| Resumo: |
The effect of lettuce as cover crop was evaluated on sprinkler irrigation uniformity and parameters of efficiency. The experiment was carried out in field at the Universidade do Oeste Paulista, in Presidente Prudente, São Paulo, Brazil, from August to October, 2006. One treatment was performed on bare soil and the other using lettuce cultivar Vera as cover crop, at the end of the cycle. The average water depth, application rate, uniformity of distribution coefficient, Christiansen uniformity coefficient, Hawaiian uniformity coefficient, as well as the statistical uniformity coefficient were evaluated. The following plant spacing were simulated: 12 x 12, 12 x 18, and 18 x 18 m. The highest water depth retained with lettuce crop cover, at the end of the cycle was 2.4 mm, applied when sprinklers were spaced at 12 x 12 m. The same occurred in the application rate with an average reduction of 43%. When the overlapping was performed, the crop cover did not influence the parameters of efficiency and uniformity, assuring the distribution of the irrigation depth. Neither treatment reached the expected rate concerning the water depth average or the application rate in the spaces. The treatment using cover crop presented the lowest value, with a water depth average below the intended amount. Therefore, the lettuce as cover crop promotes the reduction of applied water depth. Consequently, the irrigation time has to be increased to assure the expected water depth.
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