Haque K M Shamsul, Eberbach Philip L, Weston Leslie A, Dyall-Smith Mike, Howitt Julia A
School of Agricultural and Wine Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; Graham Centre for Agriculture Innovation, Wagga Wagga, NSW 2678, Australia.
School of Agricultural and Wine Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; Graham Centre for Agriculture Innovation, Wagga Wagga, NSW 2678, Australia.
Chemosphere. 2015 Sep;134:16-24. doi: 10.1016/j.chemosphere.2015.03.044. Epub 2015 Apr 18.
Flooded rice soils produce elevated concentrations of soluble manganous manganese (Mn(2+)) that could be potentially toxic to subsequent crops. To provide insight into how soil pore Mn(2+) changes its concentration in a rice and post rice drying soil, we used an artificial microcosm system to follow Mn(2+) concentrations in two different soil types (red sodosol and grey vertosol) and under two irrigation regimes (flooded and saturated). Soil pore water was collected from four different depths of soil (2.5 cm, 7.5 cm, 15 cm and 25 cm) and Mn(2+) concentrations were analysed during and after the rice phase over a one year cycle. Mn(2+) increased with the advancement of anaerobic conditions at all soil depths, but the concentration was higher in flooded soil compared to saturated soil. Initially, the highest concentration of Mn(2+) was found at a depth of 7.5 cm, while at the later stage of rice growth, more Mn(2+) was found in the deepest sampling depth (25 cm). Plants grown in saturated soils showed a delay in flowering of approximately 3 weeks compared to flooded cultures. Moreover, plants grown in flooded soil produced more tillers and leaf area than those grown in saturated soil. Peak concentrations of soil Mn(2+) were associated with the reproductive stage of rice growth. Mn(2+) concentrations decreased after drainage of water. In post rice soils, Mn(2+) remained elevated for some time (lag phase), and then rapidly declined. Regression analysis revealed that the process of oxidation of Mn(2+) to Mn(4+) following water drainage decreased with soil depth.
淹水的稻田土壤中可溶性二价锰（Mn(2+)）浓度升高，这可能对后续作物具有潜在毒性。为深入了解土壤孔隙中的Mn(2+)在水稻生长及水稻收获后土壤干燥过程中是如何变化其浓度的，我们使用了一个人工微观系统来跟踪两种不同土壤类型（红色铁铝土和灰色变性土）以及两种灌溉方式（淹水和饱和）下的Mn(2+)浓度。从土壤的四个不同深度（2.5厘米、7.5厘米、15厘米和25厘米）采集土壤孔隙水，并在一年周期内分析水稻生长期间及之后的Mn(2+)浓度。在所有土壤深度，Mn(2+)浓度都随着厌氧条件的发展而增加，但淹水土壤中的浓度高于饱和土壤。最初，Mn(2+)的最高浓度出现在7.5厘米深度处，而在水稻生长后期，最深采样深度（25厘米）处发现了更多的Mn(2+)。与淹水栽培相比，在饱和土壤中生长的植物开花延迟了约3周。此外，淹水土壤中生长的植物比饱和土壤中生长的植物产生更多的分蘖和叶面积。土壤Mn(2+)的峰值浓度与水稻生长的生殖阶段相关。排水后Mn(2+)浓度下降。在水稻收获后的土壤中，Mn(2+)在一段时间内（滞后阶段）仍保持较高水平，然后迅速下降。回归分析表明，排水后Mn(2+)氧化为Mn(4+)的过程随土壤深度而降低。
