Aims Increasing the leaf silicification of cereal crops to ameliorate defenses against stresses and improve yield constitutes a major challenge in (sub-)tropical regions with highly desilicated soils.We tested the efficacy of different biochars -as readily available alternatives to commercial fertilizers -to increase leaf silicification and understand subsequent impacts of leaf traits that might benefit crops. MethodsWe compared the application of two biochars (rice-derived biochar with 198 g kg -1 of Si and cotton-derived biochar with 4 g kg -1 of Si) and wollastonite (240 g kg -1 of Si) at two application rates on the leaf silicification patterns and leaf traits of rice growing in pots containing highly desilicated soil (Ferric Lixisol) from Burkina Faso.Results Leaf Si increased from 19.0 to 70.4 g kg -1 with Si addition (control < cotton biochar < wollastonite < rice biochar), resulting in larger epidermal silica deposits. Leaf carbon (C), leaf mass per area (LMA) and leaf arc decreased and were negatively correlated with leaf Si, however, surprisingly, the leaf force to punch and the plant biomass decreased. ConclusionsWe demonstrate the effective use of rice biochar in desilicated environments to improve the Si status of cereal crops and their associated leaf traits. In particular, the decrease in LMA with rice biochar application shows a promising capacity of rice biochar to reduce rice leaf 2 C costs. In situ trials are now needed to investigate whether or not these beneficial effects may result in increased crop yields through resilience against environmental stresses.

Agriculture in Burkina Faso relies on mineral fertilizers to reach decent crop production. Therefore, there is an urgent need to implement sustainable solutions that improve soil nutrient status while maintaining crop yields. Here we experiment with the recycling of nutrients through the production of biochar from cotton (Gossypium hirsutum L.) stalks and its mixing with compost to improve soil properties of highly weathered Lixisol. The trials included three treatments: conventional compost (COMP-100), co-composted biochar (COMPBI-100), each with recommended fertilization rates [cotton = 16.3 kg N ha -1 , 15.1 kg P ha -1 and 17.4 kg of K ha -1 ; maize (Zea mays L.) = 21.8 kg N ha -1 , 20.1 kg P ha -1 and 23.2 kg K ha -1 ], and co-composted biochar with 75% of recommended NPK fertilizer rate (COMPBI-75).We amended the soil with compost at conventional rates used in Burkina Faso, that is, 2.5 t ha -1 at each crop year (2018 and 2019). We measured the effect of the amendments on cotton and maize yield cropped in rotation using a randomized block design with four replicates for each of the studied treatments. Our results showed that the soil properties and crop yield in COMPBI-75 were not significantly lowered compared to COMPBI-100, which did not differ compared to soil and plant responses in COMP-100. Even not significant, COMPBI-100 and COMPBI-75 tend to have higher grain yields for cotton and maize. Our results highlight that co-composted biochar may be a promising amendment to increase crop productivity parameters in Burkina Faso while decreasing the NPK doses. The reduction of fertilizer rates can have essential implications considering the socio-economic and environmental advantages of reducing by quarter fertilizer doses in the Sudanese climatic region of Burkina Faso.Abbreviations: CEC, cation exchange capacity; COMP-100, conventional compost and 100% of recommended NPK fertilizer dose; COMPBI-75, co-composted biochar and 75% of recommended NPK fertilizer dose; COMPBI-100, co-composted biochar and 100% of recommended NPK fertilizer dose; C org , organic carbon; Ca tot , total calcium; DAS, days after sowing; K tot , total potassium; Mg tot , total magnesium; N tot , total nitrogen; Na tot , total sodium; P tot , total phosphorus.

Soil nutrient depletion, low crop nutrient‐use efficiency, and limited access to fertilizers are serious issues leading to poor yield in agroecosystems of Burkina Faso. Blending biochars with organic or inorganic nutrients could slow down nutrient release, which can enhance fertilizer‐use efficiency. This study investigates whether charging biochar with nutrients and Acacia gum (Acacia senegal L.) coating can improve nutrient‐use efficiency in a cotton (Gossypium hirsutum L.)–maize (Zea mays L.) rotation system using low application rates (<5 t ha−1). The experiment was conducted in western Burkina Faso during three cropping seasons (2018–2020) with five treatments: T0, control; T1, conventional practice with compost and nitrogen (N), phosphorus (P), and potassium (K) application; T2, microdose (planting hole application) of NPK; T3. nutrient‐charged biochar activated with dissolved NPK; T4, nutrient‐charged biochar activated with dissolved NPK and coated with Acacia gum. Biochar‐based fertilizers significantly increased soil organic C content, as well as bioavailable P and calcium (Ca), without significantly improving crop yields, compared to conventional practice and microdose of NPK. When nutrient‐charged biochar was coated with Acacia gum, N‐use efficiency (NUE; N recovered in grain/N fertilized) was improved compared to uncoated nutrient‐charged biochar, although the difference was not significant. Despite no significant effects on crop yields during three cropping seasons, the use of coated biochar‐based fertilizer may be a technically effective solution to improve NUE in the long term in agroecosystems characterized by nutrient‐impoverished soils under a constraining South‐Sudanese climate.