Calibração e desempenho da sonda Diviner 2000 no cultivo da alface irrigada com água salobra

Abstract

The biggest challenge in irrigated agriculture is the quick and accurate determination of the soil water content, for the rational and efficient use. Thus, the study of equipment that estimate soil water content is fundamental for irrigation. The objective of this research was to calibrate and evaluate the performance of the Diviner 2000 capacitance probe, in estimating the irrigation depth in the cultivation of crisp lettuce, irrigated with brackish and non-brackish water, seeking to verify its sensitivity in comparison with the standard method Penman-Monteith FAO ( PM-FAO). The research was carried out in the experimental area of the Agricultural Engineering Post-Graduate Program at the Federal Rural University of Pernambuco. In the first experiment was performed the Diviner 2000 probe calibration in a greenhouse, with Spodosol collected from the municipality of Goiana-PE, in the 0 - 0.20 m depth. The soil was packed in pots, then saturated by capillarity, with water of electrical conductivity (CE) of 0.24 dS m-1 (TA) and 6.4 dS m-1 (TB), separately in four pots for each. Then, a probe access tube was installed in each pot and daily, the pots were weighed on a precision scale and readings were carried out via the probe, until the daily variation in the mass became constant. The calibration equation was obtained through the regression analysis between volumetric soil water content measured and estimated by the probe. R2 values were 0.98 for TA and 0.95 for TB. After calibration, there was a reduction in the RMSE values and an improvement in the agreement index (d > 0.97). In the second experiment, the performance of Diviner compared to PM-FAO was evaluated. Therefore, 20 pots were used to growth curly lettuce. The treatments consisted of two levels of salinity irrigation water (TA and TB) and two systems for determining the irrigation depth (via climate-PM-FAO and via soil-probe Diviner 2000). The experimental design used was completely randomized in a 2 x 2 factorial scheme, with five replications. At the 41 days after transplanting the harvest was done and the plants was evaluated according to: number of total leaves (NF), head diameter (DC), stem diameter (DAC), plant height (AP), root length (CR), aerial fresh mass (MFPA), aerial dry mass (MSPA). The data were submitted to analysis of variance and when significance was detected by the F test, the means were submitted to the Tukey test (p <0.05). Based on the results, there was no effect, in the lettuce biometric variables, of the interaction between irrigation water salinity and irrigation management at 1% probability by the F test. The use of non-brackish irrigation water (EC=0.24 dS m-1) in the crisp lettuce, provided greater crop development, when compared to the treatment with brackish irrigation water, regardless of the form of determination of the irrigation depth.