Concentration, accumulation and critical level of potassium in mombança grass grown in nutrient solution

Abstract

The experiment was carried out in a greenhouse with Panicum maximum cv. Mombaça, grown in nutrient solution with potassium rates (0; 9.75; 39; 78; 156; 234; 312 and 468mg L-1). The objective was to evaluate accumulation and concentration of potassium in plant components and to estabilish parameters to determine the critical level. A complete randomized block design was used, with four replicates. Plants were harvested at 30 and 52 days after transplanting for the first and second growth periods, respectively. In each harvest, plant tops were separated into: emerging leaves (LE), blad of recently expanded leaves (FNE), blad of mature leaves (LM) and stems plus heaths (CB). After the second harvest, roots were colleted. There was a positive effect of potassium rates in the dry matter yield of plant tops and roots, that fitted on quadratic models. Potassium concentration in the emerging leaves, blad of recently expanded leaves, blad of mature leaves, stems plus sheaths and roots increased with potassium increasing in the nutrient solution. The highest and lowest potassium accumulation in the dry matter of plant tops were observed in stems plus sheaths and blad of mature leaves, respectively. The blad of recently expanded leaves showed to be suitable for the evaluation of the nutricional status in potassium of the mombaça grass and the critical level were 15.4 and 17.3g kg-1.