Indian Journal of Fundamental and Applied Life Sciences ISSN: 2231-6345 (Online) An Open Access, Online International Journal Available at http://www.cibtech.org/jls.htm 2014 Vol. 4 (4) October-December, pp.292-298/Shirvanian et al. Research Article © Copyright 2014 | Centre for Info Bio Technology (CIBTech) 292 THE EFFECT OF PLANTING DATE AND SEED INTERCROPPING RATIO ON DRY MATTER DISTRIBUTION IN MAIZE INTERCROPPED WITH SOYBEAN *Maryam Shirvanian, Mojtaba Alavifazel and Mani Mojaddam Department of Agronomy, College of Agriculture, Ahvaz branch, Islamic Azad University, Ahvaz, Iran *Author for Correspondence ABSTRACT In order to investigate the effect of planting date and seed mixing ratio on dry matter distribution in maize and soybean, a split plot experiment in as randomized complete block design with three replications was carried out in Shahid Salemi Field located in Ahvaz in 2013. The treatments included four planting dates (D1 = July12, D2 = July 22, D3 = August 1, and D4 = August 11) as the main factor and the mixing ratio of maize and soybean at four levels (P1 = maize monoculture, P2 = 50% maize intercropped with 50% soybean, P3 = 75% maize intercropped with 25% soybean, P4 = 25% maize intercropped with 75% soybean) as the sub factor. The results showed that the effect of different levels of intercropping ratio on dry weight of the plant organs and total dry matter was not significant, but the intercropping ratio of 25% maize and 75% soybean was determined as the superior intercropping ratio. In this ratio, the maize allocated the highest total dry weight (14.37 t/ha) and the highest leaf dry weight (3.51 t/ha) and the highest corn ear dry weight (6.97) to itself in intercropping. Moreover, the results showed that the effect of planting date on total dry weight and dry weight of plant organs was significant. Accordingly, the planting dates of July 12 and 22 were reported as the superior planting dates in soybean. According to the results, early planting of soybean can produce more dry matter by means of the shadowing of maize and can have heavier weight compared to the later planting dates and thus the highest total dry matter in soybean was obtained in the planting date of July 22 by 13.20 t/ha and the highest dry matter of stem and leaf was obtained in planting date of July 12 by 3.55 and 3.63 t/ha, respectively. Keywords: Planting Date, Maize, Intercropping Ratio, Soybean, Dry Matter Distribution INTRODUCTION Intercropping is known as one of the most important viable agricultural systems in many developed countries which is highly significant due to the variety of products and the increase of profits within the time and area units (Mahfooz et al., 2004). According to the obtained results when two different species with various plant height, vegetation, and planting pattern are intercropped concurrently they make the least competition with each other and this leads to the increase of intercropping yield compared to monoculture (Klindet et al., 2007). The main reason of the superiority and the increase of intercropping product is the high efficiency of the use of limited water resources and nutrients, the decrease of weeds growth (Tahir et al., 2003), and the decrease of damage caused by pests and diseases (Bolson, 1997). Due to high sensitivity of soybean to the day length, its yield is affected by planting date more than any other factors. Planting date has a great effect on the maturity time, seed size, grain yield, and biological yield (Kouchaki, 1994). Singh et al., (1968) found that intercropping maize with soybean led to the increase of produced biomass by 20-40%. Ghamari et al., (2011) reported that there was a significant difference between the treatments in terms of the dry weight of corn cob at 1% level in the maize intercropped with soybean. Mansoori (2010) stated that the effect of planting ratios on dry weight of corn cob was significant at 1% level. Tohidi Nejad et al., (2004) reported that the highest dry forage was obtained through 25:75 intercropping (maize-sunflower). Manjit et al., (2009) evaluated intercropping (mustard- pea) and reported that the highest dry matter belonged to 66: 33 and 75: 25 ratios. Mahfooz and Meigor (2004) reported that intercropping canola with pea had a significant effect on biological yield. Farahani et al., (2004) stated that sufficient chance for biomass production and the inconsistency between growth and maximum temperature led to the increase of stem dry weight in soybean. Darby and Laure (2002) stated that the increase of leaf dry weight in soybean was due to the increase of the number of soybean leaves