Soil the best decomposer: PAU study

Published on Nov 15, 2022 03:28 AM IST

Use of added microbial consortia confers no additional advantage over native soil microbes after paddy straw incorporation as reflected in wheat productivity comparisons, the PAU study found

A recent PAU study has found that if the straw is cut and chopped and incorporated with soil it decomposes naturally and in 20 days the field is ready to sow wheat crop. (HT File)
A recent PAU study has found that if the straw is cut and chopped and incorporated with soil it decomposes naturally and in 20 days the field is ready to sow wheat crop. (HT File)
ByMohit Khanna, Ludhiana

Soil is the best decomposer, states the findings of Punjab Agricultural University (PAU). A study conducted by the microbiology department of PAU has found that if the straw is cut and chopped and incorporated with soil it decomposes naturally and in 20 days the field is ready to sow wheat crop.

The PAU arrived at this conclusion while conducting the field trials of Pusa decomposers developed by Indian Agricultural Research Institute (IARI), PAU and trials of other decomposers.

Sharing details of the finding, Dr GS Kochar, head, department of microbiology at PAU said that a number of studies revealed that enhanced decomposition of rice straw can be achieved through application of microbial consortium (fungi, bacteria and actinomycetes).

However, trials were conducted at PAU Ludhiana during the year (2020-21) using different in-house and commercial cultures and following three step regimes i.e. chopping/spreading, manual or tractor mounted spray and incorporation revealed some important facts.

Use of added microbial consortia confers no additional advantage over native soil microbes after paddy straw incorporation as reflected in wheat productivity comparisons, stated Dr Kochar in his findings.

Large scale trials on PAU seed farms covering about 170 acres also showed no significant increase in wheat yield due to use of microbes.

“Various permutations and combinations were tried employing more microbes, two sprays rather than one, but with little success. Wheat yields in fields sown after paddy straw incorporation (with Rotavator or Super Seeder) with and without use of microbes was compared. We found out that wheat yields with and without microbial decomposer treatment were similar at all four - Gurdaspur, Kapurthala, Faridkot, Hoshiarpur- locations where experiments were conducted. Various decomposers (IARI, AFC and PAU) did not vary in their effect and provided no yield advantage,” observed Dr Kochar, while quoting his study.

He said that field trials showed different results than the lab-based trial carried out in a controlled environment. The paddy straw spread out relatively thinly (and not heaped) in dry conditions and lowering temperature regime of September-October did not allow microbial decomposition to take off and reach the required thermophilic phase.

“During the trial of Pusa decomposer (which promises decomposition in 15-days) it was found that with or without the use of a decomposer the field is ready to sow the next crop within 20 days. So, there is no point incurring an extra cost on buying a decomposer. We recommend that after incorporation the field is ready for sowing wheat seed - with simple drill- in 25 days while with smart seeder and supper seeder the seed could be sown after 7 days,” said Dr Kochar.

He added that incorporation has many benefits. “By carrying out the in-situ degradation the organic matter content per hectare can be increased with simultaneous increase in nitrogen content, phosphoric anhydride and potassium oxide,” stressed Kochar.

The university vice chancellor Dr SS Gosal has recommended short duration varieties particularly PR 126, which matures by the end of mid or last week of September and leaves enough time for stubble management.

Anoopraj Singh Grewal said that incorporation could be possible if the government offers incentives. “Why farmer would incur additional burden on fuel for chopping and cutting the straw, incorporate it in the field with tractor and water the field. Government should offer something to encourage the farmers. With a short window period no one wishes to take the risk,” said Grewal.

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