Observation point technique (OPT) for root growth study in relation to nutrition management of litchi

Observation point technique (OPT) is a simple and low cost technique used to study the seasonal growth pattern and density of feeder roots of litchi in horizontal surface of top soil layer. The months of August during post harvest vegetative growth period and April during fruit growth and development period were found as two peak periods of growth activity of feeder roots, while the radial distance between 3 and 4 m from the trunk of 15 years ‘Bombai’ litchi tree showed maximum density of feeder roots in the horizontal surface of top soil layer. It appears that application of fertilizer in July and March and incorporating the fertilizer in surface soil layer at a radial distance between 3 and 4 m from the tree trunk would result in maximum possible contact between feeder roots and applied nutrients leading to increased nutrient use efficiency in litchi.