Sustaining Productivity while Reducing Methane Emission in Calcareous Soils: Implications of Combining Inorganic Fertilizer and Biochar

Abstract

A considerable proportion of applied nutrients are adsorbed by the calcite surface of calcareous soils, making them unavailable to plants. A combination of organic amendments and fertilizers can improve nutrient retention and mineralization, and also reduce greenhouse gas (GHG) emissions. A two-years field experiment was undertaken to investigate the impacts of inorganic fertilizer, biochar and silicon on nutrient uptake, growth, yield and post-harvest soil chemistry in calcareous soil using rice ( Oryza sativa L.) as a test crop. The implication of each treatment on methane emissions was also investigated. The combination of NPK, biochar and silicon significantly improved rice growth, yield, P and Si uptake; and post-harvest soil nutrition. Biochar increased soil organic carbon content between 4.2 and 108.5% across the years. An increase from 2.4 to 6.1% was observed in the inorganic fertilizer treatments, 11.4–12.0% for the biochar treatments and 2.5–19.0% for ½NPK + biochar from 2020 to 2021. Maximum grain yield was achieved with the treatment ½NPK + biochar + 100 kg Si ha − 1 which was comparable to NPK + 100 kg Si ha − 1 . Also, the combination of ½NPK + biochar + 50 kg Si reduced CH 4 emissions and produced a comparable yield to NPK + 50 kg Si in both years. While further research is required to explore the effects of the length of time biochar is applied on reducing CH 4 emissions, this study suggests a basis for predicting the impact of biochar on the management of CH 4 emissions in calcareous soils.

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