USDA, Agricultural Research Service Canal Point, Florida 33438
ABSTRACT
Sugarcane cultivars respond differently to mechanical harvesting. The object of this research was to examine the performance of current cultivars over a 3-year crop cycle. Twelve commercial and unreleased cultivars were grown in replicated plots at the Everglades Research and Education Center (EREC), Belle Glade, Florida. The cane was planted on December 22-23, 1987 and was harvested for three crops (plant, first, and second ratoon) with a combine harvester.
Gross cane weight was determined for each experimental plot. Each year, a random sample of cane stalks was collected from each plot, milled in a 3-roller sample mill, and juice quality was determined from the extracted juice. Using juice quality factors and net cane weights from each plot, estimated sugar yield was calculated. Additionally, each plot of cane was rated for cane erectness/adaptability for mechanical harvesting. Significant yield differences were found among cultivars.
Differences in ratooning ability among cultivars were noticeable after 3 years of mechanical harvesting. CP 80-1827 had the best regrowth rating and the highest stalk counts in the third- ratoon crop, with CL 73-239, CP 74-2005 and CP 80-1743 also providing acceptable stands. CP 78-2114 had the poorest ratings and the lowest stalk counts in the third-ratoon crop.
INTRODUCTION
Sugarcane acreage in Florida has continued to increase since its rapid rise in the early 1970's, with approximately 440,000 acres grown for the 1990-91 crop (Coale and Glaz, 1991).
Mechanical harvesting of sugarcane remained fairly constant at 26-32% of the total crop from 1975-1988 (Unpublished data from USDA, ARS, Sugarcane Harvesting Laboratory). Reasons for not increasing mechanical harvesting during this time were: (1) the continued availability of imported manual labor; (2) cane stubble was damaged by mechanical harvesters and more frequent replanting was required; and (3) producers were still assessing the reliability and real cost of mechanical harvesting. Mechanical harvesting comprised 40% of the 1990-91 crop (Florida Sugar Cane League, Personal Communication). In our opinion the increase in mechanical harvesting has occurred because recent versions of mechanical harvesters have become more reliable and effective whereas handcut costs have continued to increase. This increase in mechanical harvesting has coincided with industry expansion onto mineral soils and the utilization of cultivars more adapted to mechanical harvesting.
Clayton et al. (1982) conducted two previous experiments during 1973-78 comparing the yield performance of 17 commercial and unreleased cultivars, subjected to mechanical harvesting.
Of these 17 cultivars, only three were grown commercially in 1990, representing only 17.5% of the acreage (Coale and Glaz, 1991). A new experiment, comparing 12 cultivars grown on 90%
of the crop area for the 1990-91 crop (Coale and Glaz, 1991), was planned and initiated in 1987.
The objective of this experiment was to evaluate the performance of these 12 cultivars over a three crop cycle on an organic soil when subjected to current mechanical harvesting equipment.
MATERIALS AND METHODS
The field for the experiment was located at the University of Florida, Everglades Research and Education Center (EREC), Belle Glade, Florida. The experimental design was a randomized- complete-block with three replications. Each plot consisted of 3 rows (15 ft. wide) of cane 200 ft. in length. Twelve cultivars (CL 61-620, CL 73-239, CP 70-1133, CP 70-1527, CP 72-1210, CP 72-2086, CP 73-1547, CP 74-2005, CP 78-1247, CP 78-2114, CP 80-1743, and CP 80-1827) were selected from commercial, recently released, and experimental cultivars, representing diverse stalk and growth characteristics. Seedcane of each cultivar was handcut and planted in organic soil (Histosol-Pahokee muck), using two continuous lines of seedcane per row, on December 22- 23, 1987. The plots received herbicide spray treatments and 2-3 mechanical cultivations during each growing season. The cane in the plots was burned on the afternoon prior to harvesting.
Cane in each plot was harvested using an Austoft 77001 combine harvester. The plant-cane crop was harvested on February 26, 1989. The first-ratoon crop was harvested on February 25, 1990 because a deterioration study was conducted using the cane damaged by the December 24-26, 1989 freeze, delaying the planned early January harvest. The second-ratoon crop was harvested on December 5, 1990. The field was not chiseled after harvest. The harvest schedule was planned to simulate a typical harvesting strategy in Florida.
For the plant-cane and second-ratoon crops, a 10-stalk random sample was collected from each plot after the preharvest fire, milled in a 3-roller sample mill within 2 days, and the extracted juice analyzed for Brix and sucrose. For the first-ratoon crop, unburned stalk samples were collected for juice analysis on December 29, 1989 before any significant deterioration caused by the severe freeze had occurred. These unburned samples were processed in a similar manner to the other samples. To approximate mechanical harvesting, all samples were topped at the top visible dewlap, ie. the immature tops were included in the mill samples and leaf trash adhering to the stalks was not removed before milling. Cane in each plot was rated for stalk erectness/machine adaptability on a scale of 1 (poor) to 10 (excellent). The stalk erectness/machine adaptability rating was a subjective attempt to rate erectness, the ease and efficiency with which stalks could be collected by the harvester gathering mechanisms and how well the stools were anchored into the soil. Root anchoring characteristics of the second-ratoon crop prior to harvest were visually rated on a scale of 1 (poor) to 4 (excellent). For instance, uprooted stools rated 1 and stools showing no evidence of uprooting rated 4. Regrowth was evaluated several months after each harvest on the basis of potential yield (tons per acre/10).
Stand counts were also taken on 100 ft. of the center row of each plot. Cane from each 3-row plot was loaded into high-dump wagons, weighed on a hydraulic scale at the EREC, and loaded into highway cane trailers. (No effort was made to separate cultivars for milling purposes because of logistics.) Cane in each plot was cut by deadheading the mechanical harvester and transport equipment. A random sample (100+ pounds) of cane was collected at the sugar mill each year for trash determination. It was recognized that individual cultivars would have different trash values, but we could not sample satisfactorily on an individual cultivar basis and chose to use a random trash sample.
Using loaded wagon weights and their tares, gross cane weight for each plot was determined. Gross cane weight from each plot and the plot area were used to calculate gross tons/acre of cane for each plot. Using the trash factor from the mill trash determination, net cane/acre was calculated for each plot. Brix and sucrose values from each sample were used to calculate the estimated yield of sugar in lb/net ton of 96° recoverable sugar using the Winter-Carp- Geerligs formula (Arceneaux, 1935). This value was used with the net cane yield to estimate yield 96° recoverable sugar per acre.
1 Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by USDA or Okeelanta Corporation or an endorsement over other products not mentioned.
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All data were analyzed using an analysis of variance with sample means tested for significant differences using Duncan's multiple range test (Steel and Torrie, 1960). Data were summarized and evaluations are based on the three-year means of the data because that is the amount of sugar that growers are paid for. These are also the figures that are needed to assist producers in making management decisions about which cultivars to plant.
RESULTS
Abnormal harvesting losses were not observed in the field after harvest. Two cultivars (CL 73-239 and CP 80-1743) had extreme rat damage in the plant-cane crop and each tended to have slightly higher field losses than cultivars without rat damage. Consequently, yields of cane are representative of cane which can be delivered by a combine harvester, which is the basis for a grower's payment. Since the objective of this test was to measure production under a combine harvesting system, no attempt was made to scrap plots for harvesting losses. Sugarcane rust (Puccinia melanocephala) severely infected CP 78-1247 as plant cane and moderately infected CP 72-1210 and CP 74-2005.
Table 1 summarizes cultivar production over the three-crop cycle. The highest yielding cultivars for tons of cane per acre were CP 80-1827, CP 73-1547, and CP 70-1133. These three cultivars are noted for vigor, disease resistance, and tonnage yield of cane. Further, these three cultivars along with CL 61-620 were the highest yielding cultivars in sugar per acre. The cultivars with the lowest yields (tonnage and sugar per acre) were CP 72-1210, CP 78-1247, and CP 78- 2114. CP 78-2114 did not ratoon acceptably under the management system in this experiment.
Table 1. Performance of twelve cultivars of sugarcane over a three-crop cycle harvested mechanically at EREC, Belle Glade, Florida.+
-f- Each value represents the average of three replications over three crops. Mean values with different letter values are significantly different at the 10% level according to Duncan's multiple range test.
(a) Gross Tonnage/acre (b) Net Tonnage/acre
Crusher juice quality parameters (Table 2) show that the high tonnage cultivars had slightly lower juice quality than other cultivars. Juice purity indicated that all cultivars had good maturity.
The cultivars with the highest sugar/net ton were CP 74-2005, CL 73-239, CL 61-620, CP 80- 1743, and CP 72-2086.
-f- Each value represents the average of three replications over three crops. Mean values with different letter values are significantly different at the 10% level according to Duncan's multiple range test.
Growth characteristics of the cultivars (Table 3) were diverse. CP 70-1527 was the most erect cultivar with CP 72-1210 and CP 80-1827 exhibiting acceptable erectness/machine adaptability across the three crop cycle. Cultivars with the lowest erectness ratings were CP 70-1133, CP 73- 1547, CP 78-2114, CP 80-1743, and CL 73-239. Cultivars with an erectness rating over 3.0 are capable of being mechanically harvested by the Austoft 7700 without significant feeding problems or travel speed reductions.
One of the requirements for cultivars adapted to mechanical harvesting is sufficient vigor to insure stool survival after harvesting. Visual rating of the root anchoring system (Table 3) before the second-ratoon crop harvest caused us to believe that cultivars differed in this characteristic.
However, the rating system utilized was not sufficiently sensitive to detect significant statistical differences. It should be noted that the two cultivars (CP 80-1827 and CP 80-1743) with the highest third-ratoon crop growth ratings had high root system ratings, but diverse erectness ratings. Growth ratings (potential cane yield) of the ratooning cane (Table 3) averaged for three
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Table 3. Cultivar growth characteristics of twelve cultivars harvested mechanically at EREC, Belle Glade, Florida.+
+ Each value represents the average of three replications over three crops. Mean values with different letter values are significantly different at the 10% level according to Duncan's multiple range test.
1/ 1 - 1 0 Scale, 1 = erect, 10 = recumbent.
2/ 1 - 4 Scale, 1 = uprooted, 4 = root system well anchored.
3/ 1 - 5 Scale, rating equal to estimated tonnage per acre/10.
harvests showed CP 80-1827 and CP 73-1547 with the highest expected yields. The lowest growth ratings occurred with CP 78-2114, CP 72-1210, and CP 78-1247.
Growth ratings after the second-ratoon harvest (Table 4) showed CP 80-1827 was superior to all other cultivars. These growth ratings were supported by stand counts of the third- ratoon crop (Table 4). Other cultivars with acceptable stands in some plots included CP 80-1743, CP 74-2005, and CL 73-239. The remaining cultivars did not have sufficient stands to produce acceptable yields in third ratoon. As a result, the experiment was terminated after evaluating these ratings.
Table 4. Cultivar regrowth characteristics of twelve cultivars as third ratoon after three years of mechanical harvest at EREC, Belle Glade, Florida.+
-f- Each value represents the average of three replications. Mean values with different letter values are significantly different at the 10% level according to Duncan's multiple range test.
1/ Estimated tonnage yield/acre divided by 10.
Yields of sugar/acre in the plant cane crop are shown in Table 5. Better performing cultivars were CL 61-620, CP 70-1133, and CP 73-1547. CP 78-1247 and CP 72-1210 had the lowest yield of sugar/acre. A concern of producers is the decrease in yield of sugar/acre exhibited by the second-ratoon crop compared to plant-cane crop. Table 5 shows the percent yield of sugar/acre of the second-ratoon crop compared to the plant crop. Two cultivars (CP 80-1743 and CP 78- 1247) essentially maintained yield of sugar/acre. However, the plant-crop yields of these two cultivars were lower than normal because of severe rat damage in CP 80-1743 and sugarcane rust in CP 78-1247.
DISCUSSION
Cultivars with high vigor produced the most sugar/acre over the three crop cycle. Satisfactory cultivar performances with mechanical harvesting after three crops on organic soil appears related to sufficient vigor to overcome damage caused by mechanical harvesting and transport equipment.
Cultivar growth characteristics did not interfere with mechanical harvesting in these plots.
Growers should recognize that the root system of a sugarcane cultivar will affect its long term performance on organic soil when subjected to mechanical harvesting.
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Table 5. Percent reduction of sugar/acre between second ratoon and plant cane harvested mechanically at EREC, Belle Glade, Florida.+
+ Each value represents the average of three replications. Mean values with different letter values are significantly different at the 10% level according to Duncan's multiple range test.
ACKNOWLEDGEMENTS
The authors thank New Hope Sugar Cooperative for providing seedcane of three cultivars and helping to plant the cane, U.S. Sugar Corporation for providing seedcane of two cultivars, Okeelanta Corporation for providing the mechanical harvester with operator, and the University of Florida for their assistance. Without the above cooperation, it would have been impossible to complete this experiment.
REFERENCES
1. Arceneaux, G. 1935. A simplified method of making theoretical sugar yield calculations in accordance with Winter-Carp-Geerligs formula. Intl. Sugar J. 37:264-265.
2. Clayton, J. E., B. R. Eiland, J. D. Miller, and P. Y. P. Tai. 1982. Evaluation of sugarcane characteristics for mechanical harvesting in Florida. J. ASSCT 1:40-46.
3. Coale, F. J. and GIaz, B. 1991. Florida's 1990 sugarcane variety census. Sugar y Azucar 86(1): 20-26.
4. Steel, R. G. D. and J. H. Torrie. 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., N. Y.
PREEMERGENCE CONTROL OF ITCHGRASS (ROTTBOELLIA COCHINCHINENSIS) IN SUGARCANE1
James L Griffin and Reed J. Lencse2
Department of Plant Pathology and Crop Physiology Louisiana Agricultural Experiment Station, LSU Agricultural Center
Baton Rouge, Louisiana 70803 ABSTRACT
Itchgrass has become a serious weed problem in Louisiana sugarcane. Soil-incorporated trifluralin is the standard preemergence treatment for control of itchgrass, but grower concerns over the potential yield reduction associated with its mechanical incorporation has stimulated interest in alternative preemergence soil-surface applied herbicides. Itchgrass control and sugarcane injury with both soil-incorporated and surface applied preemergence herbicides were compared at several locations in the sugarcane growing regions of Louisiana. Itchgrass control with pendimethalin, fomesafen, and clomazone applied in the spring to unshaved sugarcane beds was comparable to that of soil- incorporated trifluralin. In other studies, soil-surface applications of pendimethalin plus atrazine (2.2 and 3.4 plus 3.3 kg/ha), prodiamine (1.7 to 2.8 kg/ha), clomazone (1.1 to 2.2 kg/ha), and fomesafen (0.8 and 1.1 kg/ha) provided acceptable (>80%) itchgrass control when compared to the untreated check. Fomesafen (0.6 kg/ha), quinchlorac (0.3 to 1.1 kg/ha), terbacil (2.1 kg/ha), metribuzin (2.6 kg/ha), and atrazine (3.3 kg/ha) provided poor itchgrass control. Sugarcane injury was minimal with the exception of clomazone, which caused a temporary bleaching of sugarcane foliage at only one location. Sugarcane stalk populations following treatment with quinchlorac, terbacil, metribuzin, and atrazine were comparable to the untreated check and were reflective of poor early-season itchgrass control. Compared with soil-incorporated trifluralin, use of pendimethalin, prodiamine, fomesafen, and clomazone applied to the soil surface would reduce trips across the field and may minimize sugarcane injury, but may not provide consistent itchgrass control when rainfall is not received for activation.
Nomenclature: Atrazine, 6-chIoro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine; clomazone, 2- [(2-chlorophenyI)methyl]-4,4-dimethyl-3-isoxazolidinone; fomesafen, 5-[2-chloro-4- (trifluoromethyl)phenoxy]-N.-(methylsulfonyl)-2-nitrobenzamide; metribuzin, 4-amino-6-(1,1 - dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one; pendimethalin, N-(1 -ethylpropyl)-3,4-dimethyl- 2,6-dinitrobenzenamine; prodiamine, 2,4-dinitro-N,N-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine;
quinchlorac, 3,7-dichloro-8-quinoline-carboxylic acid; terbacil, 5-chloro-3-( 1,1 -dimethylethyl)-6-methyl- 2,4-(1 H,3H)-pyrimidinedione; trifluralin, 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine].
INTRODUCTION
Itchgrass [Rottboellia cochinchinensis (Lour.) Clayton] was introduced into southern Louisiana in the 1920's (4) and has become a serious weed problem in sugarcane (Saccharum sp.), corn (Zea mays L.), and soybeans [Glycine max (L.) Merr.]. Itchgrass is an aggressive, erect annual grass that may grow to 3 m tall (1). Germination in late-season, prolific seed production, and ability to persist under a crop canopy, contribute to making itchgrass a potential major weed problem in many cropping systems (8). Lencse and Griffin (2) reported a 34, 42, and 43% reduction in sugarcane stalk production, and cane and sugar yields, respectively, when itchgrass was allowed to compete with sugarcane in early-season prior to layby.
1Approved for publication by the Director of the Louisiana Agricultural Experiment Station as manuscript number 91-38-5167.
2Reed J. Lencse is a former Graduate Research Assistant and is presently employed with American Cyanamid Company, Lonoke, AR.
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In Louisiana, itchgrass in sugarcane is controlled with a soil-incorporated treatment of trifluralin in the spring followed by asulam [methyl[(4-aminophenyl)sulfonyl]carbamate] early postemergence if needed (7). To facilitate trifluralin incorporation, the top of the bed is removed in a shaving operation and the soil above the sugarcane is loosened with one pass of a rolling cultivator. The herbicide is applied on a band on top of the bed and incorporated with two additional passes of a rolling cultivator.
At the layby (last) cultivation, trifluralin is reapplied as a broadcast spray directed below the crop canopy and incorporated with rolling bed choppers.
Pendimethalin applied preemergence to the soil surface at rates of 3.3 to 4.5 kg/ha has provided good itchgrass control with no adverse effect on sugarcane yield (5). Weed control with pendimethalin was most effective when rainfall of at least 1.25 cm was received within 10 days after treatment. In other studies, itchgrass control was at least 80% with pendimethalin at 3.4 kg/ha and prodiamine at 2.2 to 3.4 kg/ha (7). Fomesafen at 0.6 kg/ha and clomazone at 2.2 kg/ha gave 60 to 75% control. Soil-incorporated treatments of terbacil, at 3.6 kg/ha and trifluralin at 2.2 kg/ha provided about 60 days of itchgrass control (3). Trifluralin at 2.2 kg/ha followed by asulam at 3.7 kg/ha controlled 94% of itchgrass and was more consistent than either treatment applied alone (6).
Since growers are concerned about potential sugarcane yield reductions associated with the incorporation of trifluralin, soil-surface applications of herbicides currently registered in sugarcane along with others presently registered or near registration in other crops were evaluated for itchgrass control and sugarcane injury under similar conditions at several locations in the sugarcane growing regions of Louisiana.
MATERIALS AND METHODS Trifluralin Comparison Studies
Studies were conducted at Rougon and Thibodaux, LA in 1988 and at Maringouin and Thibodaux, LA in 1989. The Rougon and Maringouin sites were located in the northern sugarcane growing region of Louisiana whereas the Thibodaux site was located in the southern growing area.
The sugarcane cultivar 'CP 70-321' (plant cane) was present at Rougon in 1988, 'CP 70-321' (second stubble) was present at Thibodaux in 1988 and 1989, and 'CP 76-331' was present at Maringouin in 1989. Natural itchgrass infestations occurred at each location.
Treatments consisted of soil-incorporated trifluralin at 2.2 kg/ha and pendimethalin at 2.2 and 3.3 kg/ha, fomesafen at 0.84 kg/ha, and clomazone at 1.1 and 1.7 kg/ha applied directly to the soil surface. Plots to be treated with trifluralin were shaved (2.2 to 5 cm of soil removed) prior to application. Trifluralin was applied to a 90-cm band on top of the sugarcane bed and incorporated immediately after treatment with two passes of a rolling cultivator. Soil-surface treatments were applied as a 90-cm band over-the-top of the sugarcane. In 1988, herbicides were applied on April 20 at Rougon and on March 22 at Thibodaux, and in 1989 on March 15 at Maringouin and on March 14 at Thibodaux. At all locations sufficient rainfall to activate herbicides was received within 10 days after application. At the time of application, sugarcane was 64 to 76 cm, 10 to 15 cm, and 8 to 10 cm in height at Rougon, Maringouin, and Thibodaux (1989), respectively. Green cane growth was not present when herbicides were applied at the Thibodaux site in 1988 due to top-kill of emerged cane by frost. Itchgrass was not present at any of the sites when the herbicides were applied. Visual itchgrass control and sugarcane injury were rated just prior to the layby cultivation in mid-May.
A randomized complete block experimental design with 4 replications in 1988 and 5 replications in 1989 was used. Data were subjected to analysis of variance for individual locations.
Differences among treatment means were determined using Fisher-protected Least Significant Difference (LSD) tests at the 5% level of probability.