EFFECTS OF ADDITION OF MAGNESIUM AND CALCIUM SUPPLIED IN LIMING AND NON-LIMING MATERIALS ON THE GROWTH OF CAMELLIA JAPONICA IN AN ACID SOIL, AND ITS SOIL pH CHANGES, NUTRIENT UPTAKE, AND AVAILABILITY

Abstract

Long-term effects of applying locally mined crushed crystalline dolomitic-limestone, to tea (Camellia sinensis L) are being investigated in field trials, in Sri Lanka. From these trials, it appeared that an understanding of the roles of both Mg and Ca during liming was necessary to understand the nutrition of the tea plant. A pot experiment was carried out in the glasshouse, to investigate the effect of raising Mg status of soils of differing soil pH and Ca availability using a Camellia species, in particular concern to the Sri Lankan tea industry. To address this concern, treatments that supplied Mg and/or Ca in the presence or absence of liming materials were used. Leaves of plants were harvested after 6, 12 and 24 months, and analyzed for P, K, Mg, Ca, Al, Mn, Fe, Cu, Zn and B using Inductively Coupled Plasma-Atomic Emission Spectrophotometer (ICP-AES). Total N contents were obtained by combusting dried material in a NC analyzer. Soils in the pots were removed and dismantled from the roots lump, determined the soil pH levels and analyzed for exchangeable cations including Al, using 1 N ammonium acetate solution at soil pH level and a recently developed mixed resin method. Leaf yield of Camellia japonica was unaffected either due to higher Mg and/or Ca levels in soil or due to increased soil pH. Camellia plants in preference to Ca took up Mg when Mg and Ca were added. Uptake of K was reduced by the addition of Mg. Increase in soil pH caused a reduction of leaf Al, Mn and B in Camellia plants whereas Fe, Zn and Cu concentrations were unaffected. The amounts of soil nutrients extracted with mixed resin and ammonium acetate solution were compared with their uptake by Camellia plants. Both methods extracted similar amounts of Mg and Ca but in limed soil the amount of Al taken up by plants was more closely correlated to resin Al values than those in ammonium acetate solution adjusted to soil pH level.