Interactive effects of biochar and microbial biofertilizers on sandy soil fertility and cowpea yield in Egyptian agroecosystems

Cowpea (Vigna unguiculata ssp. unguiculata) is a promising legume crop for arid and semi-arid regions due to its short growth duration, nutritional value, and drought tolerance. However, sandy soils in Egypt suffer from low fertility, weak aggregation, and poor water-holding capacity, which limit crop productivity. This study evaluated the combined effects of biochar and microbial inoculants (Bacillus amyloliquefaciens and Saccharomyces cerevisiae) on sandy soil fertility and cowpea productivity in Egypt. A two-season (2020–2021) field experiment was conducted in the Ismailia Governorate, Egypt, using cowpea cv. Dokki 126 in a randomized complete block design with 12 treatments (biochar, microbial inoculants, nitrogen fertilizer, and their combinations) and three replicates. The integrated application of biochar and microbial inoculants significantly increased total microbial counts by up to 65% and dehydrogenase activity by 42% compared to the control. Soil bulk density decreased by 18%, total porosity increased by 22%, and available soil N, P, and K contents increased by 45%, 52%, and 39%, respectively, leading to higher chlorophyll content (+ 28%), plant length (+ 21%), and seed yield (+ 33%) relative to the control. These findings indicate that integrating biochar with microbial inoculants significantly enhances sandy soil fertility and cowpea productivity, offering a sustainable pathway for soil restoration in arid ecosystems.