Salt effects on germination and seedling emergence of several vegetable crops and guayule

Summary

Salt effects on seed germination and seedling emergence of several crops are evaluated to understand poor plant stands occurring in furrow-irrigated fields in saline areas. The test crops were carrot (Daucus carota L. cv. Imperator 58), chile pepper (Capsicum annuum L. cv. New Mexico 6-4), tomato (Lycopersicon esculentum M. cv. Rutgers), and guayule (Parthenium argentatum G. cv. 593). Seed germination was measured in petri-dishes containing saline solutions (0.8 to 32 dSm⁻¹ with a Na to Ca + Mg ratio of about 2 : 1); and seedling emergence in potted fine loamy sand subirrigated in a greenhouse with saline waters (0.8 to 7.6 dSm⁻¹ with SAR < 16). Seedling emergence through a thin layer of salted-loamy sand (having EC _e up to 46 dSm⁻¹) placed on emerging seedlings was also evaluated. Germination of tomato and carrot seeds began to decline at solution salinities of 12 and 18 dSm⁻¹, respectively, and was virtually zero at 23 dSm⁻¹, Chile pepper and guayule germinated well at 23 dSm⁻¹, Tomato had the highest emergence, and guayule the lowest, showing less than 20% when subirrigated at 2.2 dSm⁻¹, Seedling emergence which increased in the order of guayule, carrot, chile pepper and tomatoes did not quantitatively correlate with seed germination. However, it did correlate with the emergence through the thin layer of the salted-sand placed over emerging seedlings except in tomato. Salinity of the saturation extract of the surface 5 mm soil increased to 21 and 31 dSm⁻¹, in 7 days when subirrigated with water of 4.3 and 6.4 dSm⁻¹, respectively. Poor seedling emergence of guayule, carrots and, to some extent, chile pepper appeared to be caused by hypocotyl mortality associated with the salts accumulated at the soil surface, but not by reduced seed germination. The control of surface accumulated salts should be the target of management for improved emergence of these crops.