Utilização de imagens termométricas na estimativa do estado hídrico do meloeiro cultivado em solo com e sem cobertura vegetal

Abstract

Commonly, the cultivation of melon (Cucumis melo L.) has been carried out in regions that need irrigation in order to have a satisfactory productivity, as in the semi-arid region of Northeast Brazil. However, the sources of water are limiting to its cultivation, being imperative the use of an adequate irrigation management. For this, infrared thermometric images appear as an alternative to other traditional methodologies, especially in déficit irrigation strategies. And, the use of vegetal cover can help the performance of plants under irrigation with deficit, because it reduces the evaporation of the water and the surface runoff in the soil. Therefore, the main objective since the study was to analyze the feasibility of using thermometric images to estimate the water status of melon plants cultivated in soil with and without plant cover under different irrigation regimes. The experimental design was of complete blocks at random, in subdivided plots. The plots were composed of 5 irrigation regimes (TL1, 120%, TL2, 100%, TL3, 80%, TL4, 60% and TL5, 40% of ETc) and subplots with soil with vegetation cover (SCC) and without vegetation cover (SSC). The following variables were evaluated: canopy temperature (TF); leaf water potential (ΨF) and soil moisture (UA) at 15, 30, 45 and 60 days after transplanting (DAT); the thermal index Δ (Tdossel - Tar); productivity; the average fruit weight, the number of fruit per repetition, the firmness of the pulp and the soluble solids content. Data on soil cover factors and irrigation depths were submitted to analysis of variance. Subsequently, the results of the treatments with or without soil cover, when significant, were submitted to Tukey test at the 5% level (*). And the data referring to the irrigation slides (LI), when significant by the F test, were submitted to regression analysis. It can be stated that: the use of infrared images is efficient in the identification of the water status of the melon, and can be used as irrigation management strategy; the productivity of the melon increased as the thermal index, Δ (Tdossel - Tar), decreased; the higher irrigation depths allowed lower canopy temperatures and termal indexes; the vegetal cover contributed to reduce the water deficit of the melon in the smaller slides, except under very reduced water supply. And, that the use of soil cover influenced the firmness of the pulp; the irrigation slabs influenced the number of fruit per plant, the soluble solids content and the average fruit weight.