种稻年限对苏打盐碱土腐殖质含量及组成的影响

Effects of Different Rice Cultivation Years on Humus Content and Composition of Soda Saline-alkaline Soil

种稻是苏打盐碱土改良利用的有效措施之一,研究种稻对苏打盐碱土的改良作用及其机理,有助于丰富盐碱土改良利用理论。通过田间试验,研究了不同种稻年限对苏打盐碱土腐殖质含量及组成的影响。结果表明:随着种稻年限的增加,土壤剖面各层次有机碳含量显著增加,种稻40年的土壤与未种稻的废弃草原土壤相比,耕作层、犁底层、心土层土壤有机碳含量增加了19. 89、15. 72、10. 71 g/kg,可提取态腐殖质总量在耕作层中随种稻年限的增加呈上升趋势;游离态腐殖质含量在种稻40年最高,相比较于废弃草原耕作层、犁底层、心土层分别增加了7. 1、6. 9、3. 62 g/kg;结合态腐殖质含量也在种稻40年时最高,相比较于废弃草原耕作层、犁底层、心土层分别增加了8. 37、9. 36、7. 70 g/kg。种稻40年各层次游离态胡敏酸(HA)、富里酸(FA)含量均达到最大值;结合态HA含量在种稻40年各层次最大,FA含量随种稻年限增加呈增长趋势。随种稻年限的增加,耕作层PQ值均有所增长。随着种稻年限的增加,各剖面层次游离态HA均向着RP型转变;结合态胡敏酸在耕层中由A-P-B-A,犁底层中由A-B-A,这说明种稻使游离态胡敏酸芳香化度降低,结构趋于简单化,而结合态胡敏酸仍保持较复杂的结构。

Rice cultivation is one of the effective measures in improving soda saline-alkaline soil,and the study of improvement effects and mechanisms of soda saline-alkaline soil by growing rice can enrich improvement and utilization theory of soda saline-alkaline soil. In this paper,we have studied the effects of different rice cultivation years on humus content and composition of soda saline-alkali soil by field experiment. The results show that with the increase of planting age,organic carbon content of each soil profile layer has increased obviously. The comparison between soil of growing rice for 40 years and waste grassland soil with no rice cultivation shows that organic carbon content of tillage layer,plough bottom layer,subsoil layer of soil profiles has increased by 19. 89,15. 72 and 10. 71 g /kg,respectively. In tillage layer,with the increase of planting age,total content of extractable humus is on the increase;content of free humus extracted by 0. 1 mol /L NaOH in 40-year rice growing soil is the highest,increasing by 7. 1,6. 9 and 3. 62 g /kg compared with tillage layer, plough bottom layer, subsoil layer of waste grassland soil with no rice cultivation;content of combined humus extracted by 0. 1 mol /L Na4 P2 O7 in 40-year rice cultivation is the highest,increasing by 8. 37,9. 36 and 7. 70 g /kg compared with tillage layer,plough bottom layer, subsoil layer of waste grassland soil with no rice cultivation. Content of free HA and FA in each profile layer has reached the peak in soil of growing rice for 40 years;content of combined HA in each layer of soil of growing rice for 40 years is the highest,content of FA tends to increase with the years added. PQ in tillage layer has increased with the increase of planting age. HA has been classified by Kumada method, and with the increase of planting age,free HA of each profile layer has all turned to Rp type;combined HA has changed from A to P to B to A in tillage layer and from A to B to A in plough bottomlayer layer,indicating that rice cultivation will reduce aromatization degree of free humic acid,and structure tends to be simplified while combination state of humic acid remains more complex structure.