Spatial analysis of soil water depletion and biomass production in the transition zone between a Eucalyptus camaldulensis stand and a maize field in Ethiopia

• Published in: Agricultural and forest meteorology 2022-06, Vol.320, p.108956, Article 108956
• Main Authors: Schume, Helmut, Hailu, Zerfu, Hailu, Tenaw, Sieghardt, Monika, Godbold, Douglas L.
• Format: Article
• Language: English
• Subjects: aboveground biomass; Biomass inventory; biomass production; corn; edge effects; Ethiopia; Eucalyptus camaldulensis; Eucalyptus-crop interaction; fine roots; forests; Geostatistics; inventories; land use; meteorology; Resource competition; Root distribution; soil depth; Soil moisture; soil water; soil water storage; Zea mays
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2022.108956

•Clearly differing water depletion in the two land use forms and the transition zone.•Soil water depletion patterns mirror aboveground biomass production.•Productivity loss in the maize field balanced by surplus increment of border trees.•Shading alone cannot explain growth depression in maize. Growth depressions in crops grown adjacent to Eucalyptus stands are often reported. The reasons for this observation range from competition for the resources light, nutrients and water to allelopathic effects. We investigated the effect of a Eucalyptus camaldulensis stand on soil water relations of an adjacent field of Zea mays. We used a geostatistical network spanning the Eucalyptus camaldulensis stand and the maize field. We measured changes in soil water storage in high spatial resolution (356 sample points over 3700 m²) in weekly to monthly intervals. In addition, an intensive root inventory of the Eucalyptus, covering a depth of 3.1 m, as well as aboveground biomass inventories in both land use forms were carried out. The majority of the fine root biomass of the Eucalyptus (70.5%) was found in the first 60 cm soil depth, which corresponded to the depth of the soil moisture measurements. Soil water depletion in the maize field was greatest up to 20 m from the forest edge, which coincided with the zone of least maize biomass production. In contrast, the water depletion across the first 6 m into the forest was 34% lower than in the border zone on the field side. Growth of the Eucalyptus was greatest at the forest edge, and the increased biomass production of the Eucalyptus balanced the decrease in maize production found in the first 20 m of the field. These changes in spatial growth patterns are explained by intense competition for soil water between the Eucalyptus and the maize.