Nutrient cycling in an excessively rainfed subtropical grassland at Cherrapunji

Abstract

Cycling of six mineral elements (N, P, K, Na, Ca and Mg) was studied in a humid subtropical grassland at Cherrapunji, northeastern India during 1988-1989. Elemental concentrations in the shoot of four dominant grass species, viz., Arundinella khaseana, Chrysopogon gryllus, Eragrostiella leioptera and Eulalia trispicata were very low, and none of the species appears suitable for fodder use. Among different vegetation compartments, live root was the largest reservoir of all the nutrients (except Ca) followed by live shoot, dead shoot, litter and dead root. For Ca, live shoot was the major storage compartment. The total annual 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 and belowground detritus. A major portion of Ν, Ρ and Na was recycled through the belowground system, whereas nearly half of K, Ca and Mg was recycled through the shoot system. Precipitation acts as the source of Ν and Ρ input, but at the same time causes loss of cations.

Evaluating second year cropping on jhum fallows in Mizoram, north-eastern India—Phytomass dynamics and primary productivity

“…Addition of nutrients through slashing and burning is more in old than young field in the first year, due to better standing crop in former than latter (Tawnenga 1990). Since added nutrients remain on soil surface, they are vulnerable to loss in runoff and leaching under the influence of high rainfall (Ramakrishnan et al 1981; Pandey et al 1993). Added nutrients though enhanced productivity during first year, an appreciable proportion of them might have been lost through outflowing water.…”