Abstract:
Chrysopogon aucheri (Boiss) Stapf., and Cymbopogon jwarancusa (Jones) Schult., are the dominated perennial range grasses in highland Balochistan. Seasonal concentration dynamics of nitrogen (N), phosphorus (P), magnesium (Mg) and calcium (Ca) in Chrysopogon aucheri and Cymbopogon jwarancusa were determined at a protected site. The concentration of nitrogen in spring ranged from 12.4 to 13 mg g-1, early summer 15.4-17.26 mg g-1 and late summer 6.7 to 10.7 mg g-1, respectively during 2001 and 2002 seasons. In 2001, the concentration of P in spring and early summer was (1.1-3.4 mg g-1) and least in late summer (0.26-0.81 mg g-1) while in 2002 the concentration of P in spring and early summer was significantly higher (1.28-3.35 mg g-1) and least in late summer (0.38-1.01 mg g-1). In both grass species, there was a similar response of concentrations of K, Mg and Na and the concentration of these elements were higher during spring and then dropped and remained static for the remainder of the year while the concentration of Ca was lower in early spring and significantly (p<0.05) increased with the passage of time during the season. In both grasses the N: P ratio was below < 14 suggesting N-limitation during March and July and showed more than >16 during drier months of August and September. Overall, both the grasses are low in N, P and other nutrients except Na and Ca. These findings suggest that heavy but short-term grazing of very long protected grasslands after substantial rainfall may be one strategy to increase palatability and animal nutrition. Results of this study also indicate the need for direct and high quality mineral supplementation for grazing stock.
