Thermal sum in the determination of the phenological stages of Chihuahua and Cuauhtémoc oats in Güémez Tamaulipas

Objective: To determine the thermal sum requirements in degrees days of development (GDD) varieties Avena sativa, Cuauhtémoc and Chihuahua by phenological stage its effect on accumulation total forage morphological component Güémez, Tamaulipas.
 Design/methodology/approach: The sowing was carried out plots 6×6 m four repetitions through mechanized preparation land, with doses 120 kg ha-1 seed and, subsequently, irrigation fertilization work out. treatments were made up two six stages (Zadoks scale: Z2, Z3, Z4, Z7, Z8, Z9) a random complete block design.
 Results: It found that, months November to March allow obtain 1923.5 1831.5 GDD as requirement crop biological cycle varieties. Yields depended observed highest leaf yield obtained 2.7 3.6 t Chihuahua, respectively (P<0.05) an 1032 980 stem elongation stage.
 Limitations study/implications: These results are applicable only for evaluation area, because they physiological responses where environment intervenes.
 Findings/conclusions: In Tamaulipas, oat variety requires cycle, while GDD. difference between has impact component.