Adubação nitrogenada, densidade e espaçamento de híbridos de milho em sistema de plantio direto na região sudeste do Tocantins

Abstract

RESUMOEntre as técnicas empregadas para a obtenção de maior produtividade de milho, o arranjamento de plantas e a época de aplicação da cobertura nitrogenada estão entre as mais importantes, associados à escolha do híbrido e do sistema de cultivo. O objetivo deste trabalho foi estudar, em sistema de plantio direto, a influência de quatro tratamentos com adubação nitrogenada, associadas a três densidades de semeadura e dois espaçamentos entre linhas, para duas cultivares de milho na Região Sudeste do Tocantins. No local, foram instalados dois experimentos em sistema de plantio direto, sendo o primeiro instalado com o espaçamento de 0,45 m e o segundo com 0,90 m. Em cada experimento foram avaliados dois híbridos de milho (P 30K75 e TORK), quatro densidades de semeadura (55 mil, 70 mil e 85 mil plantas ha -1 ) e quatro tratamentos com adubação nitrogenada: 40 kg ha -1 de N aplicados por ocasião da semeadura, sem nenhuma cobertura nitrogenada; 40 kg ha -1 de N na semeadura + 120 kg ha -1 de N aplicados em cobertura logo após a semeadura; 40 kg ha -1 de N na semeadura + 60 kg ha -1 de N em cobertura no estádio de 4 a 5 folhas + 60 kg ha -1 de N em cobertura no estádio de 7 a 8 folhas; 40 kg ha -1 de N na semeadura + 120 kg ha -1 de N em cobertura no estádio de 6 a 7 folhas. O parcelamento da adubação nitrogenada em cobertura contribuiu para o aumento da produtividade de grãos de milho. O aumento na densidade de plantas resultou no aumento da altura de plantas e da produtividade de grãos de milho. O espaçamento de 0,45 m proporcionou maior produtividade de grãos, independentemente da densidade de plantas e do híbrido de milho. O híbrido P 30K75 obteve maior produtividade de grãos que o híbrido TORK.Palavras-chave: Zea mays, manejo da adubação nitrogenada, arranjo de plantas, sistema de cultivo. ABSTRACT NITROGEN FERTILIZATION, SOWING RATE AND ROW SPACING IN CORN CROP UNDER NO-TILLAGE SYSTEM IN SOUTHEASTERN TOCANTINS STATE, BRAZILAmong the practices and techniques employed for obtaining increased corn yield, the choice of plant arrangement and time of nitrogen topdressing are, among the most important, associated with the choice of the hybrid and cropping system. The objective of this trial was to study the influence of four nitrogen application timing, associated with three sowing rates and two row spacings, under no-tillage system, using two corn hybrids in southeastern Tocantins State. On the site, two experiments in no-tillage system were established, the first one being set up with the spacing of 0.45 m and the second spacing of 0.90 m. In each experiment, two corn hybrids (P 30K75 and TORK), three sowing rates (55 thousand, 70 thousand and 85 thousand plants ha -1 ) and four nitrogen application timing: 40 kg ha -1 of N applied at sowing time without nitrogen topdressing; 40 kg ha -1 of N at sowing + 120 kg ha -1 of N topdressed just after sowing; 40 kg ha -1 of N at sowing + 60 kg ha -1 of N topdressed at the stage of 4 to 5 leaves + 60 kg ha -1 of N topdressed at the stage of 7 to 8 leaves, 40 kg ha -1 of N at ...

Spacing, population density and nitrogen fertilization in corn grown in an Oxisoil

“…By fixing the spacing effect, it was possible to observe that the average yield of the spacing 0.45 m (10.69 t ha -1 ) was significantly higher than the spacing 0.90 m (9.59 t ha -1 ) ( Table 1), which was also confirmed by Von Pinho et al (2008) with different corn hybrids. These authors observed that the spacing 0.45 m yielded 6.67 t ha -1 of grains, while 0.90 m yielded 5.81 t ha -1 , occurring more equidistant plant distribution in the area with the hybrids 30K75 and Tork in the spacing 0.45 m. Similarly, Argenta (2001) and Kaneko et al (2010) obtained increased yield by reducing the row spacing from 0.90 to 0.45 m.…”

“…Our results are consistent with Brachtvogel et al (2009), who found increase in grain yield from 30,000 to 70,000 plants ha -1 and decrease in 90,000 plants ha -1 , regardless of the spacing, with maximum yield in the spacing of 0.80 m and density of 67,000 plants ha -1 . On the other hand, Von Pinho et al (2008) achieved maximum grain yield with 85,000 plants ha -1 and Alvarez et al (2006) observed higher grain yield with increasing rates of topdress nitrogen in association with 0.80 m between lines and 80,000 plants ha -1 . Moreover, Melo et al (2011) observed maximum corn grain yield with 120 kg ha -1 N and density of 80,000 plants ha -1 , whereas higher N rates lead to luxury consumption by the plant as it increases the concentration of N in the shoot and decreases grain yield.…”

“…However, the increase in N rates requires the split of nitrogen fertilization to enhance the increase in yield (Von Pinho et al, 2008). The use of higher nitrogen rates, adequate plant density and sowing speed may increase the corn yield without changing the spacing between lines (Alvarez et al, 2006;Trezzi et al, 2008;Alvarez et al, 2009;Kappes et al, 2011;Sangoi et al, 2011).…”

“…The spatial arrangement of corn plants varies depending on the spacing between rows and between plants in the row (Von Pinho, 2008;Kappes et al, 2011). Research shows that improving plant arrangement, in equidistant spacings, has contributed to decreasing competition between plants in the row and reducing soil water evaporation due to increased shading (Argenta, 2001).…”

“…The use of reduced row spacing has provided higher productivity in corn due to more equidistant plant distribution (Von Pinho et al, 2008) coupled to the reduction of the number of plants in the row (Amaral Filho, 2005). The increase in corn yield with reduced spacing identified by Kaneko et al (2010) and Modolo et al (2010) facilitates the no-tillage system in crop succession with soybean and corn while maintaining the same spacing for both cultures, without the need to rearrange the seed distribution in seeders.…”