Soybean agronomic performance in response to seeding rate and phosphate and potassium fertilization

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

Soybean growth affected by seeding rate and mineral nitrogen

ABSTRACT This study aimed to evaluate the effect of seeding rates and nitrogen (N) fertilization on plant growth in soybean cultivar with indeterminate growth habit. Two experiments were conducted in the 2013/14 and 2014/15 growing seasons, in a complete block design with split-plot scheme and six replicates. Four seeding rates (150, 300, 440 and 560 000 viable seeds ha-1) and two N doses (0 and 45 kg ha-1) were allocated in the plots and subplots, respectively. The cultivar NK7059 RR was used. The following traits were assessed: leaf, stem and total shoot dry matter, leaf/stem dry matter ratio, stem and leaf N content, SPAD index, plant height, first pod height, number of branches per plant and grain yield. Soybean growth is not affected by the interaction of plant density and mineral N fertilization. Higher seeding rates increase plant dry matter in the initial development stages and reduce leaf/stem ratio and the number of branches per plant. The effects of N fertilization on soybean growth vary between growing seasons, but do not affect grain yield, even considering a wide range of seeding rates

Soybean agronomic performance in response to seeding rate and phosphate and potassium fertilization

<div><p>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.</p></div

Interferência de picão-preto e guanxuma com a soja: efeitos da densidade de plantas e época relativa de emergência Interference of hair beggarticks and arrowleaf sida with soybeans: effects of plant density and relative emergence time

O objetivo deste trabalho foi avaliar as influências de densidades de picão-preto (Bidens pilosa L.) e guanxuma (Sida rhombifolia L.) e de épocas de sua emergência em relação à da soja, no grau de interferência que ocasionam à cultura. Foram realizados experimentos em duas condições em Porto Alegre - RS, em 1998/99 e 1999/00. Os fatores testados foram espécies e densidade de plantas daninhas e épocas de emergência. A convivência das plantas daninhas com a soja deu-se durante a fase vegetativa da cultura. Em experimentos em vasos, avaliaram-se cinco épocas de emergência das plantas daninhas (11, 7, 2 dias antes e 4 e 8 dias após a emergência da soja). Em microparcelas, avaliaram-se três épocas de emergência das plantas daninhas em relação à soja (4 dias antes, no mesmo dia e 4 dias após) e seis densidades de plantas daninhas (0, 4, 8, 16, 32 e 64 plantas m-2). Verificou-se que a época de emergência das plantas daninhas em relação à soja modifica as relações de competição entre essas espécies e que picão-preto exerce maior efeito de competição à soja e é menos afetado pela presença da cultura do que guanxuma. O atraso na emergência da soja em relação às plantas daninhas aumenta os efeitos negativos dessas sobre a cultura, os quais são potencializados pelo incremento da densidade, principalmente no caso de picão-preto.<br>The objective of this research was to evaluate the effects of hairy beggarticks (Bidens pilosa L.) and arrowleaf sida (Sida rhombifolia L.) densities and relative emergence time, on the degree of interference they may cause on soybeans. There were studies carried out under two conditions in Porto Alegre, RS, Brazil, in 1998/99 and 1999/00. The factors tested were weed species, emergence times, and weed densities. Weed-soybean associations occurred during the vegetative period of the crop. In pot assays, five weed emergence times were evaluated (11, 7, and 2 days before, and 4 and 8 days after soybean emergence). In microplot assays, three weed emergence times were compared in relation to soybeans (4 days before, at the same day, and 4 days after) and six weed densities (0, 4, 8, 16, 32 and 64 plants m-2). It was found that weed relative emergence time, in relation to soybeans, modifies competitive relations between these species, and that beggarticks performs greater competition effects on soybean and is less affected by the crop than is sida. Delay in soybean emergence in relation to weeds increases the negative effects of these species on the crop, which are potentialized by increase in weed density, mainly in presence of beggarticks