微藻生物肥促进谷子生长和改善土壤菌群及肥力

Microalgae-based fertilizer promotes foxtail millet growth and improves the microbial community and fertility of soil

摘要:

土壤养分缺乏是影响作物产量的主要限制因素。化肥过量使用会导致土壤板结、环境污染以及农产品质量下降。微藻肥作为一种新型绿色生物肥料，在多种逆境土壤条件下均可有效促进作物生长并提升土壤肥力。目的 探究不同类型肥料配施对贫瘠土壤下谷子生长、土壤理化性质、土壤酶活性及微生物群落特征的影响，为微藻肥在化肥减量及绿色可持续生产中的应用提供理论支撑。方法 供试谷子品种为‘晋谷21’。采用土培试验，设置全化肥组(T1)、微藻肥耦合化肥减施组(T2：80%化肥+20%微藻肥；T3：60%化肥+40%微藻肥；T4：40%化肥+60%微藻肥)、全藻肥组(T5)共5种处理组。在谷子生长90 d后测定各处理组谷子的生长指标、生物量、色素含量，检测土壤的理化性质和土壤酶活性，以及土壤细菌群落特征指标。结果 在5种肥料处理中，微藻耦合化肥处理(T4)对贫瘠土壤下谷子的促生效果最为明显。相较于全化肥处理(T1)，在贫瘠土壤条件下T4处理组谷子幼苗株高提高了26.41%，地上部干重增加了126.47%，叶绿素a、叶绿素b与类胡萝卜素含量分别升高了17.1%、24.5%与28.0%。与全化肥(T1)相比，施用全藻肥(T5)和微藻肥耦合化肥减施(T2、T3、T4)增加了土壤全氮、有效磷、有机质的含量，提高了土壤蔗糖酶、硝酸还原酶、过氧化氢酶、磷酸酶的活性，且T4处理组对土壤的改良效果最显著。进一步对土壤微生物16S rRNA基因扩增子测序分析表明，与单一施肥处理(T1、T5)相比，T4处理提高了土壤微生物的多样性，酸杆菌门(Acidobacteriota)和绿屈挠菌门(Chloroflexi)的相对丰度显著增高。同时，相关性分析显示土壤微生物多样性组成与脲酶呈显著正相关，土壤细菌群落组成与有效磷、蔗糖酶、过氧化物酶和脲酶呈显著正相关。冗余分析(redundancy analysis, RDA)显示脲酶和有效磷是影响土壤细菌群落结构的主要环境因素。其中，绿屈挠菌门相对丰度与脲酶和有效磷呈显著正相关。结论 藻肥耦合化肥减施处理可有效提高土壤养分含量及土壤酶活性，同时改善土壤微生物多样性及群落结构，进而促进贫瘠土壤下谷子幼苗的生长。

Abstract:

Soil nutrient deficiency is a major limiting factor affecting crop yields. Excessive use of chemical fertilizers can lead to soil compaction, environmental pollution, and decreased crop yields and quality. Microalgae-based fertilizer, functioning as a novel green bio-fertilizer, not only effectively promotes crop growth but also enhances soil fertility under various adverse soil conditions.Objectives This study investigated the effects of different fertilizer treatments on the growth of foxtail millet (Setaria italica L.) and the physicochemical properties, enzymes activities, and microbial communities of infertile soil, aiming to provide theoretical support for the application of microalgae-based fertilizer in chemical fertilizer reduction and green sustainable agricultural production.Methods The foxtail millet cultivar ‘Jingu 21’ was cultivated in this study under five fertilizer treatments: full chemical fertilizer (T1), chemical-microalgae integrated fertilizer (T2: 80% chemical fertilizer+20% microalgae-based fertilizer; T3: 60% chemical fertilizer+40% microalgae-based fertilizer; T4: 40% chemical fertilizer+60% microalgae-based fertilizer), and full microalgae-based fertilizer (T5). The growth indexes, biomass, and pigment content of foxtail millet in each treatment were determined, and the physicochemical properties, enzyme activities, and bacterial community characteristics of the infertile soil were measured, after 90 days of cultivation.Results Among the five fertilizer treatments, T4 had the most significant effect of promoting the seedling growth of foxtail millet in the infertile soil. Compared with T1, T4 increased the seedling height, the aboveground dry weight, and the content of chlorophyll a, chlorophyll b, and carotenoids by 26.41%, 126.47%, 17.1%, 24.5%, and 28.0%, respectively. In addition, T5, T2, T3, and T4 increased the content of total nitrogen, available phosphorus, and organic matter and the activities of sucrase, nitrate reductase, peroxidase, and phosphatase in the soil, compared with T1, and T4 had the most significant soil improvement effect. The 16S rRNA gene amplicon sequencing results showed that compared with T1 and T5, T4 increased the diversity of soil microorganisms, in which the relative abundance of Acidobacteriota and Chloroflexi was significantly increased. The correlation analysis showed that the composition of soil microbial diversity was significantly and positively correlated with urease, and the soil microbial community composition had significantly positive correlations with available phosphorus, sucrase, peroxidase, and urease. Redundancy analysis showed that urease and available phosphorus were the main environmental factors affecting the soil bacterial community structure. The relative abundance of Chloroflexi had significantly positive correlations with the urease activity and the available phosphorus content.Conclusion The combined application of microalgae-based fertilizer with reduced chemical fertilizer not only effectively improves the nutrient content and enzyme activities but also enhances the microbial diversity and community structure in the soil, thereby promoting the growth of foxtail millet seedlings in infertile soil.