Recent advancements have demonstrated the potential of biochar as a carrier for slow-release fertilizers (SRFs), but its efficacy, particularly when synthesized from pristine biochar, has exhibited limitations compared to conventional nitrogen fertilizers. To address this, researchers explored the creation of biochar-based slow-release fertilizers (BSRF) using modified, de-ashed biochar as the nitrogen carrier.
The study, conducted at the Institute of Soil and Environmental Sciences at PMAS-Arid Agriculture University, Rawalpindi, Pakistan, aimed to test the efficacy of BSRFs formulated using a 1:1 mass ratio of de-ashed biochar and urea. Compared to conventional urea (CU) and commercial slow-release fertilizer (CSRF), BSRFs were hypothesized to significantly improve nitrogen-use efficiency (NUE) under wheat (Triticum aestivum L.) and maize (Zea mays L.) cropping systems.
The findings revealed notable improvements: using BSRFs led to increased retention of soil mineral nitrogen—specifically ammonium (NH4+-N) and nitrate (NO3−-N)—and enhanced nitrogen uptake by crops. Wheat demonstrated nitrogen uptake improvements of up to 23.71%, whereas maize saw increases of 26.55%.
Further enhancements included significant increases of soil organic carbon (SOC), which raised by 50.79% for wheat and 47.61% for maize at harvest. The addition of BSRFs also enhanced soil cation exchange capacity (CEC) by 32.95% under wheat and 27.73% under maize, reflecting improved nutrient availability and uptake.
The research applied six treatments within two types of alkaline calcareous soils, each with three replications across 36 plots. The two soil types examined were Gujranwala (fine-loamy) and Pindorian (coarse-loamy). Treatment variations consisted of control (CK), conventional urea at 100% N (U100), commercial SRF at 100% N (C100), and BSRFs at varying dosages (B100 at 100% N, B75 at 75% N, and B50 at 50% N). Recommended nitrogen, phosphorus, and potassium (NPK) doses were established at 120-100-60 kg/ha for wheat and 160-120-60 kg/ha for maize.
Statistical analyses confirmed significant differences among treatments, particularly with BSRF treatments outperforming CU and CSRF. The BSRFs led to grain yield increases of 12.04% and 40.44% increased NUE for wheat, and 21.06% and 45.56% for maize, showing the superior effectiveness of BSRFs as innovative approaches to improve agricultural productivity.
The study addresses the acute challenge of nitrogen availability in alkaline calcareous soils, where losses through leaching and volatilization are prominent. The researchers hypothesized and demonstrated through this study how blending conventional nitrogen fertilizers with organic materials such as biochar could not only retain nitrogen but also extend its availability, mitigating the detrimental impacts of such losses.
These results provide compelling evidence articulately advocating for the modification of biochar as an effective N-carrier, establishing BSRFs as pivotal to sustainable agriculture practices aimed at enhancing NUE. Given the pressing agricultural needs and environmental concerns tied to nitrogen management, this research sets the foundation for future inquiries to optimize BSRFs, explore varying compositions, and examine their broader applicability beyond alkaline calcareous soils. It indicates potential avenues to improve soil fertility and environmental sustainability, thereby addressing food security challenges.
Conducting lifecycle assessments and cost-benefit analyses could also illuminate the operational viability and economic benefits of using BSRFs, promising impactful advancements for agricultural ecosystems.