Eragrostis tef (Zucc.) Trotter (tef) is a small annual grain, panicle-bearing, C₄ cereal crop native to Ethiopia, where it is a major staple food. The objectives of the present study were to characterize the responses of two tef genotypes to escalating nitrogen (N) levels in terms of shoot, root, and grain biomass production, N concentration and uptake, and to determine an optimum N range at which tef performance is maximized. The N was applied in the irrigation water (Fertigation) in order to provide a consistent concentration of N in the root zone. A second goal was to test the feasibility of growing tef in the hot, arid conditions of the Northern Negev Desert. Two experiments were carried out in the Gilat Research Station (Negev region, Israel), each testing two different genotypes of tef (405B and 406W), and each including five replicates for each treatment. In the winter of 2015–2016, tef plants were grown in perlite filled pots in a walk-in plastic-covered tunnel. Five different N treatments were applied through fertigation, meaning the fertilizer was applied with the irrigation water (10, 20, 40, 80, 120 mg L⁻¹). All other nutrients were applied at the same sufficient rate. In the summer of 2016, tef plots were sown in open-field and applied with four different rates of N fertilization (0, 30, 60, 120 mg L⁻¹). Biomass of the different plant parts, SPAD values, N, P and K concentration, and the lodging index were recorded in each experiment. The harvest index was also calculated. Optimum N fertigation concentration in both experiments was between 40 and 80 mg L⁻¹, under which the time to flowering was decreased, and yield and grain protein concentration were optimized. Underfertilization caused a decrease in overall plant growth, whereas overfertilization caused an increase in vegetative growth at the expense of grain yield. Potassium uptake increased along with increased N availability, whereas P uptake did not. The fertilization rate will always need to take into account local soil and climate conditions. The field experiment also pointed to low harvest index as a major limitation on tef cultivation in the Northern Negev.

Tef (Eragrostis tef (Zucc.) Trotter) is an annual small grain, panicle bearing, C₄ cereal crop native to Ethiopia, where it is a major staple food. The objectives of the present study were to characterize the responses of two tef genotypes to escalating phosphorus (P) and potassium (K) levels and to determine an optimum range for P and K at which tef performance is maximized. Two experiments were carried out in the Gilat Research Station, each testing two different genotypes of tef (405B and 406W), one experiment in pots in controlled conditions, and the other in the field. In both experiments, the highest grain yield increased until 6 mg L⁻¹ P, and declined at 12 mg L⁻¹ P. The decline was precipitous and significant in the pot experiment, and gradual and statistically insignificant in the field experiment. In the pots experiment, the grain yield increased until 40 mg L⁻¹ K, with no significant decrease thereafter. The effect of K concentration was only seen in the grain yield and not in the size of the other plant organs. In the field experiment, grain yield was highest at 80 mg L⁻¹ K, but it was not statistically different from 40 mg L⁻¹. The effect of K on growth was only apparent at maturity and not at flowering.

Background and Aims Rising atmospheric CO₂ and silicon supply each alter cereal physiology, but their combined action in wheat ( Triticum aestivum L. cv. Omer) has not been resolved across growth, oxidative status, hormone signalling, metabolism, and stoichiometry. We aimed to define the combined state elevated CO₂ and silicon produce in wheat, and where the two converge, diverge, or interact. Methods Wheat was grown under a factorial combination of ambient or elevated CO₂ and with or without added silicon, replicated across two vegetative experiments, with a maturity experiment for yield and grain nitrogen and a separate imposed stress experiment. Growth, root architecture, oxidative-stress markers, phytohormones, metabolite profiles, mineral nutrients, and leaf and grain nitrogen were measured. Results Both factors increased plant size, root development, and spike mass but the combination rarely exceeding the better single factor. Oxidative damage fell under silicon at ambient CO₂ but not in elevated CO ₂ . Hormone signalling diverged: elevated CO₂ raised salicylic acid roughly two-fold, whereas silicon lowered salicylic acid and raised jasmonic acid, an induction that elevated CO₂ largely abolished. The metabolome shifted to a carbon-rich state under elevated CO₂, and both factors lowered leaf nitrogen concentration while uptake was maintained, indicating dilution by growth. Conclusions Elevated CO₂ and silicon act as parallel drivers that converge on growth and redox but oppose one another in hormone signalling. Silicon’s benefit was largest at ambient CO₂ and small once CO₂ was elevated, bearing on its value as an input under rising CO₂.

ISHS IX International Symposium on Mineral Nutrition of Fruit Crops Increasing N uptake in elevated [CO2] conditions through manipulation of NO3:NH4 ratio in fertigated tomatoes