Produtividade de cultivares de soja em baixa e alta adubação no oeste do Paraná

Abstract

The increase in grain yield and sustainability are strategic objectives for stakeholders in the soybean production system. To achieve these goals, both the cultivars and the inputs used are essential. Thus, this study aimed to evaluate ten soybean cultivars under two different fertilization regimes in Western Paraná. Two side-by-side experiments were conducted with ten soybean cultivars, sown on the same date in October 2023, with fertilizer applications of 41 kg/ha of P₂O₅ and 61 kg/ha of K₂O for low fertilization, and 120 kg/ha of phosphorus and potassium for high fertilization. Each experiment was arranged in a randomized block design with three replications and two border rows. Each plot consisted of four rows, five meters long, spaced 50 cm apart. The final plant population was 260,000 plants/ha. During the crop cycle, the total precipitation was 600 mm, considered below the optimal range for soybeans, which require between 800 and 1000 mm. In addition, the average temperatures remained high, with maximum values above 30°C and minimum temperatures exceeding 20°C, which may have affected flower and pod formation and retention. The study evaluated cultivar yields under low and high fertilization rates, as well as phenotypic plant characteristics, including number of seeds (NS), number of pods (NV), number of branches (NR), plant height (AP), and first pod height (APV). Pearson's correlation coefficients were calculated to assess relationships among these traits. Analysis of variance revealed significant differences (p<0.05) among the evaluated cultivars for all studied characteristics. The cultivars with the highest yields under high fertilization were Nidera NA 5909 RR and Pioneer 96R29 IPRO, producing 3215 kg/ha and 3170 kg/ha, respectively. The phenotypic correlation between traits was classified as moderate to strong, showing that NV (number of pods) had the highest correlation with yield (0.76). Path coefficient analysis with a single chain demonstrated that NV had the greatest direct effect on the number of soybean seeds (0.817). However, NR (number of branches) had a strong positive indirect effect on NS through NV. Thus, it is concluded that to achieve high productivity, fertilization rates should be increased, and cultivars should be selected based on optimal plant height, greater branching, and higher pod number per plant. Additionally, climatic conditions, particularly precipitation and temperature, significantly influence crop performance, affecting both fertilization efficiency and cultivar development.