Effects of incorporating pine-woodchip biochar with reduced NP fertilizer on calcareous soil characteristics, organic carbon, NPK availability, and maize productivity

Abstract

Purpose: One of the successful and sustainable methods to restore low-fertility soils over the past few decades has been the integrated effect of biochar made from various feedstocks and chemical fertilizers. However, the impact of combining chemical fertilizers with pinewood-chip biochar to restore low-fertility calcareous soils has not been studied. The current study aimed to describe the integrative effects of pine-woodchip biochar and reduced NP fertilizer on soil fertility and maize productivity and to reduce dependency on inorganic fertilization. Materials and methods: In this regard, a 55-day pot experiment was conducted in the semi-arid agroecosystem to assess the integrated effect of pine-woodchip biochar (pyrolyzed at 450 °C) with reduced NP fertilizer on soil organic carbon, NPK availability, its uptake by maize, and maize productivity. The experimental design was completely randomized and consisted of six treatments: control, 100%-NP (NP), 5 tons ha−1 biochar (5-BC), 10 tons ha−1 biochar (10-BC), 5 tons ha−1 BC integrated with 50%-NP (5-BC + NP), and 10 tons ha−1 BC with 50%-NP (10-BC + NP). Results: Biochar amendments at 5 and 10 tons ha−1 with and without reduced NP fertilizer significantly increased maize growth and biomass production. Soil pH and electrical conductivity also varied between the treatments, and values were generally higher in BC and NP treatments. Soil organic carbon and soil total nitrogen concentrations were significantly higher in the 5-BC + NP and 10-BC treatments. Effects on NPK availability and their uptake by maize plants varied between the treatments. A significant positive correlation between soil nitrogen and plant nitrogen and uptake was observed, whereas similar relationships were non-significant and non-consistent for phosphorus and potassium. However, the relationships between the phosphorus and potassium concentrations of the soil and the plant were not significant and inconsistent. However, soil organic carbon was positively correlated with plant NPK uptake, suggesting the contrasting effects of pine-woodchip biochar on NPK availability and their uptake. Conclusion: Our study concluded that the pine-woodchip biochar with reduced NP fertilizer could enhance maize growth and biomass production while improving soil organic carbon with differential effects on NPK availability and uptake.