The role of local earthworms in plant nutrient addition in the Ethiopian Drylands

ABSTRACT The Ethiopian Drylands are rich in their variety of local earthworm species. However, the category of species, and the effect of their performance on additions to plant nutrients have not been adequately evaluated. Thus, local earthworm samples were collected from the three major agroecological zones (highland, midland, and lowland) in Tigray (northern Ethiopia) and classified down to species level. Moreover, a vermicomposting experiment with four treatments (three local earthworm species, Eisenia fetida , and a conventional composting method) and three replications was established. Finally, each bin’s mature compost sample was taken to analyze plant nutrient content. The study results indicated that earthworm species in the highland, midland and lowland agroecological zones were Dendrobaena veneta, Eisenia andrie and Lumbricus rubellus , respectively. The use of these earthworms in the composting process (average of the four earthworm species) yielded higher nutrient content, ranging from 21.9 % for Sodium to 3300 % for Boron, compared to the conventional one. The highest total nitrogen (an increase of 44.4 %) and organic carbon (an increase of 33.4 %) were recorded in the Eisenia fetida and Dendrobaena veneta treated bins, respectively. Composting with Eisenia andrie has resulted in increases in P (96.1 %), K (125 %), Mg (83 %) and all micro-nutrients (between 91 % for Zn and 4400 % for B). Both Eisenia andrie and Lumbricus rubellus species contributed to the increased additions of Sulfur (85.7 %) compared to the control. It can be concluded that the use of local earthworms (particularly Eisenia andrie) in the composting process plays a significant role in plant nutrient addition.

摘要 埃塞俄比亚旱地拥有丰富的本地蚯蚓物种资源，但目前针对该区域蚯蚓的物种分类，以及其活动对植物养分添加的影响尚未得到充分评估。为此，研究团队从埃塞俄比亚北部提格雷地区的三大农业生态区（高地、中地、低地）采集了本地蚯蚓样本，并鉴定至物种水平。此外，本研究设置了包含三组本地蚯蚓物种、赤子爱胜蚓（Eisenia fetida）以及常规堆肥方法在内的四组处理，并开展了三次重复的蚯蚓堆肥实验。最终，采集每个堆肥箱中的腐熟堆肥样品以分析其植物养分含量。研究结果显示，高地、中地和低地农业生态区的优势蚯蚓物种分别为浅黄远蚓（Dendrobaena veneta）、安德爱胜蚓（Eisenia andrie）以及红陆蚓（Lumbricus rubellus）。与常规堆肥相比，使用上述四种蚯蚓进行堆肥（四种蚯蚓的平均效果）可获得更高的养分含量，提升幅度从钠（Sodium）的21.9%至硼（Boron）的3300%不等。其中，总氮提升44.4%的处理组与有机碳提升33.4%的处理组分别为赤子爱胜蚓（Eisenia fetida）和浅黄远蚓（Dendrobaena veneta）处理的堆肥箱。安德爱胜蚓（Eisenia andrie）堆肥可使磷（P）提升96.1%、钾（K）提升125%、镁（Mg）提升83%，且所有微量营养素的含量均有所提升，范围从锌（Zn）的91%至硼（B）的4400%。与对照组相比，安德爱胜蚓（Eisenia andrie）与红陆蚓（Lumbricus rubellus）均能使硫（Sulfur）的添加量提升85.7%。综上，在堆肥过程中使用本地蚯蚓（尤其是安德爱胜蚓（Eisenia andrie）），对植物养分添加具有显著的促进作用。