【摘要】 为了探讨红壤性水稻土锰的迁移和转化行为 ,通过长达 1 6a的定位试验研究了不同稻作制、有机肥以及地下水位对土壤剖面中全锰、活性锰和交换态锰分布的影响。试验结果表明 ,长期淹水种稻引起 0～ 2 0 cm土壤层次全锰、活性锰和交换态锰含量的显著下降 ,而在 2 0～ 40 cm和 40～ 75 cm土层相对累积。不同稻作制比较 ,0～ 2 0 cm土层中全锰、活性锰和交换态锰含量以稻稻泡显著高于稻稻绿和稻稻油处理 ,而 2 0～ 40 cm和 40～ 75 cm土层 3种锰形态的含量各稻作制之间无显著差异 ,表明实行水旱轮作的稻稻绿与稻稻油两种稻作制耕层土壤锰的淋溶损失比持续淹水的稻稻泡制更为严重。相对而言 ,不同有机肥施用水平和地下水位对土壤剖面中锰分布的影响要小于稻作制 ,总的趋势为 :土壤剖面中锰的空间分异程度以高量有机肥 >常量有机肥 >单施化肥 ;低水位 >高水位。从土壤中锰的空间分布规律可以看出 ,水旱轮作 (尤其是在低水位和有机无机配合的条件下 )比长期淹水更有利于土壤锰氧化还原引起的深层淋溶与淀积 ,加速了典型水稻土剖面的形成。更多还原

【Abstract】 The chemical behavior of manganese (Mn) in paddy soils has been paid increasingly more attention since 1950’s due to its nutritional and environmental effects under rotation of rice and upland crops or transition of upland to paddy soil. A long term experiment, conducted at Hunan Agricultural University since 1982, was used to evaluate the effects of rice based cropping system, amount of organic manure and groundwater level on distribution of several chemical fractions of Mn in the profile of paddy soil derived from arable red earth. The experiment included three rice based cropping systems (rice rice flooding, rice rice green manure, rice rice oilseed rape), and two groundwater levels (0.2 m and 0.8 m), and three levels of organic manure application (only chemical fertilizer as control, medium amount of organic manure, high amount of organic manure). All treatments received the same rates of N, P, K application. The rate of N fertilizer as urea was 150 kg N/hm\+2 for both rice growth seasons. The ratios of N∶P\-2O\-5∶K\-2O were 1∶0.5∶1 for first rice and 1∶0∶1 for second rice, respectively. The sources of chemical fertilizer were urea (N), superphosphate (P) and potassium chloride (K) respectively. The amounts of organic manure were 22.5 t/hm 2 fresh green manure for first rice and 7 5 t/hm 2 fresh rice straw for the second rice as medium level and 45 t/hm 2 fresh green manure for first rice and 11.25 t/hm 2 fresh rice straw for the second rice as high level. A completely randomized block design was used in the experiment. Each treatment replicated 2 times and the size of each plot is 1 2m×1 2 m. The original soil was arable red earth with pH 6 2, O.M. 13 3 g/kg, and Total Mn 480 mg/kg. In the spring of 1998, soil samples were collected from the stationary experiment to identify the distribution of Total Mn, Active Mn and Exchangeable Mn (Exc Mn) in soil profile as affected by rice based cropping system, organic manure and groundwater level. It was found that long term cultivation of rice has led to significant decline of Total Mn, Active Mn and Exc Mn in 0～20 cm and their corresponding accumulation in 20～40 cm and 40～75 cm soil compared with the original red earth, relatively. Total Mn content in 0～20 cm soil ranked by the sequence of “rice rice flooding” > “rice rice green manure” and “rice rice oilseed rape”, indicating more leaching of Mn from top soil to lower layers under rotation of paddy with upland crops than that under continuous flooding. It could be explained by the stronger oxidation and reduction of Mn under alternation of wetting and drying compared with continuous flooding. The differences in Total Mn content for 20~40 cm and 40～75 cm soil layers were not significant among different cropping systems. Distribution of Active Mn and Exc Mn in soil profile showed the similar tendency to Total Mn. \;The effect of organic manure on Mn distribution in soil profile was also obvious because fresh organic manure could promote the reduction and movement of Mn under waterlogged conditions. The contents of Total Mn, Active Mn and Exc Mn in different soil layers basically obeyed the order of high amount organic manure < medium amount organic manure and no organic manure (chemical fertilizer only), showing that much more leaching loss of Mn occurred under high amount of organic manure than under low or medium amount of organic manure. Groundwater level had also effect on Mn distribution in soil profile. The contents of Total Mn, Active Mn and Exc Mn in 0～20 cm soil were not different but significantly different in deep soil layers (20～40 cm and 40～75 cm) between two groundwater levels. The contents of Total Mn and Active Mn in two deep soil layers were higher at low groundwater level (0 8 m) than at high groundwater level (0.2 m) while Exc Mn was reverse. That is to say, the leaching loss of Mn might be somewhat more at low groundwater level than at high groundwater level. In general, the chemical behavior and distribution of Mn in soil profile wa更多还原