A greenhouse study was conducted to explore the effect of various rates of potassium sulfate (K 2 SO 4 ) nanoparticles on alfalfa (Medicago sativa L.) growth and physiological response under salt stress. One salt-tolerant genotype (Mesa-Sirsa) and one salt-sensitive genotype (Bulldog 505) were selected based on germination under salt and were planted in pots containing 2 kg of sand. The two genotypes were subjected to 0 and 6 dS•m −1 salt levels using CaCl 2 •2H 2 O: NaCl (2:1) mixed with Hoagland solution. Three K 2 SO 4 nanoparticle treatments consisting of, 1/4, 1/8, and 1/10 of the potassium (K) level in full strength Hoagland solution (235 mg•L −1 ) were applied. Adding K 2 SO 4 nanoparticles at the 1/8 level resulted in the highest shoot dry weight, relative yield, root length and root dry weight in both genotypes. The different rates of K 2 SO 4 nanoparticles affected significantly Na/K ratio and the concentrations of Calcium (Ca), Phosphorus (P), Copper (Cu), Manganese (Mn), and Zinc (Zn) in plant tissue. The application of K 2 SO 4 nanoparticles at the 1/8 rate enhanced the plant's physiological response to salt stress by reducing electrolyte leakage, increasing catalase and proline content, and increasing antioxidant enzymes, activity. These results suggest that the application of K nanoparticles may have better efficiency than conventional K fertilizers in providing adequate plant nutrition and overcoming the negative effects of salt stress in alfalfa.

Salinity is a major impediment to crop production. This study was undertaken to compare the effect of seaweed extract, humic acid, and potassium sulfate nanoparticles in alleviating salt stress in Alfalfa (Medicago sativa L.). Seeds of ten alfalfa genotypes were germinated in a growth chamber at five salt concentrations (0%, 0.5%, 1.0%, 1.5%, and 2.00%). Salt concentrations above 1% reduced seed germination by more than 70% in most genotypes. One salt tolerant genotype (Mesa-Sirsa) and one salt sensitive (Bulldog 505) were selected and planted in greenhouse pots containing 2 kg of sand and subjected to two salt levels (10 and 15 dS·m . Plant biomass was reduced under both salt concentrations in both genotypes, with a greater magnitude in the salt sensitive genotype. Application of seaweed extract resulted in higher relative water content and proline under both salt concentrations (10 and 15 dS·m −1 ) in the salt sensitive genotype, and lower electrolyte leakage in both salt tolerant and salt sensitive genotypes, under both salt concentrations. Seaweed extract also resulted in higher catalase and SOD activities in both genotypes under 10 dS·m −1 . Catalase and SOD activities were associated with significantly (p < 0.01) reduced electrolyte leakage and increased shoot dry weight. Overall, seaweed extract seemed to have a positive effect in alleviating salt stress in alfalfa.

Salt impedes plant growth and yield. This study was conducted to explore the effect of plant growth stimulants (seaweed extract, humic acid) and potassium sulfate in alleviating salt stress in barley (Hordeum vulgare L.). Initially, 10 barley genotypes were germinated in a growth chamber at five salt levels (0, 0.5, 1.0, 1.5, and 2.0%). Increasing salt concentration reduced germination percent, the speed of germination, and seedling weight. One salt-tolerant genotype (Sharqiya Estate) and one salt-sensitive genotype (Red Sea) were selected and planted in greenhouse pots containing 2 kg of sand, then subjected to 10 and 15 dS m -1 salt levels using CaCl 2 .2H 2 O: NaCl (2:1) mixed with Hoagland solution. Four treatments consisting of (1) , and (4) potassium sulfate at 300 Kg ha -1 were applied to each genotype under both salt levels. Seaweed extract resulted in higher shoot dry weight in the salt-sensitive genotype under both salt levels and maintained a low Na + /K + ratio compared with humic acid and potassium sulfate. It also resulted in higher relative yield, relative water content, higher proline, and lower electrolyte leakage in the susceptible genotype at 10 dS m -1 , but the result was not different from humic acid and potassium sulfate treatments at 15 dS m -1 . Seaweed extract resulted in the highest catalase activity at 15 dS m -1 in both genotypes, with higher magnitude in the salt-tolerant genotype. These results suggest that seaweed extract has potential in improving barley growth under salt stress.