Commercial-oriented farming practices have seriously deteriorated soil health along with contributing to environmental pollution. This study suggested that the soil amendment with biosolid materials could reduce the application of NPK fertilizer by 25% less, leading to a substantial decline in the cost of rice production, increase paddy yield, and can contribute to reducing the methane gas emission from the rice fields.
To ensure the food security of the increasing population, high-yielding rice cultivars are being cultivated on large scale with intensive use of chemicals (fertilizers, pesticides, etc.), but commercial-oriented farming practices have seriously deteriorated soil health along with contributing to environmental pollution.
In addition to soil degradation, the modern intensive cropping systems have increased methane emission from paddy fields along with soil acidity, depletion of surface and underground water, pollution of farm and non-farm environment, and heavy metals toxicity.
The soil fertility status is very alarming in Bangladesh, the current average organic matter in the soil is less than 1% which has multiplied the need of fertilizers input. The use of rice residues as animal feed has seriously declined its application as soil amendment source.
In addition, the use of organic matter from external sources is also negligible. The current practice where mostly depends on inorganic fertilizer is not a sustainable practice for soil fertility as well as the environment.
Organic matter is called the heart of soil and amendments of soil; by applying organic matter solely or in combination with inorganic fertilizers can be a biologically and economically viable approach to maximize rice yield sustainably along with a significant reduction in methane emission from rice fields. Cultivation of rice is an important distribution channel of anthropogenic greenhouse gas (GHG) emission, contributing to global warming and climate change aspects.
It has been revealed that over 50% of CH4 emissions are of anthropogenic origin globally, while irrigated and puddled rice accounts for up to 12% of this flux. Another study estimated that CH4 emission from rice fields ranged 39–112 Tg CH4 annually. Therefore, the reduction of CH4 emissions from paddy fields without adversely affecting crop production is direly needed to curb environmental pollution through reduced use of chemical fertilizers.
Nowadays, the use of biogas and plant by-products are becoming popular to boost the fertility status of the soil. Among plant by-products, biochar, and charcoal, also called black carbon, have emerged as valuable amendments for degraded soils. Biochar application has also been reported to reduce N2O and CH4 emissions depending upon agro-environmental conditions. In addition, it was found to be equally effective in alleviating heavy metal stress which severely hampers plants’ growth and microbes’ functioning in soil.
The rice straw compost or farmyard manure (FYM) was reported effective in minimizing CH4 emissions from the rice field, with the co-benefits of increased soil fertility and crop productivity. From the above aspects, the present study was conducted to evaluate the effects of different rates of NPK (inorganic) fertilizer along with the single or combined application of biosolids and FYM concerning soil fertility, rice productivity, and CH4 emission from the transplanted aman rice field.
Our findings proved in line with the postulated hypothesis as different sources and doses of organic amendments applied solely or in conjunction with chemical fertilizers had varying effect on rice productivity and methane emission. The combination of 75% recommended fertilizer along with biosolid 2 tons/hectare (t/ha) performed better by increasing the soil fertility and rice productivity along with moderately reducing CH4 emission.
Therefore, the present study suggested that the soil amendment with biosolid materials (2t/ha) could reduce the application of chemical fertilizer (25% less NPK fertilizer), leading to substantial decline in the cost of rice production, increase paddy yield and can contribute to reduce the CH4 emission from the rice fields.
Further study may be needed to ensure the treatment performance in another agro-ecological zone of Bangladesh to observe adaptability and more organic amendments and application rates may be evaluated with different rice cultivars.
Read the study:
Haque MM, Datta J, Ahmed T, Ehsanullah M, Karim MN, Akter MS, Iqbal MA, Baazeem A, Hadifa A, Ahmed S, EL Sabagh A. (2021) Organic amendments boost soil fertility and rice productivity and reduce methane emissions from paddy fields under sub-tropical conditions. Sustainability 13(6):3103.
