Phenology and thermal accumulation of irrigated malting barley genotypes under nitrogen rates in the Cerrado

Abstract

Barley cultivation in the Brazilian Cerrado has contributed to domestic malt production and adaptation to irrigated tropical environments, reducing imports. Understanding genotype × environment interactions is essential for optimizing crop performance, particularly through phenological characterization and thermal time dynamics. This study evaluated the phenological response of six malting barley genotypes to nitrogen rates under irrigation in the Cerrado in Central Brazil. The experiment was conducted at the experimental station of the Brazilian Agricultural Research Corporation (Embrapa Cerrados) in Planaltina, Federal District, in a randomized complete block design with split plots and three replications. Four nitrogen rates (0, 20, 40, and 80 kg ha⁻¹) and six genotypes (BRS Savanna, CEV 98074, Lacey, Prestige, BRS 180, and BRS 195) were evaluated. Phenological stages were monitored, and thermal accumulation was expressed as growing degree days (°C day⁻¹). Genotype, phenological stage, and their interaction significantly affected thermal requirements, whereas nitrogen rates did not affect thermal accumulation or phenological progression. BRS 195 had the longest cycle, requiring                       1,562.83 °C day⁻¹ up to heading, whereas Lacey and CEV 98074 were the earliest, requiring 1,119.93 and 1,190.28 °C day⁻¹, respectively. The 388.88 °C day⁻¹ difference between the most contrasting genotypes corresponded to approximately 19 days in flowering, indicating high phenological variability. Thus, phenological development and thermal accumulation of irrigated malting barley were primarily determined by genotype rather than nitrogen rates under the evaluated environmental conditions.