Vertical Distribution of Magnesium in the Laterite Soils of South India
High levels of exchangeable potassium or ammonium can interfere with the uptake of magnesium by crops. This antagonism is a major concern in some tea growing soils with low magnesium. Soil samples were collected from tea fields and a nearby forest, at various depths. The pH of tea soil ranged between 4.60 and 4.88 and the values were lower when compared to the forest soils. This could be due to the continuous application of nitrogen containing fertilisers. Water soluble magnesium content was higher in forest area when compared to the tea fields which could be attributed to the application of magnesium in the form of carbonate once in four year. Total magnesium was estimated in both cultivated and forest soils and the amount of total magnesium was higher in forest area when compared to the cultivated area. The total magnesium content in forest area ranged between 370 and 1550 mg kg-1, while in tea soils it ranged between 228 and 968 mg kg-1. The available magnesium content ranged between 10 and 40 mg kg-1 in tea soil and 20 and 70 mg kg-1 in forest soil. Water soluble magnesium had negative correlation with pH of the tea soils. There existed a linear relationship between water soluble magnesium and electrical conductivity of cultivated soils. The magnesium status of tea soils is generally low when compared to the forest area due to continuous exploitation of this nutrient by tea plants. This study confirmed that there is need for soil application of magnesium fertilizer in tea fields to preserve the magnesium status.
Cited References Fulltext