Biochars have long been associated with elevating plant productivity. An increasing number of studies, however, report that char application might also impair plant nutrient availability and reduce yields. In particular, char accompanying compounds as well as a hypothesized immobilization of nitrogen have been identified as playing a significant role in possibly diminishing plant productivity following char application. Herein, we tested the fertilizing effects of modified biochars in order to derive knowledge required to develop tailor-made chars, which predictably affect plant nutrition. Slow-pyrolysis maize cob biochar was modified by washing with either ethanol or hydrochloric acid to remove ash and organic compounds or by loading it with nutrient-rich residues in the form of digestate from the bioenergy sector. Maize plants were grown for 35 days on biochar-amended sand. We analyzed both substrate properties (pH, total carbon, and nitrogen, available magnesium and potassium) and plant functional traits (biomass, leaf area, root to shoot ratio, specific leaf area). Our results suggest that total plant biomass production remained unaffected by the application of biochar and its washed forms. Contrastingly, nutrient-loaded biochar induced a significant increase in productivity at similar nutrient levels due to improved plant nutrient uptake. Further research is required to understand the role of biochar modifications that facilitated improvements in plant productivity.

Digestate and biogas slurry (BS) are the byproduct of biogas engineering that could be used for elevating plant growth. However, the consequent emissions of ammonia from BS are considered a severe threat to the atmosphere. Herein, we conducted two consecutive field experiments with wheat–maize rotations to find out the optimum ratio of BS to combine with chemical fertilizer (CF) to reduce ammonia volatilization (AV) while keeping the stable crop yield. In maize season, 226.5 kg N/ha of CF was applied. In wheat season, 226.5 kg N/ha was applied at different ratios (100%, 80%, and 50%) between BS and CF. Our results found that the maximum yield of 6250 kg/ha was produced by CF, and this yield could be obtained through a combined application of 38% BS mixed with CF. Highest AV produced of 16.08 kg/ha by CF. BS treatments significantly reduced the emission from 18% to 32% in comparison to CF. The combined application of BS-CF produced the highest yield due to essential nutrients coming from both BS-CF. Subsequently, it reduced the AV depending on fertilizer type and fertilizer rate. An optimal ratio of 38% BS was recommended to produce the highest yield and lowest ammonia emissions. The application of BS together with different ratios of CF could be an alternative agricultural strategy to obtain desired crop yield and reduce AV in North China Plain (NCP).

Agriculture is the cornerstone of South Asian economies, but it faces challenges such as limited land, soil degradation, and unpredictable weather. This study evaluates a legume-oilseed mixed cropping system (LOMCS) as a sustainable intensification strategy for the region. We assessed the intercropping of field pea ( Pisum sativum ) and mustard ( Brassica spp.) across various planting combinations during the Rabi seasons of 2020–21 and 2021–22 in Jashore, Bangladesh. The combination of 100% field pea with 30% mustard (T3) demonstrated superior performance, achieving the highest field pea equivalent yield (1.76 t ha ⁻¹ ), gross return of 800 USD ha ⁻¹ (87,868 BDT ha ⁻¹ ), and gross margin of 450 USD ha ⁻¹ (49,393 BDT ha ⁻¹ ), with a benefit–cost ratio of 2.18. This treatment also showed the highest land equivalent ratio (1.05), indicating 5% greater land-use efficiency than monocultures. The findings demonstrate that the strategic integration of legumes and oilseeds can significantly enhance productivity, profitability, and resource use efficiency, offering a viable pathway to improve socioeconomic conditions for smallholder farmers in South Asia.