Biochar increases wheat crop yield, say experts

Tribune News Service

Ludhiana, October 22

Paddy is cultivated on 30 lakh hectares with annual production of 225 lakh tonnes of straw in Punjab. The paddy stubble has to be mopped up in about 15-20 days to plant wheat. As a result, farmers’ burn paddy residue after harvesting crop.

Other than environmental hazards, substantial loss of plant nutrients (nitrogen and sulphur) is witnessed which impacts soil health.

Experts from the Punjab Agricultural University apprised with latest techniques to utilise hidden nutrients in paddy straw.

Dr RK Gupta, soil scientist from the PAU said, “Parali char/biochar is carbon rich porous product obtained after thermo-chemical conversion of paddy straw at low temperatures in presence of little or no oxygen. It is prepared by heap method.”

He said, “In this traditional method, a heap or pyramid like structure is raised to a height of 14 ft having 10 ft diameter. Then it is filled with straw. To start the combustion, stubble is ignited from the top of the dome, covered with an iron lid and then immediately sealed with mud. The paddy straw is subjected to partial combustion until the fire becomes clear and thin blue smoke starts coming out from vents located in upper portion of the dome.”

Dr Gupta said, “It indicates that biochar has been formed in this zone. Seal the vents located in upper portion of the dome with clay. Now, combustion advances to the middle portion of the dome. Wait till very thin blue smoke starts coming out from these vents. The moment it starts, seal the vents located in middle portion of the dome immediately with clay as biochar is ready in this portion as well. As combustion reaches the lower portion of the dome, seal the vents located in the lower portion with clay and wait for thin blue smoke.”

He said the whole process usually takes 10-12 hours and after two days, biochar could be taken out. It could also be removed on the same day by cooling it with water. In this process, 12 quintals of paddy straw could be converted in to approximately 6.5 quintal of prali char.

“Application of 2 tonnes of parali char along with recommended fertilisers results in rise in wheat yield. On an average 11.5 per cent increase in wheat yield was recorded at Krishi Vigyan Kendra (KVK) Ferozepur, Gurdaspur, Amritsar and Pathankot, respectively,” said OS Sandhu from the Department of Soil Science.

Vicky Singh from the Department of Soil Science said the addition of prali char after two years resulted in increase of 26.8 per cent organic carbon, 57 per cent phosphorus and 200 per cent potassium.

“Besides these properties, physical properties of the soil also increased significantly. Farmers should stop burning paddy straw. The above mentioned steps will increase crop yield, improve soil and human health, reduce consumption of chemical fertilizers and protect environment,” he said.