this research aimed to evaluate the sensibility of maximal non-erosive flow rate, which was first proposed by Walker & Skogerboe (1987), to furrow shape empirical parameters, 1 (rho1) varying from 0.170 to 0.800 incremented in 0.063, and 2 (rho2) varying from 2.60 to 3.00 incremented in 0.04 for an open furrow irrigation system with continuous flux and silty clay loam soil. The sensibility analysis was obtained by simulations through the SASIS software (software specifically developed for superficial irrigation simulation), developed by Pordeus & Azevedo (2005). Input data was obtained from four experimental areas under distinct field conditions. When 2 was maintained constant and 1 increased, it was observed a reduction for the maximum flow rate, opposite results was found for constant 1 and increased 2. It was also observed that an increase in 2 contributes to a reduction in the percentage variation between the maximum flow rates obtained for highest and lowest 1 values. The inverse occurs when 1 is increased, leading to an increment in the percentage variation between the maximum flow rates generated for the highest and lowest 2 values. The analysis of sensibility for maximal non-erosive flow rates could identify combinations of soil superficial rugosities and slope which resulted in non-practicable flow rates, thus, demonstrating their effects when combined. KEYWORDS: PALAVRAS-CHAVE:Irrigação, sulco aberto, software de irrigação.

This research aimed to analyse the sensibility of maximum non-erosive flow rate, proposed by Walker & Skogerboe (1987), in response to the variation of field parameters: slope (varying from 0.007 to 0.019 m m-1) and soil superficial rugosity (varying from 0.01 to 0.0477 m-1/3 s) under the conditions of open furrow irrigation with continuous flux in silte clay loam soil. The sensibility analysis was carried out by simulation through the SASIS software (software specifically developed for superficial irrigation simulation), developed by Pordeus & Azevedo (2005). Input data was collected from four experimental areas under distinct field conditions. As a result, impracticable maximum non-erosive flow rates could be identified in response to certain combinations of soil superficial rugosity and slope. It was observed that the increase of both rugosity and slope caused the maximum non-erosive flow rate variation to decrease.

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