Cotton Sown in Different Row Distances after Wheat Harvest: Seed Cotton Yield and Yield Components

Cotton is an industrial cash crop which has an important role in world agriculture and trade. In Turkey, the area of cotton during 2015 was 434 000 hectares with lint production of 738 000 tones and average lint yield of 1700 kg ha-1. Recently, cotton consumption has increased tremendously owing to the expanding textile industry in Turkey. Currently, over 50% of lint cotton consumed is imported. Increased demand has created a need to revitalize the cotton industry. The Mediterranean region of Turkey, with a warm and long growing season, allows a small grain crop to be followed by other field crops in the same season, thereby increasing the productivity of the land (Killi and Bolek, 2006). Therefore, planting cotton after a winter cereal in regions having a long growing season, such as the Mediterranean region, may be one of the means of meeting the increasing demand. In Kahramanmaras city, located in the eastern part of the Mediterranean region, the textile industry is expanding very fast, but the land used for cotton planting is not. 

Historically cotton has been grown in 28 to 32 inch rows due to equipment considerations in Turkey. A proper space between plants and row spacing is a key agronomic factor to optimize the crop profit (Zaxosa et al. 2012). Plant density directly influences the radiation interception, moisture availability, wind movement and humidity (Heitholt et al. 1992) that in turn affects the canopy height, branching pattern, fruiting behavior, crop maturity and yield. Plant populations in narrow row cotton production systems are higher, but more plants/acre could increase cotton yields, especially on poorer soils (Balkcom et al. 2010). Jost and Cothren (2000) reported a yield increase for cotton grown in narrow rows during a dry growing season, while Boquet (2005) reported no yield advantage for narrow row cotton production. In a study of eight transgenic cultivars, yields for cotton planted in ultra-narrow rows were higher than conventional row spacings (Witten and Cothren, 2000). In a 2-yr study in South Carolina, seed cotton yield, lint yield, and gin turnout were different among row spacings and cultivars (Jones, 2001). Significant row spacing by cultivar interaction was reported for seed cotton yield. Nichols et al. (2004) reported that plant height, number of fruit per plant, number of total nod per plant and number of boll per plant were decreased in narrow row planting. Jahedi et al. (2013) reported that plant height, sympodia and total bolls per plant were reduced in cotton grown in narrow row spacing. In most cases, cotton grown in narrow rows had lint yields equal to or higher than those attained in the 70 cm spacing. A study in Texas, narrow row planting (40 cm) was compared with 60 cm spacing for yield and yield components of eight cotton varieties. It was determined that higher seed cotton yield was obtained from 40 cm row spacing, and the value of yield and yield components had changed according to cultivars (Smit, 1989). Past research has also indicated that in higher plant populations (> 15.3 plants m²) cotton plants typically produce fewer apical main-stem nodes and monopodial branches plant (Siebert, 2006; Bednarz, 2000; Jones and Wells, 1998; Siebert and Stewart, 2006). In dense plant populations (> 10.0 plants m²), shading caused by excessive vegetative growth may result in a greater potential for boll rot, fruit abscission, increased plant height, and delayed maturity, leading to reduced yield and fiber quality (Bednarz, 2000; Bednarz et al. 2005, York, 1983; Siebert and Stewart, 2006). Recent research has reported optimal yields in plant populations ranging from 9.0-21.5 plants m² in Georgia [Bednarz et al. 2005], 3.4-15.3 plants m² in Louisiana [Siebert, 2006], 9.0-13.0 plants m² in Mississippi (Pettigrew and Johnson, 2005), and 2.0-12.0 plants m² in North Carolina (Jones and Wells, 1998). Yield reduction can occur at plant populations of 3.4-7.0 plants m² (Siebert, 2006, Bednarz et al. 2005, Siebert and Stewart, 2006, Pettigrew and Johnson, 2005), and may be magnified by early season stress caused by seedling diseases, sand blasting, hail, and soil crusting prior to emergence (Gannaway et al. 1995). Low plant populations may also result in delayed maturity (Siebert, 2006, Jones and Wells, 1998, Siebert and Stewart, 2006) and reduced harvest efficiency due to increased branching (Gannaway et al. 1995). Due to its perennial and indeterminate growth habit, cotton is extremely sensitive to environmental conditions and management practices (Oosterhuis, 1994). The growing of early maturing cotton cultivars has an advantage of proper time for rotation of other crops allowing timely sowing of wheat in cotton-wheat-cotton cropping system in Pakistan and other countries (Ali et al. 2003). Narrow row production systems with high plant populations planting cotton as a second crop after cereals have not been examined in East Mediterranean cotton production areas.

 The aim of this study was to determine the seed cotton yield by increasing the number of plants in second crop planting after wheat harvest. Therefore, yield and yield components in sown cotton after wheat harvest at 70 cm (traditional row) and 35 cm (narrow row) spacing were compared using different cotton cultivars.