VOL. 5, NO. 3, MAY 2010 ISSN 1990-6145 ARPN Journal of Agricultural and Biological Science © 2006-2010 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com SEEDING RATE EFFECT ON SEED YIELD AND YIELD COMPONENTS OF ALFALFA (Medicago sativa) Majid Rashidi 1 , Behnam Zand 2 and Saeed Abbassi 3 1 Member of Young Researchers Club, Islamic Azad University, Takestan Branch, Iran 2 Agronomical and Horticultural Research Department, Tehran Province Agricultural and Natural Resources Research Center, Iran 3 Department of Agricultural Machinery, Faculty of Agriculture, Islamic Azad University, Takestan Branch, Iran E-Mails: majidrashidi81@yahoo.com , m.rashidi@tiau.ac.ir ABSTRACT A four year field experiment was conducted at the Research Site of Tehran Province Agricultural and Natural Resources Research Center in Varamin, Iran to study the effect of seeding rate on seed yield and seed yield components of alfalfa (Medicago sativa) during 2005-2008 growing seasons. Seeding rate treatments were 2.5 kg ha -1 (SR 1 ), 5.0 kg ha -1 (SR 2 ), 7.5 kg ha -1 (SR 3 ), 10.0 kg ha -1 (SR 4 ) and 12.5 kg ha -1 (SR 5 ). Seed yield and seed yield components (number of pods per m 2 , number seeds per pod and 1000-seed weight) were determined for all treatments. The statistical results of the study indicated that seeding rate significantly (P = 0.01) affected seed yield and number of pods per m 2 , but there was no significant difference in number seeds per pod and 1000-seed weight. The maximum value of seed yield (805.0 kg ha -1 ) and number of pods per m 2 (6610) was obtained in case of SR 1 treatment. Conversely, the minimum value of seed yield (605.7 kg ha -1 ) and number of pods per m 2 (4620) was observed in case of SR 5 treatment. Therefore, 2.5 kg ha -1 was found to be more appropriate seeding rate in improving seed yield of alfalfa in the semi-arid lands of Varamin, Iran. Keywords: alfalfa, seeding rate, seed yield, semi-arid, Varamin, Iran. INTRODUCTION Alfalfa (Medicago sativa) is an ancient crop. Charred seeds has been found in archeological sites in Iran dating back 8000 years, and charred from small seeded legumes and grasses collected by people 12000 years ago in present day Syria has also been unearthed. It is speculated that alfalfa was used as forage crop and its seed was eaten by humans (Russelle, 2001). Additionally, alfalfa is a nutrient rich forage crop that is productive and beneficial agronomically and environmentally in the world (Azarfard, 2008). Alfalfa improves and protects the soil as a result of its robust and perennial root system, fast growing protective canopy and ability to fix atmospheric nitrogen (Shahriari et al., 2007). Its deep and extensive root system reduces erosion by holding soil together, improves water infiltration and contributes to a rhizosphere conducive to growth of beneficial microorganisms (Rezaee-Danesh et al., 2007). Because of its perennial nature, annual tillage is reduced. Its vigorous growth combined with annual harvest during the growing period provides excellent weed control (Martens, 2001). Alfalfa’s pesticide requirements are much lower than for other crops (often none). Alfalfa’s residual benefit to succeeding crops has been shown to range from 5 to 13 percent probably from disease suppression and fixed nitrogen (Peel, 1998). Moreover, wildlife enhancement goes hand in hand with alfalfa production. It provides direct feed for deer, upland birds and rodents. It also provides protective habitat for these wildlife and as a consequence, it provides hunting opportunity for predators. Alfalfa also provides feed and habitat to honey bees and other beneficial insects as well as insects that provide feed for birds, reptiles, bats and other small mammals (Putman et al., 2001). Under normal conditions, 50% to 60% of planted alfalfa seeds emerge and 60% to 80% of emerged seedlings die the first year. A reasonable goal for alfalfa plant density in a year old stand after the first winter is 130 plants per m 2 . Math based on the above survival rates leads to a seeding rate of 17.0 kg ha -1 . However, research in Wisconsin shows that under good seeding conditions there is no advantage in stand establishment to planting more than 6.0 kg ha -1 (Undersander, 1999). Taking into consideration that not all seeding conditions are ideal, extension seeding rate recommendations have been in the range of 14.0-17.0 kg ha -1 . Over the years, seeding rates have continued to creep upwards. In addition, seed cost for alfalfa varieties has continued to increase over the years along with the increased seeding rates (Undersander et al., 1999). Considering the importance, a new look at the effect of seeding rates on long-term alfalfa seed production is necessary to see if reducing seeding rates is an economically viable option to help cut input costs, without sacrificing seed yield and income. At this time, a wide range of seeding rates is being used in Iran without evaluating their effects on seed yield and seed yield components of alfalfa. Therefore, the purpose of this study was to investigate the effect of different seeding rates on seed yield and seed yield components of alfalfa (var. Bami) in the semi-arid lands of Varamin, Iran. MATERIALS AND METHODS Experimental site: The experiment was carried out for four consecutive growing seasons (2005-2008) at the Research Site of Tehran Province Agricultural and Natural Resources Research Center in Varamin, Iran. The site is located at latitude of 35° 19' N and longitude of 51° 39' E and is 1000 m above mean sea level, in semi-arid 42