Hidalgo County Carrot Production Management Trial 1995-1996
Holden Wallace Inc., Gerber Products Company and Asgrow Seed Company Cooperating with Texas Agricultural Extension Service including: L. Brandenberger and T. Isakeit
Introduction:
Commercial carrot production in the Lower Rio Grande Valley accounted for more than 8,000 acres in the 1994-95 season, for both fresh and processing markets. Producers, packing sheds and processors are searching for methods to increase both the yield and quality of carrots produced. Some potential means for improving the production system include improved hybrid varieties and additional fertilizer and fungicide applications to the crop.
Objective:
To evaluate increased production inputs for processor carrot production in the Lower Rio Grande Valley.
Methods and Materials:
During the fall of 1995, a production management trial was established in a commercial carrot field east of La Joya in western Hidalgo County on a McAllen fine sandy loam. Large plots were utilized to simulate commercial production conditions. Each plot consisted of 24 raised beds on 40 inch centers, running the entire length of the field (1100 feet long) and averaged 2.1 acres in area. Furrow irrigation was utilized for watering. The four treatments utilized in the study consisted of 'Danvers 126`, with and without additional inputs, and 'Convert' a hybrid carrot variety from Asgrow Seed, with and without additional production inputs. The additional inputs consisted of four fungicide applications plus one additional fertilizer application.
There were two fertilizer rates: 101 lbs. and 163 lbs. of actual nitrogen per acre. Fertilizer was applied in split applications: Pre-plant applications applied 400 lbs. of 6-27-11-11 per acre, (24 lbs. nitrogen/acre) to all plots; A side-dress application was applied on December 3, 1995 to all plots, as 25 gallons per acre of 28-0-5, (77 lbs. nitrogen/acre); A second side-dress application was applied on January 3, 1996 to the additional input plots, as 20 gallons per acre of 28-0-5, (62 lbs.nitrogen/acre).
The additional input plots had foliar applications of Bravo 720 to control Alternaria leaf blight (Alternaria dauci). Fungicide applications were made on 1-8-96, 1-23-96, 2-15-96 and 2-22-96 utilizing Bravo 720 at the 1.5 pt./acre rate on the first three dates and the 2.0 pt./acre rate on 2-22-96. Plot operations are summarized in table 1.
Plots were rated for blight severity on 2-20-96, 3-11-96 and 4-22-96. Blight was rated on a 1 to 4 scale, where 1= light severity and 4 = heavy severity. Five sub-plots per plot were examined on 4-22-96 for incidence of powdery mildew (Erysiphe polygoni) and cotton root rot (Phymatotrichopsis omnivora). Incidence was recorded for each disease as the percent of sub-plots where symptoms were seen.
Carrot samples were removed by digging both lines of carrots from each six-foot-long length of bed. Evaluation included counting, sizing into three categories, and grading out carrots which were forked, broken or which exhibited root rot. The three root size categories were: less than 1.25" in diameter, greater than 1.25" to <1.50" in diameter, and 1.50" or greater in diameter. Percent marketable yield was calculated from the weights, with roots >1.5" considered as marketable. In addition, ten roots were selected from each sub-sample and sent to Gerber Products Co. and a 50-root composite sample for each plot was sent to T.A.M.U. Horticulture Department, for testing these root quality factors: nitrates, brix, sodium, acidity, total solids, and organic compounds.
The plots were harvested between 5-3-96 and 5-11-96 with a commercial carrot harvesterand loaded onto commercial trucks for transport to the packing plant. Plot number and net weights were recorded for each load.
Experimental Design:
A factorial design with three replications was used. Plots ran the full length of the field to permit easier field operations.
Results and Discussion:
Yield and Quality. There were no significant differences in yield between controls and treatments receiving additional fertilizer and fungicide inputs, for either of the cultivars (Table 2). When averaged for all treatments, Danvers 126 yielded more than Convert.
Overall yields ranged from a high of 56451 lbs./acre to a low of 42873 lbs./acre, (table 2). The yield of 'Danvers 126' was 55209 lbs./acre and was significantly higher than the 44507 lbs./acre that was recorded for 'Convert'. Marketable yield was significantly higher for 'Danvers 126', compared to 'Convert' with marketable yields of 34,139 and 15,370 lbs./acre, respectively. Yields of 'Convert' for root classes <1.25", >1.25-<1.5" and culls were significantly higher compared to 'Danvers 126', (Table 2). The small root classes and culls accounted for 50 and 26 percent of the overall yield, respectively, of 'Convert' and 'Danvers 126'.
Root quality factors of nitrates and percent dry weight varied significantly for the two cultivars included in the study, but not between cultural practices, (Table 3). 'Convert' was significantly lower for nitrates than 'Danvers 126' with recorded nitrates of 45.4 and 63.8 ppm, respectively. The percent dry weight was significantly higher for 'Convert' treatments compared to 'Danvers 126'. Percent dry weights were 14.1 and 13.6%, respectively, for 'Convert' and 'Danvers 126'.
Generally, the differences recorded in yield and in quality characteristics are a result of the two different cultivars included in the trial. Treatments utilizing 'Danvers 126' consistently yielded higher than those with 'Convert', except for the smaller root sizes, where 'Convert' produced significantly higher small root yields. Observations made throughout the season indicated that 'Danvers 126' had a more vigorous top growth and this may account for some of the yield difference between these two cultivars. One trend noticed in the results was that treatments that included additional inputs (fungicide and additional fertilizer) had lower yields compared to those that did not, although the differences were not significant statistically. One possible explanation for this trend may be that some root damage occurred with the extra fertilizer application, possibly physical damage from the application equipment or burning of the roots from the fertilizer. The two cultivars differed significantly on two of the root quality measurements, nitrates and percent dry weight. These differences may prove important to processors regarding product quality and the amount of packout that can be expected for a given cultivar.
Diseases. The growing season was exceptionally dry and this was reflected in the low incidence of Alternaria leaf blight throughout the season. There were no apparent differences in leaf blight severity among the treatments (Table 4). In some instances, the severity decreased over time, probably because of the appearance of new, disease-free foliage. This was a production year where the use of a foliar disease forecasting system would have resulted in few spray recommendations, allowing cost savings, in comparison with the use of a fixed spray schedule.
Conditions were so dry that powdery mildew - not a common disease in the Lower Rio Grande Valley - became prevalent later in the season. There were differences in incidence of powdery mildew between cultivars. 'Danvers 126', incidence ranged from 66 - 100%, while incidence ranged from 0 - 66% for 'Convert' (means shown in Table 4). However, disease severity in all treatments was low and there was no noticeable effect on plant growth.
The carrots were affected by cotton root rot and root knot nematodes. Normally, cotton root rot is not a problem on carrots grown in infested soil because carrots are usually harvested before soil temperatures become high enough to promote infection by the pathogen. Patches of wilted and dead plants were seen in the field on 4/22. From Table 5, it appears that there was a greater severity and incidence of cotton root rot with 'Convert' than with 'Danvers 126'. The range in incidence among replicates of 'Danvers 126' was 0-1%, while with 'Convert', it was 0-8%. These results only suggest a trend and no conclusions about relative susceptibility are warranted, since this trial was not designed to test cultivar or treatment effects on cotton root rot. Furthermore, although there are no effective control measures for this disease, it can be avoided simply by harvesting fields earlier in the season.
Yield loss caused by root knot nematode ranged from 5-16% among treatments (Table 5). There was great variability in its occurrence, reflecting a patchy distribution within the field. There were no apparent treatment or cultivar differences. This pathogen can be controlled by employing a weed-free fallow or by rotation with non-susceptible crops such as sorghum. Also, Telone II and Vydate L are nematicides registered for use on carrots. There were no other diseases observed in this field.
The study results as presented represent one year's work at one location on the cultural aspects of commercial carrot production. We would recommend that prior to using this information that another season's worth of data from a different location be studied to determine if the differences observed remain consistent. The authors would like to acknowledge the assistance given by: Mr. Joe Lucio for taking care of all the field operations at his farm; Ms. Dorthy Valdez for coordinating many of the arrangements needed to complete this study; Mr. Holden Wallace, Mr. Jim Breinling, Dr. Larry Baker for initiating and supporting the study; Dr. Bob Wiedenfeld for help on the statistical analysis.
Table 1. Plot operations.
| Date | Treatments1 | General | Fertilizer applications | Fungicide applications |
| 10/12/95 | 1-2-3-4 | NA | Preplant applied 400 lbs. 6-27-11-11 |
NA |
| 10/19/95 | 2-4 | Planted Convert hybrid carrot seed | NA | NA |
| 10/20/95 | 1-3 | Planted Danvers 126 carrot seed | NA | NA |
| 10/22/95 | 1-2-3-4 | 1st irrigation | NA | NA |
| 11/30/95 | 1-2-3-4 | 2nd irrigation | NA | NA |
| 12/03/95 | 1-2-3-4 | NA | 1st side dress applied 25 gal./acre 28-0-5 |
NA |
| 01/03/96 | 3-4 | NA | 2nd side dress applied 20 gal./acre 28-0-5 |
NA |
| 01/08/96 | 3-4 | NA | NA | 1st Bravo 720 applied at 1.5 pt./acre rate |
| 01/23/96 | 3-4 | Insecticide applied to all plots for carrot weevil control | NA | 2nd Bravo 720 applied at 1.5 pt./acre rate |
| 02/08/96 | 1-2-3-4 | 3rd irrigation | NA | NA |
| 02/15/96 | 3-4 | NA | NA | 3rd Bravo 720 applied at 1.5 pt./acre rate |
| 02-22-96 | 3-4 | NA | NA | 4th Bravo 720 applied at 2.0 pt./acre rate |
| 03-21-96 | 1-2-3-4 | 4th irrigation | NA | NA |
| 04-18-96 | 1-2-3-4 | 5th irrigation | NA | NA |
1 Treatment 1=Danvers 126 cultivar without additional fertilizer or fungicide; Treatment 2=Convert cultivar without additional fertilizer or fungicide; Treatment 3=Danvers 126 cultivar with additional fertilizer and fungicide; Treatment 4=Convert cultivar with additional fertilizer and fungicide.
Table 2. Yield data.
| Treatment1 | Yield lbs./acre2 |
Root yield <1.25" lbs./acre | Root yield >1.25-<1.5" lbs./acre | Cull roots lbs./acre |
Marketable yield >1.5" lbs./acre | Average root count/6 ft. of bed |
| 1 | 56451 | 3598 | 10313 | 3253 | 35390 | 66.3 |
| 2 | 46140 | 6997 | 11942 | 3766 | 16604 | 70.0 |
| 3 | 53967 | 2049 | 6721 | 2928 | 32887 | 63.1 |
| 4 | 42873 | 7085 | 9876 | 4852 | 14136 | 66.2 |
| Danvers 126 | 55209 | 2824 | 8517 | 3091 | 34139 | 64.7 |
| Convert | 44507 | 7041 | 10909 | 4309 | 15370 | 68.1 |
| Significance | * | * | * | * | * | NS |
Table 3. Nitrate, brix, brix/ta, sodium, acidity and total solids for carrot samples collected on 4-22-96.
| Treatment 1 | Nitrates ppm 2 |
Brix | Acidity | Brix/ta | Sodium mg/100g |
% dry wt. |
| 1 | 61.1 | 10.4 | 0.1 | 116.0 | 73.7 | 13.7 |
| 2 | 44.9 | 10.4 | 0.1 | 95.2 | 72.2 | 13.9 |
| 3 | 66.5 | 09.8 | 0.1 | 116.4 | 79.6 | 13.4 |
| 4 | 45.9 | 10.6 | 0.1 | 92.7 | 74.9 | 14.3 |
| Danvers 126 | 63.8 | 10.1 | 0.1 | 116.2 | 76.6 | 13.6 |
| Convert | 45.4 | 10.5 | 0.1 | 93.9 | 73.5 | 14.1 |
| Significance | * | NS | NS | NS | NS | * |
1 Treatment 1=Danvers 126 cultivar without additional fertilizer or fungicide; Treatment 2=Convert cultivar without additional fertilizer or fungicide; Treatment 3=Danvers 126 cultivar with additional fertilizer and fungicide; Treatment 4=Convert cultivar with additional fertilizer and fungicide; Danvers 126 = average of all treatments utilizing Danvers 126; Convert = average of all treatments utilizing Convert.
2 Two separate statistical comparisons are reported in each column. The comparisons between treatments 1, 2, 3, 4 exhibited no significant statistical differences at P=0.05. Danvers 126 and Convert exhibited significant statistical differences at P=0.05 as indicated by an asterisk.
TABLE 4. Leaf blight disease ratings and incidence of powdery mildew.
Danvers-- Conventional Production |
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Convert-- Conventional Production |
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Danvers-- Increased Inputs |
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Convert-- Increased Inputs |
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* Severity on three sampling dates. Mean of three replicates. The value for each replicate was the mean of 5 measurements. Rating scale of 1-4, where 1 = light severity and 4 heavy severity. Standard deviations in parentheses.
** Incidence measured on 4/22 is the mean of three replicates. The value for each replicate was the mean of 5 measurements. Standard deviations in parentheses.
TABLE 5. Severity and incidence of soilborne diseases.
Danvers-- Conventional Production |
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Convert-- Conventional Production |
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Danvers-- Increased Inputs |
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Convert-- Increased Inputs |
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* By weight of sub samples removed from plots. Mean of three replicates. Each replicate consists of 5 pooled sub samples. Standard deviations in parentheses.
** Based on sub samples removed from plots. Mean of three replicates. Each replicate consists of 5 pooled sub samples. Standard deviations in parentheses.
