Management practices can affect the yield, maturity, and fiber quality of cotton. One practice used to increase yield has been to adjust the spacing between cotton rows. Typically cotton is planted in row spaced 70-100 cm apart. Ultra narrow row cotton production has been proposed as an economical means to increase yields and reduce production costs. A field study was conducted to assess the effects of ultra-narrow row (20 cm-UNR) and conventional row (80 cm-CR) production systems on canopy closure, yield, and fiber quality at three commercial cotton cultivars (Golestan, Sahel, and Sepid) at Gorgan in 2011. Results showed that cotton canopy closure more occurred rapidly in 20 cm rows compared to 80 cm rows (about 18 to 36 days earlier). Cotton in 20 cm rows was produced more yield than cotton in 80 cm rows. The yield increase in 20 cm rows was a result of increase in the number of boll production per unit area and increase radiation interception by canopy. No conclusive differences for fiber quality could be ascertained between in 20 cm and 80 cm rows. A higher yield in UNR compared to CR indicated that UNR system is an agronomic feasible option for farmers.

To determine the most appropriate method of weed management in conventional row and ultra narrow row spacings of cotton, a factorial experiment was based on a randomized complete block design with three replications was conducted in Sabzevar in 2015-2016. Factors under study were plant spacings in two levels, conventional (70 cm row spacing) and ultra-narrow row (20 cm row spacing) and weed management in six levels: without controlling of weeds (control), application of herbicide at recommended dose of Ethalfluralin (Treflan 48% EC) at 1160 g/ai ha), application of herbicide at 50% recommended dose + hand weeding at 45 days after emergence (DAE), application of herbicide at 50% recommended dose + two times hand weeding at 30 and 60 DAE, three times hand weeding at 30, 45 and 60 DAE, and full weed free condition. The results showed that traits like weed density, by 33. 71 percent, lateral branches by 14. 77 percent, number of bolls per plant by 16. 88 percent, and boll weight by 12. 30 percent were lower in narrow row spacing, while seed cotton yield by 39. 85 percent and fiber yield by 23. 71 percent higher, as compared to, conventional row spacing. In the conventional cultivation system, if 50% of the herbicide dose is reduced, it needs two hands weeding at 30 and 60 DAE,while in ultra-narrow row spacing condition, with a 50% reduction in the recommended herbicide dose, one hand weeding at 45 DAE is needed to achieve suitable seed cotton yield. As a whole, the results showed that, under ultra-narrow row spacing, with a 50% reduction in herbicide dose and reduced weed control times (only one hand weeding at 45 DAE) it can be obtained seed cotton yield similar to other control treatments.

Introduction: 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. Materials and Methods: 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. Results and Discussion: 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 -1 ha in the first and second year, respectively. Seed cotton yields were 3462 kg ha-1-1 and 4702 kg ha 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. Conclusions: 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.

With the purpose of determining critical time of weed control under conventional and ultra-narrow row spacing conditions of cotton (Gossypium hirsutum L. ) (Khordad cultivar), a field experiment has been conducted as a factorial arrangement in a randomized complete block design with three replications in Sabzevar during the water year of 2015. The studied factors include the conventional cultivation system (70-cm row spacing), ultra-narrow row (20-cm row spacing), and duration of weed interference (0, 30, 45, 60, and 7 days after emergence and during the full season). Results from the experiment show that in ultra-narrow row condition, seed cotton yield losses of 2. 5%, 5%, and 10% are estimated to occur 27. 4, 36. 1, and 44. 7 days after emergence, respectively. Also, under the conventional condition, yield losses of 2. 5%, 5%, and 10% are estimated to occur 8. 1, 13. 5, and 24. 4 days after emergence, respectively. It is proven that the onset of seed cotton yields on lint yield loss occurs earlier (i. e., 46. 3 and 53. 7 days after emergence, respectively) under conventional condition, while under ultra-narrow row condition the onset of seed cotton yield and lint yield loss is postponed to 57. 9 and 65. 9 days after emergence, respectively. Overall, the experiment results show that cotton cultivation in ultra-narrow row spacing under weed interference conditions could provide a better seed cotton yield than conventional spacing.

In order to investigate the effects of reduced row spacing from usual 75 cm to 25 cm (UNR), an experiment has been conducted in two locations: Davarabad agricultural research station (Semnan Province) and Varamin Central Agricultural Research Station. The experimental design is RCBD laid out in split plots with three replications. The main plots are the planting dates (May 22 and Jun 5, 2020) and five cultivars, i.e. Khorshid, Kashmar, Sajedi, Hekmat, and Khordad serve as the sub plots. The results show that location effect on vegetative and reproductive attributes has been significant. UNR boosts the yield in Aradan, but in Varamin region, this planting method, not only has failed to increase the yield, but has reduced it significantly. This is due to reducing the boll number as a result of rank growth of plants in UNR system. Reduction of row spaces from 75 to 25 cm enhances the number of monopodials, sympodials, and plant height. In Varamin, plant height of all cultivars are higher than 119 cm. the highest yield in this region obtained from Khordad as Control (3886 kg seed ha -1). The highest yield in Aradan, obtained from Khorshid (5702.5 kg seed ha -1) in UNR system. This shows that the UNR planting of zero type varieties is more adabtable for Garmsar condition than that of Varamin.

Field experiments were conducted to determine whether soybean grown in 36-cm rows and a 2* population could improve weed control relative to 60-cm rows and 1* population under reduced herbicide options. Experiment was conducted in split plot design with four replications at Karaj and Lorestan. Main plots were 1) 36-cm rows and 2* population and 2) 60-cm rows and 1* population. Five treatments of herbicides were as supplots included 1) a standard treatment of Basagran + Nabues (100%), 2) Basagran + Nabues (25% of the standard rates), 3) a standard treatment of Treflan + Sencor (100%), 4) Treflan + Sencor (25% of the standard rates),  5) without herbicide (control). Weed control was better with Basagran + Nabues than Treflan + Sencor. Weeds control was less in the 25%- herbicide treatments than in the standard treatments when soybean was grown in 60-cm with 1* population. The 25%-herbicide treatments when soybean was grown in 36-cm rows with a 2* population provided weed control and grain yield similar or further than 60-cm rows and 1* population with 100% herbicide. Weed control was poor and yield was reduced when no herbicides were applied regardless of row spacing or population.  

Cotton has been traditionally grown in rows spaced from 75 to 100 cm. Narrow row spacing have been found to increase yield potential in cotton due to better sunlight penetration and more uniform spacing of the cotton plants in the field. A field experiment was conducted to study the effect of planting date on yield and yield components of cotton with three planting systems at Sabzevar Agriculture and Natural Resources research center in 2013. This experiment was carried out as split plot design based on randomized complete block design with three replications. Factors were: planting date (Conventional (22 May) and late planting (22 June) as main plots and planting system; ultra narrow row spacing (20 cm (25 plant. m-2), conventional spacing (50 cm (10 plant. m-2) and broadcast seeding (8 plant. m-2) as subplots. The results showed that planting date and planting system had significant effect on plant height, number of bolls, boll weight and seed cotton yield. Late planting was decreased plant height (13. 61%), number of boll (27. 41%), boll weight (14. 63%) and seed cotton yield (24. 83%) as compared with conventional planting date. Narrow row spacing was better than other planting system for all traits. There was no significant difference between conventional spacing and broadcast seeding. Overall, ultra narrow spacing rows and conventional planting date (May 22) was the best treatment for achieving high yield in cotton under Sabzevar conditions.

In order to study the possibility of changing corn planting pattern by using narrower rows and eliminating some furrows, an experiment was conducted in the fields of Agriculture Training Center of Shahid Dehghanpur of Jiroft, Iran in 2001 on the basis of a Randomized Complete Block Design with three replications. The studied was composed of 18 treatments including inter-row spacing of 35 cm with the densities of 75000, 85000 and 95000 plants. ha-1 (T1, T2 and T3, respectively), inter-row spacing of 35 cm with the elimination of four unplanted furrows with the densities of 75000, 85000 and 95000 plants.ha-1 (T4, T5 and T6, respectively), inter-row spacing of 75 cm with the densities of 75000, 85000 and 95000 plants. ha-1 (T7, T8 and T9, respectively), inter-row spacing of 75 cm with the elimination of one planting row with the density of 75000, the elimination of two unplanted rows with the density of 85000 and the elimination of two unplanted rows with the density of 95000 plants. ha-1 (T10, T11 and T12, respectively), inter-row spacing of 55 cm with the densities of 75000, 85000 and 95000 plants. ha-1 (T13, T14 and T15, respectively) and inter-row spacing of 55 cm with three unplanted rows and the densities of 75000, 85000 and 95000 plants. ha-1 (T16, T17 and T18, respectively). Measured traits included grain yield, row number per ear, grain number per row, 1000-grain weight, grain ratio to total, plant height, biomass, mean ear weight and harvest index. Results showed that the effect of treatments was significant on grain yield, 1000-grain weight, plant height and biomass at 5% statistical level and on grain number per row, ear length and mean ear weight at 1% probability level. But, their effect was not significant on other traits. The highest grain yields were obtained from treatments T1, T12, T5, T7, T4 and T14 which resulted in the production of 17.51, 16.81, 15.99, 15.66, 15.26 and 15.25 t grains per hectare, respectively. Finally, treatments T12, T4 and T5 can be recommended for studied region given the results of all measurements and the decrease in applied water level (lower area of land was irrigated).