Genotypic characteristics of groundnut for nitrogen-use efficiency based on Specific Leaf Nitrogen in Ghana

Groundnut (Arachis hypogaea L.) is an important legume crop in Ghana, where its productivity is often constrained by suboptimal nitrogen availability. Specific Leaf Nitrogen (SLN), a physiological trait derived from SPAD chlorophyll meter readings, offers a rapid and non-destructive proxy for nitrogen-use efficiency (NUE) in crop selection. This study aimed at evaluating the variation in SLN among selected groundnut genotypes in Ghana, with a strategy to identify high-performing and nitrogen-efficient lines that could be prioritised in future breeding programmes. A field experiment was conducted across two cropping seasons, at the Department of Ecological Agriculture, Bolgatanga Technical University, in Ghana. Results indicated significant genotypic variation in SPAD-derived SLN values, pod number, and seed yield. A moderate, statistically significant positive correlation (r = 0.497, P < 0.05) was observed between SLN and pod number; while pod yield and seed weight were strongly correlated (r = 0.603, P < 0.01). Plant height, however, did not significantly correlate with SLN (r = 0.219, P > 0.05), indicating that it is not a good predictor of NUE. High SLN values and superior yield traits were recorded by genotypes like Agric Bola and Sumnut-22; indicating their potential as donor parents in NUE-targeted breeding. In conclusion, SLN as determined by SPAD readings is a useful physiological marker for determining the nitrogen efficiency of groundnut genotypes.