Economic Activities of Banana Cultivation and Phosphorus Contribution to a Brazilian RAMSAR Estuarine System

The Ribeira River valley, region with important banana cultivation and P mining, presents economic activities that exert environmental impact on the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC), located at the river downstream and member of the Biosphere Reserve and the Ramsar list of wetlands. The aim of this work is to verify how much the influence of fertilizers used on riverine banana crops can impact the Ribeira River nutrient concentrations and reach the estuarine system considering the phosphogypsum mining contribution. For it, the amount of fertilizer used and lost by banana cultivated area was estimated and also the nutrient concentrations (N and P) in a salinity gradient were determined. The use and loss of nutrients from fertilized areas were calculated using Google Earth Pro to distinguish the planted plots and the number of banana plants. It was verified that nutrients from fertilizing were estimated as 200 kg of N per ha and 80 kg of P per ha year−1 considering its different mobility in the soil and the needs to support 744.5 tons of bananas produced in this area. Considering that 10% of P and 30% of N from fertilizer are lost to the hydrological system, around 5 tons/year for P and 44 tons/year for N are transported. Phosphate values (maximum 13.02 μmol L−1) present in a freshwater downstream and the highest values of nitrate (maximum 14.59 µmol L−1) at the Valo Grande (artificial channel) demonstrating a N/P (2/1) ratio imbalance influenced by anthropogenic activities and confirming P contribution to estuarine system.