Selection of suitable additives for seed pelletizing to enhance germination and growth of <i>Onobrychis viciifolia</i> in restoration of semi‐arid degraded rangelands

Abstract Despite direct seeding, seed pelletizing with useful materials is one of the effective methods to improve plant growth. This experiment assessed the impacts of different additives used in seed pelletizing on germination and growth of Onobrychis viciifolia at a degraded semi‐arid rangeland. Seed pellets were prepared for the 16 treatments, which included 14 amendments (seven additives at two 10% and 20% concentration levels) and two controls (a clay‐only pellet and direct seeding). After the planting, germination indices and growth traits were recorded and analyzed. A completely randomized design was considered in planting experiment using 12 seedballs as replications per treatment. The results revealed that corn starch 20% treatment had the lowest value for growth and germination, while the livestock manure 20%, sawdust 20%, ash 10%, and wheat straw 10% showed better germination indices. Based on the significance summation ranking method, sawdust was the most favorable amendment, enhancing root length by 23%, root weight by 234%, aerial biomass weight by 189%, and plant height by 31% compared to the direct seeding. The efficacy of seed pelleting over direct seeding was clearly demonstrated. Notably, seedballs prepared solely from clay, without any amendments, also showed acceptable performance in enhancing seed germination and plant growth. However, some of the used additives, such as ash, sawdust, and manure, were more beneficial than using clay alone in the seedball production. Seed pelletizing did not always have favorable results with all materials. For instance, additives such as starch, especially in high concentrations, had adverse effects.