Cotton Planting Date and Plant Population Effects On Yield and Quality. In the Mississippi Delta

Cotton Planting Date and Plant Population Effects On Yield and Quality In the Mississippi Delta Discipline: Agronomy and Soils J. A. Wrather, University of Missouri Delta Center, PO Box 0, Portageville, MO, E mail: wratherj@missouri.edu, Phone: 1, FAX: ; B. J. Phipps, PO Box, CR, Quitman, TX ; W. E. Stevens, and A. S. Phillips University of Missouri Delta Center, PO Box 0, Portageville, MO. These studies were supported in part by the University of Missouri Agriculture Experiment Station, by the National Cotton Foundation, and the cotton farmer checkoff administered through the Cotton Incorporated State Support Committee Projects #0 MO and 0 MO. Abbreviations: High volume instrumentation, HVI. 1 JCS 1

Cotton Planting Date and Plant Population Effects On Yield and Quality In the Mississippi Delta 1 0 1 0 1 JCS

1 ABSTRACT Cotton producers in the Mississippi Delta plant in early spring, but wet, cold weather often develops then and may reduce plant population directly or indirectly. Producers must occasionally decide if replanting is necessary. The objective of these studies was to determine planting date and plant population effects on cotton yield, lint quality, and crop maturity in the Mississippi Delta. Three separate field experiments were conducted during 01 0. For the planting date plant population experiment, seed cotton yields for the late Apr. plantings were significantly greater than for other planting dates, and seed cotton yields for,,,, and,0 plants ha 1 were significantly greater than for, plants ha 1. Yield for late Apr. planted cotton at, plants ha 1 was significantly greater than or equal to yields for mid May planted cotton at all plant populations. For the planting date experiment, lint yields and percent lint were significantly greater for early than late plantings three of five years, and micronaire was significantly greater for early than late plantings each year. For the plant population experiment, lint yields were significantly greater for,,0 than, plants ha 1 two of four years. There were no plant population effects on lint quality. In all experiments, crop maturity was delayed for late planting dates and low plant populations. Producers in the Mississippi Delta should not replant cotton after mid May if the plant population from a late April planting is, or more plants ha 1. Keywords: Cotton, Gossypium hirsutum, planting date, plant population, yield, lint quality. JCS

Cotton producers in the Mississippi Delta often plant in early spring. Unfortunately, wet, cold weather often develops then in this region, and this weather sometimes contributes to reduced plant population directly through flooding or indirectly through increased seedling death due to diseases. Producers must occasionally decide in mid to late May if a lower than expected cotton plant population is acceptable or if replanting is necessary. To make informed decisions, producers in the Mississippi Delta region need information about planting date and plant population density effects on cotton yield and lint quality. Studies have been conducted in the US to determine either cotton planting date or plant population effects on yield and quality (Bilbro & Ray, ; Guthrie, 1; Jones & Wells, ), and some of these studies were reported from the Mississippi Delta region (Cathey & Meredith, ; Heitholt, ; Micinshi et al., 0; Siebert et al., 0; Smith et al., ). Only one study conducted in Greece in mid 0 reported in a refereed journal the planting date plant population effects on cotton yield (Galanopulou Sendouka et al., 0). The affect of cotton planting date and plant population interaction on yield in the US is not known but is needed to help producers make replant decisions. Our objective was to determine planting date and plant population effects and their corresponding interactions on cotton yield, lint quality, and maturity over years in the Mississippi Delta. 1 MATERIALS AND METHODS Three experiments were established to determine planting dates and plant population density effects on cotton yield and lint quality in the Mississippi Delta region of the US. The soil was a Tiptonville silt loam (fine silty, mixed, thermic, Typic Argiudoll), and the JCS

fields had been planted to cotton the two previous years. Prior to planting each year, the fields were disked twice, and row beds ( cm spacing) were formed. The top cm of the beds were pushed off just prior to planting to form a flat top ridge. University Extension recommended agronomic practices were used for weed control; fertilization; irrigation; and treatment with plant growth regulators, insecticides, and defoliants. In all experiments, each four row plot was m long and was end trimmed to m long at first open boll to eliminate end row effects on yield. Plots were defoliated as each reached 0% open boll, and plots were harvested as they reached maturity. The center rows of each plot were harvested by spindle picker. For all experiments, statistical analyses of data were performed using SAS Mixed Model procedures (SAS Institute, Cary, NC). Mean separation was evaluated through a series of protected pairwise contrasts among all treatments (Saxton, ). 1 Experiment 1: Planting Date Plant Population The planting date population experiment, conducted 0 0, was designed to determine planting date and plant population density effects on seed cotton yield. A split plot experimental design with four replications was employed to evaluate three planting dates (main plots) and four plant populations (subplots). Planting dates were late Apr., early May, and mid May in all years. The plant populations established were,,,,,, and,0 plants ha 1. The cultivar Paymaster BG/RR was planted in 0, and DPL 1 BG/RR in 0 and 0 at seed m 1 of row. Plots were hand thinned when the cotton had developed the third true leaf (Jones & Wells, JCS

). Seed cotton was weighed to determine yield. Samples of seed cotton from each plot could not be kept for lint yield and lint quality analysis due to equipment limitations. Experiment : Planting Date The planting date experiment, conducted 01 0, was designed to determine planting date effects on cotton lint yield and quality. A randomized complete block experimental design with four replications was employed to evaluate five planting dates; late Apr. to early May and then every seven to days thereafter for four subsequent plantings. The cultivar Paymaster BG/RR was planted each year at seed m 1 of row. The plant population at d after emergence each year was,000 to,000 plants ha 1 depending on seedling emergence. To compare crop maturity among treatments, the percent of bolls open was recorded during early Oct. each year. Seed cotton was ginned on a twenty saw Continental gin stand preceded by an inclined cleaner and a feeder extractor followed by one stage of lint cleaning. Lint was weighed to determine yield per plot, and the lint percent was calculated. One lint sample per plot was analyzed for quality using HVI at the International Textile Center at Texas Technical University. Lint was analyzed for micronaire, fiber length in hundredths of an inch, fiber length uniformity index, fiber strength (g tex 1 ), elongation, leaf trash (classers leaf grade), percent reflectance (Rd), and yellowness (+b) (Ramey, ). 1 Experiment : Plant Population The plant population experiment, conducted 01 0, was designed to determine plant population effects on cotton lint yield and quality. A randomized complete block JCS

experimental design with four replications was employed to evaluate four plant populations;,,,,,, and,0 plants ha 1. The cultivar Paymaster BG/RR was planted at seed m 1 of row during very late Apr. or early May each year. Plots were hand thinned when the cotton had developed the third true leaf (Jones and Wells, ). To compare crop maturity among treatments, the percent of bolls open was recorded during early Oct. each year. Cotton lint yield and fiber quality were determined as in the planting date experiment. 1 RESULTS Experiment 1: Planting Date Plant Population Analysis of variance for seed cotton yield indicated there were significant year, planting date, and plant population effects (Table 1). There was a significant year planting date interaction, and a year plant population interaction. There was a planting date plant population interaction significant at the 0.0 level. There was no year planting date plant population interaction. Seed cotton yield for the late Apr. planting was significantly greater than for the other plantings each year, and yield for the early May planting was significantly greater than for the mid May planting two of three years (data not shown). Seed cotton yields for,,,, and,0 plants ha 1 were significantly greater than for, plants ha 1 each year (data not shown). Seed cotton yield for the late Apr. planting at, plants ha 1 was significantly greater (0.0 level) than or equal to yields for the mid May planting at all plant populations (Table ). JCS

1 Experiment : Planting Date Analysis of variance indicated that year significantly affected cotton lint yield, percent lint, and all lint quality variables (Table ). Planting date significantly affected lint yield, percent lint, lint quality variables other than uniformity, and percent open bolls. There was a year planting date interaction for yield, percent lint and all lint quality variables except leaf trash and lint reflectance. Generally, cotton lint yields were significantly greater for the first two planting dates than for the other planting dates in three of five years (Table ). These results are slightly different than the results from experiment 1 that showed seed cotton yields were significantly greater for late Apr. than early and mid May plantings each year. The reason for this difference is not clear. The sites for the experiments were 1 km apart, and the weather was similar, but the cultivars planted were different some years. The percent course sand was greater in the soil where experiment 1 was conducted than where experiment was conducted. Generally, percent lint was significantly greater for the first two planting dates than for the others in three of five years (Table ). Micronaire was significantly greater for the first than the last planting date all years. Fiber length was similar for all planting dates three of five years; and it was significantly longer for the last then the first planting date two of five years. Fiber strength, fiber elongation, and lint yellowness was similar for all planting dates in three of five years but were significantly greater for the last than the first planting date in two of five years. Leaf trash varied among planting dates and was greater for the last than all other planting dates averaged over years (Table ). Lint reflectance varied among planting dates averaged over years, and trends were not apparent. Percent open JCS

bolls were similar for the first two planting dates and were significantly greater for the first two than the other planting dates averaged over years. Experiment : Plant Population Analysis of variance indicated that year significantly affected cotton lint yield, percent lint, and all lint quality variables (Table ). Plant population significantly affected cotton lint yield, lint yellowness, and percent open bolls. There was a significant year plant population interaction for yield and micronaire. Cotton lint yields were similar among plant populations in two of four years and were significantly less for, plants ha 1 than other populations in two of four years (Table ). Averaged over years, lint yellowness was generally greater for the low than high plant populations, and percent open bolls was significantly greater for the highest than lowest plant populations (Table ). 1 DISCUSSION This is the first report in the US of a cotton planting date plant population interaction for yield. Galanopoulou Sendouka et al., (0) previously reported no planting date plant population interaction for cotton yield in Greece. The differences between their results and ours may be due to environment and cultivars used. Cotton producers in many areas especially the Mississippi Delta should consider replanting cotton only if the plant population of the early planting is less than, plants ha 1. This is assuming uniform plant spacing. The impact of irregular plant spacing, skips, on yield was not a factor in these experiments but would probably greatly impact yield. JCS

1 Guthrie (1) and Cathey and Meredith () reported lint yields were significantly greater over years for early May than mid and late May plantings, and Micinski et al. (0) reported similar cotton yields for mid Apr. and mid May plantings over years. The results from our studies do not always agree with theirs. The results from our longterm experiments, site years, show that yields for late Apr. and very early May planting dates were always greater than or equal to the greatest yields for the other planting dates, but yields may be similar among planting dates some years. The study reported by Cathey and Meredith () and Micinski et al. (0) were conducted in the Mississippi Delta, but their experiments were conducted over fewer years than ours. We speculate that cotton yields may be greater for early than late plantings when the weather is suitable for seedling growth from early plantings, but cool weather after early planting may slow seedling growth resulting in yields similar to other plantings. Cotton producers in the Mississippi Delta should focus on planting as early as possible for optimum yield. We expected all lint quality variables would be greater for late Apr. and very early May plantings than later plantings, but the results do not confirm this. Our results show that percent lint and micronaire were significantly greater for early than late plantings as did Bilbro and Ray (), but fiber strength, leaf trash, and lint yellowness were significantly greater for late than for early plantings. Producers in the Mississippi Delta should plant early for the greatest percent lint and lowest leaf trash, but micronaire may be a problem for early plantings. Our results on plant population effects on cotton lint yield are similar to those reported by Siebert et al (0). However, our results do not agree with those reported by Heitholt () that lint yield was greater for 0,000 than 0,000 and 0,000 plants JCS

ha 1, by Jones and Wells () that cotton lint yield was similar for,000 and 0,000 plants ha 1, and by Smith et al. () that cotton lint yield was similar for 1, and,1 plants ha 1 and significantly greater than for, plants ha 1. The cause of these differences is not known. Producers in the Mississippi Delta should strive for a plant population of, to, plants ha 1. A greater plant population was not beneficial, and a lower population resulted in lower yields some years and later crop maturity. We did not observe any affect of plant populations on micronaire, fiber length, and strength, and these results agree with those reported by Siebert et al. (0). Late planting dates and low plant population density delayed crop maturity, and this has been observed by others (Jones and Wells ; Smith et al., ; Siebert et al., 0). Producers that save a thin stand of early planted cotton rather than replant must manage the crop for late maturity. 1 JCS

REFERENCES Bilbro, J.D. and L.L. Ray.. Effect of planting date on the yield and fiber properties of three cotton cultivars. Agron. J. :0 0. Cathey, G.W. and W.R. Meredith, Jr.. Cotton response to planting date and mepiquat chloride. Agron. J. 0:. Galanopoulou Sendouka, S., A.G. Sficas, N.A. Fotiadis, A.A. Gagianas, and P.A. Gerakis. 0. Effect of population density, planting date, and genotype on plant growth and development of cotton. Agron. J. :. Guthrie, D.S. 1. Cotton response to starter fertilizer placement and planting dates. Agron. J. :. Heitholt, J.J.. Canopy characteristics associated with deficient and excessive cotton plant population densities. Crop Sci. :1. Jones, M.A. and R. Wells.. Fiber yield and quality of cotton grown at two divergent population densities. Crop Sci. :0. JCS

Micinski, S., P.D. Colyer, K.T. Nguyen, and K.L. Koonce. 0. Effects of planting date and early season pest control on yield in cotton. J. Prod. Agric. : 0. Ramey, H.H., Jr.. Classing of fiber. p. 0. In C.W. Smith & J.T. Cothren (eds) Cotton: Origin, history, technology, and production. John Wiley & Sons, New York. Saxton, A. M.. A macro for converting mean separation output to letter groupings in Proc Mixed. Pages in: Proc. rd Annu. SAS Users Group Inter. Conf. SAS Institute, Carey, NC. Siebert, J. D., A. M. Stewart, and B. P. Leonard. 0. Comparative growth and yield of cotton planted at various densities and configurations. Agron. J. :. Smith, C.W., B.A. Waddle, and H.H. Ramey, Jr.. Plant spacings with irrigated cotton. Agron. J. 1: 0. 1 JCS

Table 1. Analysis of variance for seed cotton yield (Mg ha 1 ) for year, planting date, and plant population z Pr F Source of variation Yield Year (Y) 0.000 Planting date (PD) <.0001 Y PD <.0001 Plant population (PP) <.0001 Y PP <.0001 PD PP 0.0 Y PD PP 0. z Years were 0, 0, and 0. Planting dates were late Apr., early May, and mid May. Plant population was,,,,,, and,0 plants ha 1. JCS

Table. Planting date and plant population effects on seed cotton yield (Mg ha 1 ) averaged over years z Plant population ha 1 Plant date,,,,0 Late Apr..0 cd. b. a. ab Early May. ef.0 c. b. b Mid May. g. f. de. ef z Years were 0 0. Values followed by the same letter are not significantly different (P=0.0) JCS

Table. Analysis of variance for cotton lint yield (Mg ha 1 ), and lint quality variables for year and planting date z Pr>F Source of variation Variables Year (Y) Planting date Y * PD (PD) Yield <.0001 <.0001 <.0001 Percent lint <.0001 <.0001 <.0001 Micronaire <.0001 <.0001 <.0001 Fiber length <.0001 0.000 0.0 Fiber uniformity index <.0001 0.0 0.01 Fiber strength <.0001 0.000 0.0 Fiber elongation <.0001 0.000 0.0 Leaf trash <.0001 0.0001 0. Lint reflectance (Rd) <.0001 0.00 0.0 Lint yellowness (+ b) <.0001 <.0001 0.00 Percent open bolls 0. <.0001 0.0 z Years were 01, 0, 0, 0, and 0. Planting dates were late Apr. to very early May then every days after for four subsequent plantings. Percent lint is % seed cotton that was lint, fiber length is in hundredths of an inch, fiber strength is in grams tex 1, leaf trash is classers leaf grade, and percent open bolls was determined early Oct. each year. JCS

Table. Year and planting date effects on cotton lint yield (Mg ha 1 ) z, percent lint, lint micronaire, fiber length, fiber uniformity index, fiber strength, fiber elongation, and lint yellowness z Planting Years date 01 0 0 0 0 Yield 1 1. a 1. b 1. a 1. b 1. a 1.0 b 1.0 ab 1. a 1. ab 1. ab 0. c 1. a 0. b 1. ab 1. b 0. c 1. a 0. b 1.0 a 0. c 0. d 1. a 0. c 1. c 0. d Percent lint 1 a a a 1 a 0 a b a a 0 a 0 a b a b 1 a ab c a b 1 a bc d a c 1 a c Lint micronaire 1. a. a.0 a. a.0 a. b. ab. b.0 b. a. bc. b. c. a. a. c.0 c. c. b. ab. c. b. d.0 b.0 b JCS

Table. Continued Years Planting date 01 0 0 0 0 Fiber length 1 1. b 1. a 1. ab 1.0 b 1.0 c 1. ab 1. a 1. ab 1.0 a 1.0 b 1. ab 1. a 1. a 1. a 1.0 b 1. a 1. a 1.0 b 1.0 a 1.0 b 1. ab 1. a 1. ab 1. a 1. a Fiber uniformity index 1. a.0 b. a. b. b. a. a. a.0 ab.0 e. a.0 a. a.0 b. d. a. a.0 a. b. c. a. ab. a. a.0 a Fiber strength 1. b. a. a. a.0 d. a 0. a.0 a. a.0 cd. a. a.0 a. a. bc.0 a 0. a.0 a.0 a 0. ab. a 0. a. a. a 1. a JCS

Table. Continued Planting Year date 01 0 0 0 0 Fiber elongation 1. a. a. c. ab. bc. a. a. c. ab. c. a. a. abc. b. bc.0 a. a.0 a. ab.0 ab. a. a. ab.0 a.0 a Lint yellowness 1 1. b. a. a 0.0 b 1. b. a. a. a. a 1.0 a.0 a. a.0 a 1. a 1. ab. a. a. a. a.00 a. a.0 a.0 a 1. a 0. ab z Years were 01 0. Planting dates were very late April or early May and then every seven to ten days after for four subsequent plantings. Percent lint is % of seed cotton that was lint. Fiber length is in hundredths of an inch, and fiber strength is in grams tex 1. Values within a column by variable followed by the same letter are not significantly different (P=0.0). JCS

Table. Planting date effects on leaf trash, lint reflectance, and percent open bolls averaged over years z Planting date Leaf trash Lint reflectance Percent open bolls 1 1. bc. c 0 a 1.0 c.01 a a 1. bc. bc b 1. b. ab c. a. c c z Planting dates were very late April or early May and then every seven to ten days after for four subsequent plantings. Leaf trash is classers leaf grade. Percent open bolls was determined early Oct. each year. Values within a column followed by the same letter are not significantly different (P=0.0). JCS

Table. Analysis of variance for cotton lint yield (Mg ha 1 ), lint quality variables, and percent open bolls for year and plant population z Pr F Source of variation Variables Year (Y) Plant populat. (PP) Y * PP Yield <.0001 <.0001 0.000 Percent lint 0.00 0.0 0.0 Micronaire <.0001 0.1 0.0 Fiber length 0.000 0. 0. Fiber uniformity index 0.000 0. 0. Fiber strength 0.0001 0. 0. Fiber elongation <.0001 0. 0.0 Leaf trash 0.000 0. 0. Lint reflectance (Rd) <.0001 0. 0.01 Lint yellowness (+ b) <.0001 0.000 0. Percent open bolls 0.0 <.0001 0.01 z Years were 01, 0, 0, and 0. Plant population was,,,,,, and,0 plants ha 1. Percent lint is % of seed cotton that was lint, fiber length is in hundredths of an inch, fiber strength is in grams tex 1, and leaf trash is classers leaf grade. Percent open bolls was determined early Oct. each year. JCS 1

Table. Year and plant population effects on cotton lint yields (Mg ha 1 ) and lint micronaire Plant Year Populat. ha 1 01 0 0 0 Lint yield, 1. a 1. a 0. b 1. b, 1. a 1. a 1.0 a 1. a, 1.1 a 1. a 1. a 1. a,0 1. a 1. a 1. a 1. a Values within a column followed by the same letter are not significantly different (P=0.0). JCS

Table. Effect of plant population on lint yellowness, and percent open bolls averaged over years z Plant populat. ha 1 Lint yellowness Percent open bolls,. a c,.1 ab b,. bc a,0.0 c a z Years were 01, 0, 0, and 0. Fiber uniformity is fiber length uniformity index, and percent open bolls was determined early Oct. each year. Values within a column followed by the same letter are not significantly different (P=0.0). JCS