Background:The growing use of nitrogen topdressing fertilisation, combined with late sowing of maize crops, causes greater sensitivity to lodging and breaking of plant stems, and poses risks to yield and grain quality. Thus, plant growth retardants are currently an option to mitigate losses resulting from adverse effects. Aims: The objective of this work was to evaluate the influence of using the plant growth retardant prohexadione-calcium (Pro.Ca) in response to application of different nitrogen levels on morphometric and productive characteristics of maize after late sowing. Study Design: The experiment used a randomized block design (RBD) with four replications.

Sowing density is one of the management techniques that most influence wheat crops. This management practice may affect the plant productive behavior, leading to changes in tillers growth, and also interferes with the plant architecture by influencing solar radiation uptake by the plant canopy, the production components and grain yield. This work aimed to assess the agronomic performance of two wheat cultivars (low tillering and high tillering) under influence of four sowing densities. The experiment was conducted in field conditions from July to November 2017. The experimental design consisted of randomized blocks with split-plots and five replicates. The factors consisted of two wheat cultivars in main plot (TBIO Sossego and TBIO Toruk), subjected to four different sowing densities as sub-plots (208; 312; 416 and 500 viable seeds m-2). Morphological  characteristics, relative chlorophyll content, NDVI, production components and grain yield were evaluated. Among the assessed traits, only the stem diameter was affected by sowing density. The highest plant height, peduncle length and flag leaf length were found in cultivar Sossego, whereas the largest stem diameter was observed in cultivar Toruk. Relative chlorophyll content and NDVI were higher in cultivar Sossego. The agronomic performance of the cultivar Sossego was higher and exceeded the grain yield of Toruk at 673 kg ha-1. Suboptimal sowing densities promote a decrease in the productive performance of wheat and under conditions of rainfall limitation and genetic potential of reduced tillering while sowing densities above the recommended ones are more efficient.

The use of prohexadione-calcium (ProCa) is a management alternative to mitigate greater predisposition to vegetative growth. The objective of this study was to evaluate the use of ProCa in combination with two doses of nitrogen fertilizer in cover, in the morphophysiological and productive performance of corn hybrids. Experiments were performed with corn hybrids AS1757 VTPRO3 and AG9025 VTPRO3 , in a randomized block design, factorial 2×2, with four replications. The treatments consisted of the application of nitrogen fertilizer in cover, 1x and 2x the recommended dose, and in the absence or presence of the application of ProCa. The single effect of ProCa on the hybrid AS1757 VTPRO3 increased the SPAD index by 20%; in the AG9025 VTPRO3 hybrid there was a reduction of 8.6 cm in the height of ear insertion and increments of 2.2 mm in the stem diameter. The application of ProCa with 2x N ha -1 increased, on average, 8.2% the number of leaves of the AS1757 VTPRO3 hybrid compared to the application to 1x N ha -1 . There is single effect of ProCa on morphophysiological characteristics in the tested hybrids, but without affecting its grain yield. The use of ProCa in association with 2x N ha -1 does not mitigate the vegetative growth in the genotypes, sown late in the South of Brazil.

A emissão e sobrevivência de perfilhos em trigo depende de diversos fatores. Neste estudo, objetivou-se avaliar a influência da densidade de semeadura, do potencial de perfilhamento e da ordem temporal de emissão de perfilhos, na emissão, na sobrevivência e no desempenho de perfilhos individuais em cultivares de trigo contrastantes quanto ao potencial de perfilhamento. O experimento foi realizado em delineamento de blocos casualizados, com quatro repetições, em esquema fatorial 2x4; sendo duas cultivares de trigo (TBIO Toruk e TBIO Sossego) e quatro densidades de semeadura (208; 312; 416 e 500 sementes aptas m−2). Os perfilhos foram identificados semanalmente, conforme a ordem temporal de emissão durante quatro semanas consecutivas. Foram avaliadas a emissão, a sobrevivência e o desempenho produtivos de todos os perfilhos, além disso, foram avaliadas a altura de plantas, comprimento do pedúnculo, diâmetro de colmo, massa verde e presença de grãos. A mortalidade geral de perfilhos emitidos foi de 24%. Houve um decréscimo de 73% na emissão e 92% na sobrevivência de perfilhos ao longo de quatro semanas. O aumento da densidade de semeadura promoveu decréscimo de 43% na emissão e 44% na sobrevivência de perfilhos. A cultivar Sossego apresentou menor potencial de perfilhamento, mas com sobrevivência superior a Toruk. Os dois primeiros perfilhos emitidos representaram 77% do total de perfilhos emitidos. Perfilhos sobreviventes emitidos na primeira semana foram responsáveis por 40% do total da presença de grãos ao final do ciclo.

Trinexapac-ethyl (henceforth referred to as trinexapac) is a growth regulator that can mitigate some undesirable vegetative growth in Poaceae plants, reducing lodging and optimizing the distribution of photoassimilates to reproductive organs. The objective of this research was to evaluate the morphophysiological and productive responses of rye cultivars and trinexapac doses applied at different phenological stages of plants. Two field experiments were performed in two different seasons. In the 2015 growing season, 8 doses of trinexapac were evaluated: 0, 75, 85, 100, 115, 130, 150, 200 g ha-1 of active ingredient (a.i.), applied at the plant growth stage with the 4th node visible on the main stem (GS34). In the 2018 growing season, two cultivars (IPR 89 and BRS Serrano) and five doses of trinexapac were evaluated: 0, 50, 100, 150 and 200 g a.i. ha-1, applied at the plant growth stage with the 6th node visible on the main stem (GS36). The morphophysiological, productive and qualitative characteristics of grains were evaluated. In the 2015 season, trinexapac applied to shoot plants at GS34 only have low response in decreased plant lodging from around 20% to 10%. However, in the 2018 season, the application of trinexapac on plants at GS36, resulted in lower plant height, associated with reduced lodging and better quality of rye grains. Cultivar IPR 89 showed higher values for yield components and grain quality in comparison to cultivar BRS Serrano. Reduced lodging is dependent on speed of resumption of plant height growth, and the magnitude of response to trinexapac is also stage-cultivar-dose-dependent; in rye, the best response to trinexapac was found at GS 36 in comparison to GS 34, and for IPR 89 in comparison to BRS Serrano cultivar, respectively, with a dose range from 100 to 150 g ai ha-1. In conclusion, trinexapac (around 150 g a.i. ha-1), when applied to plants at GS36, reduces plant height, reduces the lodging index and enables the harvest of high-quality grains.

No abstract