RÉSUMÉ
Nitrogen is a crucial element for all living organisms especially plants which rely on substantial nitrogen quantities to sustain their growth and productivity. Crop production is greatly influenced by nitrogen consumption efficiency and a significant amount of nitrogen fertilizers is used to increase yield. Approximately half of N fertilizers are not utilized by the crops and are lost to the environment by polluting water sources or by releasing pollutants into the atmosphere. From the rhizosphere, plants absorb nitrogen in the form of nitrate (NO3-), ammonium (NH4+), or organic nitrogen (amino acids and urea). Plants exhibit an array of sensing and adaptive mechanisms to respond to the diverse nitrogen nutrition conditions which include morphological and physiological responses. Two primary systems govern nitrogen uptake in plants: the High-affinity transport system (HATS) and the Low-affinity transport system (LATS). Nitrate transporters fall into two categories, Nitrate Transporter 1 (NRT1) and Nitrate Transporter 2 (NRT2) transporters, Chloride Channel Family (CLC) transporters and Slow Anion Associated Channel Homologs (SLAC/SLAHs). The ammonium transporter family includes Ammonium Transporter 1 (AMT1) and Ammonium Transporter 2 (AMT2) transporters. The uptake of organic nitrogen is facilitated through amino acid and urea uptake and transport systems. In fluctuating environmental conditions, plants employ nitrogen response mechanisms to fine-tune homeostasis. A comprehensive understanding of these regulatory mechanisms holds the potential to yield valuable insights for the development of crops with enhanced nitrogen use efficiency.
RÉSUMÉ
Avaliaram-se a composição mineral e a produtividade de matéria seca do capim-tifton 85 (Cynodon nlemfüensis x Cynodon dactylon) sob diferentes doses de N e idades de rebrotação. Os tratamentos foram dispostos em esquema de parcelas subdivididas, com as doses de N (0, 100, 200, 300 e 400 kg/ha/ano) nas parcelas e idades de rebrotação (28, 42 e 56 dias) nas subparcelas, no DIC, com três repetições. O rendimento forrageiro variou de 5.751 a 20.466, de 8.138 a 22.852 e de 10.525 a 25.239 kg/ha/ano de MS, em função do aumento das doses de N, em plantas colhidas em intervalos de corte de 28, 42 e 56 dias, respectivamente, com eficiência de resposta de 36,8 kg MS/kg N. Os teores de P foram reduzidos com o aumento das doses de N e da idade da planta, variando de 0,27 a 0,16 por cento. Os teores de K decresceram com o aumento da idade da planta, estimando-se teores máximos de K de 1,25; 1,11; e 0,96 por cento, em plantas colhidas com 28, 42 e 56 dias de rebrotação, respectivamente, adubadas com 55 kg/ha/ corte de N. O teor médio de Ca foi 0,48 por cento. Os teores de Mg aumentaram com o incremento das doses de N e decresceram com o aumento da idade da planta, variando de 0,24 a 0,45 por cento.
The dry matter production and mineral content of Tifton 85 bermudagrass (Cynodon nlemfüensis x Cynodon dactylon) on nitrogen rates (0, 100, 200, 300 and 400 kg/ha) and regrowth ages (28, 42 and 56 days) were evaluated. The experimental design was completely randomized with a split plot feature. The main plots referred to N-rates whereas subplots were regrowth ages. The forage yield ranged from 5.75 to 20.46, from 8.13 to 22.85 and from 10.52 and 25.23 t/ha of DM, in response to rates of 0 to 400 kg N/ha, in plants harvested at 28, 42 and 56 days of regrowth, respectively, with a response efficiency of 36.8 kg DM/kg N. The P contents decreased with N rates and plant age increased ranged from 0.27 to 0.16 percent. The K contents decreased as plant age increased; the maximum K content of 1.25, 1.11, and 0.96 percent were recorded for plant harvest with 28, 42 and 56 days of regrowth, respectively, fertilized with 55 kg N/ha/cutting. The average Ca content was 0.48 percent. The Mg content increased as N rates increased and decreased as plant age increased, with values between 0.24 and 0.45 percent.