Inorganic nitrogen fertilizer, biochar particle size and rate of application on lettuce (Lactuca sativa L.) nitrogen use and yield

Abstract

Lettuce (Lactuca sativa L.) efficient use of nitrogen (NUE) determines its growth and yield. We assessed the interaction effect of N fertilizer and biochar of different particle sizes and rates on NUE, growth and yield of lettuce. A factorial design arranged in Randomized Complete Block Design with four replications was used to conduct a field experiment at the FRNR farm, Kwame Nkrumah University of Science and Technology, Ghana. The treatment consisted of biochar at 8.33 t and 16.67 t ha−1 with different particle sizes (<2, 5 and 10 mm) and five rates (0, 31.3, 62.5, 93.83 and 125 kg ha−1) of inorganic N fertilizer. Our result showed that integrating 8.33 t ha−1 of <2 mm and 5 mm biochar with 62.5 and 93.8 kgN ha−1, respectively improved lettuce growth, NUE by 30% and yield. The yield (19.3 t ha−1) obtained with these applications is comparable to the achievable yield (20 t ha−1) of lettuce under the sole N recommended rate (125 kgN ha−1). In conclusion, with 8.33 t ha−1 of <2 mm biochar, farmers can reduce the recommended inorganic N rate of lettuce by half (62.5 kg ha−1) and still attain good yield with improved post-harvest soil fertility. This has implications for farmers’ production costs, agriculture waste management and climate change mitigation strategies.