## 1 Introduction  
Land degradation is a broad term and is defined as the temporary or permanent decline in the productive capacity of land resources to perform essential functions and services, which decreases land biological productivity and/or usefulness to humans [1, 2]. Land degradation problems may occur through different physical, chemical, and biological processes that are induced naturally and/or by human activities such as deforestation, shifting cultivation, overgrazing, steep-slope farming, and overuse of chemical fertilizers and forest resources [3]. These problems prevent land from functioning effectively within an environmental system, which poses a major long-term challenge to humans in terms of adverse impacts on biomass productivity, food security, biodiversity, and environmental sustainability [1, 4, 5]. Land degradation is becoming a major problem in many regions of the world, especially in arid and semi-arid regions, and it affects the ability of land resources to perform essential ecosystem services and functions by indirectly affecting the type of plant grown in an area, reducing the availability of potable water, decreasing volumes of surface water, depleting aquifers, and causing biodiversity loss [6, 7, 8, 9, 10, 11, 12]. Problems related to land degradation can be prevented by using various mechanisms and activities [13], such as maximizing vegetation cover in degraded lands which should be given a priority since this action can prevent erosion and replace soil nutrients removed by erosion [4; 14; 15]. However, to maximize vegetation cover through natural regeneration and artificial plantations, factors such as shortages in soil nutrients and limited available water during the dry season in degraded lands affect the restoration process [16; 17]. To enhance tree growth and facilitate natural regeneration, studies recommend placing different soil and water conservation structures in degraded lands, as it is assumed that these structures can improve soil water by improving infiltration and soil nutrients [16; 18; 19; 20]. Establishing different soil and water conservation structures in degraded lands can play an important role in supplying water directly to the root zone and in reducing the sediment load and erosion at downstream sites [21]. Increasing soil water availability in degraded lands, especially in dry seasons, promotes the survival and growth rate of planted juvenile tree seedlings, while soil water limitations may increase seedling mortality and limit the growth of trees [22]. Research has shown that implementing rainwater harvesting structures in degraded lands increased water supplies, vegetation cover, and facilitated plant growth and biomass production [18; 20; 23; 24; 25; 26]. Although many rainwater harvesting structures are used to conserve soil and water in degraded lands, research findings have shown variability in their effectiveness for plant growth, biomass production, restoration of degraded lands, etc. [14; 21; 24; 27]. This result shows that the extent to which different soil and water conservation structures influence plant growth and rehabilitation on severely degraded lands needs to be further investigated, as their effect could vary depending on the severity of the degraded land, precipitation pattern, and the type of planted species used for restoration. In addition to this, the different pieces of research conducted on the impacts of rainwater harvesting structures on the growth of trees were performed at a plot level [14; 21; 24; 27], which is confined to a small space in an experimental area. However, findings on the impact of moisture harvesting structures on large scale degraded land restoration projects on the growth performance of trees are scant. The objectives of this research paper are (1) to evaluate the impact of water harvesting structures, mainly trenches established at the back of a tree-planting pit (\(T\)), on the growth and dry biomass production of _Acacia saligna_ (Labill.)