ABSTRACT

Nitrogen (N), phosphorus (P) and potassium (K) fertilizer use in cotton production remains important.  Data from a long-term experiment initiated in 1972 was used to evaluate effects of N, P and K fertilization on upland cotton lint yield and lint quality in Oklahoma.  The experimental design was a randomized complete block with four replications. Eleven treatments containing different rates of N-P-K were evaluated for each of three cultivars (Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR). Analysis of variance (ANOVA) was carried out initially using general linear models (GLM) procedure in SAS. Using this preliminary analysis a quadratic plateau model for lint yield against N rates was evaluated for each cultivar using nonlinear (NLIN) procedure in SAS. Application of all the three nutrients had some effect on lint yield although most of the response was attributed to N (all cultivars) and to some extent P (Paymaster 2326 BG/RR). The critical N rate for Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR was 45, 45 and 67 kg N ha^-1 with a corresponding plateau lint yield of 734, 1156 and 1468 kg ha^-1, respectively. The results for all quality factors suggest that K fertilization is a key to better quality while N rates greater than 90 kg ha^-1 significantly deteriorate lint quality variables with continuous application of N, P and K fertilizers.

 
INTRODUCTION

The availability of N, P, K, and water are the major constraints in cotton (Gossypium hirsutum L.) production in most cotton producing environments (Morrow and Krieg, 1990). Nitrogen is generally considered a yield limiting factor in both dry-land and irrigated cotton production systems with due focus on optimizing lint yield, while avoiding excessive applications that reduce quality (Hutmacher et al., 2004).

Mullins and Burmester (1990) and Unruh and Silvertooth (1996) reported that the cotton crop contains about 22.7-25.0 kg N bale^-1.  According to Gerik et al. (1994) deficiency of N in cotton can reduce both vegetative and reproductive growth, induce premature senescence leading to potential yield loss. Alternatively, N in excess of cotton crop requirement promotes vegetative development often at the expense of reproductive development especially at bloom or at early boll fill (Mullins and Burmester, 1990; Howard et al., 2001; Tewolde and Fernandez, 1997). Excess N can indirectly affect lint yield by enhancing aphid (Aphis gossypii Glover) infestation which can complicate cotton defoliation (Cisneros and Godfrey, 2001) and can cause sticky cotton problems due to aphid honeydew secretions (The University of Arizona, 1999; Slosser et al., 1999).

In a three-year experiment Fritschi et al. (2003) found that lint yield was increased linearly each year with N fertility levels, attaining a maximum yield of 1842 kg ha^-1 at the 224 kg N ha^-1 rate. They found that with increased N, gin turnout was decreased at one location although not significant at the other sites. Several research findings reported that the yield advantages due to optimal N application were attributed to larger bolls at a greater number of fruiting sites (Boquet and Breitenbeck, 2000; Boquet et al., 1994; McConnell et al., 1998; Moore, 1999). Boquet (2005) reported that increasing N rates from 90 to 157 kg N ha^-1 did not result in increased lint yield in irrigated or rain-fed cotton.

One aspect of N nutrition in cotton is its effect on lint quality. Fritschi et al. (2003) reported a positive linear relationship between fiber strength and N fertility level from a three year study. Others, for example Boman and Westerman (1994) showed no relationship between fiber strength and N rate. In their study, Bauer and Roof (2004) found that lower lint quality including fiber length, length uniformity and fiber strength was observed in plots that did not receive N fertilization.

Several factors including soil type affect cotton response to P. The critical level of P is a function of actual concentration of the labile pool that in turn determines the available P at a given time during the growth of cotton (Crozier et al., 2004). Bronson et al. (2003) reported that several variables including early P accumulation, biomass, and lint yields positively responded to P fertilization in calcareous soils. Reiter and Kreig (2000) reported some positive and notable P effects on lint fiber quality factors although both lint yield and lint quality were driven more by moisture availability than P.

Potassium influenced cotton lint yield by affecting late season growth. According to Pettigrew (2003) K fertilization of cotton increased yield by 9% in 2 out of 3 years. In that experiment K showed little effect on lint quality. The positive effect of K on lint quality characteristics have been documented in several reports (Bennet et al., 1965; Pettigrew, 1999; Pettigrew and Meredith, 1997). According to these authors its effect on fiber quality characteristics tended to be more critical than its effect on lint yield, especially when deficiency is expected in a field. Growth rate and maturity of cultivars were reported to be important factors with K and its effect on fiber quality (Pettigrew et al., 1996; Pettigrew, 1999).

Early maturing genotypes of cotton are more susceptible to K deficiency than late maturing cultivars (Pettigrew, 1999). This shows that assessment of K nutrition in today’s cotton production will remain significant since current cotton cultivar improvement strategies involve hastening maturity. These types of cultivars when grown under limited K will become deficient of the nutrient and plants can be forced to terminate reproductive growth and subsequently reduce lint yield (Pettigrew et al., 1996) to some extent and quality to a larger extent. Pettigrew et al. (2005) reported that lint yield in eight out of nine genotypes did not increase with the application of 112 kg K ha^-1, but had a positive effect on lint quality. According to Minton and Ebelhar (1991) K deficiency is also known to affect lint yield and quality indirectly through exacerbating root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood).

The benefit of N and P fertilizer nutrients largely depends on the input responsiveness of cotton cultivars (Nichols et al., 2004) as with the case for K shown above. According to Meredith et al. (1997) over time N responsive cotton cultivars have been developed focusing on early maturity, more determinate growth habits. Most cotton cultivars under production today are far more input responsive than older cultivars as a result of improved agronomic practices, breeding, molecular genetics and transgenic traits, and boll weevil (Anthonomous grandis boheman) eradication in most cotton producing regions of the U.S. The principal objective of the experiment was to evaluate effects of N, P and K fertilization on upland cotton lint yield and lint quality in Oklahoma.

 

MATERIALS AND METHODS

One long-term experiment was established in 1972 on the western side of the Irrigation Research Station at Altus, OK on a soil that had previously been in continuous cotton under conventional tillage since 1964. Data from 1989-2004 was used to evaluate effects of N, P and K fertilization on cotton lint yield and quality. The soil is classified as a Tillman-Hollister clay loam (fine, mixed, thermic Typic Paleustolls). Soil test characteristics (samples collected from the check plots in 1988) of the experimental site are given in Table 1. The plot dimensions were six rows wide (1.02 m row spacing) by 18.3 m long. The experimental design was a randomized complete block with four replications. Eleven treatments containing different rates of N-P-K were evaluated. These were: a check (0-0-0 kg N-P-K ha^-1), six N rates (0, 45, 90, 135, 180 and 225 kg ha^-1 at a fixed rate of 20-75 kg P-K ha^-1), three P rates (0,39 and 59 kg ha^-1 at a fixed rate of 135-75 kg N-K ha^-1), and  an additional treatment of 135-20-0 kg N-P-K ha^-1. The N, P, and K fertilizer sources used were ammonium nitrate (34-0-0 N-P-K), triple super phosphate (0-20-0 N-P-K) and potassium chloride (0-0-51 N-P-K), respectively. All treatments were surface broadcast applied and incorporated prior to planting and irrigation was applied as needed from the Lugert Altus Irrigation District, OK with amounts varying from year to year . Since the irrigation water is furrow applied, the amount applied per irrigation was approximately 50 to 60 mm. Cultural practices and other information pertaining to the experiment are summarized in Table 2 for data compiled from 1989-2004. Recommended rates of herbicide, fungicide and insecticide were applied each year. Also, each year before harvesting defoliant was applied to facilitate harvesting. At maturity the middle two rows of each plot (15.2 m long) were mechanically harvested with a commercial cotton striper. Grab samples were collected from the harvested material in each plot and ginned on small ginning equipment in order to approximate lint turn out and ginning percent.

Preliminary analysis of data from 1989 to 2004  showed that yield was different for the different cultivars used in the study. To overcome these confounding problems and to address the objectives stated in this experiment, yearly data was grouped by cultivar (Table 2). Furthermore, data from 1995 where lack of moisture at planting and hail damage made treatment comparisons difficult were removed from analysis.

Initially, Analysis of Variance (ANOVA) was carried out using general linear models (GLM) in SAS (SAS Institute, version 8.1, Cary, NC) to assess the effect of N, P, K, and two way interactions on lint yield. Using the significant components from this model a more practical model was developed for N effect. Thus N rate was evaluated by fitting a quadratic plateau model (Nelson et al., 1985) for each cultivar using non-linear regression (NLIN) procedure in SAS. The Nelson et al. (1985) model was:

                                             if  X< X₀

                                                              if X> X₀

where: Y is lint yield (kg ha^-1), β₀ is intercept (yield when X=0); β₁ and β₂ are   coefficients of the linear and quadratic phases of the model, respectively; X is  N level (kg ha^-1); X₀ denote the critical N level (kg ha^-1) at which maximum lint yield is achieved (p).

Lint samples were sent to the International Textile Center, Texas Tech University (Lubbock, Texas) for cotton lint quality analysis for Paymaster 145 (1989-1994),  Paymaster HS26  (1998-2000), and Paymaster 2326 BG/RR (2001-2003). Lint quality data for 1995-1997 was not available. The High Volume Instrument (HVI) system of testing was used. Variables measured were fiber length (cm), length uniformity (%), strength (g tex^-1), micronaire and color. Definition of the different fiber quality characteristics and instrument procedures, as well as scales of measurement can be consulted in the literature (Cotton Incorporated, 2005; USDA, 2005). Statistical data analysis on fiber quality data was also performed using the combination of SAS procedures indicated above.

 

RESULTS AND DISCUSSION

Lint Yield

Mean lint yield for different cultivars are presented in Table 3. In this study there was  fertilizer input response in lint yield for cultivars. The older cultivar (Paymaster 145)  had much lower lint yield than recent cultivars and was poor in responding to fertilizer application (659 kg lint ha^-1on average). Paymaster HS26 and Paymaster 2326 BG/RR (a “stacked gene” modern transgenic stripper type cultivar with both Bt insect resistance and glyphosate tolerance) were superior (1205 kg lint ha^-1 on average) to Paymaster 145. These cultivars may be fertilizer responsive partly because the state wide cotton boll weevil eradication program was in effect since 1995.

All cultivars attained maximum lint yield with application of 135-39-75 kg N-P-K ha^-1(Table 3). Statistical tests however, revealed there was no significant difference between the higher and lower rates of fertilizers applied. Application of N and P had a significant effect on lint yield only for Paymaster HS26 and Paymaster 2326 BG/RR. Paymaster 145 responded to N fertilization but not P. This could be due to poor responsiveness to fertilizer of Paymaster 145.

Potassium fertilization and all two way interactions did not affect lint yield for all cultivars (Table 3). The inclusion of these factors resulted in relatively high coefficient of determination (R²) for Paymaster HS26 (0.86) and Paymaster 2326 BG/RR (0.76) while the ability of the model to account for variability was poor for Paymaster 145 (0.15).  The results suggest that N and P were the nutrients that most affected lint yield level for Paymaster 2326 BG/RR while N was the only nutrient that significantly affected lint yield of Paymaster 145 and Paymaster HS26. Application of K might not be necessary from a lint yield perspective unlike previous studies (e.g. Pettigrew, 1999) that recommended 112 kg K ha^-1. This is presumably due to the high inherent soil K at the experimental site.  Soil samples collected in 1988 had soil K level of 677 mg kg^-1, on average in the plot that never received K fertilizer since the start of the experiment.

Lint yield response to applied N follows a diminishing return trend. the quadratic plateau model for lint yield against N rates showed that the model accounted for 3, 32 and 75% of lint yield variability for Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR, respectively (Table 4). For Paymaster 145 a very poor relationship was observed between N rates and lint yield. This was consistent with the results of ANOVA for this cultivar. The critical N rate (X₀) for Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR was 45, 45 and 67 kg N ha^-1respectively with corresponding plateau (p) lint yield of 734, 1156 and 1468 kg ha^-1, respectively. These critical N rates are based on the N rates used in this study and did not account for N supplied by the environment. Although cotton requires 25-27 kg N ha^-1 per bale to attain maximum yield, the crop apparently obtained the additional unaccounted N from atmospheric deposition (about 22 kg N ha^-1), mineralization (34-56 kg N ha^-1) (Cowling et al., 2001; Hons et al., 2001). For Paymaster 2326 BG/RR for example, our recommendation shows 67 kg N ha^-1which can support the production of lint yield of 3 bales. The check lint yield (no N fertilizer, i.e. the intercept β₀) for this cultivar was 757 kg ha^-1. This yield is the result of N supplied from previous year available residual N, atmospheric deposition, and mineralization. For this cultivar the residual N, atmospheric deposition, and mineralization supplied approximately up to 66 kg N ha^-1.  

 

Fiber Quality

Mean fiber quality data is presented in Table 5. Average fiber length  obtained in this study was slightly lower than the average for the Western cotton growing regions that included Oklahoma (Cotton Incorporated, 2005) while micronaire was higher than the region’s average. Average length for this region is 2.74 cm while the average obtained in this study was 2.58, 2.63 and 2.69 cm, for Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR, respectively. The average length obtained in this study and the one obtained for the region were both categorized as medium length. Micronaire for the region is 3.9 (fine) while the average for Paymaster 145, Paymaster HS26 and Paymaster 2326 BG/RR was 4.2, 5.06 and 5.23, respectively which lies in the same classification category for Paymaster 145 and in ‘coarse’ micronaire classification category for the latter cultivars. The difference in these fiber quality characteristics from region to region is presumably related to cultivar difference and difference in performance of the same cultivars due to weather and soil related factors. For example, Bradow et al. (1997); Reddy et al. (1999) found that weather factors that affect carbon assimilation such as temperature were known to strongly influence micronaire. In their study Reddy et al. (1999) showed that micronaire increased linearly with the increase in temperature up to 26°C, but decreased at 32°C.

Fiber length uniformity and strength were higher for both cultivars in this study than that of the Western region average. Fiber length uniformity for the region was 81% (medium) while it was 83% for Paymaster 145 and 84% for Paymaster HS26 and Paymaster 2326 BG/RR. Again both numbers are in the same ‘high’ category of fiber uniformity index for all cultivars. Similarly, fiber strength was 29.0 g tex^-1 (base) for the region while it was 29.8 and 30.2 g tex^-1 (strong category) for Paymaster HS26 and Paymaster 2326 BG/RR, respectively.

Fiber quality characteristics were relatively different for the three cultivars. Fiber length, length uniformity and strength were all higher for Paymaster 2326 BG/RR (Table 5). The study by Segarra and Gannaway (1994) established that micronaire and strength are to some extent a function of cultivar. Overall treatments effect on length and strength was significant for Paymaster HS26 and Paymaster 2326 BG/RR (Table 5). Micronaire for all cultivars was not significant across treatments. Separate analysis of the effect of different N rates (at a fixed 20 kg P and 75 kg K ha^-1) revealed that length decreases with N rate for Paymaster 2326 BG/RR and Paymaster HS26. Fiber length uniformity and micronaire showed no significant decrease with increasing N rate for both cultivars (Figures 1 and 2). Fritschi et al. (2003) reported a positive linear relationship between fiber strength and N fertility level over three years. Boman and Westerman (1994) documented the absence of any relationship between fiber strength and N rates. The decrease in lint fiber micronaire with N rate might be good as more fine fiber is a desired characteristic. Our results suggest that, the soil N released from both inorganic and organic pool was sufficient to maintain good fiber quality. This is true given that plots were fertilized continuously with the same rate year after year. Likewise, for the three P rates (at fixed 135 kg N and 75 kg K ha^-1 rates) all quality characteristics were higher for Paymaster 2326 BG/RR. Increase in P rate from 39 to 59 kg ha^-1 did not result in considerable deterioration in measured lint quality variables for Paymaster HS26 and Paymaster 2326 BG/RR (Table 5). This shows that the high P rate had no negative effect on fiber quality, unlike N.  

Table 5 also showed an interesting result with respect to K fertilization. The 135-20-0 combination was significantly lower in length than any of the fertilizer combinations containing K for Paymaster HS26 and Paymaster 2326 BG/RR, implying the critical role of K in improving fiber length. Length uniformity however was not significantly different among the aforementioned fertilizer combinations for both cultivars.

The results from all quality characteristics suggest that K fertilization is a key to better quality while N rates (greater than 90 kg ha^-1) slightly reduce lint quality in upland cotton (except for micronaire which was improved with presence of moderate to high rates of N in this study at this location with the planted cultivars).  These results were generally consistent with previous reports (Pettigrew, 1999; Bennet et al., 1965; Cassman et al., 1990) that showed the benefits of K fertilization on lint quality.  

 The results of this study show that as we have moved from the old to the new transgenic cultivars, and without boll weevil pressure, yield potential has dramatically changed which obviously has driven increases in nutrient uptake specially N. This means new nutrient management practices need to be developed for sustainable cotton production. The fiber quality results also show that the earlier cultivar was short staple and low strength.  The data presented here is a very good resource for planning research in cotton producing areas of Oklahoma and else where.

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

REFERENCES

Bauer, P.J., and M.E. Roof. 2004. Nitrogen, Aldicarb, and cover crop effects on cotton yield and fiber properties. Agron. J. 96:369-376.

 

Bennett, O.L., R.D. Rouse D.A. Ashley, and B.D. Doss. 1965. Yield, fiber quality and potassium content of irrigated cotton plants as affected by rates of potassium. Agron. J. 57:296-299.

 

Boman, R.K., and R.L. Westerman. 1994. Nitrogen and mepiquat chloride effects on the production of nonrank, irrigated, short-season cotton. J. Prod. Agric. 7:70-75.

 

Bronson, K.F., J.W. Keeling, J.D. Booker, T.T. Chua, T.A. Wheeler, R.K. Boman, and R. J. Lascano. 2003. Influence of Landscape position, soil series and phosphorus fertilizer on cotton lint yield. Agron. J. 95:949-957.

 

Boquet, D.J. 2005. Cotton in ultra-narrow row spacing: Plant density and nitrogen fertilizer rates. Agron. J. 97:279-287.

 

Boquet, D.J., and G.A. Breitenbeck. 2000. Nitrogen rate effect on partitioning of nitrogen and dry matter by cotton. Crop Sci. 40:1685-1693.

 

Bonquet, D.J., E.B. Moser, and G.A. Breitenbeck. 1994. Boll weight and within-plant yield distribution in field-grown cotton given different levels of nitrogen. Agron. J. 86:20-26.

 

Bradow, J.M., P.J. Bauer, O. Hinojosa, G.F. Sassenrath-Cole. 1997. Quantitation of cotton fibre-quality variations arising from boll and plant growth environments. Eur. J. Agron. 6:191-204.

 

Cassman, K.G., T.A. Kerby, B.A. Roberts, D.C. Bryant, and S.L Higashi. 1990.  Potassium nutrition effects on lint yield and fiber quality of Acala cotton. Crop Sci. 30:672-677.

 

Cisneros, J.J., and L.D. Godfrey. 2001. Mid-season pest status of the cotton aphid (Homoptera: Aphididae) in California cotton: Is nitrogen a key factor? Environ. Entomol 30:501-510.

 

Cotton Incorporated. 2005. The classification of cotton. [online]. Available at www.cottoninc.om [Accessed 20 Dec. 2005].

 

Cowling, E. B., J. N. Galloway, C. S. Furiness, M.C. Barber, T. Bresser, K. Cassman, J. W. Erisman, R. Haeuber, R.I.  Howarth, J. Melillo, W. Moomaw, A. Mosier, K. Sanders, S. Seitzinger, S. Smeulders, R. Socolow, D. Walters, F. West, and Z. Zhu. 2001. Optimizing nitrogen management in food and energy production and environmental protection. Summary Statement from the Second International Nitrogen Conference, October 14-18, 2001. Ecological Society of America, Washington, DC. 17 pp.

 

Crozier, C.R., B. Walls, D.H. Hardy, and J. S. Barnes. 2004. Response of Cotton to P and K Soil Fertility Gradients in North Carolina. J. Cotton. Sci. 8:130-141.

 

Fritschi, F. B., B.A. Roberts, R.L. Travis, D.W. Rains, and R.B. Hutmacher . 2003. Response of irrigated Acala and Pima cotton to nitrogen fertilization: Growth, dry matter partitioning, and yield. Agron. J. 95:133-146

 

Gerik, T.J., B.S. Jackson, C.O. Stockle, and W.D. Rosenthal. 1994. Plant nitrogen status and boll load of cotton. Agron. J. 86:514-518.

 

Green, C.J., D.R. Krieg, and J.S. Reiter. 1999. Cotton response to multiple applications of nutrient mixtures. Pp. 1272-1273. In Beltwide Cotton Conferences Proceedings. National Cotton Council, Memphis, TN.  

 

Hons, F.M., M.L. McFarland, and R.G. Lemon. 2001. Assessment of an improved nitrogen recommendation system for cotton. Cotton Incorporated Summary Reports. Cary, NC, pp. 154-155. 

 

Howard, D.D., C.O. Gwathmey, M.E. Essington, R.K. Roberts, and M.D Mullen. 2001. Nitrogen fertilization of no-till cotton on loess-derived soils. Agron. J. 93: 157-163.

 

Hutmacher, R. B., R. L. Travis, D. W. Rains, R. N. Vargas, B. A. Roberts, B. L.

Weir, S. D. Wright, D. S. Munk, B. H. Marsh, M. P. Keeley, F. B. Fritschi, D. J. Munier, R. L. Nichols, and R. Delgado. 2004. Response of recent Acala cotton cultivars to variable nitrogen rates in the San Joaquin valley of California. Agron. J. 96:48-62.

 

McConnell, J.S., W.H. Baker, and R.C. Kirst, Jr. 1998. Yield and petiole nitrate concentrations of cotton treated with soil-applied and foliar-applied nitrogen. J. Cotton Sci. 2:143-152.

 

Meredith, W.R., Jr., J.J. Heitholt, W.T. Pettigrow, and S.T. Rayburn, Jr. 1997. Comparison of obsolete and modern cotton cultivars a two nitrogen levels. Crop Sci. 37:1453-1457.

 

Minton, E.B., and M.W. Ebelhar. 1991. Potassium and aldicarb-disulfoton effects on verticillium wilt, yield, and quality of cotton. Crop Sci. 31:209-212.

 

Moore, S.H. 1999. Nitrogen effect on position of harvestable bolls in cotton. J. Plant Nutr. 22:901-909.

 

Morrow, M.R. and D.R. Krieg. 1990. Cotton management strategies for a short growing season environment: water-nitrogen considerations. Agron. J. 82:52-56.

 

Mullins, G.L., and C.H. Burmester. 1990. Dry matter, nitrogen, phosphorus and potassium accumulation by four cotton cultivars. Agron. J. 82:729-736.

 

Nelson, L.A., R.D. Voss, J.T. Pesek. 1985. Agronomic and statistical evaluation of fertilizer response. pp. 53-90. In O.P. Angelstad (Ed.), Fertilizer technology and use, 3rd Edition. ASA, Madison, WI.

 

Nichols, S.P., C.E. Snipes, and M.A. Jones. 2004. Cotton growth, lint yield, and fiber quality as affected by row spacing and cultivar. J. Cotton. Sci. 8:1-12.

 

Pettigrew, W.T. 1999. Potassium deficiency increases specific leaf weights and leaf glucose levels in field-grown cotton. Agron. J. 91:962-968

 

Pettigrew, W. T. 2003. Relationships between insufficient potassium and crop maturity in cotton. Agron. J. 95:1323-1329.

 

Pettigrew, W. T., J.J. Heitholt, and W.R. Meredith, Jr. 1996. Genotypic interactions with potassium and nitrogen in cotton of varied maturity. Agron. J. 88:89-93.

 

Pettigrew, W.T., and W.R. Meredith, Jr. 1997. Dry matter production, nutrient uptake, and growth of cotton as affected by potassium fertilization. J. Plant Nutr. 20:531-548.

 

Pettigrew, W. T., W. R. Meredith, Jr., and L. D. Young. 2005. Potassium fertilization effects on cotton lint yield, yield components, and reniform nematode populations. Agron. J.  97:1245-1251.

 

Reddy, K.R., G.H. Davidonis, A.S. Johnson, and B.T. Vinyard. 1999. Temperature regime and carbon dioxide enrichment alter cotton boll development and fiber properties. Agron. J. 91:851-858.

 

Reiter, J.S, and D.R. Kreig. 2000. Texas research shows fertigation is a viable option to save cotton growers both time and money on fertilizer inputs. Fluid J. Issue 29, 8 (2):20-22.

 

SAS Institute. 2001. SAS/STAT User’s Guide. Release 8.1 ed. SAS Inst., Cary,

NC.

 

Segarra, E. and J. Gannaway. 1994. The economics of cotton cultivar selection: an application to the Texas High Plains. Pp. 503-506. Beltwide Cotton Conferences Proceedings. National Cotton Council, Memphis, TN. 

 

Slosser, J., J. Leser, D. Rummel, T. Fuchs, E. Boring, M. Muegge, and C. Sansone. 1999. Suggestions for Management of Cotton Aphid in West Texas. [online]. Available at  entowww. tamu.edu/extension/bulletins/aphweb99.html. (accessed 6 Jan, 2006). Agricultural Communications, The Texas A&M University System, College Station, Texas.

 

Tewolde, H., and C.J. Fernandez. 1997. Vegetative and reproductive dry weight inhibition in nitrogen and phosphorus deficient Pima cotton. J. Plant Nutr. 20:219-232.

 

The University of Arizona. 1999. Sticky cotton sources and solutions. IPM series no. 13, Publication# AZ1156-12/1999. Tucson, AZ: The University of Arizona Cooperative Extension. 4 pp.

 

United State Department of Agriculture. 2005. Cotton classification: Understanding the data, April 2005. [online]. Available at http://www.ams.usda.gov/cotton/ [accessed 20, Dec. 2005].Agricultural Marketing Service cotton program, USDA.

 

Unruh, B.L. and J. C. Silvertooth. 1996. Comparisons between and Upland and Pima Cotton Cultivar: II. Nutrient uptake and partitioning. Agron. J. 88:589-595. 

 

Table 1. Surface (0-15 cm) Soil chemical characteristics sampled from check plots, long-term cotton experiment, Altus, OK, 1988.

pHz	NH4_N	NO3_N	P	K	Total N		Organic Carbon
--------------------------mg kg-1-----------------------------						-g kg-1-	-----%----
7.4	5.11	4.37	64.8	677.3	750		0.85

^z Chemical analysis: pH  1:1 soil:water;  Organic C and Total N  dry combustion; NH₄-N and NO₃-N  Lachat  P and K: Mehlich-3

 

 

Table 2. Treatment applications and experimental management, long-term cotton experiment, Altus, OK, 1989-2004.       

	1989-1994	1995-2000	2001-2004
Cultivar	Paymaster 145	Paymaster HS26	Paymaster 2326 BG/RR
Fertilization date	Mar-May	May	Mar- Apr
Planting dates	May	May	May
Ave seed rate, kg/ha	21	19	18
Ave. frequency of furrow irrigation	3	4	5
Harvest date	Oct- Mar	Oct- Nov	Oct-Nov

 

Table 3. Treatment means and significance test results for main and two way interaction effects for each cultivar, cotton experiment, Altus, Oklahoma.

N-P-K	Paymaster 145 (89-94)	Paymaster HS26 (95-00)	PM2326 BG/RR (01-04)
------------------------------------------------Kg ha-1 --------------------------------------------------------
0-0-0	568	758	681
0-20-75	584	798	757
45-20-75	735	1169	1240
90-20-75	753	1164	1467
135-20-75	758	1178	1514
180-20-75	725	1159	1478
225-20-75	700	1112	1412
135-0-75	728	1121	1315
135-39-75	759	1212	1574
135-59-75	742	1155	1571
135-20-0	743	1166	1498
SEDy	117	73	63
N rate	**	***	***
P rate	ns	ns	*
NxP	ns	ns	ns
K rate	ns	ns	ns
NxK	ns	ns	ns
PxK	ns	ns	ns
Model R-square	0.15	0.45	0.86

*, **, *** Significant at the 0.05, 0.01 and 0.001 levels of probability, respectively

ns is not significant. 

^y Standard Error of the difference of two means

 

 

 

Table 4. Parameter estimates of N versus lint yield prediction using a quadratic plateau model for each cultivar, long-term cotton experiment, Altus, Oklahoma, 1989-2004.

Parameter	Paymaster 145 (89-94)	Paymaster HS26 (95-00)	PM2326 BG/RR (01-04)
Β0	584	798	757
β1	4.01	13.1	11.0
β2	-0.015	-0.113	-0.006
X0	45	45	67
p	734	1156	1468
R2	0.02	0.32	0.75
prob.	ns	*	**

*, ** Significant at the 0.05, and 0.01 levels of probability, respectively;  ns denotes not significant.  Β₀ is intercept (yield when X=0); β₁ and β₂ are   coefficients of the linear and quadratic phases of the model, respectively; X₀ denote the critical N level (kg ha^-1) at which maximum lint yield is achieved (p).

 

 

 

Table 5. Effect of N-P-K fertilizers on mean lint quality characteristics measured using High Volume Instrument (HVI) for Paymaster 145 (1989-1994 average), Paymaster HS26 (1998-2000 average), and Paymaster 2326 BG/RR (2001-2004 average), long-term cotton experiment Altus, OK. 

N-P-K	Paymaster 145			Paymaster HS26				Paymaster 2326 BG/RR
	Length	LU	Micronaire	Length	LU	Strength	Micronaire	Length	LU	Strength	Micronaire
Kg ha-1	cm	%		cm	%	g tex-1		cm	%	g tex-1
0-0-0	2.57	83	4.1	2.62	83	29.0	5.0	2.68	84	30.0	5.2
0-20-75	2.57	83	4.0	2.65	84	30.2	5.1	2.73	84	31.0	5.3
45-20-75	2.59	82	4.1	2.64	84	30.1	5.1	2.71	84	30.6	5.3
90-20-75	2.61	84	4.1	2.64	84	29.7	5.1	2.71	84	30.3	5.3
135-20-75	2.56	83	4.2	2.64	84	29.8	5.1	2.70	84	30.3	5.3
180-20-75	2.57	82	4.1	2.64	83	29.6	5.1	2.70	84	30.3	5.2
225-20-75	2.57	82	4.2	2.64	83	29.5	5.0	2.70	84	30.1	5.2
135-0-75	2.59	83	4.2	2.63	83	29.4	5.0	2.68	84	30.0	5.2
135-39-75	2.60	83	4.2	2.63	83	29.3	5.0	2.68	84	30.0	5.2
135-59-75	2.54	82	4.2	2.63	83	29.2	5.0	2.67	84	29.9	5.2
135-20-0	2.57	83	4.2	2.61	83	28.7	4.9	2.67	84	29.5	5.2
LSD0.05z	ns	1.2	ns	0.06	ns	1.2	0.20	0.07	ns	1.1	ns

^z Least significant difference at  critical p-value of 0.05

ns denotes not significant. 

Figure 1.  Effect of N rates on fiber length uniformity (LU,%) and fiber length (cm)

            for two cultivars, Altus, Oklahoma.