عنوان مقاله [English]
Corn (Zea mays L.) is the third most important cereal crop in the world after wheat and rice (Lashkari et al., 2011). Corn production has been extended in to the whole world during the course of the last century due to its compatibility. It has more diversity compare to other cereal. Many corn types are cultivated, including field corn, ornamental corn, popcorn, sweet corn and several different supersweet corns. Sweet corn, considered a vegetable, is a special type of corn with particular characteristics, such as sweet taste, thin pericarp and endosperm with delicate texture, and high nutritional value. It is destined exclusively for human consumption, in fresh form or in processed foods, whereas the straw can be used for silage after harvest (Santos et al., 2014). Sweet corn seeds germinate slowly and exhibit poor seedling vigour. Poor germination in sweet corn has been attributed to low seed vigour and susceptibility to seed and soilborne diseases (Ratin et al., 2006). Seed priming is the one of efficient method to improve germination and emergence. In addition, transplanting provides optimal environmental conditions for seed germination and avoids planting seeds in disease-contaminated soil (Khalid et al., 2012).
Materials and methods
To investigate the effect of seed priming and transplanting on morphological characteristics, yield and yield components of supersweet corn a series of greenhouse and field experiments were conducted in a factorial based design on a randomized complete block in 2013. This experiment was conducted in the greenhouse to determine the best seed priming treatments. The treatments were hydro priming, Poly ethylene glycol (6000) -0.4 and -0.8 MPa, Sodium Sulphate 0.1 and 0.5%, Zinc Sulphate 1 and 0.5%, Copper Sulphate 0.1 and 0.5% and Control for 36 hours. After that the seeds washed by distillated water and dried back in laboratory conditions. Then treated seeds were sown in trays that contained by cocopeatand vermicompost. The emerged seeds were counted daily for fourteen days. Based on mean emergence time (MET) and percentages of emergence, the best priming treatments were selected to prime the seeds for transplant production and direct sowing in the field experiment. The factors for field experiment included four treatments of seed priming (hydropriming, polyethylene glycol (PEG) -0.4 MPa, sodium sulfate 0.1% and control) and planting methods in four levels (transplanting the seedlings grown in two different cell sizes (25 ml and 100 ml) and two direct seeding dates (the first one was at the time of planting seeds in the trays (5th June) and the second was at the time of transplanting to the field (26th June)). The determined parameters were established plants, plant height, number of leave, number of leave above ear, ear length, number of rows per ear, number of kernel per row, 1000 seeds weight and grain yield.
Results and discussion
The results of greenhouse experiment showed that the highest and the lowest amount of mean emergence time related to control and Sodium Sulphate 0.1% respectively. The highest percent of emerged plant (94%) was observed in the hydropriming treatment while there was no significant difference between hydropriming, Sodium Sulphate 0.1 % and Polyethylen Glycol -0.4 MPa. Therefore, hydropriming, Sodium Sulphate 0.1 % and Polyethylen Glycol -0.4 MPa alongside control were used to prime the seeds sowing in order to produce transplants for the field experiment for further investigation. The results of the field experiment showed that seed priming had no effect on the studied traits in the field. Planting methods had significant effect on crop establishment, plant height, number of leave, number of leave above ear, ear length, number of rows per ear, number of kernel per row and the grain yield. The highest and lowest grain yield were recorded for transplanting in 25 CC cell sizes (10.11 t.ha-1) and direct seeding in 26th June (6.5 t.ha-1) respectively. The result showed there was a high correlation (r =0.64**) between number of established plants and grain yield.
Priming was not useful in field, but farmers could use seed priming to produce seedlings. It seems that the most important benefit of transplanting is obtaining high value of plant establishment in order to achieve optimum plant density.