Effect of organic coats with superabsorbent polymers on improving the germination and early vigor Milk thistle (Silybum marianum L.) seeds under salinity stress

Salinity is a major environmental stress negatively influencing germination and seedling establishment in a wide variety of crops. The objective of this study was to use the organic materials with superabsorbents to improve the emergence rate and seedling traits of Milk thistle (Silybum marianum L.) under salinity stress. A factorial experiment in a completely randomized design with three replications was conducted in outdoor pots. Treatments included: organic coats at two levels (C1= peat moss and C2= vermicompost), superabsorbent polymers at seven levels (A1= without superabsorbent, A2-A4= coats with 2, 4, and 6 g superabsorbent of A200 per kg organic material, and A5-A7= coats with 2, 4, and 6 g superabsorbent of F1 per kg organic material), and salinity (S) stress at five levels (0, -2, -4, -6, and -8 bar). Results showed that organic material and the type and amount of superabsorbent significantly (p ≤ 0.05) affected emergence, emergence rate, plant vigor index, shoot dry weight, leaf area, specific leaf area, relative water content, and total chlorophyll. Application of superabsorbent polymers with organic material reduced salinity stress in the primary growth stage of Milk thistle. Generally superabsorbent A200 is more effective than superabsorbent F1 and vermicompost coats better are than peat moss coats.