The application of N at the appropriate time and dose can increase oat crop efficiency by increasing grain yield through changes in production components. High doses of N, depending on the genotype and the environment, can result in plant lodging, which can be addressed with the use of growth retardants. The aim of this study was to evaluate the yield components, lodging, and productivity of white oat cultivars cultivated at two planting locations under different N levels with trinexapac-ethyl growth retardant. Two assays (with and without the application of the growth retardant agent) were used in the experiments, which were set up in the region of Londrina and Mauá da Serra, Parana State, Brazil, in a randomized block design with split plots and four replications. The plots consisted of four white oat cultivars (IPR Afrodite, IPR Artemis, URS Corona, and URS Guria) and the subplots of four doses of N (0, 30, 60, and 90 kg ha-1). Plant height, number of panicles per unit area, number of grains per panicle, thousand grain weight, lodging of plants, and grain yield were evaluated. For the conditions under which the experiments were conducted, the growth regulator decreased plant height and lodging. Furthermore, the growth regulator in combination with N topdressing increased the number of panicles per unit area. Thus, the increase in grain yield with the application of a growth retardant was dependent on the characteristics of the plant growth environment. The response of genotypes to N fertilization was also dependent on the soil and climatic characteristics of the environment.
Sweet corn is an important crop because of its seeds with high total sugar and low starch contents. As common corn, this group requires an adequate amount of nitrogen to reach high yields. However, the studies on nitrogen and sweet corn are performed for ear yield instead of seed yield. As seeds are the main propagation method for this species, we proposed to evaluate the effects of nitrogen rates as side-dressing at different plant stages of a sweet corn seed production. Sweet corn seeds (variety BR 400) were sown in Latosol (Oxisol), and a 3×2+1 factorial scheme was designed with three nitrogen rates (40, 80, and 120 kg ha-1) at two plant stages (V6 and R1) plus the control (no nitrogen side-dressing). The evaluated variables were seed yield, protein content, P and Zn contents, germination, and vigor rates. We concluded that nitrogen applied at a rate of 120 kg ha-1 at V6 increases seed yield and maintains unaltered the protein content in seeds of sweet corn (BR 400 variety). Neither germination nor seed vigor increases when nitrogen rates are increased or administered at different stages of plant development. We also noted a slight decrease in P content or an increase in Zn content of seeds at low nitrogen rates; however, they are insufficient to promote changes in the physiological potential of sweet corn seeds.
RESUMO -O presente trabalho objetivou avaliar o efeito de subdoses de glifosato sobre o processo germinativo e o desenvolvimento de plântulas de cultivares convencionais de milho em condições de laboratório. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 2 x 6, com quatro repetições. Os tratamentos consistiram da interação de dois genótipos convencionais de milho (Sintético UEL e AG 9010 PRO) submetidos a seis subdoses de glifosato (0; 3,5; 7,0; 10,5; 14,0 e 17,5 g e.a. ha -1 ). As avaliações consistiram da germinação de sementes (plântulas normais, anormais e sementes mortas), comprimento e massa seca de plântulas (parte aérea, raiz e total). O desempenho germinativo e o crescimento inicial das plântulas de milho são alterados pelas subdoses de glifosato. Existe efeito de hormese para germinação e massa seca de parte aérea nas subdoses de 0,084 e 7 g e.a. ha -1 respectivamente para o genótipo AG9010 e para massa seca da parte aérea na subdose de 8,16 g e.a. ha -1 para o genótipo Sintético UEL.O incremento das subdoses de glifosato favorece a anormalidade de plântulas e a mortalidade de sementes, além de diminuir o comprimento e a massa seca das radículas e de plântulas.Palavras-chave: hormese, germinação, Zea mays. LOW RATES OF GLYPHOSATE ON THE PROCESS GERMINATION AND CORN SEEDLING DEVELOPMENTABSTRACT -This work aimed to evaluate, in the laboratory, the effect of low rates of glyphosate on the germination and seedling development of conventional corn cultivars. The experimental design was completely randomized in a factorial 2 x 6, with four replications. The treatments consisted of the interaction of two conventional corn genotypes (Synthetic UEL and AG 9010 PRO) submitted to six low rates of glyphosate (0, 3.5, 7.0, 10.5, 14.0 and 17.5 g a.e. ha -1 ).Evaluations consisted of seed germination (normal seedlings, abnormal and dead seeds), seedling length (shoot, root and total) and seedling dry weight (shoot, root and total). Low rates of glyphosate change germination performance and early growth of corn seedlings . There hormesis effect for the germination and dry mass of shoots in rates of 0.084 and 7 g e.a. ha -1 respectively for the AG9010 genotype and dry weight of shoot in doses of 8.16 g e.a. ha -1 for Synthetic UEL genotype. The increase of the low rates of glyphosate promotes abnormal seedlings and seed mortality, and reduce the length and dry mass of radicles and seedlings.
Optimization of seed density range, combined with the use of quality seeds may help generate more profit from wheat production, as these factors affect grain yield and the quality of seeds. The aim of this study was to evaluate the effects of initial vigor level and sowing densities on the productive performance of the plants and the physiological performance of the seeds of two wheat cultivars in two cultivation environments. The experiment was carried out in the cities of Londrina and Ponta Grossa, Paraná, Brazil, in a randomized block design with four replications, following a 2 × 2 × 4 factorial scheme with two levels of seed vigor (high and low), two cultivars (BRS Gralha-Azul and BRS Sabiá), and four sowing densities (150, 250, 350, and 450 seeds m-2). The following characteristics were evaluated: emerged seedlings, shoot dry matter, spike density, vegetation index, and grain yield. Additionally, the physiological potential of the seeds produced in Londrina was evaluated by first germination count, germination, accelerated aging, seedling emergence, and emergence speed index tests. The increase in density up to 450 seeds m-2 favored the productive performance of the crop in both cultivation environments; however, it reduced the physiological performance of the seeds produced in Londrina. The cultivars BRS Gralha-Azul and BRS Sabiá had better performance and grain yield in Londrina and Ponta Grossa, respectively. High-vigor seeds favored the establishment of the stand, especially under unfavorable environmental conditions.
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