The Degradation Rate of Straw Returned to Limestone Soil and the Effect on Soil Fertility

石灰土中秸秆还田降解率及其对土壤肥力的影响（英文）

Limestone soil is a poor quality soil with a low rate of nutrient supply due to the accumulation of organic carbon. Here, we examined the degradation of maize straw in limestone soil and red soil using indoor simulation. Dynamic testing was conducted on soil chemical properties and soil fertility. We found that the degradation rate of straw in karst soil is higher than for non-karst soil. The highest degradation rate of straw occurred during the first 60 d, after which it rose slowly and balanced out at 98 d. The peak value of degradation of straw in karst soil was found at 28 d, while that in non-karst soil occurred at 42 d. The total period of degradation lasted 160 d; the degradation rate of straw in karst soil and non-karst soil was 77% and 75%, respectively. During the period of straw degradation, the pH of soil tended to decrease in the early stage and rise slowly in later stages and this is consistent with the pattern of degradation products during different stages of straw degradation. Straw return to fields can increase soil fertility, and the growth rate of available N and K content is significant. Compared to karst soil, the content of various fertility indicators in non-karst areas were lower according to total content tests, although the increase （percentage） in nonkarst area was higher; available P and K content were found to be higher in non-karst areas according to availability tests. Some available nutrients Jn straw return can be more readily released in non-karst soil, while karst soil can contribute to the accumulation of total nutrient content due to its special soil texture features, the firm binding of many nutrients with clay minerals and the slow supply of nutrients.

石灰土具有高的有机碳的积累,但营养成分的供给速率偏低,导致土壤贫瘠。本文通过室内模拟实验,研究相同来源玉米秸秆在岩溶土与非岩溶土中的降解情况,对秸秆降解率、土壤理化性质、土壤肥力等进行动态检测,结果表明:(1)总体上岩溶土秸秆降解速率比非岩溶土快。秸秆降解速度最快主要集中在最初60天,之后呈缓慢上升趋势,到98天基本达到平衡。非岩溶土降解峰值出现时间为第42天,岩溶土为第28天,峰值出现时间前者比后者滞后14天。总降解时间持续160天,岩溶土降解率为77%,非岩溶土为75%。(2)秸秆降解期间,土壤p H值前期有下降的趋势,后期慢慢回升,这与秸秆降解过程中不同时期降解产物变化规律相吻合。秸秆还田可以提高土壤肥力,其中速效氮和速效钾含量增加非常明显。(3)与岩溶土相比,全量检测结果显示各肥力指标在非岩溶土含量低,但升幅百分比高;有效态检测结果显示非岩溶土速效磷和速效钾含量高。说明秸秆还田一些营养元素有效态在非岩溶土中更易于释放,而岩溶土由于其土壤质地的特殊性,许多养分被土壤粘土矿物牢固结合,营养元素供给速率慢,但因此也易于养分全量的累积。