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Crop Rotations

Nitrogen and Phosphorus Fertilizer and Residual Response in Cotton–Sorghum and Cotton–Cotton Sequences

^a Texas Agric. Exp. Stn.
^b Texas Coop. Ext., 1102 E FM 1294, Lubbock, TX, 79403

^* Corresponding author (k-bronson{at}tamu.edu)

Received for publication April 20, 2006.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Nitrogen and P fertilizer response for cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench] in a reduced tillage rotation system in the Southern High Plains has not been well studied. During 2000 to 2003, an irrigated study of cotton–sorghum rotation vs. continuous cotton evaluated the crop rotation effects on cotton lint yield and assessed N and P fertilizer and residual fertilizer response for the two systems. Preplant soil samples were collected each spring to determine fertilizer rates. Cotton lint yields and cottonseed N were not affected by rotation with sorghum compared with continuous cotton. Nitrogen fertilizer response was observed in lint yields from 2001 to 2003 in cotton following sorghum, but not in continuous cotton. No P fertilizer or soil residual P response in cotton lint yields was found, regardless of rotation. Grain sorghum yields responded to N fertilizer in 2 yr. No grain sorghum response was observed to P fertilizer, but in 1 yr a yield response to residual P fertilizer relative to zero-P plots was noted. Seed N uptake was greater in sorghum than in cotton. Nitrogen fertility level increased seed N in sorghum and in cotton following sorghum. Infrequent crop response to P fertilizer was not unexpected, especially when Mehlich-3 soil P in zero-P subplots was near the 95% sufficiency level of 20 mg P kg^–1. The main finding of this study is that N fertilizer response was more consistent for cotton following sorghum than in a continuous cotton system. In refining N fertilizer recommendations, N debits may be needed for N immobilization in sorghum residue. Nitrogen credit may be appropriate from leaf litter for crops following cotton and for NO₃–N in irrigation water.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
MORE THAN 1.5 MILLION ha of cotton and 0.4 million ha of sorghum are planted each year on the Southern High Plains of Texas (Texas Agricultural Statistics Service, 2005). Sorghum in this region is planted after cotton, often after a severe weather-induced early season cotton crop loss (Segarra et al., 1991; Howell et al., 2003). Although lint yield or income benefits from rotating cotton with sorghum are limited (Segarra et al., 1991; Clark et al., 1996), monocropped irrigated cotton production in the Southern High Plains contributes to the declining water levels of the Ogallala aquifer (Allen et al., 2005). Including sorghum in cotton-based rotations may conserve water in limited irrigation situations (Baumhardt et al., 1993). Wind erosion potential in the Southern High Plains in continuous cotton under conventional or reduced tillage can average 22 Mg ha^–1 (Lacewell et al., 1989), but residue left by a sorghum crop under reduced tillage can mitigate wind erosion.

Many studies have been published on N or P fertilizer response in monocropped cotton (Segarra et al., 1989; Bronson et al., 2003; Hutchmacher et al., 2004; Bronson et al., 2006) and monocropped sorghum (Gordon and Whitney, 2000; Yang et al., 2001). However, published studies on N and P management for the two crops within the cotton–sorghum rotation system are few. Brawand and Hossner (1976) studied grain sorghum yields and leaf N and P content in continuous sorghum vs. sorghum in rotation with cotton and wheat. They found that sorghum leaf N and P responded to fertilization, but they did not report cotton yields. Franzluebbers et al. (1994) conducted field studies assessing N fertilizer response in corn and sorghum in continuous and rotated sequences. Liebig et al. (2002) reported on N fertilization effects in four crop sequences that included grain sorghum. None of these studies included the continuous cotton sequence common in the Southern High Plains.

Gass (1987) and Zhang et al. (1998) reported regional fertilizer recommendations for monocropped cotton and sorghum for Texas and Oklahoma, respectively. Nitrogen fertilizer recommendations for grain sorghum and cotton have historically been based on 0- to 15-cm soil NO₃ tests (Gass, 1987). This approach, however, ignores subsoil NO₃, and using a 0- to 60-cm soil test NO₃–N is a better approach (Franzluebbers et al., 1994; Zhang et al., 1998; Bronson et al., 2000).

Besides depth of soil test NO₃, crop rotation might be an important consideration in N fertilizer recommendations. Bronson et al. (2001) reported from N fertilizer rate studies that the optimal N fertilizer requirement was higher in a terminated rye (Secale cereale L.) cover crop system than in a conventional tillage system. They proposed that the difference was associated with the decomposition of residue. Similar N limitations might exist in cotton–sorghum rotation with sorghum residue production being about 1:1 ratio with grain production (Larson et al., 1978).

Current recommendations for P in the region for all crops set the critical soil level (i.e., 95% sufficiency) at 20 mg Mehlich 3 P kg^–1 (Zhang et al., 1998). However, recent research conducted in the Southern High Plains has suggested that the critical level for P may actually be lower for cotton (Bronson et al., 2001, 2003). The effects of a sorghum–cotton rotation on P fertilizer response for cotton are not known.

The objectives of the study were to (i) determine crop rotation effects on cotton lint yield and cottonseed N uptake, (ii) compare response of lint yields and cottonseed N to N and P fertilizer and residual soil fertility levels in continuous cotton vs. cotton–sorghum rotations, and (iii) evaluate response of sorghum grain yield and grain N uptake to N and P fertilizer and residual soil fertility levels in the cotton–sorghum rotation.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
This experiment was begun in 2000 on an Acuff sandy clay loam (fine-loamy, mixed, superactive, thermic Aridic Paleustolls) soil with a 0 to 1% slope, near Lubbock, TX. The experiment was designed as a split-plot, randomized complete block design with three replications (Fig. 1 ). The three main plots (24, 1-m rows wide by 30 m long) were continuous cotton and two annually alternating rotation plots: cotton followed by sorghum, and sorghum followed by cotton. Each of the main plots was split into six subplots (8, 12-m rows wide by 15-m long). The six fertilizer treatments were a factorial arrangement of 3 N fertilizer rates [0, 1, and 2 times the soil test recommendation (0x, 1x, and 2x treatments)] and 2 rates of P fertilizer (0x and 1x the soil test recommendation) (Fig. 1).

View larger version (19K): [in this window] [in a new window]   Fig. 1. Experimental design, 2000–2003.

Application rates for N fertilizer were based on recommendations for yield goals of 840 kg ha^–1 cotton lint and 4500 kg ha^–1 sorghum grain and the 0- to 60-cm soil NO₃–N. Nitrogen recommendations for these yield goals are 101 kg N ha^–1 for cotton and 78 kg N ha^–1 for sorghum minus the NO₃–N in the 0- to 60-cm soil profile (Zhang et al., 1998). If soil NO₃–N test results were greater than these amounts in the 1x subplots, then no N fertilizer was applied in that year, for either the 1x or 2x subplots. Although soil test based fertilizer treatments in field experiments (Chua et al., 2003; Ottman and Pope, 2000; Thompson et al., 2000) are less common than fixed fertilizer rate studies, they have several advantages. Fertilizer is applied according to the soil test, as researchers and extension workers promote, and excessive residual effects at high fertilizer rates are avoided.

Application rates for P fertilizer were based on the 0- to 15-cm soil analyses. The critical soil test level for P is 20 mg kg^–1, and the level when no P fertilizer is recommended is 33 P mg kg^–1 for cotton and sorghum (Zhang et al., 1998). The recommended rates of P fertilizer ranged from 0 to 37 kg P ha^–1. These P fertilizer recommendations do not vary with yield goal. Unlike fixed rate fertilizer field studies, if soil test P was >33 mg kg^–1, then no P fertilizer was applied.

Fertilizer applications were made using a four-row liquid application system, fitted with a Soilteq Falcon controller (Bronson et al., 2003). Recommended quantities of P fertilizer were applied within 2 wk of planting. The 1x and half of the 2x N treatments were applied during this same period. The remainder of the 2x N was applied during early squaring of the cotton and 0.3-m height growth stage of sorghum. Fertilizers were applied on the nondrive side of the seed row, 0.1 m deep and 0.1 m to the side of the seed row. Nitrogen was applied as urea ammonium nitrate (320 g N kg^–1), P was applied as phosphoric acid (2000 and 2001, 79 g P kg^–1) or ammonium polyphosphate (2002 and 2003, 148 g P kg^–1).

Glyphosate-tolerant cotton (Paymaster 2326 RR) and sorghum (Golden Acres Genetics 1506) were planted in early May of each year. Cotton was planted at 17 kg seed ha^–1, and sorghum 5 to 6 kg of seed ha^–1. The study field received 8 cm of preplant all furrow (drive and nondrive furrows) irrigation. The crops were alternate-furrow irrigated 4 to 6 times during the season, applying from 19 to 32 cm of irrigation. Target irrigation was 75% replacement of estimated evapotranspiration for cotton, with the same amounts applied to sorghum. Table 1 shows irrigation and rainfall during the growing season for each year. Sorghum and cotton were hand harvested at maturity. From each plot, 8 m² of sorghum and 4 m² of cotton were collected.

Analysis of variance was performed for each year on the soil test and yield data using PROC MIXED (SAS Institute, 1999). Rotation, N, P, and interactions of these were considered fixed effects. Replicate and interactions of fixed effects with replicate were considered random effects. If rotation effects were significant (P = 0.05), then LSDs were calculated to compare rotation means. If rotation x N or rotation x P treatments were significant (P = 0.05), then LSDs were calculated to compare N or P treatment means within each rotation.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Rotation Effects
Rotating cotton with sorghum did not increase lint yields during the 3 yr compared with continuous cotton (Table 2), similar to other studies in the Southern High Plains (Segarra et al., 1991; Clark et al., 1996; Howell et al., 2003). Although lint yield was not affected by rotation (P > 0.05), the sorghum contributed a significant amount of residue to the soil, but this was not quantified. Residue levels were adequate to provide protection from wind-blown sand for the following year's cotton seedlings. This is in contrast to the small amount of residue left after cotton harvest.

2001
The 2001 growing season was the first year of results for rotation effects (Tables 2, 4). Spring soil samples indicated a significant increase in NO₃–N in the 1 x N and 2 x N subplots compared with the 0x subplots related to fertilization in 2000 within continuous cotton (Table 4). In the cotton–sorghum rotation, only the 2 x N plots had greater soil NO₃–N than the control (Table 4). Residual soil NO₃–N concentrations were high enough in the 1x subplots that no N fertilizer was added. However, in sorghum–cotton, soil NO₃–N was very low for all N treatments and required the addition of N fertilizer. Lower soil NO₃–N following sorghum reflected greater seed N uptake in sorghum than in cotton in 2000.

Lint yields ranged from 82 to 100% of the yield goals. Grain sorghum yields, however, were 60% of target yield. The month of June in 2001 was hotter and drier than average, and both crops suffered from water stress (Table 1). Sorghum grain yields did not respond to residual soil NO₃ or P fertilizer in 2001. Lint yields for 2001 responded to N fertilizer relative to the control in the sorghum–cotton only, up to the 1 x N treatment level (Table 4). Lint yields in the continuous cotton plots did not respond to residual NO₃ or residual soil P.

2002
Spring soil samples indicated that soil NO₃–N in the 2x subplots was significantly higher than in the 0x subplots in all three systems (Table 5). In the cotton–cotton rotation, the 1x subplot also had greater soil NO₃–N than the zero-N subplots. Soil NO₃–N in the 1x subplots indicated that N fertilizer was required for all three systems. As in 2001 spring, soil NO₃–N in the sorghum–cotton plots was lower than in the continuous cotton plots (Tables 2, 5). The 2x subplots in the sorghum–cotton averaged lower soil NO₃–N than the 0x subplots in the other two systems. Although grain sorghum yields were low in 2001, the residue may have contributed to immobilization of N fertilizer applied to the 2002 cotton crop.

Lint and grain sorghum yields were both greater than the yield goals. 2002 was the year with the greatest lint yields (1200 kg ha^–1). Similar to 2000, June rainfall in 2002 was above average. Lint yields for 2002 responded to N fertilizer in the sorghum–cotton rotation, as in 2001, up to the 1x treatment level (Table 5). Lint and grain yields did not respond to P fertilizer or residual soil P in any of the three systems. Seed N uptake in 2002 was affected by N fertilizer in sorghum and in both cotton systems (Table 5). As in 2000, grain sorghum N uptake was greater than cottonseed N removal (Tables 2, 5). Grain sorghum yields responded linearly to N fertilizer rate in 2002 (Table 5).

2003
Spring soil samples indicated that soil NO₃–N was notably lower in all three systems than in previous years, but in the 2x subplots were again significantly higher than in the 0x subplots in all three systems (Table 6). Soil NO₃–N in the 1x subplots indicated that N fertilizer was required for all three systems. Similar to the previous 2 yr, soil NO₃–N in the sorghum–cotton plots was lower than in the continuous cotton plots (Tables 2, 6). Lower soil NO₃–N in all three systems was apparently a result of high N removal by the high-yielding crops of 2002. As in the previous years, the sorghum grain and the residue resulted in a greater demand for N than the cotton crop.

Lint and grain sorghum yields were near the expected yield goal in 2003. Lint yields for 2003 responded to N fertilizer in sorghum–cotton at the 2x level (Table 6). Lint yields in the sorghum–cotton and continuous cotton plots did not respond to higher soil P levels relative to the control, but grain sorghum yields did. Seed N removal in 2003 followed the same trend as in 2002, with N fertilizer response in sorghum and in cotton following sorghum (Table 6) and with greater seed N removed in grain sorghum than in cotton (Table 2). Nitrogen fertilizer response in grain sorghum was observed, but was not linear as in 2002.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Lint yields were not affected by rotation in this study (P > 0.05). Lint yields responded to N fertilizer in sorghum–cotton in all of 3 yr of rotation data, and reduced residual soil NO₃–N reflected this. Lint yields in the continuous cotton plots did not respond to N or P fertilizer or residual soil NO₃ or P. Grain sorghum yields responded to N fertilizer in 2002 and 2003. The only yield response to P observed in the study was for grain sorghum in 2003 to residual soil P. A significant finding of this study was that N fertilizer response was more consistent for cotton following sorghum than for cotton following cotton.

At the yields achieved in this study, N uptake in sorghum grain was greater than in cottonseed. This may not have been true for 2001 when sorghum yields were low, but we did not analyze grain or seed for N that year. Sorghum grain N uptake apparently resulted in lower soil residual soil NO₃, which can help explain N response in cotton following sorghum. However, there was surprisingly no N fertilizer response in the high-yielding sorghum crop of 2000, despite relatively low soil NO₃ levels at the start of the study.

Soil test NO₃–N levels had significant N fertilizer rate affects in all rotation–year combinations, except cotton following sorghum in 2001. Greater residual NO₃–N following cotton reflected the lack of N fertilizer response and lower N uptake compared with grain sorghum. Low soil NO₃–N following sorghum, even low yielding sorghum, may have been due to N immobilization in sorghum residue. Cotton yield levels also strongly influenced soil NO₃ levels each spring following harvest. For example, high cotton yields in 2002 resulted in lower soil NO₃ in spring 2003.

Net N mineralization of soil organic matter and NO₃ additions in the irrigation water may have affected N response. Bronson et al. (2003) and Chua et al. (2003) reported that, in this Acuff sandy clay loam soil, about 50 kg N ha^–1 is potentially available from mineralization of soil organic matter and from previous cotton crop leaf litter. Bronson et al. (2003) also reported 32 kg N ha^–1 of leaf N accumulation at peak bloom in irrigated cotton at this site. In addition, the irrigation water (12.3 mg NO₃–N L^–1) used for the study added 25, 24, 40, and 27 kg N ha^–1 to the experimental area in 2000, 2001, 2002, and 2003, respectively (Tables 3, 4, 5, 6). As mentioned, sorghum residue may have enhanced biological immobilization of N. All of these factors may have contributed to the more consistent N fertilizer responses in cotton following sorghum vs. cotton–cotton. As N fertilizer recommendations for these cropping systems are refined, N credits should be considered for soil organic matter mineralization and irrigation NO₃, and N debits could be made for immobilization of N in sorghum residue.

The prevalent lack of P fertilizer response was not unexpected, especially with Mehlich-3 P levels of 19–20 and 22–25 mg P kg^–1 in the zero-P subplots in 2000 and 2001. Infrequent cotton response to P fertilizer at 15–25 mg Mehlich-3 P kg^–1 was also reported by Bronson et al. (2003). Increased P availability to cotton and sorghum roots above that reflected by soil tests may be attributed to vesicular-arbuscular mycorrhizae colonization (Pugh et al., 1980; Raju et al., 1990; Zak et al., 1998). Gordon and Whitney (2000) reported significant response in grain sorghum yield to banded P fertilizer in a 3-yr study in Kansas, but their soil had low soil test P. Our study did demonstrate that low band applications of 10 to 15 kg P ha^–1 were effective in not only maintaining soil test P levels in the 25 to 33 mg kg^–1 range, but in building up Mehlich-3 P to the 33 mg P kg^–1 level. Small changes in soil test P in Southern High Plains in soils with low rates of P fertilizer addition were also reported by Bronson et al. (2003).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Lint yields were not increased by rotating cotton with sorghum compared with continuous cotton. However, more consistent yield response to N fertilizer was observed for cotton after a sorghum crop in the previous year. Lint yields in the continuous cotton system did not respond to N or P fertilizer or residual soil NO₃ or P in any year. Cotton leaf N may be an N credit that needs to be considered in N fertilizer recommendations. Nitrate-N concentration in the irrigation water in this study was 12 mg L^–1, and may have reduced N response. Grain sorghum responded to N fertilizer in two of four years and to residual soil P in 1 yr. In the rotation system, the sorghum residue apparently immobilized significant amounts of N, and N fertilizer recommendations may need to debit for this. The lack of a positive rotation effect for cotton, greater N fertilizer response of cotton following sorghum, and the greater economic return from cotton compared with sorghum (Segarra et al., 1991; Lee et al., 1988) all need to be considered in cost and returns analysis of the cotton–sorghum rotation.

	ACKNOWLEDGMENTS

 
The authors would like to acknowledge the financial support of the Texas Legislature Special Initiative on Productive Rotations on Farms in Texas. We also thank Jimmy Mabry and Jim Barber for their capable field assistance.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Allen, V.G., C.P. Brown, R. Kellison, E. Segarra, T. Wheeler, P.A. Dotray, J.G. Conkwright, C.J. Green, and V. Acosta-Martinez. 2005. Integrating cotton and beef production to reduce water withdrawal from the Ogallala aquifer in the Southern High Plains. Agron. J. 97:556–567.[Abstract/Free Full Text]
• Baumhardt, R.L., J.W. Keeling, and C.W. Wendt. 1993. Tillage and residue effects on infiltration into soils cropped to cotton. Agron. J. 85:379–383.[Abstract/Free Full Text]
• Brawand, H., and L.R. Hossner. 1976. Nutrient content of sorghum leaves and grain as influenced by long-term crop rotation and fertilizer treatment. Agron. J. 68:277–280.[Abstract/Free Full Text]
• Bronson, K.F., J.D. Booker, J.P. Bordovsky, J.W. Keeling, T.A. Wheeler, R.K. Boman, M.N. Parajulee, E. Segarra, and R.L. Nichols. 2006. Site-specific irrigation and nitrogen management for cotton production in the Southern High Plains. Agron. J. 98:212–219.[Abstract/Free Full Text]
• 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.[Abstract/Free Full Text]
• Bronson, K.F., R.J. Lascano, J.D. Booker, J. Booker, S. Machado, E.D. Bynum, Jr., T.L. Archer, H. Li, and J.W. Keeling. 2000. Grid soil sampling: Comparisons of grid size with landscape and soil texture-based sampling strategies [CD-ROM]. In P.C. Robert et al. (ed.) Proc. of the 5th Int. Conf. on Precision Agriculture, Minneapolis, MN. 16–19 July 2000. ASA, CSSA, and SSSA, Madison, WI.
• Bronson, K.F., A.B. Onken, J.D. Booker, R.J. Lascano, T.L. Provin, and H.A. Torbert. 2001. Irrigated cotton lint yields as affected by phosphorus fertilizer and landscape position. Commun. Soil Sci. Plant Anal. 32:1959–1967.[ISI]
• Chua, T.T., K.F. Bronson, J.D. Booker, J.W. Keeling, A.R. Mosier, J.P. Bordovsky, R.J. Lascano, C.J. Green, and E. Segarra. 2003. In-season nitrogen status sensing in irrigated cotton: I. Yields and nitrogen-15 recovery. Soil Sci. Soc. Am. J. 67:1428–1438.[Abstract/Free Full Text]
• Clark, L.E., T.R. Moore, and J.L. Barnett. 1996. Response of cotton to cropping and tillage systems in the Texas Rolling Plains. J. Prod. Agric. 9:55–60.
• Franzluebbers, A.J., C.A. Francis, and D.T. Walters. 1994. Nitrogen fertilizer response potential of corn and sorghum in continuous and rotated crop sequences. J. Prod. Agric. 7:277–284.
• Gass, W.B. 1987. Soil, Plant, and Water Testing Laboratory. Texas Agric. Ext. Service, Texas A&M Univ., College Station.
• Gordon, W.B., and D.A. Whitney. 2000. Effects of phosphorus application method and rate on furrow-irrigated ridge-tilled grain sorghum. J. Plant Nutr. 23:23–34.[ISI]
• Howell, T.A., J.A. Tolk, S.R. Evett, and R.L. Baumhardt. 2003. Cotton and sorghum rotation under deficit furrow irrigation. Paper no. 032134. 2003 ASAE Ann. Int. Meeting, 27–30 July 2003, Las Vegas, NV.
• Hutchmacher, 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 varieties to variable nitrogen rates in the San Joaquin Valley of California. Agron. J. 96:48–62.[Abstract/Free Full Text]
• Lacewell, R.D., J.G. Lee, C.W. Wendt, R.J. Lascano, and J.W. Keeling. 1989. Crop yield and profit implications of alternative rotations and tillage practices: Texas High Plains. Bull. B-1619. Texas Agric. Exp. Stn., Lubbock.
• Larson, W.W., R.F. Holt, and C.W. Carlson. 1978. Residues for soil conservation. p. 1–15. In W.R. Oschwald (ed.) Crop residue management systems. ASA Spec. Publ. 31. ASA, CSSA, and SSSA, Madison, WI.
• Lee, J.G., J.R. Ellis, and R.D. Lacewell. 1988. Crop selection and implications for profits and wind erosion in a semi-arid environment. Agric. Econ. 2:319–334.
• Liebig, M.A., G.E. Varvel, J.W. Doran, and B.J. Wienhold. 2002. Crop sequence and nitrogen fertilization effects on soil properties in the Western Corn Belt. Soil Sci. Soc. Am. J. 66:596–601.[Abstract/Free Full Text]
• Ottman, M.J., and N.V. Pope. 2000. Nitrogen fertilizer movement in the soil as influenced by nitrogen rate and timing in irrigated wheat. Soil Sci. Soc. Am. J. 64:1883–1892.[Abstract/Free Full Text]
• Pugh, L.M., R.W. Roncadori, and R.S. Hussey. 1980. Factors affecting development of vesicular-arbuscular mycorrhizae in cotton. p. 22. In 1980 Beltwide Cotton Production Res. Conf. Proc. 6–10 Jan. 1980. National Cotton Council of America, Memphis, TN.
• Raju, P.S., R.B. Clark, J.R. Elles, R.R. Duncan, and J.W. Maranvile. 1990. Benefit and cost analysis and phosphorus efficiency of VA mycorrhizal fungi colonizations with sorghum (Sorghum bicolor) genotypes grown at varied phosphorus levels. p. 165–170. In Plant nutrition: Physiology and applications. Proc. of the 11th Int. Plant Nutrition Colloquium, Wageningen, the Netherlands. 30 July–4 Aug. 1989. Kluwer Academic Publ., Dordrecht, the Netherlands.
• SAS Institute. 1999. The SAS system for Windows. v. 8.0. SAS Inst., Cary, NC.
• Segarra, E., D.E. Ethridge, C.R. Deussen, and A.B. Onken. 1989. Nitrogen carry-over impacts in irrigated cotton production, Southern High Plains of Texas. Western J. Agric. Econ. 14:300–309.
• Segarra, E., J.W. Keeling, and J.R. Abernathy. 1991. Tillage and cropping systems effects on cotton yield and profitability on the Texas Southern High Plains. J. Prod. Agric. 4:566–571.
• Texas Agricultural Statistics Service. 2005. Texas agricultural facts. Bull. SM-02–05. 14 Jan. 2005. USDA and Texas Dep. of Agriculture, Austin.
• Thompson, T.L., T.A. Doerge, and R.E. Godin. 2000. Nitrogen and water interactions in subsurface drip-irrigated cauliflower: I. Plant response. Soil Sci. Soc. Am. J. 64:406–411.[Abstract/Free Full Text]
• Yang, C., J.H. Everitt, and J.M. Bradford. 2001. Comparisons of uniform and variable-rate nitrogen and phosphorus fertilizer applications for grain sorghum. Trans. ASAE 44:201–209.[ISI]
• Zak, J.C., B. McMichael, S. Dhillion, and C. Friese. 1998. Arbuscular-mycorrhizal colonization dynamics of cotton (Gossypium hirsutum L.) growing under several production systems on the Southern High Plains, Texas. Agric. Ecosyst. Environ. 68:245–254.
• Zhang, H., B. Raun, J. Hattey, G. Johnson, and N. Basta. 1998. OSU soil test interpretations. Publ. F-2225. Oklahoma Coop. Ext. Service, Oklahoma State Univ., Stillwater, OK.

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