• ISSN 1008-505X
  • CN 11-3996/S

玉米秸秆替代部分化肥提高黑土的团聚体稳定性和结构

Replacing part chemical fertilizer with maize straw enhances the aggregate stability and the structure of black soil

    摘要
  • 摘要:
    目的 施肥影响土壤结构，长期施化肥易破坏土壤结构的稳定性，同时导致土壤酸化。研究等氮条件下玉米秸秆替代部分化学氮肥对黑土养分含量、团聚体粒级分布及稳定性的影响，可为合理调节土壤结构提供理论支撑。
    方法 依托始建于1989年的吉林公主岭市黑土定位试验，选取3个处理：不施肥(CK)；施化肥N 165 kg/hm2、P2O5 82.5 kg/hm2、K2O 82.5 kg/hm2 (NPK)；施化肥N 112 kg/hm2、P2O5 82.5 kg/hm2、K2O 82.5 kg/hm2、配施玉米秸秆7500 kg/hm2 (NPKS)，于2010年和2022年秋季收获后，采集0—20 cm土壤样品，测定土壤pH、有机质、全氮、有效磷、速效钾、交换性钙镁离子含量，同时利用湿筛法筛分出四个级别的团聚体(>2 mm、0.25—2 mm、0.053—0.25 mm、<0.053 mm)，计算团聚体平均重量直径(MWD)和几何平均直径(GMD)。
    结果 随着试验年限的增加，与CK相比，2010年和2022年NPK处理土壤MWD分别降低了44.8%和22.2%，GMD分别降低了59.3%和25.6%，土壤交换性钙含量显著降低40.6%和22.6%，土壤pH在两年间下降1.32和1.50个单位。相关性分析表明，土壤pH、交换性钙离子、有机质含量与MWD和GMD显著正相关(P<0.05)。长期施用化肥阻碍土壤颗粒胶结过程及其团聚效果，显著降低团聚体稳定性。相较于NPK处理，2010年和2022年NPKS处理土壤> 2 mm团聚体含量分别显著增加159.0%和109.2%，MWD由此显著升高33.6%和46.0%，GMD升高61.1%和68.9%，土壤有机质含量增加14.7%和28.3%，交换性钙离子含量增加121.2%和97.9%，pH分别升高1.41和1.66个单位。随机森林模型表明，土壤pH和交换性钙离子越来越成为提高黑土团聚体稳定性的关键因素，土壤有机质的相对重要性由第一位下降到第四位。
    结论 在黑土上，以秸秆替代部分化肥氮不仅减缓了化肥施用导致的土壤酸化，还提高了有机质和交换性钙含量，从而显著提高水稳性大团聚体含量及团聚体稳定性，这一有益效应随时间的延长而提升。因此，以玉米秸秆替代部分化肥是维持并改善黑土养分含量及土壤结构的有效措施。

     

    Abstract:
    Objectives Fertilization affects soil structure. Long-term application of chemical fertilizers tends to degrade soil structural stability and acidification. We studied the effect of integrated application of chemical fertilizer and maize straw on black soil nutrient availability, aggregate size distribution and stability, aiming to propose nutrient management for sustainable use of black soil.
    Methods A long-term fertilization experiment was established in 1989 in Gongzhuling, Jilin, under single maize cropping system. In 2021 and 2022 after harvest of maize, 0—20 cm top soil samples were collected from the three treatment plots: no fertilization (CK); application of chemical N 165 kg/hm2, P2O5 82.5 kg/hm2, and K2O 82.5 kg/hm2 (NPK); and combined application of NPK with maize straw 7500 kg/hm2 (NPKS). The soil pH, organic matter (SOM), total nitrogen (TN), available phosphorus (AP), available potassium (AK), and exchangeable Ca2+ (exCa) and Mg2+ (exMg) were analyzed. A wet-sieving method was used to divide soil aggregates into four size classes: >2 mm, 0.25−2 mm, 0.053−0.25 mm, and <0.053 mm. The mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates were calculated to evaluate aggregate stability.
    Results With increasing of the experiment years, compared to the CK, NPK treatment significantly reduced the MWD by 44.8% and 22.2%, and the GMD by 59.3% and 25.6% in 2010 and 2022, respectively; and the soil exchangeable calcium content decreased significantly by 40.6% and 22.6%. The soil pH decreased significantly by 1.32 and 1.50 units within two years. Correlation analysis revealed that soil pH, exCa and organic matter were positively (P<0.05) correlated with the MWD and GMD. Long-term application of chemical fertilizers hinders the cementing process of soil particles and their agglomeration effect, significantly reducing the stability of aggregates. Compared to NPK, the NPKS treatment significantly increased the content of >2 mm aggregates by 159.0% and 109.2% in 2010 and 2020, respectively, thereby increased the MWD by 33.6% and 46.0%, and the GMD by 61.1% and 68.9%, respectively. The content of soil organic matter increased by 14.7% and 28.3%, the content of exCa increased by 121.2% and 97.9%, and the pH increased by 1.41 and 1.66 units respectively. A random forest model analysis assessed that soil pH and exchangeable calcium ions are increasingly becoming the key factors in enhancing the stability of black soil aggregates, while the relative importance of soil organic matter has dropped from the first place to the fourth.
    Conclusions In black soil, substitution of part chemical fertilizers with maize straw can significantly increase the organic matter and exchangeable Ca content, alleviate the decline of soil pH, which is conducive to the formation of macroaggregates and enhancement of the aggregate stability. Thus, the approach is an optimal nutrient management for maintaining soil fertility and sustaining structural stability in black soil of northeast China.

     

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