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Deficit irrigation is a new strategy to increase water use efficiency of cotton in arid areas, but it is not clear if it interacts with plant density. The objective of this study was to determine the effects of deficit irrigation and plant density as well as their interaction on the growth, yield and fiber quality of irrigated cotton. Two field experiments were conducted at three sites in 2013 and one site from 2014 to 2015 in an arid area of Xinjiang. A randomized complete block design with three replicates was used to determine the effects of 6 irrigation regimes on seedcotton yield in the first experiment, while a split-plot design was used in the second experiment with the main plots assigned to irrigation regime (saturation, regular and deficit) and the subplots to plant density (high, medium and low) to examine cotton yield, fiber quality and water productivity as affected by plant density under deficit irrigation. Averaged across the three sites, drip irrigation ranging from 3650 to 4700 m 3 /ha did not significantly affect cotton yield, but seedcotton yield under 3650 m 3 /ha in S1 was 6.3% lower than that under 4000 m 3 /ha. Thus, it is quite appropriate to regularly drip-irrigate at 4000 m 3 /ha in the experimental area. Deficit irrigation at high plant density also maintained a relatively higher leaf area index (LAI) and net assimilation rate (NAR), particularly at late stages of plant growth and development, than saturation or regular irrigation. Plant density ranging from 18 to 24 plants/m 2 produced more seedcotton than 12 plants/m 2 under regular irrigation. Increasing irrigation to saturation levels had little effects on cotton yield regardless of plant density; saturation irrigation at high plant density even reduced cotton yield compared with regular irrigation at medium plant density. Under deficit irrigation, the high plant density produced 9.1-17% greater yield and 9.3-16.8% higher irrigation water productivity (IWP) than low or medium plant density, and comparable yield to medium or high plant density under regular irrigation. This high yield under deficit irrigation at high plant density was due to increased plant biomass occasioned by high plant population and improved harvest index. Deficit irrigation did not affect fiber quality in 2014, but reduced fiber length and increased fiber micronaire value in 2015. Conclusively, use of high plant density under deficit irrigation can be a promising alternative for water saving without compromising cotton yield under arid conditions. [ABSTRACT FROM AUTHOR]

Plant density, nitrogen (N) fertilization rate and plant pruning are important measures used globally to cultivate cotton. A typical combination of 52,500 plants ha −1 , intensive pruning and 255 kg N ha −1 has been widely applied in the Yellow River Valley of China. The main objective of this study is to determine whether more beneficial combinations exist than the typical one for profitable cotton production in this region. Using a split–split plot design with four replications, we conducted a three-year field experiment to study the individual and interaction effects of plant density (52,500 and 82,500 plants ha −1 ), plant pruning (intensive and extensive) and N fertilizer rate (195 and 255 kg N ha −1 ) on yield, plant biomass and partitioning, N uptake and use efficiency, as well as input and output values. The results showed that cotton yield was affected by individual and interaction effects of the three agronomic factors. When planted at a moderate density (52,500 plants ha −1 ), the seedcotton yield of intensively pruned cotton under a low N rate (195 kg N ha −1 ) and of extensively pruned cotton under low and high (255 kg N ha −1 ) N rates was reduced by 6.9, 6.7 and 5.4%, respectively, whereas the four combinations with high plant density (82,500 plants ha −1 ) produced a yield value that was comparable to that of the typical combination, indicating a relatively stable yield at high plant density irrespective of pruning mode and N rate. Vegetative branches of the extensively pruned cotton accounted for 18.7–23.6% of the total biomass at moderate plant density compared with only 2.8–2.9% of the total biomass at high plant density. At moderate plant density, intensively pruned cotton exhibited a higher harvest index than the extensively pruned plants. By contrast, the harvest index for the four combinations with high plant density did not differ, suggesting a relatively stable harvest index among these combinations. There was no difference in the N biomass utility index (NBI) among all combinations. The combination of high plant density, extensive pruning and reduced N rate had a 6.7% lower nitrogen yield utility index (NYI) than the typical combination but a 5.4% higher NYI than the combination of high plant density, extensive pruning and high N rate. More importantly, the combination of high plant density, extensive pruning and reduced N rate produced comparable yield with less input, leading to 21.7% more net revenue than the typical combination. Our results support the use of high plant density, reduced N rate and extensive pruning to ensure profitable cotton production in the Yellow River Valley and other cotton-growing areas with similar ecologies. [ABSTRACT FROM AUTHOR]

Cotton ( Gossypium hirsutum L.) yield under extensive field management across a certain range of plant population densities can be stabilized by manipulating the number of bolls and boll weight, but little is known of similar yield stability under intensive management and how the yield stability is achieved by dry matter accumulation and partitioning under various plant densities. A field experiment was conducted to study the effects of plant density (1.5, 3.3, 5.1, 6.9, 8.7 and 10.5 plants m −2 ) on dry matter accumulation and partitioning in relation to cotton yield. The seedcotton and lint yields at 1.5 plants m −2 were significantly lower than those at other plant densities, but there was little difference in either seedcotton or lint yield among plant densities ranging from 3.3 to 10.5 plants m −2 . Plant biomass increased gradually with increasing plant density. The ratio of dry weight of fruiting forms to plant biomass (DWFF/PB) at 135 days after sowing (DAS) at 1.5 plants m −2 exceeded those under 5.1 plants m −2 by 12.3%, 6.9 plants m −2 by 12.7%, 8.7 plants m −2 by 20.5% and 10.5 plants m −2 by 21.8%. Also, the harvest index at 1.5 plants m −2 exceeded those at 5.1, 6.9, 8.7 and 10.5 plants m −2 densities by 16.2, 16.2, 34.3, 38.7%, respectively. Seedcotton yield was positively correlated with total biomass at extremely low plant density (1.5 plants m −2 ), but was better correlated with DWFF/PB at higher densities (5.1–10.5 plants m −2 ). The boll weight of the last harvest was 6.0–6.3% lower than those of the first two harvests at 1.5 plants m −2 . Leaf senescence as indicated by reduced Pn and leaf area index (LAI) in later season occurred earlier at 1.5 plants m −2 than other plant densities. It was concluded that cotton yield is relatively stable across a wide range of plant densities even under intensive field management. The stability was achieved mainly through manipulation of dry matter accumulation and partitioning. The reduced boll weight of the last harvest was mainly due to earlier leaf senescence at 1.5 plants m −2 , which might explain the lower cotton productivity per unit ground area at such a low plant density. [ABSTRACT FROM AUTHOR]

Abstract: Plant density and nitrogen fertilization are two important practices for field-grown cotton (Gossypium hirsutum L.). The objective of this study was to investigate the effects of plant density and N fertilization rate, especially their interactions, on yield, yield components, late-season leaf senescence and Cry1Ac expression in Bt (Bacillus thuringiensis) cotton under salinity conditions. To achieve this goal, we conducted a three-year experiment with a high-yielding Bt cotton cultivar (SCRC 28) in a moderately saline (ECe=11dS/m) field, using a split-plot design in the Yellow River Delta of China. The main plots were assigned to low, medium and high plant densities (3.0, 5.25 and 7.5plants/m2), while low, moderate and high nitrogen rates (120, 225 and 300kgN/ha) were assigned to the subplots. Biological yield, lint yield, yield components, harvest index, boll load, Cry1Ac expression and leaf senescence were significantly affected by plant density and N rate. Lint yield was also affected by plant density×N rate interaction. Increased plant density or N rate enhanced biological yield, but reduced harvest index. Considerably high lint yield (1604kg/ha) was achieved only with a high dose of N fertilizer under low plant density, but comparable yields (1693 and 1643kg/ha) were achieved with moderate and low N rate under medium and high plant density. Increased plant density and N rate reduced boll load, which had highly significant negative correlation with late-season leaf photosynthesis (r =−0.928) and significant correlation with Cry1Ac protein concentration (r =−0.8131). Leaf senescence was delayed by increasing plant density and N rate mainly due to reduced boll load and a combination of reduced boll load and nutritional effect. Medium plant density with moderate N rate or high plant density with low N rate would enhance cotton yield and moderate Cry1Ac expression at reduced cost in the Yellow River Delta of China and other areas with similar ecologies. [Copyright &y& Elsevier]

Abstract: As the most important cultural practices for cotton production, the single effects of plant density and [nitrogen (N) and potassium (K)] fertilization on yield and yield components are well documented but their combined effects on Bt cotton are poorly understood. Using a split–split plot design with four replications, we conducted a two-year field experiment in two fields, one with lower fertility and the other with higher fertility, in the Yellow River Valley of China. The aim was to evaluate both the individual and combined effects of plant density and nitrogen and potassium fertilization on yield, yield components and uptake of major nutrients. The main plots were assigned to plant density (4.5 and 7.5plants/m2), while nitrogen (0 and 240kgN/ha) and potassium fertilization (0 and 150kgK/ha) were assigned to the sub- and sub–subplots. Lint yield was improved with high plant density (7.5plants/m2) in the lower fertility field, particularly without N and K application, but not in the higher fertility field. Nitrogen or K application also increased lint yield, and a combination of high plant density, N and K application further improved lint yield in the lower fertility field, while only K application increased lint yield in the higher fertility field. Lint percentage was not affected by any of the variables studied. Thus, the yield increase due to plant density, fertilization or their combinations was attributed to increases in boll number or boll weight. The ratio of seed cotton to stalk (RSS) was linearly correlated with harvest index, and thus can be a simple indicator of dry matter allocation to reproductive structures. Increased yield due to plant density and fertilization was mainly attributed to the enhanced biological yield in the lower fertility field, while the yield increase due to K fertilization was mainly due to increased RSS in the higher fertility field. The plants used approximately equal N and P to produce 100kg lint in both fields, but the uptake of K to produce 100kg lint in the higher fertility field was about 21% more than that in the lower fertility field. Ratios of N:P:K were 1:0.159:0.604 in the lower fertility field and 1:0.159:0.734 in higher fertility field. This study suggests that K fertilization was extremely important for maintaining high yield, although luxury consumption occurred in the higher fertility field; N was applied more than required in the highly fertile field, and increased plant density would be beneficial to cotton yield in the lower fertility field. [Copyright &y& Elsevier]

Manual removal of the main-stem growth tip is traditionally used to break the apical dominance of cotton (Gossypium hirsutum L.). Chemical topping with plant growth regulators also effectively inhibits apical dominance. However, the effect of chemical topping on yield increases and whether plant density or ecological conditions affect its efficacy are unclear. Therefore, a three-year field experiment with a split-plot design was conducted to determine the effects of plant topping, plant density, and their interactions on cotton yield and related physiological and agronomical parameters at three sites with different ecological conditions in China. In each site, the main plots were assigned low, moderate, or high plant density and the subplots were assigned no topping, manual topping, or chemical topping. Growth, yield, yield components, earliness, and late-season leaf photosynthesis as well as labor and material inputs were examined each year. Compared with no topping, both chemical and manual topping greatly reduced plant height at all sites. Manual topping increased seed cotton yield and earliness in all tested plant densities and sites. However, plant density but not ecological condition greatly mediated the effect of chemical topping on yield. At low plant density, the yields with chemical topping were 4–6% lower than those with no topping and 5.5–10.8% lower than those with manual topping at the three sites. Although yields with chemical topping were comparable with those of manual topping at moderate and high plant densities, they were 8.6–12.8% higher at moderate density and 13.8–16.4% higher at high plant density than those with no topping across years and sites. Averaged across the sites, chemical topping reduced biological yield by 12.7% at low plant density. Although biological yield decreased slightly, chemical and manual topping increased the harvest index by 12.4% and 13.3% at moderate density and by 15.6% and 17.4% at high density, respectively. In comparison with no topping, the reduction in seed cotton yield with chemical topping at low plant density was attributed to insufficient biological yield, whereas the increase in yield at moderate and high plant densities was mainly due to greater partitioning of assimilates to reproductive tissues. Compared with manual topping, chemical topping produced 23.2% lower net returns as a result of lower seed cotton yield at low plant density but produced 8.1% and 20.9% higher net returns at moderate and high plant densities, respectively, because of savings in labor inputs and comparable seed cotton yields. In addition, chemical topping increased the earliness percentage compared with that of no topping. Overall, this study demonstrates that chemical topping is a promising alternative to traditional manual topping under moderate or high cotton plant density. • Manual topping increased cotton yield regardless of plant densities and ecological conditions relative to non-topping. • Chemical topping decreased yield at low plant density relative to non-topping because of greater biomass reduction. • Chemical topping increased cotton yield at moderate and high plant densities via greater assimilates partitioning to fruits. • Chemical topping could replace manual topping at moderate and high plant densities without ecological dependence. [ABSTRACT FROM AUTHOR]

Abstract: Cotton is usually managed with a normal planting production system (NPPS) that involves planting in mid-April at a moderate plant density (4.5plants/m2) in the Yellow River Valley of China, but drought or cold stress in spring often delays cotton planting, and results in reduced yield and maturity at this plant density. Two experiments were conducted for 4 consecutive years, to test if yield and fiber quality can be maintained or improved by increased plant density for relatively late-planted cotton. Results in the first experiment in 2001 and 2002 showed that average lint yields were not significantly affected by plant density (3.0, 4.5, 6.0 or 7.5plants/m2) or by planting date (mid-April or early May), but significant interactions between planting date and plant density on lint yield were detected in both years. Normal planted cotton at a plant density of 3.0–4.5plants/m2, and late-planted cotton at 7.5plants/m2 produced higher lint yield than other planting date and density combinations. Experiment 2 compared NPPS with a late planting production system (LPPS) which involves planting in early May at 7.5plants/m2 over 2 years. The NPPS and LPPS had similar lint yields in both years. Cotton plants in both systems produced approximately 75% of total lint in the first two harvests, indicating no significantly delayed earliness in LPPS relative to NPPS. Fiber from late-season bolls exhibited reduced strength and micronaire in both systems, but there were no significant differences in fiber properties for early- and mid-season fiber between the two systems. In terms of green leaf area index and leaf chlorophyll content, leaf senescence or premature senescence of cotton plants was considerably alleviated by either altered source to sink balance or the uptake of K in LPPS compared to NPPS. It was concluded that the LPPS, a relatively late-planted cotton production system with increased plant density under intensive field management, might be a potential alternative for growing cotton. [Copyright &y& Elsevier]