Teff is a staple food crop in East Africa, especially in Ethiopia, and one of the grains with the largest sown area in the country, supporting tens of millions of smallholder farmers. However, in smallholder systems, soil fertility varies greatly in space and seasonal rainfall is highly unstable. How to achieve site-specific nutrient management “by site and by rainfall” has long been a core challenge for improving teff yield and nutrient use efficiency. From the top to the bottom of a slope, soil organic matter and nutrient reserves differ significantly; whether rainfall is abundant or not directly determines the crop’s nutrient uptake efficiency.
Recently, the team led by Getachew AGEGNEHU at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) published a research paper titled “Yield-limiting nutrients for enhancing teff production in contrasting landscape positions and rainfall contexts” in ENGINEERING Agriculture (DOI: 10.15302/J-FASE-2026691), an ENGINEERING cluster journal of the Chinese Academy of Engineering. The study conducted multi-site on-farm field trials in different agroecological zones (AEZs) of Ethiopia in 2020 and 2022, systematically analyzing the response of teff to nutrients including nitrogen (N), phosphorus (P), potassium (K), sulfur (S), zinc (Zn), and boron (B) under different landscape positions (upper, middle, and lower slopes) and rainfall contexts (high-rainfall and medium- to low-rainfall areas), aiming to identify the yield-limiting nutrients.
The research team conducted trials on farmer fields: two to four farmers were selected at each landscape position, using a randomized complete block design (RCBD) with two to three replicates per trial site. The trial sites covered both unimodal and bimodal rainfall patterns, with diverse soil types and agroecological zones. The fertilization treatments included blended fertilizer (All(B), containing N, P, K, S, Zn, and B), compound fertilizer (All(C)), individual fertilizers (All(I)), nutrient omission treatments (All(B) minus K/S/Zn/B, respectively), NP only, 50% and 150% All(B), and a no-fertilizer control. A linear mixed model was used to analyze the effects of landscape position, rainfall context, and nutrients.
The results showed that, in terms of landscape position, yield at the lower-slope position was 28.7% higher than at the upper-slope position; in terms of rainfall context, yield in the high-rainfall area was 1.3 times that in the medium- to low-rainfall area. In the high-rainfall area, 150% All(B) achieved the highest grain yield of 1.52 t·ha⁻¹, increasing yield by 6.3%, 10.3%, and 154% compared with All(B), NP, and the control, respectively; in the medium- to low-rainfall area, the corresponding increases were 3.2%, 5.0%, and 84.2%. Increasing the blended nutrients by 50% further increased yield by 10%–154% in the high-rainfall area and by 5%–84% in the medium- to low-rainfall area. In terms of biomass, in the medium- to low-rainfall area, the 150% All(B) treatment achieved a total aboveground biomass of 6.21 t·ha⁻¹, an increase of 84% over the control. This result also confirms that the harvest index (HI) is affected by the interaction of landscape position, fertilization rate, and nutrient form, with the lower-slope position generally achieving the highest harvest index. Overall, soil moisture is a key prerequisite for root nutrient uptake; the more abundant the water, the more the yield-increasing potential of fertilizer can be released.
In terms of yield-limiting nutrients, nitrogen (N) and phosphorus (P) were the most yield-limiting nutrients across all landscape positions and rainfall contexts. Further analysis of yield losses caused by nutrient omission showed that, in the high-rainfall area, omitting K, S, Zn, or B alone (or all four) reduced yield by 5.9%, 5.2%, 1.6%, 3.0%, and 3.3%, respectively, compared with All(B); in the medium- to low-rainfall area, the corresponding values were 2.0%, 3.6%, −2.3%, 0.5%, and 1.7%. In other words, in the high-rainfall area, potassium (K) was relatively the most yield-limiting factor, followed by sulfur (S) and NP; while in the water-limited low-rainfall area, NP itself was the dominant limiting factor, and the omission of individual secondary and micronutrients had limited impact. The paper therefore emphasizes that identifying yield-limiting nutrients and optimizing their application is crucial for enhancing nutrient use efficiency and yield and helping producers achieve rewarding economic returns.
It is worth noting that yield losses from nutrient omission vary with water and thermal conditions: in humid areas, supplementing secondary and micronutrients such as K and S can yield considerable increases; but in arid areas, constrained by water, blindly adding secondary and micronutrients yields limited returns, and the correct approach is to prioritize ensuring N and P and improving soil fertility.
The study also found that applying nutrients in blended, individual, or compound forms did not result in significant differences in teff yield; adding K, S, Zn, and B on top of NP did not significantly differ from NP alone. Soil chemical properties gradually improved from the upper slope to the lower slope, while soil organic matter and nutrient reserves on steep slopes, especially upper slopes, have been depleted, resulting in low response to nutrient application. This indicates that “what to supplement” should vary by site: on humid slopes, priority should be given to supplementing K and S; on arid slopes, priority should be given to increasing N and P rates and soil organic matter. The paper suggests that future research should conduct soil tests across different soil types and agroecological zones to optimize NP rates, continuously monitor the need for other nutrients, and combine soil–crop system restoration of soil fertility, so as to achieve coordinated improvement of teff yield, quality, and nutrient efficiency in dispersed smallholder systems.
This study turns site-specific nutrient management from experience into quantifiable nutrient response maps: on slopes with abundant rainfall, supplementing K and S can leverage greater yields; on arid slopes, safeguarding N and P and soil fertility is fundamental. For teff-producing areas dominated by smallholders, such site-specific fertilizer recommendations are a pragmatic path that balances food security and green development.

DOI: 10.15302/J-FASE-2026691