A Geografia Histórica em questão

The retention efficiency of a large dam and reservoir eutrophication in a tropical coastal watershed under a rainfall reduction scenario

“…L M s represents each nutrient load from soil loss (t/year) as a function of which is the concentration of each nutrient in the different soil types of the watershed; Ls is the average soil loss of 410 t/km 2 /year obtained from the proposed range of 60-760 t/km 2 /year for tropical soils from gentle slopes and low mechanized agriculture for Brazilian coastal areas (Goudie, 1987;Greenland & Lal, 1977), and Lo is the average soil nutrient content from Brazilian coastal areas with slight declivity and low industrial growth, and it accounts for the different soil types in the watershed. Alluvial soils have average N and P values of 900 and 500 mg/g, 500 and 100 mg/g for sand, 500 and 100 mg/g for latosols/podzols, 500 and 500 mg/g for planosols and 500 and 500 mg/g for solonchack/solonetz, respectively (Cantarella, 2007;Silva, 1996).…”

“…where L M A are the N and P loads from the most widely grown crops in the watershed (sugarcane, coconut, orange, corn, rice, bean, banana, cassava, lemon); P tj are the N and P loads applied as fertilizer (kg/ha) (Embrapa, 2009;Filoso et al, 2006) and the percentage of nutrient loss according to crop type (Golley et al, 1978;Silva, 1996); and A tij is the amount of land that is cultivated for each crop (ha/year) (IBGE Cidades, 2019).…”

“…where L M LF are the loads originating from animal manure in the region (meat and dairy cattle, chicken, swine and horse); P tj is the annual amount of manure produced per animal in the watershed ( j) (10, 2.5, 1.0 and 0.18 kg/animal/day, for meat cattle, horses, swine and chicken, respectively) and the N and P concentrations in raw manure (mg/kg) (EMBRAPA, 2004), LF ij is the number of animals in the watershed (i) (IBGE Cidades, 2019), and α rs is the soil N and P retention rate (Malavolta & Dantas, 1980;Silva, 1996).…”