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Optimizing irrigation strategies is crucial for sustaining cotton production in the face of growing water scarcity. The three-year experimental study (2020–2022) focused on the impact of varying irrigation amounts (320, 370, and 420 mm) and frequencies (4-, 8-, and 12-day intervals) on cotton growth, yield, yield components, and fiber quality in southern Xinjiang. Employing a completely randomized design with three replications, the results indicated higher irrigation amounts resulted in numerically 2.5–7.5% higher lint yields compared to those under medium and low irrigation amounts, notably significant in 2021. Boll density emerged as the primary yield component influencing yield loss due to irrigation amount, followed by seed cotton weight boll−1. Increased boll density was associated with a greater total number of fruiting sites. Additionally, the increased seed cotton weight boll−1 could be linked to an increased seed number boll−1 and a decreased boll fraction at the lower fruiting branches with lower seed cotton weight boll−1. Higher irrigation frequency improved lint yield by increasing boll density, though a significant effect was observed only in 2020. Increased irrigation amounts generally led to longer fiber lengths but lower micronaire values, while increased irrigation frequency resulted in longer, stronger fibers and reduced micronaire values. Furthermore, the highest yield stability was observed under the condition of high irrigation amount and high frequency. This study holds certain guiding significance for water resource management in cotton production in arid regions. [ABSTRACT FROM AUTHOR]

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Optimizing irrigation strategies is crucial for sustaining cotton production in the face of growing water scarcity. The three-year experimental study (2020–2022) focused on the impact of varying irrigation amounts (320, 370, and 420 mm) and frequencies (4-, 8-, and 12-day intervals) on cotton growth, yield, yield components, and fiber quality in southern Xinjiang. Employing a completely randomized design with three replications, the results indicated higher irrigation amounts resulted in numerically 2.5–7.5% higher lint yields compared to those under medium and low irrigation amounts, notably significant in 2021. Boll density emerged as the primary yield component influencing yield loss due to irrigation amount, followed by seed cotton weight boll−1. Increased boll density was associated with a greater total number of fruiting sites. Additionally, the increased seed cotton weight boll−1 could be linked to an increased seed number boll−1 and a decreased boll fraction at the lower fruiting branches with lower seed cotton weight boll−1. Higher irrigation frequency improved lint yield by increasing boll density, though a significant effect was observed only in 2020. Increased irrigation amounts generally led to longer fiber lengths but lower micronaire values, while increased irrigation frequency resulted in longer, stronger fibers and reduced micronaire values. Furthermore, the highest yield stability was observed under the condition of high irrigation amount and high frequency. This study holds certain guiding significance for water resource management in cotton production in arid regions.

The balance between vegetative and reproductive growth is the central objective in the cotton production system, which is associated with cotton maturity and yield. In China, manual topping (MT) has been performed many years prior to or during the flowering period to inhibit vegetative growth and enhance reproductive growth. MT is gradually being replaced by chemical topping (CT) with mepiquat chloride (MC, 180 g ha−1, 98% soluble powder) due to labor shortages and increasing labor cost. To determine whether CT influences cotton maturity and yield relative to MT, we carried out field experiments at four locations in the Yellow River Valley of China during 2018–2020. The results showed that CT did not alter the boll age, and although it produced taller and slender spatial boll distribution under several environments, it had little effect on the accumulation of boll fraction (the number of bolls in a given period divided by total boll number) over time at the end of blooming across locations. As a result, there were no significant differences between MT and CT in boll opening percentage in the late season. CT did not influence yield or yield components, except under severe drought. Therefore, CT with MC (180 g/ha, 98% soluble powder) during the flowering period will not compromise the maturity or yield of cotton in the Yellow River Valley of China. Similar outcomes would be achieved in other areas with similar ecological conditions and social conditions that require an alternative to extensive manual labor. [ABSTRACT FROM AUTHOR]

The balance between vegetative and reproductive growth is the central objective in the cotton production system, which is associated with cotton maturity and yield. In China, manual topping (MT) has been performed many years prior to or during the flowering period to inhibit vegetative growth and enhance reproductive growth. MT is gradually being replaced by chemical topping (CT) with mepiquat chloride (MC, 180 g ha−1, 98% soluble powder) due to labor shortages and increasing labor cost. To determine whether CT influences cotton maturity and yield relative to MT, we carried out field experiments at four locations in the Yellow River Valley of China during 2018–2020. The results showed that CT did not alter the boll age, and although it produced taller and slender spatial boll distribution under several environments, it had little effect on the accumulation of boll fraction (the number of bolls in a given period divided by total boll number) over time at the end of blooming across locations. As a result, there were no significant differences between MT and CT in boll opening percentage in the late season. CT did not influence yield or yield components, except under severe drought. Therefore, CT with MC (180 g/ha, 98% soluble powder) during the flowering period will not compromise the maturity or yield of cotton in the Yellow River Valley of China. Similar outcomes would be achieved in other areas with similar ecological conditions and social conditions that require an alternative to extensive manual labor.

Planting density affects crop microclimate and intra-plant competition, playing an important role on yield formation and resource use, especially in areas where the cotton is grown at relatively high plant densities in Xinjiang, China. However, more studies are needed to examine how the change in planting density affects the microclimate factors such as the fraction of light intercepted (FLI), air temperature(T) and relative humidity (RH) within different canopy layers, which in turn affect the boll number per plant (BNF), boll number per unit area (BNA), boll weight (BW), and boll-setting rate (BSR) at fruiting branch (FB) positions FB1-3, FB4-6, and FB-≥7 in cotton. To quantify he relationships between boll characteristics, yield, and microclimate factors, we conducted a 2-year field experiment in 2019-2020 in Xinjiang with six plant densities: 9 (P1), 12 (P2), 15 (P3), 18 (P4), 21 (P5), and 24 (P6) plants m-2 With each three plants m-2 increase in density, the average FLI and RH across different canopy layers increased by 0.37 and 2.04%, respectively, whereas T decreased by 0.64 °C. The BNF at FB≥7, FB4-6, and FB1-3 decreased by 0.82, 0.33, and 0.5, respectively. The highest BNA was observed in the upper and middle layers in the P4 treatment and in the lowest canopy layer with the P5. The highest BW was measured in the middle canopy layer for P3, and the highest BSR was measured in the lower layer for P3. Plant density exhibited linear or quadratic relationships with FLI, T, and RH. Microclimate factors mainly affected the boll number in each layer, but had no significant effects on the BW in any layer or the BSR in the middle and lower layers. Cotton yield was non-linearly related to plant density. The 2-year maximum yield was achieved at a plant density of 21 plants m-2, but the yield increase compared to the yield with a density of 18 plants m-2 was only 0.28%. Thus, we suggest that the optimal plant density for drip-irrigated cotton in Xinjiang is 18 plants m-2, which could help farmers grow machine-harvested cotton. [ABSTRACT FROM AUTHOR]

Abstract Background Within-canopy interception of photosynthetically active radiation (PAR) impacts yield and other agronomic traits in cotton (Gossypium hirsutum L.). Field experiments were conducted to investigate the influence of 6 cotton varieties (they belong to 3 different plant types) on yield, yield distribution, light interception (LI), LI distribution and the relationship between yield formation and LI in Anyang, Henan, in 2014 and 2015. Result The results showed that cotton cultivars with long branches (loose-type) intercepted more LI than did cultivars with short branches (compact-type), due to increased LI in the middle and upper canopy. Although loose-type varieties had greater LI, they did not yield significantly higher than compact-type varieties, due to decreased harvest index. Therefore, improving the harvest index by adjusting the source-to-sink relationship may further increase cotton yield for loose-type cotton. In addition, there was a positive relationship between reproductive organ biomass accumulation and canopy-accumulated LI, indicating that enhancing LI is important for yield improvement for each cultivar. Furthermore, yield distribution within the canopy was significantly linearly related to vertical LI distribution. Conclusion Therefore, optimizing canopy structure of different plant type and subsequently optimizing LI distribution within the cotton canopy can effectively enhance the yield.

Highlights • Water deficit and nematode infection negatively affected seedcotton yield. • Increased water availability did not offset nematode-induced yield loss. • Yield loss was associated with declines in boll density not boll mass. • Boll distribution patterns were similar for both stresses. • Drought most negatively affected boll retention at positions further from the mainstem. Abstract Both root-knot nematode (RKN) infection and water deficit negatively affect yields in many cotton growing regions of the southern United States. The objective of the current study was to determine whether seedcotton yield limitations due to drought and RKN infection were brought about through similar effects on yield components and boll distribution patterns. To this end, yield component and boll distribution assessments were conducted for a seven-year study in Tifton, Georgia that included three irrigation treatments and two fumigant treatments to manage nematodes. Seedcotton yield was strongly affected by year, irrigation treatment and fumigant treatment, but no interactions were observed between the two factors, illustrating that the yield limiting effects of nematode infection could not be mitigated by providing a water-replete condition. Yield declines due to nematode infection and water deficit were primarily driven by a decline in total boll density. Yield distribution patterns revealed that water deficit negatively affected boll numbers for all branch types and at all positions along a fruiting; furthermore, the mainstem node of peak boll distribution was lower under drought. The trend was similar for nematode infected plants (except that boll density at position two was not affected by fumigation and retention at position three increased slightly). One notable difference between drought and nematode effects was that the relative decline in boll density for drought-stressed plants was greater at sympodial positions further from the mainstem, but this was not the case due to nematode infection. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium spp.) boll distribution captures important aspects of fruit development and adaptation over a long period of time. However, due to its complex fruiting habit, it is possible that the boll distribution patterns may not accurately identify the level of sink strength with respect to fruiting locations. Plant and box mapping data collected from producer fields in Georgia in 2009 (Burke and Colquitt, 5 cultivars) and from experimental fields in Texas from 2011 to 2013 (Halfway and Lubbock, 18 cultivars) were analyzed to determine the actual level of carbon sink strengths with respect to the center of mass end-of-season and to gain a better understanding of the regulation of carbon accumulation within a plant. Results showed that the end-of-season boll distribution obscures the level of sink strength in the middle of the plant. The node cohort-center of sink strength was determined to be above the node cohort-center of mass end-of-season when cotton plants were grown under a high-yielding and indeterminate growing condition. On the other hand, the node cohort-center of sink strength was located below the node cohort-center of mass under a determinate situation and low-yielding environment. This difference in the level of sink strength may have been a low risk-taking strategy by the plant to survive under a limiting-environment by partitioning resources toward early-produced fruit at the expense of later-produced fruit. These carbon accumulation dynamics quantify the propensity of cotton plants to shift production toward a conservative strategy of earlier fruiting under conditions that encourage determinate growth and toward additional risk when growing conditions favor growth, relative to the final boll distribution. • End-of-season cotton boll distribution obscures the level of carbon sink strength. • Center of sink strength is above the center of mass under indeterminate conditions. • Center of sink strength is below the center of mass under determinate conditions. [ABSTRACT FROM AUTHOR]

Nitrogen can be critical in determining fiber yield and quality in cotton. Major purpose of this 3-years (2017, 2018, and 2019) study in Faizabad-Iran was to investigate the effect of nitrogen rates, excess on the need for maximum yield and its interaction with environment on fiber quality of bolls with different spatial and temporal distribution in cotton canopy. Field experiment was a split-plot design with four replications. Main plots included two nitrogen rates (LN: 100 and HN: 200 kg ha−1). Sub plots included four boll growth habits: U P E R –Upper bolls Early in the season; L O E R –Lower bolls Early in the season; U P L A –Upper bolls Late in the season; L O L A –Lower bolls Late in the season. Results showed that fiber yield and fiber quality in terms of fiber uniformity and fiber strength were not affected by experimental factors and their interactions. In all years, LN led to an optimum micronaire (3.5–4.9 µg inch−1) and medium length (25.4–28.6 mm) fibers in all growth habits. However, in 2017, HN combined with lower temperature (25.2 °C) during the boll development decreased LAI to boll number ratio (source restriction), delayed maturity, and shifted fiber yield to U P L A boll growth habit with fine (micronaire < 3.5 µg inch−1) and short length (< 25.4 mm) fibers. In 2018 and 2019 with 1.7 °C and 2.3 °C higher temperatures than 2017, HN increased LAI to boll number ratio (sink restriction), led accelerated maturity, and shifted fiber yield to U P E R and L O E R boll growth habits, while with the increase of nitrogen, the difference between growth habits in terms of fiber quality was observed only in 2018 that led to production of coarse (micronaire > 4.9 µg inch−1) and long length (> 28.6 mm) fibers in U P E R and L O E R growth habits. In 2019, the lowest lint yield distribution was observed in U P L A treatment, but the fiber quality parameters were similar in all growth habits. These results may conclude that nitrogen consumption, in excess of what required for maximum yield, affects the source-sink relationship and leads to the formation of bolls with different fiber quality within a canopy, and the response of these processes to nitrogen is affected by the environment. • High N did not improve fiber yield but decreased fiber quality. • Low N led to an optimum micronaire and medium-length fibers in all seasons. • In cold weather, high N led to fine and short fibers. • In warm weather, high N led to coarse and long length fibers. • High N changed lint yield contribution and its quality within canopy. [ABSTRACT FROM AUTHOR]

Planting density affects crop microclimate and intra-plant competition, playing an important role on yield formation and resource use, especially in areas where the cotton is grown at relatively high plant densities in Xinjiang, China. However, more studies are needed to examine how the change in planting density affects the microclimate factors such as the fraction of light intercepted (FLI), air temperature(T) and relative humidity (RH) within different canopy layers, which in turn affect the boll number per plant (BNF), boll number per unit area (BNA), boll weight (BW), and boll-setting rate (BSR) at fruiting branch (FB) positions FB 1-3 , FB 4-6 , and FB ≥7 in cotton. To quantify the relationships between boll characteristics, yield, and microclimate factors, we conducted a 2-year field experiment in 2019-2020 in Xinjiang with six plant densities: 9 (P1), 12 (P2), 15 (P3), 18 (P4), 21 (P5), and 24 (P6) plants m -2 . With each three plants m -2 increase in density, the average FLI and RH across different canopy layers increased by 0.37 and 2.04%, respectively, whereas T decreased by 0.64 °C. The BNF at FB ≥ 7 , FB 4-6 , and FB 1-3 decreased by 0.82, 0.33, and 0.5, respectively. The highest BNA was observed in the upper and middle layers in the P4 treatment and in the lowest canopy layer with the P5. The highest BW was measured in the middle canopy layer for P3, and the highest BSR was measured in the lower layer for P3. Plant density exhibited linear or quadratic relationships with FLI, T, and RH. Microclimate factors mainly affected the boll number in each layer, but had no significant effects on the BW in any layer or the BSR in the middle and lower layers. Cotton yield was non-linearly related to plant density. The 2-year maximum yield was achieved at a plant density of 21 plants m -2 , but the yield increase compared to the yield with a density of 18 plants m -2 was only 0.28%. Thus, we suggest that the optimal plant density for drip-irrigated cotton in Xinjiang is 18 plants m -2 , which could help farmers grow machine-harvested cotton., Competing Interests: The authors declare there are no competing interests., (©2021 Zhang et al.)