Investigation of Agronomic and Morphologic Responses of Different Cotton Types in Ultra Narrow Row System

Plant density is one of methods for increasing yield in ground unit. Recently cotton cropping in high density under ultra narrow row (UNR) were extended in cotton producer countries. Increasing plant density by planting in narrow row increases seed cotton yield. Cotton cropping in narrow row or UNR (row space is 20 to 30 cm) reduces evaporation at between two rows, therefore, it reduces water consumption and weed growth and also increases radiation use efficiency. In these systems (UNR), zero type cultivars are more effective and their efficiency is higher than common cultivars, due to lower growth of monopodia and sympodia branches. Therefore, survey of growth reaction, yield and morphologic variations of these cultivars in ultra narrow row is necessary. Hence, this project was carried out to determination of optimum plant density by planting at different row spacing in zero type and common cotton cultivars.
After soil preparation, two cotton cultivars (zero type cultivars) including Kashmar and Khorshid with Khordad and Varamin cotton cultivars (as control) were planted in rows space 20, 40 and 60 cm and 20 cm on row. This experiment was carried out as factorial layout base on randomized complete block design with three replications at Agriculture and Natural Resource Research Station of Kashmar during 2014-2015. Irrigation was carried out by using of tape (under pressure irrigation system) with 20 cm dripper distance and 4 liters per hour discharge.
The measured parameters were plant height, leaf number and area, number of monopodia and sympodia branches per plant, number of boll per each of monopodia and sympodia branches, boll weight and seed cotton yield. Analysis of variance and correlation between traits were carried out using MSTATC and Excel and means were compared with least significant difference (LSD) test.
The results showed that, a significant different was observed between cultivars in related with plant height in two years. So that Kashmar cultivar had the highest plant height in two years. Reduction of row spacing, increased significantly plant height only in first year. The highest and the lowest plant height belonged to Varamin and Kashmar cultivars, respectively. Number of monopodia and sympodia branches were different among cultivars and this variation was significant. In each year, zero type (cluster) cultivars (Kashmar and Khorshid) had more monopodia and sympodia branches than common cultivars (Khordad and Varamin). With increasing row spacing, number of sympodia branches increased in zero type cultivars rather than Varamin and Khordad cultivars. Results also showed that there was significant different among cultivars relevant to leaf number and area per plant. So that these traits were less in cluster cultivars than common cultivars. The highest and lowest leaf number per plant belonged to Khordad and Kashmar cultivars, respectively. Row space had no significant effect on leaf number and area per plant. However, the leaf number and area were more in 40 cm treatment. In the first year, there was no significant different among cultivars in related with boll number per plant, but the effect of row space on this trait was significant. In the second year, a significant different was observed among cultivars and also row spacing relevant to this traits. The number of boll per plant were more in common cultivars than cluster cultivars. Also increasing row space increased boll number per plant. A significant different was observed among cultivars only in the first year. The highest and lowest yield belonged to Kashmar and Khorshid cultivars, respectively. In both years, planting in narrow rows (20 cm treatment) significantly increased seed cotton yield. For instance, the mean of yields were about 7660 kg ha-1 and 9155 kg ha-1 in the first and second year, respectively. Seed cotton yields were 3462 kg ha-1 and 4702 kg ha-1 in the first and the second years, respectively. The highest increasing yield of planting at the highest density with 167%, 86% 136% and 59% were observed in Kashmar, Varamin, Khorshid and Khordad cultivars, respectively.
In the intensive agricultural systems, we need to use of favorable cotton cultivars that are proper especially for machinery harvest. These cultivars must to be with the lowest lateral growth of vegetative and reproductive branches. In this study, Kashmar and Khorshid cultivarswere as a zero type cotton cultivars that are suitable for mechanization harvest. Results showed that these cultivars had better reaction to high plant density rather than common cultivars (Varamin and Khordad). In the ultra narrow row system, yield of zero type cultivars was higher than common cultivars.