Hubballi: More than 50 per cent of Karnataka’s farmland has low levels of soil organic carbon (SOC), with experts blaming indiscriminate use of chemical fertilisers as one of the main causes of the problem that could lead to a decline in productivity in the long run.
SOC is a key indicator of soil quality and fertility; optimum levels of SOC help in water and nutrient retention, act as a pH level buffer and prevent soil erosion.
But an analysis of soil samples collected by the Agriculture Department between 2017 and 2024 found that SOC was less than 0.5 per cent (the required limit) in 50.41 per cent of agricultural land in the state where tests were conducted, raising concerns about the extent of degradation.
The department analysed over 23 lakh soil samples that were collected in the time period, including around seven lakh samples in the last four years.
Experts say that rampant use of chemical fertilisers and a proportionate decline in organic manure usage are to be blamed for low SOC levels. Monocropping and deforestation have only added to the problem.
According to the Fertiliser Association of India, Karnataka is among the top five states when it comes to use of fertilisers, with the per hectare usage slightly above the national average.
The state’s fertiliser consumption for agriculture crops is above 40 lakh metric tonnes per year.
The department’s soil tests show that more than 94% of cultivated land in Kolar district , where vegetables are grown widely, has low levels of organic carbon. On the other hand, Dakshina Kannada, Uttara Kannada and Udupi districts, which have more tree cover, are toppers among districts having satisfactory SOC.
Fertiliser consumption, which was 38 lakh MT in 2019-20, crossed 45 lakh MT in 2020-21 and 2021-22. The Agriculture Department has projected a demand of more than 26 lakh MT of fertlisers for the kharif season alone (June to September) in 2024, and total consumption this fiscal year is likely to be more than that of 2023-24, when it stood at 40 lakh MT.
The decline in the use of cattle manure is clearly indicated by the livestock population figures compiled by the Animal Husbandry & Veterinary Services Department. As per the livestock census, the cattle and buffalo population declined from 1.48 crore in 2007 to 1.14 crore in 2019.
Compulsion, cost and convenience are driving a majority of farmers to rely more on fertilisers for plant growth and good yield. In Dharwad district, which is only next to Kolar in terms of low SOC (88.60% of area), farmer Mallesh Kurahatti said he is fully dependent on fertilisers.
“Cattle manure costs Rs 14,000 per acre while the cost of fertilisers required for the same area is Rs 3,000,” said Mallesh, who grows green gram and other crops on his 20 acres of land at Kusugal village.
Agricultural scientists advise a blend of organic manure and inorganic fertilisers to maintain a balance between good yield and soil health. Green manure, vermicompost and post-harvest crop residue can also help improve soil health, said soil science and agricultural chemistry expert V B Kuligod.
According to Agriculture Department Director G T Putra, more green manure seeds have been distributed in recent years. “We plan to take five lakh soil samples across the state this year. An app having all the details of soil tests including survey numbers will be launched, so that giving information and guidance to farmers becomes more effective,” he said.