Tillering, leaf area and momba agrass root system in response to nitrogen and potassium combinations

An experiment was carried out in a greenhouse from November 2000 to February 2001 with the objective of evaluating the effects of nitrogen (N) and potassium (K) rates on tillering, leaf area, total root length, total root surface, specific root length and specific root surface of Panicum maximum Jacq. cv. Mombaca. The forage grass was grown in nutrient solution using ground quartz as substrate. The experimental arrange used was an incomplete 52 factorial of N and K and the 13 combinations between N and K were obtained according to design points of the modified central composite nonrotatable design that was set in a randomized block design, with four replications. Plants were harvested twice. The first harvest was at 36 days after transplanting and the second at 29 days after the first harvest. Following the second harvest, the roots were separated from ground quartz, collected and also washed. Results showed that N x K interaction was significant for leaf area at both harvest, for plant tillering at the second harvest, and for total root length and total root surface. Tillering was significantly affected by N and K rates at the first harvest. Specific root length and specific root surface was significantly influenced by the supply of N as well as by K rates.