NUTRIENT CYCLING IN AN EXCESSIVELY RAIN-FED SUBTROPICAL GRASSLAND AT CHERRAPUNJI

Cycling of six.mineral elements (N, P, K, Na, Ca and Mg) was studied i n a humid subtropical grassland at Cherrapunji, north-eastern India du ring 1988-1989. Elemental concentrations in the shoot of four dominant grass species, viz., Arundinella khaseana, Chrysopogon gryllus, Eragr ostiella leioptera and Eulalia trispicata were very low, and none of t he species appears suitable for fodder use. Among different vegetation compartments, live root was the largest reservoir of all the nutrient s (except Ca) followed by live shoot, dead shoot, litter and dead root . For Ca, live shoot was the major storage compartment. The total annu al uptake (kg ha - 1) was 137.3, 10.4, 51.1, 5.5, 8.7 and 18.2 for N, P, K, Na, Ca and Mg, respectively. In an annual cycle 98% N, 77% P, 49 % K, 109% Na, 87% Ca and 65% Mg returned to the soil through litter an d belowground detritus. A major portion of N, P and Na was recycled th rough the belowground system, whereas nearly half of K, Ca and Mg was recycled through the shoot system. Precipitation acts as the source of N and P input, but at the same time causes loss of cations.