Amaranthus cruentus L. is suitable for cultivation in Central Italy: field evaluation and response to plant densities

The aim of this study was to determine the possibility of amaranth cultivation in Central Italy and to determine the optimum plant density. Field trials were carried out in 2011 and 2012 under non-irrigated conditions in Tuscany (43° 18’ N, 11° 47’ E). Twelve accessions of two amaranth species (Amaranthus cruentus L. and A. hypochondriacus L.) were utilised. Genotypes were evaluated over a two-year period using a RCB design with three replicates. The effects of plant density were investigated in 2012. A with a split-plot design was used, where the A. cruentus accessions (AMES 5148, PI 511719 and PI 643045) constituted the main plots. Plant densities (7.5, 15, 30 and 60 plants m^–2) constituted the subplots. Plants were transplanted at the 3-4 true leaf stage. Morphological traits were determined using 5 plants selected from the two central rows of the sampling area. Plots were hand-harvested and cleaned with a mechanical grid with appropriate sieve diameters. A. cruentus was shown to be more suitable to the Central Italy agro-ecological conditions than A. hypochondriacus. The accessions derived from Mexico (PI 477913, PI 576481, PI 643045, PI 643053, and PI 6495079), Guatemala (PI 511719) and Puerto Rico (AMES 5148), had both higher grain yields and a greater stability over the two-year period, with a mean grain production ranging from 2.8 to 3.2 t ha^–1. The severe climatic stress in 2012 (high temperatures and aridity), resulted in a 43-60% reduction in seed production compared to that of the previous year. Under these conditions, PI 511719, AMES 26015, AMES 5386, AMES 5148, PI 477913 yielded on average 1.9 t ha^–1. Yields of A. hypochondriacus were negligible in both years, probably attributable to greater photoperiod sensitivity, resulting in reduced flowering and delayed maturity. By increasing density up to 60 and 30 plants m^–2 for PI 511719 and AMES 5148, respectively, grain production was increased by 55%. As the plant population increased, plant height, panicle length and diameter, basal stem diameter and branches per plant were reduced. AMES 5148 plants were composed of one single stem with apical panicles at a density of 30 plants m^–2, whilst the other two accessions were similar at the highest plant density. Branch number per plant was negatively correlated with grain production (r=–0.536**). Hence, A. cruentus may be grown in Central Italy even under arid conditions, using a density of either 30 or 60 plants m^–2 according to the genotype used.