水旱轮作条件下还田秸秆腐解和养分释放特征研究

Characteristics of Decomposing and Nutrients Releasing of Crop Straw under Paddy-upland Rotation

以南方稻作区主要作物(水稻、小麦和油菜)秸秆为研究对象,采用尼龙网袋法研究了干湿交替和还田方式对作物秸秆腐解及养分释放的影响,以期为水旱轮作区秸秆资源循环利用和秸秆还田提供科学依据。结果表明,水作期经过120d的腐解,覆盖处理的作物秸秆累积腐解率为20.6%~27.2%,且作物种类之间差异不显著;翻压处理的作物秸秆累积腐解率为55.4%~69.3%,腐解效果表现为水稻>油菜>小麦。旱作期覆盖或翻压处理的秸秆腐解量和腐解率均显著低于同期水作处理。3种作物秸秆在水旱轮作中无论覆盖还是翻压还田,养分累积释放率均表现为钾>磷>碳>氮。水作期腐解试验结束时(120d),覆盖处理3种作物秸秆碳、氮、磷和钾的平均释放率分别为40.1%、22.4%、54.4%和75.8%;翻压处理的养分平均释放率依次分别为75.8%、44.7%、76.5%和93.8%。旱作期腐解试验结束时(210d),覆盖处理水稻秸秆碳、氮、磷和钾的释放率分别为43.4%、30.8%、43.7%和71.0%;翻压处理水稻秸秆养分释放率依次为64.8%、46.3%、57.0%和95.2%。采用一级动力学渐进函数模型对秸秆累积腐解率进行拟合,水作期的相关系数r2介于0.981~0.991之间,均显著相关;旱作期函数拟合相关性不显著。因此,在水旱轮作体系中,同等腐解周期内秸秆腐解速率表现为水作>旱作、翻压>覆盖;旱作周期相对较长仍可达到水作时的秸秆腐解效果。

To provide basis for crop straws recycling and straw use in paddy-upland rotation system,the characteristics of decomposition and release of nutrients of crop straws(rice,wheat and rapeseed)under dry and wet alternation,different ways of straw returning condition were studied by using the nylon net bag method.The results showed that the cumulative decomposition rates of straw mulch were 20.6%~27.2% in rice period after 120 d of incubation and there were no significant difference between crop types;while the cumulative decomposition rates of straw incorporation was 55.4%~69.3% and the decomposition effect was rapeseed > rice > wheat.The decomposition amount and decomposition rate of crop straw in dryland period were significantly lower than those in rice period at the same time.Ignoring the straw returning ways,the sequence of nutrient release rate of straw in the two periods was K > P > N > C at the endpoint of the experiment.At the end of the rice period(120 d),the average release rates of carbon,nitrogen,phosphorus and potassium in three kinds of crop straw in mulch treatment were 40.1%,22.4%,54.4% and 40.1% respectively;in the incorporation treatment,they were 75.8%,44.7%,76.5% and 44.7% respectively.However,at the end of the dryland period(210 d),the average release rates of carbon,nitrogen,phosphorus and potassium in three kinds of crop straw in mulch treatment were 43.4%,30.8%,43.7% and 43.4% respectively;in the incorporation treatment,they were 64.8%,46.3%,57.0% and 46.3% respectively.First order equation was used to describe the decomposition rate of straw in paddy-upland rotation.All the correlation coefficients(r^2)of the kinetic equations of rice period were from 0.981 to 0.991,which shows the most significant correlation,but there was no significant correlation between decomposition rate and days in the dry period.Therefore,the decomposing effects were rice period> dry period,straw incorporation>straw mulch in the same incubation time,and the long incubation time could increase the decomposition rate in dryland compared with that in the paddy field.