˺ CORN SILAGE QUALITY RESPONSE TO CROP PLANTING DENSITY Ali Baghdadi *1 , Ridzwan A. Halim 1 , Majid Majidian 2 1 Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Malaysia 2 Department of Agronomy and Plant Breeding, University of Guilan, P. O. Box 41635-1314 Rasht, Iran. * Correspondence: Ali Baghdadi, Tel: +989111356118, Fax: +981334626071, E-mail: ali_baghdadi@yahoo.com Abstract Corn silage serves as high-energy forage for livestock. This is most important for high-producing livestock and on farms experiencing problems with making or buying high quality forage. A field experiment was conducted in the spring and summer of 2010 at the Research Site of Guilan Province Agricultural and Natural Resources Research Center in Rasht, Iran to evaluate effect of different planting density of corn in terms of silage nutritive quality. The plant densities were 90,000, 110,000 and 130,000 plants/ha. Increasing plant density from 90,000 to 130,000 plants ha -1 resulted in decreasing nutritive quality of silage corn. The dry matter digestibility (DMD) and crude protein (CP) declined from the lowest to the highest plant density. Acid detergent fiber (ADF) increased from the lowest to the highest plant density. The reduction in nutritive quality may be attributed to the lower leaf to stem ratio at higher planting density. With the reduced grain yield, plant population above a critical density will have a negative effect on CP and quality of forage corn. Key words: crude protein, digestibility, nutritive value, plant density, forage. Introduction Forage from corn has high value for food, high yield capability, short-growth period, and is suitable as forage and feed for poultry and livestock and it is gaining an essential position in the cropping system (Saif et al., 2003). The low protein concentration in forage corn can be augmented simply by incorporating protein rich ingredients such as soybean or sunflower (Choukan, 1997). Successful corn production requires an understanding of various management practices related to the environmental conditions and agronomic practices. Planting with appropriate plant density according to the conditions of each region is one of the most important factor in corn for production (Norwood, 2001). Corn production practices have been intensively researched and constantly improved over the past years. Crop management practices and plant density have been one of the most important research priority areas in corn production (Sangoi et al., 2002). Curran and Posch (2000) reported that good forage crops must have high digestible energy, low fiber and the desired amount of dry matter at harvest for storage. Cox and Cherney (2001) indicated effect of plant density on production and quality of forage corn. They found that increased plant density had a negative effect on CP concentrations. Averaged across years, CP concentration averaged 3 g kg -1 less at 116,000 vs. 80,000 plants ha -1 . On the contrary, Marsalis et al. (2009) demonstrated that none of the quality parameters of corn (e.g., CP, ADF) was affected by reducing the seeding rate from 74,200 to 55,600 plants ha -1 . Plant population density main effects were significant for many of the quality traits. Concentrations of ADF increased linearly as the plant population density increased (Stanton et al., 2007). Basically, there was no advantage or disadvantage by increasing plant density with respect to feed value. Forage corn is an important source of high yielding and consistent feed and is the most important feed crop for animal husbandry in many areas of world. Therefore, it is important to understand how forage corn performance is influenced by agronomic practices, such as plant density.