Despite some advantages, adoption of slow-release fertilizers in vegetables has been slow primarily due to cost. In crops fertilized with ground equipment, growers can make fewer trips through the field and assure fertilizer is present when conditions prevent application. With drip irrigation, some materials are difficult to inject, however, Nitamin is a new injectable liquid produced by Georgia Pacific. Thus, with plasticulture, growers can inject less frequently and potentially use lower rates. Granular and liquid formulations of slow-release fertilizer were tested on onions (Winter 2003–04), cabbage (Winter 2003–04) and pepper (Spring 2004) in Georgia. Combinations of traditional fertilizer with slow-release formulations and various rates of slow-release fertilizer alone were compared to a standard fertilizer program on these crops in separate experiments. The slow-release contains only N. So, other nutrients were held constant. Otherwise normal cultural practices were employed. Crops were harvested at maturity and data collected on yield and quality. In cabbage, with at least 50% of the standard N rate using the slow-release fertilizer, yields were comparable to the standard. Results on onions were similar with N rates of at least 75% of the standard for the liquid material; the granular formulation did not perform well. Split applications of slow-release fertilizer and combinations with standard fertilizer worked well for cabbage, but not for onions. Results on pepper, although inconclusive, indicated it was possible to get comparable yields at lower N rates with the slow-release material. Based on these results, lower N rates are possible on cabbage and onions with slow-release fertilizers which may make them economically feasible while providing application advantages to growers.
William Terry Kelley
William Terry Kelley
Carrots (Daucus carota L.) have become an economically important vegetable crop for Georgia. Currently the harvest season extends from December through May. One possibility for extending the harvest season would be to produce carrots in the cooler mountain area of Georgia during the summer months. This study was undertaken to examine the potential for fresh-market carrot production on Georgia mountain soils and to evaluate which varieties of carrots might be most suitable for this area. Ten commercially available carrot varieties were direct seeded into a Transylvania clay loam soil on 28 May 1999 in Blairsville, Ga. Plots consisted of three twin rows of carrots each 20 feet in length. The twin rows were each three inches apart and there were 20 inches between each set of twin rows. Each plot was replicated four times. Base fertilizer of 20 pounds of nitrogen, potassium, and phosphorous were incorporated into the plots prior to seeding. Sidedress applications of 15 pounds each of N, P, and K were applied at 3-week intervals throughout the season. Recommended pest control practices were applied. A three-foot section of the center twin row was harvested on 23 Sept. 1999. The varieties `Pacific Gold' and `Topnotch' produced the highest marketable yield; however, all yields were below acceptable levels. Percent marketability was <60% for all varieties. Percent stand was extremely variable due to variability in seed size. All carrots had severe nematode damage although a nematicide was used preplant. The length of season for spring-planted carrots was too long for the life of the nematicide at the rate and method applied. Late summer–planted carrots would likely be a more viable option for this area.
William Terry Kelley
Statistical analysis of agricultural research has traditionally been via the use of fixed model methods. However, recent advances in statistical software have made analysts through random or mixed model methods more practical. Errant or inappropriate use of statistical programs to analyze data has been a recurring problem in the reporting of agricultural research findings. Often variables are all considered to be fixed in order to facilitate analysis, when in reality some variables in field research are nearly always random. Proper selection of error terms and calculation of standard errors are also frequently done incorrectly when statistical analysts packages are not used correctly. Unbalanced data is also quite normal in field research due to unforseen circumstances that result in lost information. Most of these situations can be more early handled with a mixed model approach. In this work, a broccoli field trial involving tillage and planting dates was analyzed using the General Smear Models procedure in SAS and the General Elmer Mixed Models Procedure in GLMM. Comparison of the analyses revealed that conclusions would differ somewhat with balanced data and even more with unbalanced data. Since variance components from all random effects are used to calculate standard errors in GLMM, standard errors in the mixed model were larger, but likely more accurate Inference space was also broader and allowed prediction space to include the entire population of experimental units which were sampled in the experiment. The mixed model procedure was more efficient and thus more sensitive to differences in treatments.
William Terry Kelley
Jicama (Pachyrrhizas erosus L.) is a vigorous herbaceous vining plant of the Leguminosae family. Native to northern Central America and Mexico, it is produced commercially in Hawaii, Puerto Rico, and in warm regions of the southwestern United States. Also known as yam bean, Jicama produces a starchy edible root, although mature pods may be poisonous. This study was undertaken to evaluate the potential for Jicama as a crop in southeastern Georgia and to get some information on the N requirement of the crop. Jicama seeds were planted on 29 May 1997 in three row plots. The planting was arranged with 61 cm between rows and 20 cm between plants in the row. Plots were 6 m long. Each plot received one of five N rates: 0, 30, 60, 90, and 120 kg·ha-1. Treatments were replicated four times. Otherwise normal cultural practices were employed. Data were collected at harvest on 2 Dec. on number and weight of marketable roots, average root size, percent marketability, external and internal color, and root diameter. There were no significant differences among treatments for any of the parameters measured. However, most of the parameters measured showed some linear relationship to fertility level. Jicama produced under lower fertility levels revealed smaller roots, lower yield, and lower percent marketability. External color of roots with lower fertility levels were darker which may have contributed to a lower percent marketability. N fertilizer at between 60 and 120 kg·ha-1 seems most appropriate for this crop in southeastern Georgia.
William Terry Kelley and David L. Coffey
Three cropping sequences and three tillage systems were evaluated under reduced tillage. Sequences were spring `Packman' broccoli followed by `Sunny' tomatoes or 'm.s. Ky 14 × L8 tobacco, spring broccoli/tomatoes or tobacco/fall broccoli, and tomatoes or tobacco/fall broccoli. Each sequence was grown conventionally tilled/no winter cover, conventionally tilled/wheat winter cover and no-till transplanted directly into killed wheat. The study was conducted at Knoxville, (elev. 251m), Greeneville, (elev. 400m) and Crossville, (elev. 549m) during 1989 and 1990. Experiments were arranged in a strip-plot design with sequences stripped across tillages. No. 1 tomato yield was reduced in no-till at Greeneville (1989). Percentage of No. 1 tomatoes was not affected by tillage but the tomato-broccoli system produced a greater percentage at Greeneville (1990). Broccoli head size and subsequent yield was generally greater in conventionally tilled plots. Sequence generally had little affect on broccoli production. Yield and revenue of tobacco were generally lower in no-till treatments. Broccoli/tobacco sequences generally had the highest yield but varied by location. No-till produced lower quality tobacco both years at Knoxville but not at Greeneville.
William Terry Kelley and David L. Coffey
Three cropping sequences and three tillage systems were evaluated for increasing returns on small farms under reduced tillage. The sequences were spring 'Packman' broccoli followed by 'Sunny' tomatoes, spring broccoli/tomatoes/fall broccoli, and tomatoes/fall broccoli. Each sequence was grown conventionally tilled with no winter cover, conventionally tilled with a wheat winter cover and no-till transplanted directly into killed wheat. The study was conducted at Knoxville, TN (elev. 251m, Greeneville, TN (elev. 400m) and Crossville, TN (elev. 549m) during 1989 and 1990. Experiments were arranged in a strip plot design with sequences stripped across tillage treatments. No. 1 tomato yield was reduced in no-till at Greeneville (1989). Percentage of No. 1 tomatoes was not affected by tillage but the tomato-broccoli system produced a greater percentage at Greeneville (1990). Percentage of cull fruit was greater in Knoxville (1990) for conventional/no cover. A tomato-broccoli sequence produced more cull fruit at Knoxville (1990) and Greeneville (1989). Broccoli head size and subsequent yield and value was generally greater at most environments in conventionally tilled plots. Sequence generally had little affect on broccoli production.
William Terry Kelley and Darbie M. Granberry
Bell pepper (Capsicum annuum) is traditionally transplanted either to the top of the root ball or to the cotyledons of the transplant. Recent evidence has shown that increased and earlier yields may be obtained by deeper transplanting of pepper. Thus, a study was undertaken to investigate the effects of pepper transplanting depth on flowering and the fruit characteristics of harvest fruit. Pepper was transplanted to the top of the rootball, the cotyledons, and the first true leaf at two locations in 1994. Both `Camelot' Hybrid and `Jupiter' (open-pollinated) cultivars were planted into bareground on Mar. 24 at Tifton, Ga. Only `Camelot' was transplanted into a plastic mulch with drip irrigation on Mar. 28 at Cool Springs. Plots consisted of a single row of seven plants with the internal five plants used for data collection. Treatments were replicated three times. Normal cultural and pest control practices were used at both locations. Data on flowering were collected 5 weeks after transplanting. Data on fruit characteristics were collected at harvest. Number of bloom clusters per plant, number of blooms per cluster, number of open blooms, and number of set blooms were significantly greater in the deeper-planted pepper at Cool Springs. The same was true for bloom clusters and blooms per cluster at Tifton. Number of blooms open and set were greater in deeper-planted `Camelot' at Tifton as well. There were virtually no differences among characteristics of harvest fruit. Earlier bloom set appears to occur in deeper-planted pepper on both bareground and mulched beds.
William Terry Kelley and David B. Langston Jr.
The phase out of methyl bromide has precipitated a need to reduce usage of the all purpose fumigant. Reduction in methyl bromide use can extend the life of existing stocks and make it more likely to continue critical use exemption for future production. Traditional widths for plastic mulch covered beds in Georgia ranges from 32 to 36 inches. By reducing bed top widths, it could be possible to reduce the amount of methyl bromide applied by as much as 60%. The objectives of this work were to evaluate the effects of narrower bed tops and lower rates of methyl bromide on pepper and cantaloupe growth and yield. Bed top widths of 36, 30, and 24 inches were each tested with broadcast rates of 400 and 300 lb/acre of both 67:33 and 50:50 methyl bromide-chloropicrin at Tifton, GA in the fall of 2005. Bed widths were the main plot and methyl bromide rates the sub plot. Plots were 20 feet long with two rows of pepper planted per bed with 12 inches between plants and one row of cantaloupe planted per bed with two feet between plants. All beds were on 6-ft centers and fertilizer rates were constant across plots within a crop. There were four replications. Otherwise normal cultural practices were employed. Crops were harvested at maturity and data collected on yield and plant growth. Pepper yields were depressed by early cold weather. The 24-inch bed tops produced significantly lower yields of extra large, large and total fruit, but had greater top dry weight and root fresh weight than the 36-inch beds. There were no differences found among methyl bromide rates for cantaloupe or for pepper except extra large fruit were greater at the highest rate compared to the lowest. There were no differences among bed top widths for cantaloupe yield or plant growth.
William Terry Kelley and Darbie M. Granberry
Bell pepper (Capsicum annuum) has traditionally been transplanted to the top of the root ball or to the cotyledons of the transplant. Recent studies have shown increased and earlier yields are obtained by transplanting pepper deeper. Thus, a study was initiated to investigate effects of transplanting depth on pepper yield and plant growth. Pepper was transplanted to the top of the rootball, the cotyledons, and the first true leaf in two locations in 1994. `Camelot' hybrid and `Jupiter' (open pollinated) cultivars were planted into bare ground on Mar. 24 in Tifton, Ga. Only `Camelot' was transplanted into a plastic mulch with drip irrigation on Mar. 28 in Cool Springs. Plots consisted of single rows of seven plants with data collected from the internal five plants. Treatments were replicated three times. Normal cultural and pest control practices were used at both locations. Plant measurement data were taken 5 weeks after transplanting. Yield data were collected at harvest. Total weight per plant of three harvests was significantly greater with peppers planted to cotyledons and first true leaf than those planted to the rootball in `Jupiter'. There was no significant effect of planting depth on `Camelot', although there was a distinct trend toward greater yield with deeper planting on plastic. The same trend was evident for average weight per plant and average number of fancy-grade peppers per plant. Average stem diameter, plant height, and length of largest leaf were all greater among deeper planted peppers. Deeper planting seems to have a positive effect on yield and plant growth, particularly with hybrid pepper planted into a plastic mulch.