Biochar (BC) applications have multiple impacts on crops’ nutrient availability, growth and yield depending on the feedstock type and pyrolysis conditions. Pot and field experiments were conducted to examine the effects of biochars (BCs) prepared from three different feedstocks, Acacia modesta wood biochar (AWB), Dalbergia sissoo wood biochar (DWB) and poultry litter biochar (PLB), on soil’s nutrient availability, uptake by wheat (Triticum aestivum) and sunflower (Helianthus annuus) crops and their yield attributes. All BCs were applied at the rate of 10t ha⁻¹ in each treatment in both experiments, and pot and field trials were designed according to a two-factor factorial completely randomized design (CRD) and two-factor factorial randomized complete block design (RCBD), respectively. The concentration of soil NO₃-N, NH₄-N, Olsen P and extractable K increased by 98.5, 296, 228 and 47%, respectively, in the pot experiment with the application of PLB+polyhalite (PH) treatments. Similarly, in field experiments, NO₃-N, NH₄-N and Olsen P contents increased by 91, 268 and 156% under the PLB+PH treatment, respectively. However, in both experiments, soil’s microbial biomass phosphorus (MBP) was significantly higher after AWB+PH treatment, and the increments were 127 and 109% while microbial biomass nitrogen (MBN) contents were 16 and 14% higher than the control under DWB+PH and AWB+PH treatments, respectively, in the field experiment. Similarly, combined PLB+PH increased the total organic carbon (TOC) of soil by 193%. Moreover, PLB+PH co-applications with PH significantly increased sunflower grain yields by up to 58% and the harvest index by 45%. Overall, no negative impact with respect to BCs was observed on the soil’s nutrient content and plant growth. Hence, for immediate crop benefits and soil health, using nutrient biochar (PLB) alone or in combination with chemical fertilizers is recommended.

Compost application to soil is an effective strategy to enhance soil fertility, promote plant growth, and support sustainable agriculture. Nevertheless, the variability in the responses of plants to compost amendments across different compost types, concentrations, exposure durations, application media, and across different physiological traits of plants is not well understood. In this study, we performed a meta-analysis using data from 92 peer-reviewed scientific articles to better understand the effect of compost amendments on plant physiological, biochemical, and yield traits. The results of this study showed that compost amendment significantly improved plant growth parameters, and the increase in shoot biomass and plant height was the highest (~19.4–42.7%), followed by root length (20.4%) and root biomass (19.7%), indicating the important role of compost in promoting root development. In addition, photosynthetic efficiency was significantly enhanced, and total chlorophyll and carotenoid content increased by 13.5–49.1%. The yield-related traits, total yield, and 100-grain weight responded positively and significantly increased by ~18%. There were variations among different plant species and different exposure conditions. The mechanistic interaction between compost components, soil agrochemical properties, and plant physiological and yield responses should be further explored to maximize the benefits of compost application in sustainable agriculture.

Aim Integration of chemical and organic fertilizers not only improves soil biological health and plant growth but also reduces costs of agricultural production, and hence, is an economically feasible approach to sustain plant growth in developing countries. Methods We performed a field experiment to evaluate the impact of poultry litter derived biochar (BC; 10 and 20 t ha^-1) with and without chemical fertilizers (CF) on soil nutrient availability, microbial abundance, and soil enzymatic activity. Results Combined application of BC and CF significantly increased soil nutritional status and organic carbon (SOC), and these improvements were more prominent at higher BC level (20 tons ha^-1), which increased soil microbial biomass carbon, nitrogen, and phosphorus by 27, 58, and 61%, respectively. Furthermore, BC20+CF treatment improved soil microbial abundances such as actinomycetes (24%), bacteria (70%), AMF (49%) and saprophytic fungi (38%). In terms of wheat growth and yield attributes, BC20+CF application enhanced spike length (55%), leaf area index (30%), tillers (12%), along with biological yield (26%) and grain yield (36%). BC20+CF application was also proved to be positively correlated with different soil enzymatic activities i.e., urease (24%), dehydrogenase (44%), and β-glucosidase (93%). Principal component analysis (PCA) analysis proved that co-application of BC @ 20 t ha^-1 along with CF was the most efficient treatment in terms of improving soil nutrient status and microbial activities. Conclusions Hence, combined application of BC and CF could be an efficient tool to improve soil health, plant growth and reduce cost of agricultural production.