1. Optimizing Revenue Through Defoliation Timing
L.T. Barber 1, M. Bowman1, F. Groves1, and B. Robertson2
1Cooperative Extension Service, University of Arkansas, Little Rock, AR
2National Cotton Council, Memphis, TN
Introduction
Discussion
Results
Timing of harvest aids has become easier in the last few years with tools such as the Hal Lewis method and COTMAN. The current COTMAN rules suggest defoliating when 850 heat units beyond cutout (NAWF=5) have been obtained. These methods, like most, have their strengths and weaknesses. An Arkansas pilot program initiated in 2002 was successful in identifying the potential for high micronaire and closely mirrored the actual values of the 2002 crop from samples collected for 93 fields with 13 varieties in 12 counties. The current COTMAN rules suggest defoliating when 850 heat units beyond cutout (NAWF=5) have been obtained. It is our hypothesis that the integration of these two methods would result in better identifying problem situations, namely high micronaire values, on an area basis and allow for management decisions needed to minimize the problems on a field by field basis. The objective of this study was to determine if the Hal Lewis method could be incorporated with the decision making process of COTMAN to evaluate optimum defoliation timing.
Results indicate that defoliation timing according to COTMAN recommendations may optimize revenue potential. The statistical analysis of the defoliation treatment of 750 HU after cutout was only included in 2007 due to the treatment not being used in all years and varieties. There was no significant differences among treatments when data were averaged over year and variety. When the data were analyzed by year significant differences for yield occurred only in 2007 due to a delay in maturity caused by a decrease in fruit retention (Table 4) was the only year when defoliation at 1050 HU after cutout resulted in greater lint yield than at other timings. In other years, significant differences arose for net loan in 2005 (Table 2) and 2006 (Table 3). Significant differences were also found when the data were analyzed by variety (Table 5). No significant differences were detected in lint yield regardless of timing in varieties DPL445BGRR, DPL555BGRR, and ST5599BR. ST4554B2RF had significantly greater lint yields at There were no significant differences for micronaire value for any of the defoliation timings. Not all varieties were utilized in all three years of the study. The results of this three year study indicate that variety selection may have the greatest impact on defoliation timing.
Results from 2007 (Table 6) confirm previous research findings that the Hal Lewis method is a valuable tool in estimating micronarie values. Predicted micronaire values for 30% to 70% open boll were comparable to actual micronaire values for defolation timings of 750 HU to 1050 HU after cutout. Yet, the Hal Lewis method appears impractical for producer use. During the study, favorable weather conditions, access to a gin, and a vast amount of time was required in acquiring the samples and receiving the predicted micronaire values.
Table 1. Quantity, quality, and value results from
655.89
0.524
4.85
1050
659.26
0.531
4.76
950
647.36
0.528
4.83
850
$/A
¢/lb
lb/A
Total Value
Net Loan
Micronaire
Lint Yield
Heat Unit
663.24
0.542
1050
690.79
0.553
950
670.07
0.548
850
$/A
¢/lb
lb/A
Total Value
Net Loan
Lint Yield
Heat Unit
Table 2. Quantity and value results from 2005.
a b a
a,b Means in columns without common superscripts differ (P < 0.05) b
631.28
0.510
4.80
1050
618.84
0.503
4.82
950
608.95
0.499
4.76
850
$/A
¢/lb
lb/A
Total Value
Net Loan
Micronaire
Lint Yield
Heat Unit
a,b Means in columns without common superscripts differ (P < 0.05) b a
a b
Table 3. Quantity, quality, and value results from 2006.
700.76
0.530
4.87
1050
665.00
0.532
4.72
950
672.16
0.538
850
657.75
4.63
750
$/A
¢/lb
lb/A
Total Value
Net Loan
Micronaire
Lint Yield
Heat Unit
Table 4. Quantity, quality, and value results from 2007. b
a b a
a,b Means in columns without common superscripts differ (P < 0.05)
Table 5. Quantity, quality, and value results separated by variety. b
a b a
708.15
0.532
4.6
1050
647.28
4.65
950
658.87
0.534
4.72
850
604.59
0.526
4.4
750 1
ST4554B2RF
$/A
¢/lb
lb/A
Total Value
Net Loan
Micronaire
Lint Yield
No. Years
Heat Unit
666.14
0.516
5.11
1290.9
700.22
0.535
5.15
1310.3
683.91
5.24
1280.5 3
DPL555BGRR
650.39
0.523
4.83
626.75
0.509
4.59
651.09
0.530
4.69 2
DPL445BGRR
a,b Means within a variety and in columns without common superscripts differ (P < 0.05)
1 Varieties were each analyzed separately.
675.14
4.9
680.54
4.7
639.27
0.512
4.8
ST5599BR
Methods
Based on a previous four year defoliation study, this three year study was initiated in 2005, with study locations in south Arkansas. Treatments were defoliation timing scheduled at 750, 850, 950, and 1050 HU beyond cutout. Study sites with replicated rows running the length of the field and standard cotton grower production practices were used throughout the study. Cotton varieties used during the study included DPL445BGRR, DPL555BGRR, ST4554B2RF, and ST5599BR. Cotton samples were taken from study fields prior to defoliation to acquire predicted micronaire values for studying the possible integration of the Hal Lewis method of defoliation with COTMAN. Study sites were harvested and average lint yields were determined using the producer’s picker when treatments were harvest-ready and weather permitted. Boll samples were taken at the time of harvest and were processed through a 20-saw gin with one lint cleaner. Samples were then subjected to HVI analysis, and net loan values were calculated. Total value was calculated by multiplying lint yield by the loan value. Cotton yield and quality data were analyzed as a randomized complete block design using PROC GLM of SAS (SAS Inst., Inc., Cary, NC). In the presence of significant treatment effects (P < 0.05), means were separated using least significant differences.
Acknowledgements
Table Average predicted and actual micronaire values.
1 Predicted micronaire values were taken from cotton samples collected at 15%-20% open boll. 2 1
4.6
4.7
4.4
4.1
3.9
ST4554B2RF
5.2
5.1 5
4.8
4.5
DPL555BGRR
DPL445BGRR
60%-70%
50%-60%
40%-50%
30%-40%
Average Actual Micronaire
Average Predicted Micronaire
Variety
2 Average actual micronaire for 40%-50%, 50-60%, and 60%-70% were determined from cotton samples collected at 850, 950
and 1050 HU, respectively.
Cotton Incorporated
Steve Stevens
Perry Wilson
Terrance Nichols