Less Is More: Lower Sowing Rate of Irrigated Tef (Eragrostis tef) Alters Plant Morphology and Reduces Lodging

Abstract

Tef (Eragrostis tef (Zucc.) Trotter) is a panicle-bearing cereal crop plant, originating from and grown mainly in Ethiopia. Tef yields highly nutritious gluten-free grain as well as high-quality forage, therefore, interest is rising regarding tef cultivation for grain and forage outside Ethiopia. Lodging is a major factor limiting tef quality and yield, with losses estimated at 30%–35% and presumably higher under mechanical harvest. Studies in other cereal crops suggested that lowering plant density would lead to sturdier plants less prone to lodging. In this work, we reported on the effects of sowing rate on lodging, lodging-related traits, and productivity of tef under irrigated conditions. Four tef genotypes were grown under irrigation across two years at three sowing rates: low (3 kg/ha), medium (6 kg/ha), and high (common, 9 kg/ha). Grain yield and biomass did not differ significantly among sowing rates. The visually assessed lodging index (LI) increased as the season progressed, with the lowest values recorded under low sowing density. A significant difference in LI values among the tested genotypes suggested potential for crop improvement. Aerial RGB images of the field taken by an unmanned aerial vehicle twice during the second season produced a high-resolution crop surface model, which was used to assess lodging. Aerial-based LI values were significantly correlated with the ground-based ones and exhibited better capacity to identify minor differences in lodging. Among the morphological traits assessed, crown diameter, crown root number, and crown root diameter were significantly affected by sowing rate and genotype and were correlated with LI values. In summary, this study demonstrated for the first time the feasibility of tef production under irrigated Mediterranean conditions and the potential of a reduced sowing rate as a remedy for lodging.

Optimizing Sowing Depth of Tef for Irrigated Mediterranean Conditions: From Laboratory to Field Studies

“…In our pot experiment, deeper sowing of tef induced a significant effect on number of internodes, whereas its effects on lodging angle, crown diameter, and crown root diameter fell below the statistical threshold (Table 4). In our previous study, lodging of four genotypes grown in the field under various plant densities was associated with crown diameter, crown root diameter, and crown root number [21]; in the pot experiment, crown diameter and crown root diameter showed similar effects.…”

“…The effect of sowing depth on tef lodging has not been reported in previous studies. Recently, we reported that lower seedling density reduces lodging index [21]. Published studies on tef [20,29] and other cereals [28] have shown an association between lower plant height and reduced lodging.…”

“…Just before harvest, the lodging angle (between the main culm and the vertical) was measured. The plants were then uprooted, the soil was washed away, and number of tillers, crown diameter, number and diameter of crown roots, and shoot and root dry weight were assessed following the protocols in Ben-Zeev et al [21].…”

“…Plant lodging, defined as the permanent displacement of the stem from the vertical, which is caused by environmental conditions as well as morphological plant traits [17], is the most significant yield-reducing problem in tef, accounting for up to 35% of yield losses [18,19]. While certain studies relate tef lodging to stem characteristics (stem lodging) [20], others [18], including our recently published paper [21], point to shoot-root junction traits (root lodging) as major contributors to tef lodging. In wheat, deeper sowing has been shown to induce a longer, deeper root crown, thus improving plant anchorage and reducing root lodging [17] (and references therein).…”

Variation Between Three Eragrostis tef Accessions in Defense Responses to Rhopalosiphum padi Aphid Infestation

“…Millets such as tef face several production constraints since they are mostly cultivated in marginal areas with low moisture and limited fertility conditions ( Dosad and Chawla, 2018 ). Inherent characteristics, such as susceptibility to pests and diseases, can cause a significant yield loss ( Assefa et al, 2011 ; Ben-Zeev et al, 2020 ). One of the main reasons for crop loss is pests, which cause an average 15% reduction in grain quality and yield ( Lee et al, 1981 ; Deutsch et al, 2018 ).…”