No abstract

RESUMO – Este trabalho foi conduzido objetivando avaliar a resposta do milho ao incremento na densidade deplantas, sob diferentes espaçamentos entre linhas. O experimento foi implantado em Lages-SC, nos dias 20/10/2014e 21/10/2015. Foram testadas cinco densidades de plantas (3, 5, 7, 9 e 11 pl m-2) e dois espaçamentos entre linhas(40 cm - reduzido, e 80 cm - convencional). Avaliaram-se características fenológicas, morfológicas, fisiológicas e aprodutividade em kg de grãos ha-1 do híbrido P30R50H. Os dados foram analisados estatisticamente pelo teste F, e asmédias foram comparadas pelo teste de Tukey e análise de regressão. A produtividade variou de 11.390 a 18.760 kg ha-1,dependendo do arranjo de plantas testado. Ele aumentou linearmente 923 e 724 kg ha-1 para cada planta adicionadapor m-2 no espaçamento entre linhas de 40 cm em 2014/2015 e 2015/2016, respectivamente. A elevação na densidadede plantas de 3 para 11 pl m-2 não promoveu assincronia floral, não reduziu a atividade fotossintética da folha índice,nem aumentou a percentagem de plantas acamadas, quando se utilizou o espaçamento entre linhas reduzido. Portanto,a utilização de densidades supraótimas (9 e 11 pl m-2) e espaçamento entre linhas reduzido (40 cm) foram estratégiasde manejo efetiva para otimizar a produtividade do milho.Palavras-chave: Zea mays, densidade, espaçamento entre linhas, rendimento. MANAGEMENT OF PLANT ARRANGEMENTTO OPTIMIZE GRAIN PRODUCTIVTY IN MAIZEABSTRACT – This work was set aiming to evaluate maize response to the increase in plant population at differentrow spacings. The experiment was conducted in Lages, SC, South of Brazil, on 10/20/2014 and 10/21/2015. Five plantdensities (3, 5, 7, 9 and 11 plants m-2) and two row spacings (40 cm – reduced; 80 cm – conventional) were tested.Phenological, morphological and physiological traits, productivity (kg of grains per ha-1) of the hybrid P30R50 wereevaluated. Data were assessed by the F test and means were compared by the Tukey’s test and regression analysis.Grain productivity ranged from 11,390 to 18,760 kg ha-1, depending on the plant arrangement. Linear increase of 923and 724 kg ha-1 was observed for each added plant per m-2 at the row spacing of 40 cm, in 2014/2015 and 2015/2016,respectively. The increase in plant density from 3 to 11 plants m-2 did not promote flower asynchrony, did not reducephotosynthetic activity of the index leaf, neither enhanced the percentage of lodged plants when the reduced rowspacing was used. Therefore, the use of supra-optimum plant densities (9 and 11 plants m-2) and reduced row spacing(40 cm) were efficient strategies of plant arrangement management to optimize maize grain productivity.Keywords: Zea mays, density, row space, productivity.

-The objective of this work was to evaluate the effect of application of the growth regulator Trinexapac-ethyl on maize response to the increase in plant density at two sowing dates. A field experiment was carried out in the municipality of Lages, state of Santa Catarina, Brazil, during the 2014/2015 and 2015/2016 growing seasons. Two sowing dates (10/15 -preferential, and 12/5 -late), four plant densities (5, 7, 9, and 11 plants m -2 ), with and without Trinexapac-ethyl application, were tested. The growth regulator was sprayed at a rate of 150 g a.i. ha -1 , when hybrid P30F53YH was at the V5 and V10 growth stages. The spraying of Trinexapac-ethyl decreased the stem length above the ear insertion node at both growing seasons. Grain yield ranged from 11,422 to 14,805 kg ha -1 , and increased in a quadratic way with the increment in plant density. The highest yields were reached when maize was sown in October. The spraying of Trinexapac-ethyl did not affect grain yield, but decreased the 1,000 kernels mass at both sowing dates. The use of Trinexapac-ethyl does not enhance grain yield of maize hybrid P30F53YH at crowded stands in response to the densification, regardless of sowing time.

Sowing date and nitrogen (N) fertilisation modify the morpho-physiological characteristics of maize (Zea mays L.) plants, which can alter the yield. The aim of this study was to analyse the effects of sowing date and N rate on the growth-pattern characteristics of maize hybrids with contrasting cycles, and the subsequent relationship with grain yield. Two experiments were set up in Santa Catarina State, southern Brazil. Two maize hybrids (AG9025, super-early cycle; P30F53, early cycle), two sowing periods (early spring and late spring), and four rates of topdressed N (0, 150, 300 and 450 kg N ha−1) were tested. Plant height, leaf area index (LAI), and relative chlorophyll content (RCC) were evaluated. The increment in N rate increased plant height at the silking stage for early spring sowing, and had no effect for late spring sowing. Higher N rates increased plant height of P30F53 and did not affect plant height of AG9025. Increasing the N rate enhanced LAI and RCC at silking more sharply when maize was sown in early spring. Higher N rates resulted in increased RCC during grain-filling, as well as maintenance of LAI, factors that were strongly associated with grain yield, especially for early spring sowing with hybrid P30F53. This research shows that the use of increasing N rates is an adequate management strategy to increase maize grain yield when the crop is sown in early spring. When applied at this sowing time, N has greater effect on the elevation of LAI and RCC and their maintenance during grain filling.

Currently, most nitrogen fertilizer is side-dressed when corn is in the four (V4) to eight (V8) expanded leaf stage. However, recent studies have shown that modern hybrids take up high amounts of nitrogen during grain filling. This indicates that a late nitrogen fertilization, at the time of crop flowering, may be important to optimize corn agronomic performance. This study aimed to evaluate the effect of the timing and splitting of nitrogen side-dress application on the agronomic performance of early corn hybrids in order to achieve high grain yield. The experiment was set in Lages, Santa Catarina, in the South of Brazil, during the 2014/2015 and 2015/2016 growing seasons. A randomized block design arranged in split plots was used. Two hybrids were tested in the main plots: P1680YH (very early) and P30F53YH (early). Six nitrogen side-dress systems were assessed in the split plots: control (without N), full N rate applied at V5, full N rate applied at V10, 1/2 N rate applied at V5 and 1/2 at V10, 1/3 N rate applied at V5, 1/3 at V10 and 1/3 at VT; and the whole N rate applied at VT. The nitrogen rate was 300 kg ha-1 N. Urea was used as the nitrogen source. Total grain yield and yield components, agronomic nitrogen use efficiency, and leaf area were determined. Grain yield ranged from 6,422 to 15,426 kg ha-1 in 2014/2015 and from 9,283 to 14,986 in 2015/2016. Nitrogen sidedress application performed one time at V5 or V10 or split into two or three applications at different growth stages had similar grain yield, number of ears per plant, kernels per ear, and 1,000 grain dry weight. Nitrogen side-dressed entirely at VT led to higher grain yield than the control. However, grain yield and agronomic nitrogen use efficiency were lower in this treatment than in the treatments involving the other growth stages of side-dress nitrogen. The early hybrid was higher yielding than the very early hybrid, regardless of the timing of nitrogen fertilization. Splitting of nitrogen fertilization up to tasseling was not an effective strategy to increase grain yield and agronomic nitrogen use efficiency of the corn hybrids P30F53YH and P1680YH.