Field assessment of blue panicum (Panicum antidotale Retz.) productivity: effects of plant density and organic amendment across three saline sites

Blue panicum ( Panicum antidotale Retz.) has been extensively studied in Southern Morocco for its ability to maintain productivity under high salinity levels. However, important knowledge gaps remain regarding crop management practices, particularly intercropping, planting density, and fertility management. Accordingly, this study evaluated, the combined effects of planting density (8 and 16 plants m − 2 ) and organic amendments (control, compost at 10 and 20 t ha − 1 , and manure at 20 and 40 t ha − 1 ) on the growth, physiology, mineral composition, and stress responses of blue panicum ( Panicum antidotale Retz.), under increasing saline conditions. Soil and irrigation water salinity were low (0.7 and 4.5), moderate (1.3 and 8.6), and high (7.8 and 2.8 dS m − 1 ), respectively. Results showed that, across sites, the highest annual biomass production was recorded under the highest density, reaching 202.5 t ha − 1 (fresh biomass) and 41.2 t ha − 1 (dry biomass). The low salinity site of Oulad Ghanem was the most productive, whereas organic amendments resulted in limited yield gains. A similar pattern was observed for stomatal conductance and chlorophyll index, which reached their highest values under low saline conditions with 393 mmol m⁻² s⁻¹ and 35, respectively. Antioxidant responses further differentiated site functioning: SOD and CAT activities increased under high salinity (72 and 9.0 U g − 1 FW, respectively), whereas POD peaked under moderate conditions (0.37 U g − 1 FW). Overall, this study demonstrates the ability of blue panicum to maintain productivity under increasing saline conditions, with organic amendments helping mitigate the adverse effect of salinity.