Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton
1
CSIRO Agriculture and Food, GPO Box 1700, Canberra, ACT 2601, Australia
2
Formerly CSIRO Agriculture and Food, Australian Cotton Research Institute, Narrabri, NSW 2390, Australia
*
Author to whom correspondence should be addressed.
Agronomy 2022, 12(4), 869; https://doi.org/10.3390/agronomy12040869
Submission received: 25 January 2022
/
Revised: 21 March 2022
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Accepted: 28 March 2022
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Published: 31 March 2022
(This article belongs to the Section Innovative Cropping Systems)
Abstract
:Research investigating row spacing in high-yielding, high-input cotton (Gossypium hirsutum L.) production systems has found higher lint yields but no maturity benefits using high plant density, 25 cm spaced ultra-narrow rows (UNR). Seven experiments comparing 38 cm UNR and conventionally spaced rows (100 cm) were conducted over three years to determine if changes in plant density or management could optimize yield and maturity in a high-input UNR cotton production system. Two of these experiments compared 25, 38 and 100 cm spaced rows under different intra-row plant density (12 to 36 plants m−2). Three experiments managed 38 cm UNR and 100 cm spaced rows separately and one had extra early application of nitrogen and water. Across the seven experiments there were no differences in lint yield or crop maturity for 38 cm UNR compared to conventionally spaced rows. The only significant response to changes in inter- or intra-row density or agronomic management was an 18% increase in handpicked lint yield in the 12 plants m−2 38 cm UNR treatment compared to the same plant density in 100 cm spaced rows in one of the two experiments. This stability of yield response across row spacings indicates that there is an opportunity to reduce seed rates whilst maintaining yields in high-input UNR systems. UNR cotton did not require any difference in mepiquat chloride or nitrogen management compared with conventionally spaced cotton, nor did extra early inputs of nitrogen or water, and we concluded that is likely that the current recommendations for mepiquat chloride or nitrogen nutrition in conventionally spaced systems are appropriate for managing high-input UNR cotton crops.
1. Introduction
In shorter-season production areas there is strong interest in developing cotton production systems that reduce the time from planting to harvest. Reducing the time to crop maturity can lead to potential savings in irrigation water and insecticide spray costs. Shorter crop cycles also allow cool temperatures to be avoided at the beginning and end of the season which can affect crop establishment, yield and fiber quality.
Ultra-narrow row (UNR) cotton systems, with rows spaced less than 40 cm apart, that increase plant density while providing a more equidistant spacing around the plants than conventionally spaced rows, have long been seen as potential systems for optimizing yield and maturity [1] in regions that have short seasons or limited yield potential.
Conceptually, UNR systems achieve earlier maturity through shortening the fruiting window by producing fewer bolls per plant; and maintain yield by increasing the number of plants per unit area [2]. A high plant population limits the resources available to the individual plant, which may restrict growth leading to smaller plants with fewer fruit [3,4]. Earlier maturity can be achieved in the smaller UNR plants if most of the fruit that are set are on the lower part of the plant and are first position fruit as the time between fruit development on successive fruiting branches is shorter than time to develop fruit along a fruiting branch (second or third position fruit) [5]. In practice, yield benefits have been highly variable and differences in crop maturity inconsistent in both low input and in high-input, high yielding (>1800 kg ha−1 lint) UNR cotton production systems [6,7,8,9,10].
Previous experiments grown under high-input management [11] with the yield of both the conventionally spaced and UNR treatments yielding >1800 kg ha−1. found a significant increase in lint yield, across a number of years, but no differences in maturity or fiber quality [10,12,13,14]. A growth analysis of a subset of those experiments indicated that the major factors affecting crop growth and development of the UNR crop were differences between the two row spacings in light interception and conversion efficiency [15]. The higher plant population in the UNR crop led to high early light interception, with most of the light in the UNR canopy being intercepted in the top part of the canopy. LAI continued to develop in the UNR crop after maximum light interception had been reached. Boll size was smaller and fruit retention lower in the UNR crop and may have been due to limitations in assimilate supply to individual plants in the UNR crop due to lower RUE. In a high-input system where growth and development are not usually limited by access to water or nutrients the plant density in the 25 cm UNR row spacings (36 plants m−2; 360,000 plant ha−1) may have been too high.
Reducing inter-row plant densities or increasing row spacing from 25 cm to 38 cm UNR spacings may alleviate inter-plant competition in high-density 25 cm UNR spaced rows by providing a more equidistant spacing between plants. An intermediate density has been recommended by some authors to achieve more consistent early maturity in cotton [16,17,18]. Plants are more evenly spaced when sown in narrower row spacings and the efficiency of light interception can be improved, which has been found in corn, sorghum, soybean and sunflowers [19]. One limitation to reducing plant densities in UNR cotton in the past has been the need to plant at high densities to produce short, columnar plants to allow efficient stripper harvesting [20]. Recommended densities for commercial production in the region of this study are 12 plants m−2 for 100 cm spaced rows; 24 plants m−2 for 38 cm spaced rows; and 36 plants m−2 for 25 cm spaced rows.
Plant competition effects in high density UNR crops may be overcome through changes in agronomic management. Earlier studies investigating yield and maturity in high-input 25 cm UNR systems applied the same management (nutrition, growth regulators and irrigation timing) to both the 100 cm and the 25 cm spaced row treatments [10,12,13,14]. If crop growth is slower in a UNR crop, monitoring and managing the crop according to its requirements may also optimize yield and maturity. Alternatively providing the UNR crop with increased early applications of nitrogen and water may increase early crop growth and alleviate the effects of increased plant competition on yield and maturity in UNR crops.
In this paper we tested the following hypotheses for UNR systems using transgenic high fruit retention and herbicide resistant cultivars: (i) reducing inter plant competition in UNR by increasing UNR inter-row spacing from 25 to 38 cm would reduce the time to crop maturity while maintaining yields; (ii) reducing plant densities would optimize yield and maturity in high yielding UNR production systems; and (iii) managing UNR (38 cm) for mepiquat chloride and nitrogen applications according to crop requirements would increase yield and reduce time to crop maturity compared to 100 cm row spaced systems.. and (iv) increasing early inputs of nitrogen and water would alleviate plant competition and optimize yield and maturity in the UNR (38 cm) spaced crops. To eliminate potential differences in machine harvesting efficiencies in the three row spacings, all three row spacings were handpicked to enable assessment of the intrinsic differences between the systems.
2. Materials and Methods
2.1. Cultural and Climatic Details
Seven field experiments were conducted over three growing season and at three locations in New South Wales, Australia with distinct climates and soil types typical of Australian production systems (Table 1).
Narrabri is a semi-arid environment of northwest New South Wales, Australia. Mean annual rainfall is 660 mm with a mean maximum temperature of 26.5 °C and a mean minimum of 11.7 °C. The soil was uniform gray cracking clay (Typic Haplustert). These soils are alkaline and have a high clay fraction.
Hillston, is an arid environment of south-west New South Wales, Australia. Annual rainfall is 360 mm with a mean maximum temperature of 24.2 °C and mean minimum of 10.9 °C. The soil was red clay with a sodic sub-soil (Chromic Haplustert). These soils are alkaline and have a high clay fraction.
Hay is an arid environment of south-west New South Wales, Australia. Annual rainfall is 370 mm with a mean maximum temperature of 24.3 °C and mean minimum of 10.0 °C. The soil was brown cracking clay (Typic Haplustert). These soils are alkaline and have a high clay fraction. Both Hay and Hillston are production areas that have shorter growing seasons for cotton in Australia.
All experiments were established and grown with full irrigation using non-limiting nitrogen and thorough insect control as described in [21]. Crops were checked regularly for the presence of pests, which were controlled as required according to standard thresholds for Bollgard II® cotton [22]. Experiments were defoliated in preparation for harvest when all treatments reached 60% of bolls open. Details of all experiments are summarized in Table 1.
2.1.1. Row Spacing by Plant Density Experiments
Exps. 1 and 2 were conducted to compare yield and crop maturity of cotton grown under different combinations of row spacings and plant densities to test the hypothesis that reducing inter-plant competition in UNR by changing the inter- and intra-row densities would reduce the time to crop maturity while maintaining yield. Both experiments were sown with two target plant densities (12 and 24 plants m−2) across three row spacings (25, 38 and 100 cm spaced rows) with a third target plant density (36 plants m−2) for the 25 cm row spacing treatment.
Experiment 1 was sown 4 November 2005, and Experiment 2 was sown 17 October 2006 at the Australian Cotton Research Institute, near Narrabri. The experiment was a randomized complete block design with five replicates. All row spacings were planted on 2 m wide beds with a furrow either side of the bed for irrigation.
2.1.2. Responsive Management Experiments
Exps. 3, 4, 5 and 6 were conducted to compare yield and maturity of cotton grown with 38 cm UNR and conventionally spaced (100 cm) rows with each treatment monitored and managed separately according to each treatment’s requirement (responsive management). Treatments were also compared to control management treatments where the same management was applied to both row spacing treatments. These experiments were conducted to test the hypothesis that managing row spacings separately according to crop requirements would optimize yield and maturity in UNR (38 cm) spaced treatments.
Exp. 3 was sown in Narrabri, Exps. 4 and 6 in Hillston and Exp. 5 in Hay. Exps. 3, 4, 5 and 6 had a randomized complete block design with 4 replicates. Exps. 3, 4, and 6 were planted on 2 m wide beds with a furrow either side of the bed for irrigation. In Exp. 5 was planted on 100 cm wide beds with a furrow either side of the bed for irrigation. For the 38 cm UNR treatment in Exp. 5 two rows spaced 38 cm apart were planted on each 100 cm bed (19 cm from bed center). In the conventionally spaced treatment in Exp. 5 one row was planted on each 100 cm bed (centered on bed).
In each treatment plant height and nodes were monitored for vegetative growth rates to assess the need for application growth regulator (mepiquat chloride) using guidelines in Constable [23]. Petioles were sampled in each treatment to determine the need for additional N application using guidelines specified in Rochester et al., [24]. All other management practices were applied uniformly across all treatments.
2.1.3. Nitrogen and Irrigation Experiment
Exp. 7 was conducted to compare yield and maturity of cotton grown comparing 38 cm UNR and conventionally spaced (100 cm) rows to increased early inputs of water and nitrogen to test the hypothesis that these inputs would alleviate early plant competition and optimize yield and maturity in the UNR (38 cm) spaced cropsExp. 7 was grown at the Australian Cotton Research Institute, near Narrabri. Exp. 7 had a split-plot design with 4 replicates. Main plots irrigation treatments and row spacing and nitrogen were sub-plots. All row spacings were planted on 2 m wide beds with a furrow either side of the bed for irrigation. Nitrogen treatments were normal N treatment (120 kg N ha−1 applied one month prior to sowing), and an extra N treatment of 60 kg N ha−1 applied prior to first normal irrigation (57 days after sowing). Irrigation treatments were normal irrigation treatment and an extra irrigation treatment applied prior to first square (43 days after sowing).
2.2. Measurements
In each experiment, established plant densities were measured by counting the number of plants in 10 m2 section in each plot (5 m in row length and from furrow to furrow in a 2 m bed or two adjacent 1 m beds) (Table 2). Time to maturity (defined as days after sowing (DAS) to 60% bolls open), lint yield and fiber quality were determined. To measure maturity, all open bolls in a 2 m2 section in each plot were handpicked weekly. In all row spacing treatments all open bolls were taken from all rows across the 2 m bed (furrow to furrow) or from two adjacent 1 m beds for 1 m in row length. This sampling began once three bolls m−2 had opened (open bolls defined as when two sutures on the boll dehisce) and continued until the last boll had opened. Maturity was determined by calculating the date at which 60% of the bolls had opened. As the three row spacings require different harvesting techniques, a 2 m2 section in each plot was handpicked at maturity to distinguish difference in lint yield and fiber quality without the confounding effects of differences in harvesters affecting these parameters. The seed cotton samples were ginned in a 10-saw gin (Continental Eagle Corp, Prattville, AL, USA). Lint yields (g m−2) were calculated from ginned lint sample weights. Fiber quality of ginned lint samples was measured using a Spinlab High Volume Instrument (HVI) model 900 (Zellweger Uster, Knoxville, TN, USA). Fiber upper half mean (UHM) length, micronaire, strength, uniformity percent (ratio between the mean length and UHM length) and short fiber index (proportion by weight of fiber shorter than 12.7 mm).
2.3. Statistical Analysis
To test for difference between 38 cm UNR and conventionally spaced systems a combined analysis of the standard management treatments across all experiments was undertaken using generalized linear modeling (GLM). In this analysis the main factors were row spacing and experiment (Exp. + row spacing treatment), and the random factors replicate (rep). In Exp. 1 and 2 row spacing, plant density, and their interaction were compared using GLM. Due to the unbalanced design for plant density only the 12 plants m−2 and 24 plants m−2 treatments were compared for main effects. Regression analyses were used to calculate 60% open bolls from weekly hand picks. Statistical analyses were conducted using Genstat 11 software (Lawes Agricultural Trust, IACR, Rothamsted, UK). Unless stated otherwise significant difference were considered at 95% confidence intervals (p < 0.05).
3. Results and Discussion
3.1. 38 cm UNR Does Not Differ in Yield, Maturity or Fiber Quality
Maturity did not differ significantly between 38 cm row spacings and conventionally spaced rows in the combined analysis across the seven experiments (Table 3). For lint yield the combined analysis showed no differences between the 38 cm UNR and conventionally spaced rows (Table 3). Gin out-turn, boll number and fiber quality parameters were not different between the 38 cm UNR and conventionally spaced rows (Table 3). Boll size however, was lower in the 38 cm UNR treatments across the seven experiments.
This study confirms the findings of recent studies into 25 cm spaced rows by Brodrick et al., [10], and have not found any potential to gain earlier maturity while maintaining yield across high yielding, high-input production systems for UNR spacings. The results of this study with few differences in yield and yield components in high plant density 38 cm spaced rows compared to earlier studies in high-input high plant density 25 cm spaced rows by Brodrick et al. [10], suggests that the yield potential of a 25 cm UNR system may be higher than 38 cm spaced UNR. The higher yields gained through a three-fold increase in plant density in 25 cm spaced rows was due to increased boll numbers per m2 but this was not significantly increased by a two-fold increase in plant density in a 38 cm UNR crops; furthermore the reduction in boll size indicates there may still be some limitations in assimilate production in the 38 cm UNR crop at high plant densities. It does not appear that inter-plant competition is reduced significantly to gain earlier maturity or increase lint yield in a high-input high plant density 38 cm UNR crop.
3.2. A More Equidistant Plant Density Did Not Increase Yield or Reduce Time to Crop Maturity
Exps. 1 and 2 sought to investigate whether inter-plant competition in UNR crops could be alleviated by reducing plant densities and result in earlier crop maturity or higher yields compared with similar plant densities in conventionally spaced crops. There were significant interactions for lint yield between row spacing and plant densities in Exp. 1 (Table 4). There was higher lint yield in the lower plant density treatment for the 38 cm row spacing compared with both plant densities in the 100 cm row spacing treatment and the higher plant density in the 38 cm treatment in the first year, suggesting there may be a yield advantage with more equidistant arrangement of plants, however, this relationship was not repeated in the second year or in any of the other treatments. This study found no consistent relationship between increased plant density and row spacing or between 38 cm and 25 cm inter-row spacings, which suggests that any potential for higher yields with these spacings, may be achieved without a corresponding increase in plant density. Economically this would significantly reduce the costs of UNR cotton production with current recommended densities of 12 plants m−2 making seed cost 2.41% ($96 ha−1) of the variable cost of cotton production in a high-input system in Australia to 4.83 % ($192 ha−1) and 7.23% ($288 ha−1) for 24 plants m−2 and 36 plants m−2 [25]. In irrigated experiments in the U.S.A. decreasing plant density did not decrease lint yield in 38 cm spaced rows [26] and in one study lower plant densities (<12.4 plants m−2) increased lint yield in the 38 cm spaced rows by over 300 kg lint ha−1 [27]. A recent study in China found that narrow spaced rows (at the same or lower plant density) yielded higher than similar plant densities in UNR spacings and the authors postulated that lower plant densities might maintain yields similar to in this study [28].
There were also no differences in DAS to crop maturity between different row spacing treatments or plant density in Exp. 1 or 2 (Table 4). Variation in crop maturity was very small with LSDs across all data of 1.9 days for Exp. 1 and 1.4 days for Exp. 2. Gwathmey et al. [26] reported that at the lowest plant density in their experiment (3.6 plants m−2 in 76 cm spaced rows) maturity was delayed up to 7 days later than the earliest treatments (plant densities of 10.8 to 21.5 plants m−2) but there were no differences in maturity the 76 cm and 38 cm spaced rows at the higher plant densities.
The higher gin turnout (lint %) in UNR spacings in Exp. 2 compared to the 100 cm row spacings suggests there may have been limitations in assimilates for boll and seed development (seed number or size) (Table 5). However, these differences were not found in Exp. 1. Boll number was significantly higher in Exp. 2 for UNR spacings compared with 100 cm spaced rows but not in Exp. 1 (Table 5).
The only significant effect of plant density across the two experiments was a smaller average boll size in the 24 plants m−2 treatment in Exp. 1; however, this difference did not lead to a significant effect on lint yield or other yield components (Table 5).
Like lint yield, there were few effects on fiber quality parameters with inter- or intra-row density, apart from a significant interaction between inter- and intra-row densities for length (Table 6). In Exp. 1, shorter length in the 25 cm 12 plants m−2 treatment was just outside the ideal length for upland cotton in Australia (28.6 mm), however it was not low enough to attract discounts. This relationship was not repeated in the second year of the study. Gwathmey et al. [26] reported increased micronaire in one year of their study in lower plant densities but not the other. Few other studies have found consistent differences in fiber quality between different row spacings or plant densities [8,16,27,29,30].
As most of the research into cotton’s response to UNR production systems has been in low-input systems, it may be that competition for resources has led to inconsistent yield and maturity responses reported in those systems. Conversely, a high-input production system where growth of the plant less limited during the growing season may negate any benefits of closer plant spacing. Alternatively, the distance between plants within a row (intra-row) between the lowest and highest densities in this study may not be large enough to have a significant effect (8 cm × 100 cm between plants at a density of 12 plants m−2 in 100 cm spaced rows compared with 8 cm × 38 cm between plants at a density 24 plants m−2 in 38 cm spaced rows) on an indeterminate plant like cotton grown in good growing conditions in a row crop system.
3.3. 38 cm UNR Did Not Require Different Management to Conventionally Spaced Rows
In the four responsive management experiments (Exp. 3, 4, 5 and 6), monitoring of vegetative growth rates and petiole sampling neither row spacing required either mepiquat chloride application or additional nutrient application. As there were no difference in management between the control plots and responsive management plots, only the control plots were harvested for yield and maturity to be included in the combined analysis. The use of mepiquat chloride was often considered in the past to be essential in the management of UNR cotton in low-input systems. It is important to limit crop height when harvesting with a stripper harvester [20], but the use of a spindle harvester for 38 cm rows does not have the same limitation. However, the effects of mepiquat chloride have rarely been compared with the same treatments on conventionally spaced cotton and are often inconsistent. In a high yielding system Brodrick et al. [10] compared 25 cm and conventionally spaced rows and found that there was no interaction between mepiquat chloride application and row spacings. In a comparison of 38 cm UNR with conventionally spaced rows, where yields exceeded 1700 kg ha−1, Wilson, et al. [31] found no interactions between mepiquat chloride and row spacing. Jones [32] in a two-year study of 19 cm, 38 cm and 76 cm row spacings reported no response in lint yield to four different mepiquat chloride application rates. Nichols et al. [33] reported a yield increase in UNR to mepiquat chloride application in only one year of their three-year study. Gwathmey [34,35] reported a 7% increase in lint yield in UNR treatments with mepiquat chloride applications compared to untreated treatments. Allen et al. [36] found that mepiquat chloride reduced yields in UNR.
The outcomes of the responsive management experiments in this study support monitoring and applying mepiquat chloride in UNR systems following the guidelines developed for conventionally spaced systems. In high-input systems in Australia, the most commonly used indicator of when growth is excessive and the application of mepiquat chloride may be needed is when average internode length exceeds 5.5 cm [23].
3.4. 38 UNR Cotton Did Not Respond to an Extra Early Application of Water or Nitrogen
The extra early irrigation treatment in Exp. 7 did not lead to an increase in lint yield in the UNR crop but rather led to increases in lint yield in the conventionally spaced treatments (Table 7). This increase in lint yield in the conventionally spaced treatments was accompanied by an increase in time to crop maturity and increased boll size and fiber length but there was no difference in these measurements for the UNR treatments (Table 7). There were no interactions between the extra nitrogen application and row spacing for lint yield or maturity but gin out-turn was slightly lower in response to increase nitrogen for the conventionally spaced treatment and slightly higher in the UNR treatments. Boll size in the conventionally spaced treatment was higher in response to the extra application of nitrogen but there was no change in boll size in the UNR treatments. Most studies into agronomic management of low-input UNR cotton systems have found that nitrogen requirements are similar to that of conventionally spaced cotton [37,38,39,40]. Some studies have, found however, that the nitrogen requirements of UNR have been than conventionally spaced cotton higher [41]. McConnell et al., [42] found that increased nitrogen delayed maturity in UNR cotton in some instances. A recent study comparing typical and limited irrigation regimes also found that there was no interaction between growth and yield in UNR or conventionally spaced cotton [43]. The lack of response to the extra irrigation or nitrogen suggests that the limitations on crop growth and yield in the UNR system are not related to early water or nitrogen stress. These results are important as they indicate that increasing early inputs did not alleviate the competition stress between plants in the UNR crops and that limitations on growth and yield may be due to more complex physiological processes (e.g., light competition) occurring in the crop in response to increase plant density.
4. Conclusions
This study aimed to determine whether high-input UNR cotton production systems required different nitrogen or mepiquat chloride management or changes in plant density to optimize yield and time to crop maturity. UNR crops did not require any differences in management of nitrogen or mepiquat chloride compared to conventionally spaced crops. Importantly, yield and maturity do not appear to respond to increase early inputs indicating that there may be other limitations on crop growth in high-input UNR cotton production systems. Neither did changes in both inter- and intra-row plant densities affect yield, maturity or quality providing the opportunity to establish UNR spacings at lower plant densities than currently recommended, providing significant saving in production costs. Further research into the key physiological processes of UNR production is continuing in order to understand and optimize the cotton grown under UNR in Australian production systems; to determine why under high-input production systems UNR cotton does not mature earlier and identify any limitations to plant growth and development in UNR cotton production systems.
Author Contributions
R.R. and M.B. contributed to the design and implementation of the research, to the analysis of the results and to the writing of the manuscript. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the Cotton Cooperative Research Centre. Wee Waa Road, P.O. Box 59, 2390 Narrabri, Australia. Project Number: 1.03.03.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
Thanks to. Jane Caton and Darin Hodgson for assistance in the field, Bruce McCorkell for his statistical expertise, the late Rochester, Liu and Constable for helpful discussions about the results, and Cotton Seed Distributors for provision of planting seed. We gratefully acknowledge the support of our grower cooperators Tony Hely (Ramps Ridge Rural), Matthew Mitchell (Lachlan Farming Ltd.) and Malcolm Pritchard (Twynam Pastoral Co.).
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
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Table 1.
Details of experiments investigating yield and maturity of ultra-narrow cotton systems.
| Experiment Type | Year | Location | Cultivar | Planting Date | Plot Size | Applied N kg ha−1 | Number of Irrigations | Number of Insecticide Sprays |
|---|---|---|---|---|---|---|---|---|
| Row spacing × plant density | 2005/06 | Narrabri (1) z | Sicot 71BR | 4 November 2005 | 8 (wide) × 13 m (long) | 200 | 7 y | 9 x |
| 2006/07 | Narrabri (2) | Sicot 71BR | 17 October 2006 | 8 × 13 m | 120 | 8 | 6 | |
| Responsive management | 2005/06 | Narrabri (3) | Sicot 71BR | 4 November 2005 | 6 × 75 m | 200 | 7 | 9 |
| 2005/06 | Hillston (4) | Sicot 71BR | 11 October 2005 | 16 × 748 m | 220 | 7 | 3 | |
| 2005/06 | Hay (5) | Sicot 71BR | 5 October 2005 | 8 × 688 m | 220 | 10 | 5 | |
| 2007/08 | Hillston (6) | Sicala 60BRF | 12 October 2007 | 10 × 40 m | 205 | 8 | 2 | |
| Extra early inputs | 2006/07 | Narrabri (7) w | Sicot 71BR | 17 October 2006 | 96 × 728 m | 120 | 8 | 6 |
z Number in parenthesis specifies the experiment number. y Each irrigation refilled the soil profile to near field capacity each time; an addition of approximately 90–100 mm at each irrigation, typical of commercial practice. x Insecticides applied when pest level exceeded thresholds leading to yield damage. Various chemicals applied, primarily for green mirids (Creontiades dilutus), two-spotted mites (Tetranychus urticae) and aphids (Aphis gossypii). w This experiment included an extra treatment that provided the crop access to additional water and nitrogen early.
Table 2.
Means of established plant densities for all treatment in each experiment.
| Experiment/Target Plant Density | Row Spacing/ Established Plant Density Plants m−2 | ||
|---|---|---|---|
| 100 z | 38 | 25 | |
| plants m−2 | cm | cm | cm |
| Experiment 1 | |||
| 12 | 12.1 | 13.8 | 14.9 |
| 24 | 22.1 | 27.1 | 27.2 |
| 36 | - | - | 36.1 |
| Experiment 2 | |||
| 12 | 17.1 | 13.5 | 18.8 |
| 24 | 26.2 | 32.2 | 30.9 |
| 36 | - | - | 49.1 |
| 24 | - | - | - |
| Experiment 3 | |||
| 12 | 10.9 | - | - |
| 24 | - | 21.6 | - |
| Experiment 4 | |||
| 12 | 9.9 | - | - |
| 24 | - | 23.1 | - |
| Experiment 5 | |||
| 12 | 14.4 | - | - |
| 24 | - | 21.9 | - |
| Experiment 6 | |||
| 12 | 21.3 | - | - |
| 24 | - | 31.4 | - |
| Experiment 7 | |||
| 12 | 15.9 | - | - |
| 24 | - | 30.8 | - |
z Row spacing used to generate differences in plant density.
Table 3.
Summary of significant differences from combined analysis of experiments for lint yield, maturity, yield components, and fibre quality. Error df = 28, row spacing treatment df = 1, experiment df = 4, and spacing × experiment df = 4 for all variables except for boll number and boll size where error df = 22, row spacing treatment df = 1, experiment df = 3, and spacing × experiment df =3.
Table 3.
Summary of significant differences from combined analysis of experiments for lint yield, maturity, yield components, and fibre quality. Error df = 28, row spacing treatment df = 1, experiment df = 4, and spacing × experiment df = 4 for all variables except for boll number and boll size where error df = 22, row spacing treatment df = 1, experiment df = 3, and spacing × experiment df =3.
| Variable | Row Spacing Treatment y | |
|---|---|---|
| L.S.D.0.05 | p-Value | |
| Lint yield, g m−2 | 17.7 | 0.521 |
| DAS z to maturity, 60% open bolls | 2.02 | 0.057 |
| Gin out-turn, % | 0.4 | 0.034 |
| Final boll number, bolls m−2 | 9.0 | 0.104 |
| Mean boll size, g boll−1 | 0.20 | 0.004 |
| Fiber length, decimal inches | 0.017 | 0.172 |
| Micronaire | 0.17 | 0.757 |
| Fiber strength, g tex−1 | 0.7 | 0.140 |
| Fiber length uniformity, % | 0.8 | 0.298 |
z DAS, days after sowing. y Experiment × row spacing interaction was significant for lint yield, maturity, boll number and micronaire.
Table 4.
Yield and days after sowing (DAS) to maturity for Exps. 1 and 2 comparing inter and intra row plant density. LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
Table 4.
Yield and days after sowing (DAS) to maturity for Exps. 1 and 2 comparing inter and intra row plant density. LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
| Experiment/Treatment/Effect | Row Spacing | Row Spacing | ||||||
|---|---|---|---|---|---|---|---|---|
| 100 cm | 38 cm | 25 cm | Density Mean | 100 cm | 38 cm | 25 cm | Density Mean | |
| Lint Yield | DAS to Maturity | |||||||
| Exp. 1 | (g m−2) | (60% open bolls) | ||||||
| 12 plants m−2 z | 274.5 | 325.5 | 308.0 | 303.2 | 150.5 | 146.4 | 148.2 | 148.4 |
| 24 plants m−2 | 286.5 | 283.3 | 308.3 | 290.0 | 148.1 | 148.1 | 148.2 | 148.1 |
| 36 plants m−2 | 279.7 | 148.0 | ||||||
| Row Spacing Mean | 280.5 | 297.4 | 298.7 | 149.4 | 147.2 | 148.1 | ||
| LSD Row Spacing | 19.8 | 2.8 | ||||||
| LSD Density | 16.0 | 2.5 | ||||||
| LSD Row Spacing × Density | ** 28.0 y | 4.5 | ||||||
| Exp. 2 | ||||||||
| 12 plants m−2 | 224.8 | 235.4 | 236.9 | 232.4 | 152.9 | 154.1 | 152.8 | 153.2 |
| 24 plants m−2 | 232.2 | 253.3 | 244.7 | 243.4 | 154.2 | 152.8 | 152.5 | 153.1 |
| 36 plants m−2 | 258.4 | 152.8 | ||||||
| Row Spacing Mean | 228.5 | 244.0 | 247.0 | 153.6 | 152.7 | 153.4 | ||
| LSD Row Spacing | 24.9 | 2.1 | ||||||
| LSD Density | 21.2 | 1.9 | ||||||
| LSD Row Spacing × Density | 36.7 | 3.2 | ||||||
z Target plant density (plants m−2). y ** p < 0.01.
Table 5.
Gin out-turn, boll number and boll size for Exps. 1 and 2 comparing inter and intra row plant density. LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
Table 5.
Gin out-turn, boll number and boll size for Exps. 1 and 2 comparing inter and intra row plant density. LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
| Experiment/Treatment | Row Spacing | Row Spacing | Row Spacing | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 100 cm | 38 cm | 25 cm | Density Mean | 100 cm | 38 cm | 25 cm | Density Mean | 100 cm | 38 cm | 25 cm | Density Mean | |
| Gin Out-Turn | Mean Boll Number | Mean Boll Size | ||||||||||
| Exp. 1 | (%) | (m−2) | (g boll−1) | |||||||||
| 12 plants m−2 z | 42.8 | 43.1 | 43.1 | 43.0 | 138.4 | 155.3 | 149.4 | 147.7 | 5.03 | 4.88 | 4.77 | 4.90 |
| 24 plants m−2 | 43.2 | 43.0 | 43.5 | 43.2 | 140.8 | 147.5 | 151.3 | 146.6 | 4.53 | 4.59 | 4.45 | 4.53 |
| 36 plants m−2 | 43.4 | 148.1 | 4.34 | |||||||||
| Row Spacing Mean | 43.0 | 43.0 | 43.3 | 139.7 | 149.7 | 150.1 | 4.72 | 4.68 | 4.57 | |||
| LSD Row Spacing | 0.3 | 10.5 | 0.24 | |||||||||
| LSD Density | 0.3 | 9.2 | ** 0.15 y | |||||||||
| LSD Row Spacing × Density | 0.6 | 16.1 | 0.26 | |||||||||
| Exp. 2 | ||||||||||||
| 12 plants m−2 | 44.3 | 45.4 | 45.6 | 45.1 | 106.2 | 127.8 | 122.5 | 118.8 | 4.62 | 4.40 | 4.45 | 4.49 |
| 24 plants m−2 | 43.9 | 44.9 | 45.2 | 44.7 | 111.0 | 131.2 | 130.2 | 124.2 | 4.45 | 4.29 | 4.30 | 4.35 |
| 36 plants m−2 | 45.4 | 146.0 | 4.07 | |||||||||
| Row Spacing Mean | 44.1 | 45.1 | 45.4 | 108.6 | 129.5 | 132.9 | 4.54 | 4.34 | 4.28 | |||
| LSD Row Spacing | ** 0.6 | ** 13.3 | ** 0.20 | |||||||||
| LSD Density | 0.5 | * 9.9 | ** 0.14 | |||||||||
| LSD Row Spacing × Density | 0.9 | 17.1 | 0.24 | |||||||||
z Target plant density (plants m−2). y * p < 0.05, ** p < 0.01.
Table 6.
Fiber quality for experiments comparing inter and intra row plant density (Exps. 1 and 2). LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
Table 6.
Fiber quality for experiments comparing inter and intra row plant density (Exps. 1 and 2). LSDs are presented for comparison between plant densities, row spacing and the interaction between row spacing and plant density.
| Experiment/Treatment | Row Spacing | Row Spacing | Row Spacing | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 100 cm | 38 cm | 25 cm | Density Mean | 100 cm | 38 cm | 25 cm | Density Mean | 100 cm | 38 cm | 25 cm | Density Mean | |
| Micronaire | Strength | Length | ||||||||||
| Exp. 1 | (g tex−1) | (mm) | ||||||||||
| 12 plants m−2 z | 4.5 | 4.6 | 4.6 | 4.6 | 29.94 | 29.44 | 29.38 | 29.59 | 1.13 | 1.14 | 1.11 | 1.13 |
| 24 plants m−2 | 4.4 | 4.4 | 4.5 | 4.4 | 30.46 | 29.46 | 30.54 | 30.15 | 1.14 | 1.12 | 1.16 | 1.14 |
| 36 plants m−2 | 4.5 | 30.40 | 1.14 | |||||||||
| Row Spacing Mean | 4.5 | 4.5 | 4.5 | 30.20 | 29.45 | 30.11 | 1.14 | 1.13 | 1.14 | |||
| LSD Row Spacing | 0.2 | 0.80 | 0.02 | |||||||||
| LSD Density | 0.2 | 0.68 | 0.02 | |||||||||
| LSD Row Spacing × Density | 0.3 | 1.22 | 0.04 | |||||||||
| Exp. 2 | ||||||||||||
| 12 plants m−2 | 4.9 | 4.8 | 4.8 | 4.8 | 31.33 | 31.05 | 30.90 | 31.09 | 1.13 | 1.09 | 1.11 | 1.11 |
| 24 plants m−2 | 5.0 | 4.8 | 4.9 | 4.9 | 31.48 | 31.85 | 30.95 | 31.43 | 1.10 | 1.12 | 1.10 | 1.10 |
| 36 plants m−2 | 5.0 | 30.65 | 1.09 | |||||||||
| Row Spacing Mean | 5.0 | 4.8 | 4.9 | 31.40 | 30.83 | 30.83 | 1.11 | 1.10 | 1.10 | |||
| LSD Row Spacing | 0.2 | 0.94 | 0.03 | |||||||||
| LSD Density | 0.2 | 0.82 | 0.02 | |||||||||
| LSD Row Spacing × Density | 0.3 | 1.42 | 0.04 | |||||||||
z Target plant density (plants m−2).
Table 7.
Means for significant interactions in Exp. 7. Means for the normal irrigation and normal nitrogen × row spacing treatments for all variables are presented in Table 4, Table 5 and Table 6.
| Variable | Normal Irrigation | Extra Irrigation | Normal Nitrogen | Extra Nitrogen |
|---|---|---|---|---|
| Lint yield, g m−2 | ||||
| 100 cm | 227.7 | 296.6 | ||
| 38 cm UNR z | 267.2 | 265.4 | ||
| LSD0.05 row spacing × irrigation | 27.7 | |||
| DAS y to maturity, 60% open bolls | ||||
| 100 cm | 149.7 | 152.9 | - | - |
| 38 cm UNR | 152.2 | 150.7 | - | - |
| LSD0.05 row spacing × irrigation | 3.2 | |||
| Gin out-turn, % | ||||
| 100 cm | 44.0 | 44.0 | ||
| 38 cm UNR | 45.0 | 45.0 | ||
| LSD0.05 row spacing × nitrogen | 0.002 | |||
| Mean boll size, g boll−1 | ||||
| 100 cm | 4.82 | 5.81 | 5.08 | 5.56 |
| 38 cm UNR | 4.46 | 4.44 | 4.21 | 4.69 |
| LSD0.05 row spacing × irrigation | 0.47 | |||
| LSD0.05 row spacing × nitrogen | 0.54 | |||
| Fiber length, decimal inches | ||||
| 100 cm | 1.079 | 1.100 | ||
| 38 cm UNR | 1.088 | 1.064 | ||
| LSD0.05 row spacing × irrigation | 0.033 |
z UNR, ultra-narrow row. y DAS, days after sowing.
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Roche, R.; Bange, M. Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton. Agronomy 2022, 12, 869. https://doi.org/10.3390/agronomy12040869
AMA Style
Roche R, Bange M. Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton. Agronomy. 2022; 12(4):869. https://doi.org/10.3390/agronomy12040869
Chicago/Turabian StyleRoche, Rose, and Michael Bange. 2022. "Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton" Agronomy 12, no. 4: 869. https://doi.org/10.3390/agronomy12040869
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