Altitude and management affect soil fertility, leaf nutrient status and Xanthomonas wilt prevalence in enset gardens

Abstract

Abstract. Enset (Ensete ventricosum) is a productive, drought-tolerant and multipurpose food security crop grown in the densely populated Ethiopian highlands. It is a so-called orphan crop, and its production suffers from a lack of information on proper soil fertility management and its interaction with bacterial wilt disease caused by the pathogen Xanthomonas campestris pv. musacearum. The aim of this study was therefore to assess soil–plant nutrient variation within enset home gardens at three altitudes (ranging from 2000 to 3000 m above sea level – a.s.l.) in the Gamo highlands and investigate whether this variation affects disease prevalence. Altitude in the rift valley covaries with soil leaching, and plant available P, Ca and Mg in soils significantly raised with decreasing altitude. Soil carbon and most nutrients reached very high levels in the gardens, whereas the more distant outfields were severely nutrient deprived. Differences in management intensity within the garden caused soil pH, conductivity, total organic carbon, total N and available P, K, Ca, Mg, Mn and Fe levels to significantly decline with distance from the house; yet, this decrease in soil nutrients was not mirrored in a response of foliar nutrient content, except for N. Hence, over-fertilization is likely, and establishing evidence-based nutrient recommendations for enset would benefit soil quality and productivity both in the gardens and in the outfields. Disease prevalence was high in the study area, with one-third of the farms affected in the recent past. Although more experimental work is needed to exclude confounding factors, our data indicate that the effects of altitude, P fertilization, micronutrients and K-Ca-Mg balance are promising avenues for further investigation into Xanthomonas wilt disease susceptibility.

Xanthomonas wilt of enset in Ethiopia: Geographical spread, impact on production systems and the effect of training on disease management practices

“…Other surveys have reported various XW hotspots throughout the years, for example with increased incidences in the Gedeo zone (McKnight-CCRP, 2013), the Hadiya zone (Wolde et al, 2016) or the West Shewa zone (Hunduma et al, 2015), but it is evident that XW forms a major constraint across all regions. No indication is found of changing XW susceptibility related to environmental conditions (in this case with altitudinal variation), although this association has been suggested (Yemataw et al, 2020;Gebre et al, 2021;Shara et al, 2021).…”

Enset landrace diversity in major enset growing regions of Southern Ethiopia

“…Simpson's index is defined here as 1 -D, or the probability of selecting two individuals from different species, with replacement. The Shannon-Weaver diversity index accounts for both abundance and evenness of the landraces present and can be increased either by greater evenness or more unique landraces (Shannon and Weaver, 1949). The Shannon-Weaver index is defined as: H' = -Σ i p i ln p i Where: p i is the proportional abundance of species i.…”

“…Indeed, a perception bias in landrace environmental tolerances is observed. Namely the importance of drought tolerant landraces reportedly increased with altitude, whilst there is a tendency for more rain at higher elevations (Shara et al, 2021). At lower altitudes, farmers have more experience with drought, and as such have a better idea of which landraces are tolerant or susceptible to drought.…”

Estimating Yield Components, Limiting Factors, and Yield Gaps of Enset in Ethiopia Using Easily Measurable Above-Ground Plant Traits

“…This could be attributed to fixation of P by SOM and aluminum (Al) in the soil. Shara et al [25] observed a decline in P with increasing altitude at sites in Ethiopia and attributed this decline to fixation by Al that increased with altitude. In the current study, mean P also generally declined with increasing altitude (c.f.…”