Abstract
ABSTRACT Most studies that found soybean high phenotypic plasticity under different seeding rates adopted the same fertilization levels used for the recommended seeding rates. Therefore, the interaction between these factors is little known. This study aims to assess the interaction between seeding rate and levels of phosphorus and potassium fertilization on soybean growth, grain yield and contents of protein and oil in the grains. The experiment was carried out under a randomized complete block design, in a split-plot scheme, with six replicates. Four seeding rates (150, 300, 440 and 560 thousand viable seeds ha-1) were used in the plots, and two levels of phosphorus and potassium fertilizer were applied in the subplots to meet the export of 3 and 6 t ha-1 of grains (level 1 = 30 kg ha-1 of P2O5 + 60 kg ha-1 of K2O; and level 2 = 60 kg ha-1 of P2O5 + 120 kg ha-1 of K2O). There was no interaction between the experimental factors. Increase in fertilizer doses did not alter the evaluated characteristics, regardless of the seeding rate. Seeding rate did not change grain yield or protein and oil contents, but at low densities there was an increase in the number of pods per plant, apparent harvest index and SPAD index.
Highlights
Soybean can alter its morphology in response to the modifications in planting density to adjust to the environmental conditions, maintaining its yield even with expressive variation in plant density (Board, 2000; Cox & Cherney, 2011; Javier de Luca et al, 2014)
This study aimed to investigate the interaction between seeding rate and levels of phosphate and potassium fertilization on vegetative growth, production performance and contents of oil and protein in soybean grains
There was no interaction between seeding rate and potassium and phosphate fertilization, and fertilization levels had no significant effect on any variable (Tables 1 and 2)
Summary
Soybean can alter its morphology in response to the modifications in planting density to adjust to the environmental conditions, maintaining its yield even with expressive variation in plant density (Board, 2000; Cox & Cherney, 2011; Javier de Luca et al, 2014). Soybean plants tend to produce fewer branches, increasing the number of pods per plant, compensating the lower number of individuals per area with higher production per plant. The adjustment in the quantity of seeds per area aiming to maximize grain yield and/or reduce seed consumption is an important practice to increment the profitability of the crop, especially because of the increase observed in recent years in the costs of seeds and their chemical treatment (Board & Kahlon, 2013; Thompson et al, 2015; Gaspar et al, 2017). Increase in P and K availability in the soil may minimize intraspecific competition for these nutrients, allowing increments in soybean grain yield with the increase in seeding rate
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