Synergistic effects of syzygium cumini sawdust biochar and poultry manure on soil quality enhancement, nitrogen, organic carbon dynamics, and Amaranthus cruentus growth

The study aimed to evaluate the potential of incorporating biochar with poultry manure to address the constant challenges of sandy, loam soils due to poor water retention and low soil fertility, and their influence on the growth and yield of Amaranthus cruentus during the Rabi and Kharif seasons. The combined effect of manures on soil health over different seasons was unexplored, so the current research has been taken up to understand the impact of different treatments on physical, chemical, and microbial dynamics in the Rabi and Kharif seasons. Advanced statistical analysis was used to measure the soil and plant factor variations across seasons. Pre- and post-harvest results showed substantial progress in the soil bulk density, water-holding capacity (WHC), and nutrient retention in KR5 (biochar + poultry manure) treatment, where WHC displayed a strong positive correlation with organic matter (r > 0.82). Even chemical analysis indicated increased soil nitrogen, phosphorus, potassium, and carbon levels. Metagenomic analysis implied microbial diversity and abundance promoting nitrogen fixation and decomposition of organic matter. FTIR and SEM also revealed structural improvements that are beneficial for microbial colonization and nutrient retention. The combination of biochar and poultry manure showed higher growth, increasing plant height by 40 cm and yielding over 550 g/m² during the Kharif season. The results have revealed that the combination of biochar and poultry manure has improved soil fertility, microbial diversity, and yield of Amaranthus cruentus grown in sandy loam soils.