Effect of the water stress in the production of the orange tree in the North of the state of São Paulo / Estudo dos efeitos do déficit hídrico na produção da laranjeira no norte do Estado de São Paulo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The Brazilian citrus industry in recent years, is making a significant leap forward, currently is leading the world production, with emphasis on the state of Sao Paulo that represents 80.50% of the total produced, with an average 25 t ha-1 year1 (IBGE, 2007). Flowering is stimulated by low temperatures and water stress that changes the plant hormonal balance, having the last component greater significance. For this monitoring is recommended to monitor the potential of water on the leaf. After the flowering falls are common, reaching 98% of the total flowers formed culminating in a last outbreak of falling fruit known as "June Drop", where after that the final production is virtually guaranteed. It is observed that the interaction among the environment x water x plant is important for the conduct of culture, thus sought to define, by analyzing the potential of water on the leaf, as indicator of the water stress level, the best season of break of stress and the irrigation depth more suitable for production of fruits in quantity and quality. For a better understanding of the dynamics, a first experiment was performed at the Estação Experimental de Citricultura de Bebedouro (EECB / COOPERCITRUS), from 05/2006 to 09/2007, with orange Pêra on "Cléopatra" irrigated by microsprinkler irrigation. The treatments were defined according to leaf water potential (antemanhã): T1: -1.0; T2: -1.5; T3: -2.0; T4: -2.5 and T5: -3.0 MPa, with completely randomized desing with 6 replicates. The results were submitted to the analysis of variance, comparing the average numbers by the Tukey test at 10% of probability, and multiple regressions considering the parameters significance of the equation at 30% of probability. The daily meteorological data were obtained in loco and used by software IRRIPLUS for completion of the water balance. The vegetative, reproductive and quality characteristics of fruit were evaluated. There were statistical differences in the overall flowers fall, with the highest values in the most stressful treatments. There were no statistical differences in most of the characteristics of fruit quality and total production, and the multiple regression model that more represented the interactions between treatments was the quadratic. In a second experiment were performed simulations to compare methodologies for estimating the evapotranspiration of reference, the basic parameter to define the water consumption by crops for the main citrus producing regions of the state of Sao Paulo. The estimates of ETo were compared on a daily basis, by empirical equations proposed by Hargreaves &Samani (1985) and Blaney-Criddle FAO according to the standard of Penman-Monteith FAO. In the analysis of the same parameters of the regression equation were used, determination coefficient (r ), correlation (r), estimate the trapping data (EEP), adjusted estimate (SEEA), coefficient of correlation (r); indice of concordance (d), indice of confidence (c). There was a tendency to overestimate the values of ETo by Hargreaves- Samani (1985) and underestimation by Blaney-Criddle FAO. Hargreaves-Samani (1985) showed bigger magnitude for PM in warmer and wet months of the year to up and Blaney-Criddle FAO to down. During the coldest months the scale diminish significantly among the three methods. It concludes that for these regions the method of Hargreaves-Samani (1985) is a good option to estimate the ETo and consequently in the calculation of the water requirements of citrus. With this conclusion, it performed a sensitivity of the Hargreaves- Samani (1985) method, checking its behavior same in relation to changes "errors" in temperatures, maximum and minimum, used in the equation. It was caused variations in the order of 5% in temperatures in various scenarios, and examined the estimated data monthly, and dividing them during the coldest and hottest months of the year. It concludes that Hargreaves - Samani (1985) overestimated in 12.5% the values compared to ETo Penman-Monteith FAO 56, in all scenarios evaluated. Variations of 5% in maximum and minimum temperatures do not infer gross errors in the estimates of ETo by Hargreaves - Samani (1985) and the increase of 5% in T max generates bigger discrepancy in the estimates due to the standard.

ASSUNTO(S)

water stress production déficit hídrico agrometeorologia produção evapotranspiração laranja pêra evapotranspiration

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