玉米残体分解对不同肥力棕壤团聚体组成及有机碳分布的影响

以棕壤肥料长期定位试验(29 a)形成的高、低两种肥力水平棕壤为研究对象,采用不同部位玉米残体为试验试材,分别向两种土壤中加入玉米根茬和茎叶,进行田间原位培养试验,试验设置6个处理:低肥力土壤添加玉米根茬(LF+R)、低肥力土壤添加玉米茎叶(LF+S)、高肥力土壤添加玉米根茬(HF+R)、高肥力土壤添加玉米茎叶(HF+S)和未添加玉米残体的对照处理(LF,HF)。本研究旨在探明玉米根茬、茎叶添加后不同肥力土壤团聚体组成及有机碳分布的变化规律,为构建合理的秸秆还田与施肥措施,减少土壤侵蚀提供理论依据。结果表明:1)添加玉米残体后低肥力棕壤团聚体稳定性、较大级别团聚体(2 mm和1~2 mm)有机碳贡献率的提升幅度比高肥力棕壤大,说明低肥力土壤对外源有机质的响应更敏感,向大团聚体转化的速率更快。2)培养结束时,高肥力棕壤添加茎叶处理团聚体稳定性显著高于添加根茬处理,而添加根茬处理各粒级团聚体有机碳含量显著高于添加茎叶处理;低肥力棕壤中根茬和茎叶添加处理团聚体稳定性及有机碳含量之间差异不明显。3)在田间原位培养过程中,棕壤2 mm和1~2 mm团聚体所占比例和团聚体稳定性呈现出前期(0~360 d)快速增加,后期(360~720 d)趋于稳定的趋势。可以看出,玉米残体对土壤团聚体团聚化过程的作用强度逐渐减弱。以上结果表明,作物残体输入对棕壤团聚体组成及有机碳分布的影响与棕壤肥力水平和不同残体部位间的差异关系密切。

Effects of maize residue decomposition on aggregate composition and organic carbon distribution of different fertilities Brown soils

Soil aggregate and organic carbon are two major indices for assessing soil fertility. Besides, crop residue return is an effective agricultural way to supplement soil carbon pool and promote soil aggregate formation. However, how soil fertility level and residue type affect soil aggregate stability and organic carbon distribution is not clearly understood yet. In this study, a field incubation experiment was carried out by adding maize (Zea mays L.) root or stem and leaf to brown soil of different fertility levels. The samples of low fertility (LF) and high fertility (HF) soils were collected from a long-term (29 years) fertilization experiment. Six treatments were set, which were low fertility soil with maize root (LF+R), low fertility soil with maize stem and leaf (LF+S), high fertility soil with maize root (HF+R), high fertility soil with maize stem and leaf (HF+S), low or high fertility soil without maize residues (LF or HF). The objective of the study was to explore the dynamics of soil aggregate composition and allocation of organic carbon after residue incorporation. The study could have significant implications for developing residue management and reduce soil erosion in agro-ecosystems. The results showed that soil fertility significantly affected aggregates composition and organic carbon allocation of soil with crop residue incorporation. The addition of maize residue increased mean weight diameter, geometric mean diameter of soil aggregates and contribution rate of organic carbon in larger aggregates (> 2 mm and 1-2 mm) in LF soil compared to those in HF soil. The results suggested that LF soil was more sensitive to organic matter input and had a rapid rate of transformation to macro-aggregate. 2) At the end of experiment, the addition of maize stem and leaf to HF soil had a more pronounced effect on soil aggregate stability compared to the addition of root. Then the addition of root had a more pronounced effect on organic carbon content in soil aggregates than the addition of stem and leaf. However, there was no significant difference between soil aggregate stability and organic carbon content in LF soil aggregate supplemented with different maize parts. The results further suggested that soil fertility level could change the effects of different parts of crop residues addition on soil aggregate stability and organic carbon distribution. 3) The proportion of > 2 mm, 1-2 mm aggregates and soil aggregate stability sharply increased during the first 360 days. This then tended to stable during the later incubation period of 360-720 days. This indicated that the effect of maize residue on the formation of soil aggregate gradually weakened with time. It was concluded that the effects of maize residue addition on soil aggregates composition and organic carbon distribution were dependent on both soil fertility and residue part. Besides, crop residue addition had more obvious effect on improving the structure and stability of aggregates in LF soils.