Avaliação da adubação potássica sobre populações de Heterodera glycines em cultivares de soja resistente e suscetível

Abstract

The present study had the objective to evaluate the effect of potassium fertilization on Heterodera glycines reproduction in susceptible and resistant soybean cultivars. Two experiments were conducted under greenhouse conditions in a completely randomized design. Experiment one was set up in a 5 x 2 factorial scheme with five dosages of potassium fertilization (control - without potassium; full dose 100 kg / ha de K 2 O and double dose 200 kg / ha de K 2 O, applied only at planting or in two installments, half at planting and half 20 days later) and two soybean cultivars (BRSGO-Ipameri e BRSGO-Luziânia). Experiment two was set up in a factorial scheme 4 x 2, with four potassium doses (control; half dose 25 kg / ha of K 2 O; full dose 50 kg / ha of K 2 O; double dose 100 kg / ha of K 2 O) and two soybean cultivars (BRSGO-Ipameri and BRSGO-Luziânia). The soil of each pot was infested with 5,000 eggs of H. glycines race 4 (experiment 1) and race 14 (experiment 2). Fresh weight of shoots and roots, number of females per gram of root, number of eggs per female, reproduction factor (RF), number of cysts per 100 cm 3 of soil and number of eggs per cyst were evaluated. Reproduction of H. glycines was greater in BRSGO-Luziania, confirming its susceptibility to the nematode. Increasing doses of potassium reduced the number of females on the roots and the RF in BRSGO-Luziania. Full dose of potassium applied at planting restricted H. glycines reproduction by reducing female formation, eggs per female and delaying cyst formation.