Straw-derived biochar regulates soil enzyme activities, reduces greenhouse gas emissions, and enhances carbon accumulation in farmland under mulching

Context or problem

Film mulching can significantly increase crop yields, but long-term continuous mulching will reduce the soil fertility and lead to soil quality degradation. Incorporating exogenous carbon (C) is widely recognized as an effective countermeasure for improving degraded farmland soil under mulching in semiarid areas.

Objective or research question

We compared the effects of straw and biochar on the accumulation of C and soil biochemical properties in both mulched and non-mulched farmland, and investigated the effects of various types of straw inputs on greenhouse gas (GHG) emissions.

Methods

A field experiment was conducted to test six treatments: flat planting without mulching (NN), flat planting with straw incorporation (NS), flat planting with biochar incorporation (NB), film mulching (MN), film mulching with straw incorporation (MS), and film mulching with biochar incorporation (MB)]. Comprehensive assessments were conducted in Pengyang, Ningxia, China during the two growing seasons of 2020 and 2021.

Results

Mulching increased the soil hydrothermal conditions, maize yields (29.32 %), and GHG emissions (CO₂: 10.07 %; N₂O: 1.42 %) but decreased the soil organic C storage (SOCS: 6.91 %). Straw returning increased the plant fixed C (14.99 %), improved GHG emissions (CO₂: 4.95 %; N₂O: 4.33 %), and inhibited CH₄ uptake (3.78 %). Compared with MS, MB reduced the GHG emissions (CO₂: 9.93 %; N₂O: 20.97 %) and net global warming potential (7.08 %), but increased the SOCS (SOCS: 3.42 %), C efficiency ratio (CER: 26.93 %), CH₄ uptake (10.72 %), and soil enzyme activities (invertase: 6.48 %; urease: 13.76 %).

Conclusions

Incorporating biochar rather than straw has greater potential for enhancing the soil enzyme activities and C use efficiency while also reducing the GHG emissions and net global warming potential caused by mulching in dryland farming.

Implications or significance

In this study, we comprehensively compared the effects of incorporating straw, film mulching, and biochar incorporation on C accumulation, GHG emissions, and maize yields in dryland farming. Our findings provide a scientific basis for achieving green and sustainable high-yield production in mulched dryland farming.