According to the findings of Punjab Agricultural University (PAU), soil is the best decomposer. According to a study conducted by PAU's microbiology department, if the straw is cut and chopped and incorporated with soil, it decomposes naturally and the field is ready to sow a wheat crop in 20 days.
This conclusion was reached by the PAU while conducting field trials of Pusa decomposers developed by the Indian Agricultural Research Institute (IARI), PAU, and trials of other decomposers. According to Dr. GS Kochar, head of the department of microbiology at PAU, several studies have revealed that enhanced decomposition of rice straw can be achieved through a microbial consortium (fungi, bacteria, and actinomycetes).
However, trials were carried out at PAU Ludhiana during the year (2020-21) using various in-house and commercial cultures and following three-step regimes i.e., chopping/spreading, manual or tractor-mounted spray, and incorporation, which revealed some important facts. According to Dr. Kochar's findings, adding microbial consortia confers no additional advantage over native soil microbes after paddy straw incorporation, as evidenced by wheat productivity comparisons.
Large-scale trials on PAU seed farms covering approximately 170 acres revealed no significant increase in wheat yield due to the use of microbes. "Several permutations and combinations were tried, including using more microbes and two sprays instead of one, but with little success." Wheat yields were compared in fields sown after paddy straw incorporation (with Rotavator or Super Seeder) with and without microbes. Wheat yields with and without microbial decomposer treatment were comparable in all four locations where experiments were conducted: Gurdaspur, Kapurthala, Faridkot, and Hoshiarpur.
"Various decomposers (IARI, AFC, and PAU) had the same effect and provided no yield advantage," said Dr. Kochar, citing his research. He claimed that field trials produced different results than lab-based trials conducted in a controlled environment. In dry conditions, the paddy straw spread relatively thinly (rather than heaped) and the lowering temperature regime of September-October did not allow microbial decomposition to take off and reach the required thermophilic phase.
"During the Pusa decomposer trial (which promises decomposition in 15 days), it was discovered that the field is ready to sow the next crop within 20 days, with or without using a decomposer. So, there's no point in spending extra money on a decomposer. "We recommend that after incorporation, the field is ready for sowing wheat seed - with a simple drill - in 25 days, while the seed can be sown in 7 days with a smart seeder or a supper seeder," said Dr. Kochar.
He went on to say that incorporation has numerous advantages. "By performing in-situ degradation, the organic matter content per hectare can be increased while simultaneously increasing the nitrogen, phosphoric anhydride, and potassium oxide," Kochar emphasized. Dr. SS Gosal, vice chancellor of the university, has recommended short-duration varieties, mainly PR 126, which matures by the end of the third or fourth week of September and allows enough time for stubble management.
According to Anoopraj Singh Grewal, incorporation may be possible if the government provides incentives. "Why would a farmer incur additional fuel costs for chopping and cutting straw, incorporating it into the field with a tractor, and watering the field? The government should do something to help farmers. With such a short window period, no one wants to take the risk," Grewal explained.
