Soil Fertility and Potato Pest Spectrum in the Nilgiris, Tamilnadu, India.

Abstract

A survey was undertaken in Nilgiri district of Tamil Nadu State in India during the year 2008 to witness the status of potato cultivation as well as the disease and pest spectrum and a comparison was made with the status during 2011 by conducting another sample survey. The principal conclusions of the survey are: The area under potato cultivation in Nilgiris is decreasing year after year. Late blight is the number one problem and cyst nematodes are spread in almost all the areas of potato cultivation. The available nitrogen content of the soils is medium to low and that of phosphorus is low to medium. Potassium is available in plenty. Soils with lower pH and high nitrogen content recorded more PCN (potato cyst nematodes) populations. Inclusion of cabbage in rotation recorded no change in soil pH, lower accumulation of phosphorus and lower PCN population. During the last five years, the average increase in PCN population in entire Nilgiris is 36 per cent. The increase is more spectacular in Kundah (50%) followed by Coonoor (41%) and Kotagiri (34%) taluks and the rate of increase in Ooty area is low (20%) because of the high initial population. There is advancement in the date of first appearance of late blight disease by 10 days (i.e., from 5th October to 25th September) especially during autumn season due to change in rainfall pattern and also temperature.