Produtividade, qualidade industrial e nutricional da cana-de-açúcar sob adubação fosfatada mineral e orgânica

Abstract

The search for sustainable production systems from technical, economic, and environmental perspectives has been ongoing. In this context, sugarcane producers need viable new management alternatives to use mineral fertilizers derived from non-renewable sources. Thus, the poultry litter use has become an important alternative for to supply of macro and micronutrients. The hypothesis tested in this study was the comparative effectiveness between the use of triple superphosphate as a mineral phosphorus source and poultry litter as an organic phosphorus source, as well as the residual effect of subsequent applications. Field experiments were conducted at Destilaria Nova União S/A, located in the rural area of Jandaia, Goiás, Brazil. The experimental design was a randomized block with a 5 x 5 factorial scheme, comprising 25 treatments (five doses of triple superphosphate (TSP): 0, 60, 120, 180, and 240 kg ha-1, and five doses of poultry litter (PL): 0, 2, 4, 6, and 8 t ha-1), with four replications, evaluating three harvests (2019/2020 – plant cane), (2020/2021 – first ratoon), and (2020/2021 – second ratoon). In Chapter I, the evaluated variables were plant height (PH), average stalk diameter (SD), number of tillers (NT), foliar contents of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), recoverable total sugars (RTS), sugar yield (SY), alcohol yield (AY), and tons of cane per hectare (TCH) in sugarcane. However, it was observed that TSP and PL doses did not influence plant height, average diameter, number of tillers, productivity, and technological quality. Moreover, it was found that the PL application of 8 t ha-1 increased the nutritional content of P. Furthermore, it was observed that fertilization with TSP increases the foliar concentration of P and S with doses of 240 and 129.29 kg ha-1. Fertilization with PL increases the foliar contents of Mn and Cu with the application of 8 and 6.24 t ha-1. For the nutrients K and Cu, the combined TSP and PL application maximizes the performance of K and Cu at doses of 9.99 t ha-1 of PL + 120 kg ha-1 of TSP. In Chapter II, the variables evaluated in Chapter I were addressed. The hypothesis that the use of triple superphosphate together with poultry litter can positively influence the foliar nutrient content of the first ratoon sugarcane, with a reflection on increased growth, development, technological parameters, and production was confirmed. The TSP and PL use in the first ratoon sugarcane promotes the growth and development of the plants. Productivity gains were 11.63% and 9.67% at the estimated doses of 4.67 t ha-1 PL and 138.10 kg ha-1. For RTS, the gains came from the interaction of 4.55 t ha-1 of PL at the 0 kg ha-1 dose of TSP, obtaining 165.09 kg t ha-1. The interaction of mineral and organic fertilizers at a dose of 8 t ha-1 PL with 120 kg ha-1 TSP resulted in a higher concentration of P; 115.65 kg ha-1 TSP with 8 t ha-1 (3.20 g kg-1). In Chapter III, the hypothesis was established that mineral and organic P sources, applied at the planting of plant cane and in the first ratoon sugarcane, provide a residual effect in the second ratoon, which meets the nutrient demand and that the combination of P sources in previous applications maximizes the agronomic performance and technological quality of the second ratoon. The residual effect of subsequent TSP and PL applications positively influences the growth and development of the second ratoon sugarcane. The treatments that received doses of 8 t ha-1 PL within the 240 kg ha-1 dose of TSP achieved the highest productivity (119.36 t ha-1). The efficiency of residual P in RTS, BRIX, and POL was seen in the residual PL at the maximum dose of 8 t ha-1.