Abstract
ABSTRACT Phosphate fertilization has increased sorghum yield, but few studies are available on sorghum production and efficient fertilizer management related to liming and phosphorus (P) sources. This work evaluates production, dry matter partitioning and agronomic efficiency (AEI) in successive sorghum cycles after application of limestone and combinations of phosphorus sources. Two cycles were conducted in sequence in the same experimental field, in a 2 x 6 factorial scheme, corresponding to soil with or without liming and six combinations of P2O5 sources: control (0 kg ha-1 P2O5), 100% Itafós natural phosphate (NP), 75% NP + 25% single superphosphate (SS), 50% NP + 50% SS, 25% NP + 75% SS and 100% SS. Pots with capacity for 8 dm3 were used in a randomized block design with four replicates. The first cycle, conducted in the summer/autumn season, reached the highest dry matter production and P accumulation in treatments with higher SS proportions, leading to higher AEI. Subsequently, in the second cycle, conducted considering only the residual phosphate fertilization of the first cycle, highest dry matter production and AEI were obtained in the treatment with 100% or higher proportions of natural phosphate in the presence of liming, most likely due to the gradual release of P.
Highlights
Phosphorus (P) is one of the most limiting macronutrients for biomass and grain production in tropical soils (Restelatto et al, 2017)
Phosphate fertilization in the sorghum crop is basically performed with soluble sources at sowing, but the combined use with natural phosphates, due to the gradual release of P over time, may balance the supply of P during the cycles
Leaf dry matter and stem dry matter were higher in the soil without liming, in comparison to that with limestone, in the first cycle, and total dry matter and stem dry matter were higher in soil without liming in the second cycle, evaluating the residual effect of P (Table 1)
Summary
Phosphorus (P) is one of the most limiting macronutrients for biomass and grain production in tropical soils (Restelatto et al, 2017). Phosphate fertilization in the sorghum crop is basically performed with soluble sources at sowing, but the combined use with natural phosphates, due to the gradual release of P over time, may balance the supply of P during the cycles. In this context, scientific studies have demonstrated the agronomic and economic importance of using natural phosphates because they contribute to better P use by plants along the cultivation time (Ono et al, 2009; Souza et al, 2014)
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