Growth and nutrient absorption by flue-cured tobacco in field conditions
Knowledge of nutrient absorption during the tobacco plants development cycle is essential for the specific fertilisation programmes for long cycle varieties and its growing conditions, to fine-tune the management and fertiliser use, as well as reduce costs and environmental risks. It is therefore possible that the nutritional requirements of long cycle varieties are not the same as short cycle in which nutrient absorption was studied and described in the literature. The objective of this study was to evaluate the vegetative growth and nutrient uptake by tobacco plants in field conditions. Field experiments with flue-cured tobacco were conducted at six locations with different soil and climatic conditions. Tobacco plants were harvested every seven days and separated into leaves and stalks for plant dry matter and nutrient content determinations. The results indicated that the dry matter accumulation rate was similar to the nutrients curve uptake shape but it was not synchronous, the maximum dry matter rate occurred at 81 days after transplanting. The amounts of nutrient uptaken by tobacco plants decreased following the order K, N, Ca, Mg, S, P, Mn, Fe, B, Zn, Cu e Mo. Flue-cured tobacco absorbed very little macro and micronutrients in the first 40 days after transplanting, increasing the uptake sharply after that and achieving the maximum uptake rate from 68 to 78 days after transplanting. The greater percentage of N, P and K absorption occur from 49 to 91 days after transplanting achieving 75,2 %, 72,4 % and 79,1 % of total uptake, respectively. These results can be used for optimising the sidedressing timing and clearly indicated that the nutrient absorption of long cycle varieties is not the same of that of short cycle.