The Effect of Sulfuric Acid, Temperature, seed production locations and Agronomic Factors on Hard Seed Breakdown in Annual Medic (Medicago scutellata cv. Robinson)

ABSTRACT: This study was carried out at the agricultural research farm of Lorestan University in Khoramabad in 2010-2011 to evaluate the effect of sulfuric acid, temperature, seed origin and agronomic factors on hard seed breakdown of annual medic (Medicago scutellata cv. Robinson). Two pot experiments were conducted in a split-factorial design arranged in randomized complete blocks with four replications. In the first pot experiment, planting with pod at four levels of planting depth (0, 4, 8, and 12 cm) formed the main plot and a combination of two levels of seed origin (Khoramabad and Karaj) and two levels of soil texture (silt-clay loam and sand) formed the split treatments in a factorial manner. In the second pot experiment, planting without pod at four levels of planting depth (0, 2, 4, and 6 cm) formed the main plot and a combination of two levels of seed origin (Khoramabad and Karaj) and two levels of soil texture (silt-clay loam and sand) formed the split treatments in a factorial manner. A laboratory experiment was also conducted in a factorial design arranged in randomized complete blocks with four replications. The factors involved two levels of sulfuric acid (applied and not applied), two levels of seed origin (Khoramabad and Karaj) and four levels of temperature (5, 15, 30, and 45°C). Results showed that washing the seeds with sulfuric acid had beneficial effects on hard seed breakdown. Constant temperature did not affect hard seed breakdown but germination percentage and seed vigor decreased at 45°C. The temperature in which the seeds were kept before germination increased the length of radicles when approached the biological zero. According to the pot experiments, the highest and lowest germination percentage was observed respectively at the depth of 4 cm and 12 cm in planting with pod and 2 cm and 6 cm in planting without pod. Seed origin and soil texture also affected hard sees breakdown and seeds with Khoramabad origin and the soil with lighter texture produced a higher germination percentage. Annual medics is more noteworthy than other annual legumes in this type of cropping system due to its specific self-regeneration resulting from the gradual softening of its hard seed coat. Seed coat hardening is the main reason for seed dormancy in leguminous plants. Hardseededness of more than 90% prevents seeds from germination at the cropping stage in cereal-legume rotation systems. In the conditions and system status that the purpose cultivation is necessary that the seed with pods can be used without such rotational system of annual medic and wheat or barley (ley- farming) or similar cases and in a condition that can or should be compulsorily placed in the soil seed with pods like the end of first year rotational system of annual medics - wheat or barley (ley- farming) should be that of wheat, seed with pods in the soil should be deferred