因此，似乎是耕作造成了大量有机物的引入和掩埋，另一方面，