Conventional nitrogen (N) fertilizers particularly urea mineralized quickly in soil. Without sufficient plant uptake, this rapid mineralization favors the heavy N losses. Lignite is a naturally abundant and cost-effective adsorbent capable of extending multiple benefits as a soil amendment. Therefore, it was hypothesized that lignite as an N carrier for the synthesis of lignite-based slow-release N fertilizer (LSRNF) could offer an eco-friendly and affordable option to resolve the limitations of existing N fertilizer formulations. The LSRNF was developed by impregnating urea on deashed lignite and pelletized by a mixture of polyvinyl alcohol and starch as a binder. The results indicated that LSRNF significantly delayed the N mineralization and extended its release to >70 days. The surface morphology and physicochemical properties of LSRNF confirmed the sorption of urea on lignite. The study demonstrated that LSRNF also significantly decreased the NH3-volatilization up to 44.55%, NO3-leaching up to 57.01%, and N2O-emission up to 52.18% compared to conventional urea. So, this study proved that lignite is a suitable material to formulate new slow-release fertilizers, suiting to alkaline calcareous soils favorably where N losses are further higher compared to non-calcareous soils.

Recently biochar has widely been reported as carrier of SRFs. However, the performance of SRFs synthesized from pristine biochar is still low and could not achieve the significant benefits compared to conventional N fertilizers. To overcome this limitation and research gap, BSRFs were synthesized using modified / de-ashed biochar as N-carrier. We hypothesized that BSRFs would NUE especially in alkaline calcareous soils for whom there is no specific SRF exist previously. In this study, the efficacy of BSRF formulated with 1:1 mass ratio of de-ashed biochar and urea was compared with CU and CSRF for improving NUE under wheat (Triticum aestivum L.) and maize (Zea mays L.) cropping system in two different textured soils. The results showed that compared to CU and CSRF, the addition of BSRF significantly increased the retention of soil mineral-N (NH₄ ⁺-N, NO₃ ⁻-N) which, consequently, enhanced the crops’ N-uptake up to 23.71% in wheat and 26.55% in maize. It was further observed that SOC contents were increased up to 50.79% in wheat and up to 47.61% in maize at harvest. The addition of BSRF enhanced the CEC up to 32.95% under wheat and up to 27.73% under maize, compared to CU. Eventually, BSRF significantly increased the grain yield and NUE of wheat by 12.04% and 40.44%, while the maize grain yield and NUE increased by 21.06% and 45.56%, respectively. This study concludes that BSRFs had a stronger yield-increasing effect than CU alone attributing to enhanced N retention and crop uptake in alkaline calcareous soils. It was also found that the de-ashed biochar is a strong candidate to formulate new SRFs with improved performance.

Nutrients like nitrogen (N), phosphorus (P), and sulphur (S) play a critical role in plant and microbial growth, as well as in stabilizing soil organic carbon (SOC). Humus, the most stable fraction of soil organic matter (SOM), maintains a consistent elemental ratio of C:N:P:S at 10,000:833:200:143. To evaluate how variations in this humus based C:N:P:S ratio affect SOC stabilization, a six-month laboratory incubation was conducted using selected benchmark soil series. The soils were amended with wheat straw (WS) and maize straw (MS), both with and without added inorganic nutrients (N, P, and S), to achieve two target C:N:P:S ratios aligned with humus stoichiometry 15% and 30% (C:N 12; C:P 50; C:S 70). Results showed that the MS30% and WS30% treatments reduced CO₂ efflux by 39% and 33%, respectively, compared to treatments without added nutrients. The MS15% and WS15% treatments also led to a 14% reduction in CO₂ emissions compared to the application of MS and WS alone. Moreover, supplementing WS and MS with nutrients to achieve a 30% humus-based ratio enhanced SOC stabilization by 11–25% over straw-only treatments. The study concludes that aligning organic and inorganic inputs to maintain a 30% humus-based C:N:P:S ratio significantly improves SOC stabilization. This highlights the vital role of balanced nutrient management in promoting carbon sequestration and overall soil health.

Soil can function as a reservoir and a source of greenhouse gases (GHGs), contingent on its management. This study assesses the potential of a modified reduced tillage (MRT) approach involving the use of cover or green manure crops as a substitute for crop residues to mitigate GHG emissions from soil within smallholder rainfed farming systems. A two-year field experiment with different tillage techniques (moldboard plow, tine cultivator, and modified reduced tillage) and crop rotations (summer fallow–wheat and cover/green manure–wheat) was conducted at Rawalpindi, Pakistan. The results showed that MRT reduced carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions by 8% and 15.3%, respectively, from soil while maintaining consistently higher soil moisture than conventional tillage techniques. The modified reduced tillage reduced the global warming potential (GWP) and greenhouse gas intensity (GHGI) by 15.8% and 20.7%, respectively. The net ecosystem exchange (NEE) was unaffected by the tillage systems. Therefore, adopting the MRT technique and incorporating green manure is a viable strategy for curtailing GHG emissions from soil, particularly in the context of smallholder rainfed farming systems. Extended, multi-year studies under various climate scenarios and agronomic practices are needed to understand the long-term impacts of MRT and crop rotations on GHG emissions.