Soil acidification has assumed serious proportion in farmlands across Kerala, impairing the productivity of most crops, a multi-institutional survey on soil fertility has revealed.
The study coordinated by the Kerala State Planning Board revealed elevated levels of acidity in 91 per cent of the 200,000 soil samples collected for analysis from across the State.
As many as 54 per cent of the samples tested for strong to very strong and extremely acid reaction.
All farmlands in the State, except the southern coastal plains, Attappady hills and eastern Palakkad plains reported heavy acidity.
According to the report of the study, the primary cause for soil acidification in Kerala is indiscriminate use of chemical fertilizers, intensification of agriculture through high-yielding crop varieties and the neglect of the traditional practice of applying lime to neutralise the acidity.
Strongly acidic soils provide a stressed environment for plant growth. It impairs the absorption of nutrients and inhibits the microbial process responsible for nitrogen fixation and decomposition of organic matter in the soil.
In strongly acidic soils, the high concentration of aluminium ions affects plant roots. Biofertilizers are found to be ineffective in acidic soil.
The study involving the Department of Agriculture, Kerala Agricultural University, institutions under the Indian Council for Agricultural Research and the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP), utilised 14 laboratories to analyse the 200,000 soil samples for major, secondary and micro nutrients. The project is aimed at developing soil-based plant nutrient management plans for the 978 panchayats in the State.
Phosphorous problem
The survey also revealed exceedingly high levels of phosphorous, with 80 per cent of the soil samples showing considerable build-up of the nutrient.
The indiscriminate application of phosphatic fertilizers over a long period is blamed for the high level of phosphorous in soils which interferes with the uptake of other essential nutrients like zinc and boron.
Phosphorous run off from farms is a major source of contamination of water bodies. It promotes excessive growth of algae and weeds in streams and lakes, affecting fish and other aquatic organisms.
Washed out to sea, it also pollutes the marine environment, often triggering harmful algal blooms.
The study also revealed that 59 per cent of the soil samples were deficient in boron, a micro nutrient, while 74 per cent were deficient in magnesium and 40 per cent low in calcium.
Boron deficiency can lead to stunted growth and deformities in plants while low magnesium levels results in yellow leaves and fruit rot. Calcium deficiency is responsible for impaired root growth and fruit rot.
Recommendations
The study report, to be released here on Friday, recommends regular application of lime or cheaper alternatives like dolomite to combat soil acidity and alleviate the deficiency of calcium. It also proposes application of borax to address the deficiency of boron.
The report advocates a 50 per cent reduction in the use of phosphatic fertilizers to correct the excess of phosphorous.
