Evapotranspiração real efetiva e indicadores agrometeorológicos e econômicos em cultivo de palma forrageira irrigada

Abstract

The adoption of irrigation complementary use in the production of palm depends on proper water management, which should be based on information from the water demand of culture and economic viability of the system. The objective was to evaluate the actual evapotranspiration, economic productivity and viability of the use of complementary irrigation using saline water in cactus pear clones production system in the Brazilian semiarid region. The study was conducted in Serra Talhada, PE (2012-2013), with cactus pear clones Orelha de Elefante Mexicana (OEM) (Opuntia), IPA Sertânia (IPA) and Miúda (MIU) (Nopalea) submitted to three blades irrigation (2.5, 5.0 and 7.5 mm) and three spare frequencies (7, 14 and 28 days) + dryland, in blocks, in arrangement of sub-split plot with three replications. The growth of the palm was monitored monthly, and productivity and scale of mealybug infestation rate at the end of the cycle (18 months). The demand for water was obtained by waste water balance in the soil (ETrBAS), with the addition of estimated water retained by the plant (ARP) in order to estimate the actual evapotranspiration (ETrEF). With data throughput and depth applied obtained the efficiency of water use (EUA) and economic productivity (PEA). Economic analysis (EA) was obtained by net revenue (RL) and the benefit/cost ratio (B/C) Palm intended for sale as "fodder" or "seed." From the production data (18 months), these were extrapolated to 24 months for simulation AE for Scenarios 1 (1º cut), 2 (2º cut), 3 (3º cut) and 4 (4° shape), depending on the lifetime of the irrigation system (8 years). There was an effect of the blades and frequencies on ETrBAS (661.0 mm) and ETrEF (ETrBAS - ARP) (633.3 mm); the blade and the clone on the ARP (27.8 mm plant-1); and clone the deep drainage (18,8 mm). The reason ETrEF/ETo ranged from 0.27 (7.5 mm) to 0.29 (7 days). Regarding the USA, there was a significant difference entres the clones, and the OEM (13.0 kg ha-1 mm-1). PEAForragem already considering a value of R $ 100 ton-1, was not observed significant differences and averaged R$ 13.0 ha-1 mm-1. However, in PEASemente clone MIU had the highest average gross value (R$ 122.1 ha-1 mm-1). There was no effect (p> 0.05) of the blades and/or irrigation frequency adopted, however, among the clones, the OEM showed higher yields of green and dry matter (p<0.05), with a mean of 85±17.91 and 6.56±1.11 ton ha-1, respectively. In economic terms, the average total cost of irrigated forage palm production was R$ 7,911.42 ha-1. OEM clone (p<0.05), reported net revenue (RL) of R$ 607.80 and the benefit cost (B/C) 0.08, when intended for sale as fodder, indicating the non-viability to 18 months. On the other hand, the MIU showed the highest RL values and B/C (p <0.05), with an average of R$ 58,610.57 and 7.41, respectively. Regarding the scenarios RL and B/C with the sale for fodder ranged from R$ 2,453.91 to 12,478.45 and 0.27 to 9.30 (OEM), and sale as seed R$ 79,790.90 to 87361.49 and from 8.96 to 65.45 (MIU), respectively. Thus, it is concluded that the economic profitability of irrigated palm increases depending on the allocation of income from the second cut there viability of irrigation use in palm cultivation for all studied conditions and the palm of water demand obtained by the balance soil water must be accompanied by the estimation of the water retained in order not to overestimate the ET plant.