Adubação nitrogenada em cobertura no girassol irrigado nas condições de Cassilândia-MS

Abstract

O nitrogênio é o nutriente mais requerido pelas plantas por assumir funções importantes no metabolismo vegetal. Na cultura do girassol, sua deficiência causa desordem nutricional, sendo o nutriente que mais limita a produção. Além disso, doses elevadas podem aumentar a incidência de pragas e doenças afetando a produção de grãos. Conduziu-se o experimento com o objetivo de avaliar a resposta da cultura do girassol (Helianthus annuus L.) irrigado, submetido a diferentes doses de nitrogênio aplicado parceladamente, em cobertura. O delineamento experimental utilizado foi em blocos casualizados, com quatro repetições. Os tratamentos consistiram de quatro doses de nitrogênio (0, 20, 40 e 80 kg ha-1), na forma de uréia. A adubação nitrogenada em cobertura proporcionou um aumento em todas as características estudadas, sendo que a dose de N de máxima eficiência técnica para se ter uma boa produtividade é de 55 kg ha-1 de N para o cultivo do girassol, na região de Cassilândia-MS.

Irrigation With Saline Water and Nitrogen in Production Components and Yield of Sunflower

“…Similar results were presented by Lobo et al (2012), who concluded that the increment in N levels from 50 to 130 kg ha -1 increased sunflower productivity from 2,152 to 3,802 kg ha -1 . These results also agree with those of Biscaro et al (2008), who observed that split N fertilisation as top-dressing at the doses of 0 to 80 kg ha -1 increased the productivity of the sunflower cultivar H358 (Dekalb), with the highest value of 2,101 kg ha -1 at the maximum estimated N dose of 55 kg ha -1 . The increment in N levels negatively affected the oil content in the achenes, while the increment in water salinity levels compromised the oil yield of sunflower achenes (Figure 6).…”

“…For the factor N levels, the data best fitted to a positive linear model, according to the regression equation (Figure 3), with increment from 13.91 to 17.51 cm in relation to the lowest and highest N levels (60 and 120 kg of N ha -1 ), which represented an increase of 11.64% for every 20 kg ha -1 of N applied to the soil, between the levels of 60 and 120 kg ha -1 . Although lower than 19.9 and 22.4 cm, obtained by Lobo and Grassi Filho (2007) in the soil without and with 50 kg ha -1 of N, these values surpass the value of 11.9 cm in the capitulum diameter of the sunflower cultivar H358 at the dose of 44.9 kg ha -1 of N reported by Biscaro et al (2008). In this context, Ivanoff et al (2010) claim that adequate N fertilisation management promotes increments of approximately 16% in the mean diameter of sunflower capitulum; this was also observed by Siddiqui et al (2009) …”

“…N deficiency causes nutritional disorders; however, in H. annuus, N excess leads to losses in oil yield, increase in incidence of pests and diseases and damaged achenes (SMIDERLE, 2000). Biscaro et al (2008) claim that the number of achenes per capitulum is influenced by N fertilisation with maximum response at the dose of 46 kg ha -1 . According to these authors, the factors responsible for adequate capitulum development, with a high number of viable flowers and, consequently, higher number of viable achenes, are the sowing period, high-quality biological material, frequency of pollination agents, adequate management of soil fertilisation, especially N levels, and control of pests and diseases.…”

Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

“…Tomich et al (2003) found plant height of 2.05 m, whereas Biscaro et al (2008) estimated that the N dose of 73 kg ha -1 was associated with plant height of 1.15 m, which is inferior to the value found in the present study for a similar N dose (Figure 1). On the other hand, Schwerz et al (2016) did not observe effect of N fertilization on sunflower height.…”

“…Highest value of capitulum diameter (16.45 cm) was estimated for doses of 95 kg ha -1 of N + 120 kg ha -1 of P 2 O 5 (Y = 12.68 + 0.04768 ** N -0.0002509 * N 2 + 0.01261 ** P, R 2 = 0.67 - Figure 2B). Biscaro et al (2008) observed maximum stem diameter of 1.84 cm at the N dose of 48 kg ha -1 and maximum capitulum diameter of 11.9 cm at N dose of 45 kg ha -1 . Freitas et al (2012) found capitulum diameter of 15.38 cm with N application of 75 kg ha -1 .…”