施用水稻秸秆对酸性红壤铝形态的动态影响

Dynamic Effects of Varying Amount of Rice Straw on Different Aluminum Form

采用室内培养试验研究了施用秸秆对酸性红壤pH值和高活性的交换性铝、吸附态羟基铝和有机络合态铝的动态变化。结果表明,土壤pH值和各形态铝在前30天内变化较大,而后达到稳定。土壤pH值在前10天内快速提高,之后缓慢下降至第30天渐趋平衡,土壤交换性铝则是先降低,10天后逐渐增加至稳定状态。添加秸秆后,土壤吸附态羟基铝发生复杂的水解和聚合反应,变化不大。有机络合态铝在可溶性有机质和有机酸等小分子化合物的联合作用下,先增加而后降低。由于秸秆作用的时间较短,不能使有机质积累,故有机络合态铝不稳定易于变化,不能起到很好的络合铝的作用。

Aluminum is the most abundant metal that makes up 7% of the earth＇s crust and occurs in a number of different forms in the soil. It is harmless as oxides and aluminosilicates. Nevertheless, if the soil pH 〈5 or even 5.5, as is now the case on 40% of the arable lands in the world, A1 will be solubilised into toxic forms, generally referred to Al^3＋, which is a primary factor limiting plant growth have been attributed to several physiological pathways. A possible alternative to ameliorate Al toxicity is the application of such organic manure as rice straw. Laboratory incubation studies were conducted to determine the dynamics effects of rice straw on different Al forms, the results strongly revealed that Al forms and soil pH changed rapidly in 30 days. Soil pH increased rapidly in the first 10 days, and then decreased to the 30th days and tends to the balance. As we all know exchangeable Al are negatively correlates with pH, so exchangeable Al decreased in the first 10 days with the pH increasing, and then increased to the balance. Adsorbent hydroxyl Al had complex hydrolisis and the polyreaction after straw application and changed a little. Exchangeable Al and adsorbent hydroxyl Al transform to organically complexed Al after straw application, so the curve of organically complexed Al increased to the peak on the 10th day, and then decreased to the balance. Because the time of incubation study is short, soil organic matter will not aggregate, so organically complexed Al is instable, which will be change with the environment changes, so the capacity of alleviating Al toxicity is weak.