Resumo

RUIZ-ALVAREZ, Osías et al. Irrigation requirements and yield prediction in forage grasses using a simulation model in Tabasco, México. Agrociencia [online]. 2011, vol.45, n.7, pp.745-760. ISSN 2521-9766.

Cattle production is one of the most important agricultural/ livestock activities in Tabasco's economy, in México; it is carried out in 1.5×10⁶ ha, and is sustained primarily with pastures that are cultivated in slightly more than 50 % of the state's territory. Currently this activity is affected by multiple factors, particularly the drought that takes place between March and May, generating dry matter scarcity. The objective of this study was to estimate, through simulations with the CROPWAT model, the irrigation requirements and yield reduction of forage grasses when cultivated in rainfed conditions, with irrigation and in three precipitation scenarios (20, 50 and 80 % probability of excess). Daily data for precipitation and evaporation from 18 meteorological stations were used, as well as phenologic information (coefficient kc, duration of phenologic phases and yield response factor), and soil references from the state of Tabasco. Analysis of the results indicates that evapotranspiration from the crop is greater in the municipality of Villahermosa and in all the locations from April to August. All the regions present the lowest values for effective precipitation between March and April, the greatest water requirements from March to May, and with rain at 80 %. Under rainfed conditions, the state averages for yield reduction were 5.05 (normal) and 14 % (unirrigated), and with deficit irrigation they were 2.27 (normal) and 3.21 % (unirrigated). Yields were maintained in the humid scenario, with deficit irrigation and under rainfed conditions. In the state of Tabasco, supplementary irrigation is important to avoid yield decreases in dry and normal scenarios.

Palavras-chave : evapotranspiration; effective precipitation; irrigation requirement; scenario.

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