behnam behtari

A field study was carried out to investigate the effects of four planting depths and three soil types with different physical characteristics on green bean (Phaseolus vulgaris Var. sunray) and maize (Zea mays L. Var. Amyla) seed germination and seedling emergence.The aim of the experiments was to investigate the physical effects of the soil on seed ecology and emergence dynamics. The result revealed that germination inhibition was directly proportional to clay content and inversely proportional to sand content due to burial depth. Depth of fifty percent emergence inhibition (Di50%) were equal to 5.3 cm in clay soil for both green bean and maize, if this was for silty soil, respectively 5.4 and 2.7 cm. A significant linear regression between clay particle content and Di50% revealed that those soil components had opposite effects in terms of favoring or inhibiting depth mediated inhibition. Therefore, increasing soil clay contents increased inhibition of seedlings. The data also showed that the oxygen content in the surrounding soil of seeds can not be an important factor for seed germination differences, and its effect was insignificant. Increasing geometric mean decreased particle diameter soil inhibition. In conclusion, these experiments showed soil physical properties had a strong effect on buried-seed ecology and consequently on seed germination and seedling emergence.

Seedling emergence probably is the single most important phenological event that influences the success of an annual plant. The main objective of this study was to develop a seedling emergence model for green bean and maize and select a best-fitted model associated with sowing depth. A factorial experiment based on completely randomized design was conducted in 2015 at Research Farm of Mohaghegh Ardabili University, to quantify the response of seedling emergence to sowing depth. Treatments were four sowing depths (2, 4, 6 and 8 cm) in three replications. The results indicated that the percentage emergences of both species in the first two levels of sowing depth (2 and 4 cm) were high, but at deeper levels, seedling emergence were suffering a severe loss. Emergence indicators (MED, ERI, D50%) showed that seedling emergence of bean was greater than maize. For two species, an increase in pre-emergence mortality with increasing depth was observed. So that the highest germinated seeds mortality occurred at 8 cm depth. However, in probit fitted curves for each dataset, the rates of increasing between plants varied. The rate of emergence varied between plants and based on values of statistical criteria, because of less parameters number in linear probit model, it was showed suitable to fit model. Therefore, these models may provide a better basis for broad practical application in crop management.