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Mao L.,China Agricultural University | Zhang L.,China Agricultural University | Zhang L.,Hebei Cottonseed Engineering Technology Research Center | Zhao X.,Chinese Academy of Agricultural Sciences | And 6 more authors.
Field Crops Research | Year: 2014

Modern cotton cultivation requires high plant densities and compact plants. Here we study planting density and growth regulator effects on plant structure and production of cotton when the cotton is grown in a relay intercrop with wheat, a cultivation system that is widespread in China. Field experiments were carried out in 2010, 2011 and 2012 in Anyang, Henan province, China. Plant densities (PD) were 3.0, 4.5, 6.0 and 7.5plantsm-2, and growth regulator mepiquat chloride (MC) was applied in four different schedules. Plant density significantly affected cotton biomass, but MC did not. Aboveground biomass was linearly associated with plant density. Increasing plant density significantly increased crop light use efficiency, especially during the reproductive phase. This effect was attributed to a better light distribution in the canopy, resulting in higher crop photosynthesis. MC increased the partitioning to leaves, expressed as leaf/shoot ratio. Plant height and length of fruit branches were significantly reduced by MC, resulting in a more compact canopy. Maximum leaf area index was slightly lowered at higher MC dose, but MC did not significantly affect light interception. Plant density and MC showed a significant interaction effect on crop height, but not on leaf growth, biomass or lint yield. At high plant densities, 3-4 consecutive applications of MC improved plant architecture, resulting in a higher LUE and yield. Lint yields were about 10% higher with MC applied at a high cumulative dose with high plant densities compared to MC free control. © 2013 Elsevier B.V.

Ren X.,China Agricultural University | Zhang L.,China Agricultural University | Zhang L.,Hebei Cottonseed Engineering Technology Research Center | Du M.,China Agricultural University | And 5 more authors.
Field Crops Research | Year: 2013

The growth regulator mepiquat chloride (MC) is used in cotton production across the globe to control plant growth and maximize yield and quality of cotton. With the conversion from hand picking to mechanical harvesting in China, plant densities are increased, and more compact plants are required, leading to the need to reconsider MC application schedules. Experiments were carried out in 2009 and 2010 to identify optimal use schedules of MC at four plant densities: 3.0, 4.5, 6.0 and 7.5plantsm-2. Eleven MC schedules were compared with respect to their effect on cotton yield and quality. Application of MC at squaring stage or at both squaring and flowering stages significantly improved cotton quality parameters: fiber length (by 1.7%) and fiber strength (by 2.8%) at all tested plant densities without significant loss of yields. However, average lint yield of all MC treatments over all densities and years was decreased by 4.6% due to a decrease in boll density and lint percentage which was only partly offset by an increase in boll weight. No effects on yield were also observed if MC applications were started at flowering stage, but such later starting application schedules only slightly improved fiber quality. The results suggest that use of MC at squaring or at both squaring and flowering stages is a viable strategy to improve cotton architecture, productivity and quality at high plant density in mechanized cotton production in the Yellow River cotton growing region in China. © 2013 Elsevier B.V.

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