Best management practices (BMPs) for vegetable crops are under development nationwide and in Florida. One goal of the Florida BMP program is to minimize the possible movement of nitrate-nitrogen from potato (Solanum tuberosum) production to surface water in the St. Johns River watershed without negatively impacting potato yields or quality. Current fertilizer BMPs developed for the area focus on fertilizer rate. Controlled-release fertilizers (CRF) have long been a part of nutrient management in greenhouse and nursery crops. However, CRFs have been seldom used in field-vegetable production because of their cost and release characteristics. Nutrient release curves for CRFs are not available for the soil moisture and temperature conditions prevailing in the seepage-irrigated soils of northern Florida. Controlled-leaching studies (pot-in-pot) in 2000 and 2001 have shown that plant-available nitrogen (N) was significantly higher early in the season from ammonium nitrate, calcium nitrate and urea compared to selected CRFs. However, N release from off-the-shelf and experimental CRFs was too slow, resulting in N recoveries ranging from 13% to 51%. Cost increase due to the use of CRFs for potato production ranged from $71.66 to $158.14/ha ($29 to $64 per acre) based on cost of material and N application rate. This higher cost may be offset by reduced application cost and cost-share pro-grams. Adoption of CRF programs by the potato (and vegetable) industry in Florida will depend on the accuracy and predictability of N release, state agencies' commitment to cost-share programs, and CRFs manufacturers' marketing strategies. All interested parties would benefit in the development of BMPs for CRFs.
With the development and implementation of best management practices (BMP), extension educators are facing a new and unexpected combination of challenges and opportunities. Because the BMP mandate requires a combination of research, demonstration, and outreach, it may affirm the relevance of the land grant mission in the 21st century, engage universities in interagency alliances, and help rediscover the wonders of the proven extension method. The extension approach to water and nutrient management needs to shift from “pollute less by applying less fertilizer” to “pollute less by better managing water.” Applied research is leading to advances in areas such as nutrient cycles and controlled-release fertilizers. At the same time, universities need to walk a fine line between education and regulation, address perennial issues of overfertilization, and consider the reformulation of recommendations that are now used in a quasi-regulatory environment. A combination of education, consensus, and novel approaches is needed to adapt the rigor of research to a multitude of growing conditions and risks of nutrient discharge in order to comply with U.S. federal laws and restore water quality.
While lettuce is one of the most widely consumed vegetables in the United States, production is mainly concentrated in the western states. This research investigated the feasibility of lettuce production in the Southeast (SE), where downy mildew, tip burn, bitterness, bolting, and postharvest handling are potential production problems. Lettuce varieties were evaluated on plastic mulch and drip irrigation under several growing conditions. Cultivar and location significantly (P < 0.01) affected yield and transplant survival rate. Following these tests, 'Salinas 88 Supreme', 'Legacy', 'Bullseye', 'Epic' (crisphead); 'Nancy', 'Nevada', 'Ostinata' (butterhead); 'Parris Islands', 'Augustus' (Romaine); and 'Red Salad Bowl', 'Red Prize', and 'Slobolt' (loose leaf) are considered best-performing lettuce varieties for Alabama. These results, along with bitterness evaluation, support the potential for lettuce production in the SE.
The main limiting factor to lettuce production in the Southeast is bitterness. Bitterness in lettuce is associated with sesquiterpene lactones, a bitter principles of the latex of wild lettuce species Lactuca virosa or L. sativa. These wild species are used as parents in the development of virus-resistant cultivars. This study evaluated bitterness of 18 commercial cultivars of lettuce grown following recommended production practices at two locations. Lettuce was hand harvested, refrigerated, washed, and cut into bite-size pieces. Samples were served one by one to a group of 15 panelists, trained with caffeine solutions of increasing bitterness scores (BS; 0% = 0, 0.05% = 2, 0.08% = 5, 0.15% = 10, and 0.20% = 15). A BS of less than seven was acceptable. BS was significantly (P < 0.02) different among varieties. Varieties with lowest BS were `Epic', `Salinas 88 Supreme', `Nevada', `Red Prize', and `Legacy'. For these varieties, mean, most frequent, and highest BS were less than seven. This study suggests that it is possible to grow nonbitter lettuce in the Southeast.
Most bell peppers (Capsicum annuum L.) produced and consumed are green. However, yellow, red, orange, white, black, and purple bell peppers are also available. While bell pepper consumption in the United States has been increasing in the past 10 years, limited information is available on how their color, retail price, and vitamin C content influence consumer preferences. A conjoint analysis of 435 consumer responses showed that, for the total sample, color was about three times more important than retail price in shaping consumers' purchase decisions, while vitamin C content was nearly irrelevant. Six distinct consumer segments were identified through cluster analysis. Four segments favored green peppers, while one segment favored yellow and one favored brown. Demographic variables generally were not good predictors of segment membership, but several behavioral variables, such as past bell pepper purchases, were significantly related to segment membership. While green is generally the preferred color, market segments exist for orange, red, yellow, and even brown peppers. Applications to marketing strategies suggested that price sensitivity could explain why green peppers were priced individually, but those of other colors were priced by weight, and that promotion of increased vitamin C content would be most effective if associated specifically with yellow and orange peppers.
The quantitative assessment of nitrate-nitrogen (NO3-N) leaching below the root zone of vegetable crops grown with plasticulture (called load) may be done using deep (150-cm) soil samples divided into five 30-cm long subsamples. The load is then calculated by multiplying the NO3-N concentration in each subsample by the volume of soil (width × length × depth, W × L × D) wetted by the drip tape. Length (total length of mulched bed per unit surface) and depth (length of the soil subsample) are well known, but W is not. In order to determine W at different depths, two dye tests were conducted on a 7-m deep Lakeland fine sand using standard plasticulture beds. Dye tests consisted in irrigating for up to 38 and 60 hours (11,756 and 18,562 L/100 m of irrigation, respectively), digging transverse sections of the raised beds at set times and taking measurements of D and W at every 30-cm. Most dye patterns were elliptic elongated. Maximum average depths were similar (118 and 119 cm) for both tests despite differences in irrigation duration and physical proximity of both tests (100 m apart in the same field). Overall, D response (cm, both tests combined) to irrigation volume (V) was quadratic (Dcomb.avg = –2 × 10–7V2 + 0.008V + 34), and W responses (applying maximum and average values, Wmax and Wmean) to D (cm) were linear (Wmax = –0.65D+114: Wmean = –0.42D + 79). Predicted Wmax were 104, 84, 64, 44, and 25 cm at 30-cm depth increments. These preliminary values may be use for load calculations, but are likely to over-estimate load as they were determined without transpiring plants and may need to be adjusted for different soil types.
Most potato (Solanum tuberosum L.) is produced as a non-irrigated crop in the southeastern United States. This practice makes potato yields dependent on rainfall pattern and amount. An irrigation scheduling method based on a water balance and class A pan evaporation data (Ep) was evaluated in Spring 1996 on a fine sandy loam soil with `LaSoda' potatoes. Planting date was 9 Apr. and standard production practices were followed. The model was (12.7 DAH + 191) * 0.5 ASW = D(DAH-1) + [Ep (0.12 + 0.023 DAH - 0.00019 DAH*DAH) - R(DAH) - I(DAH)], where DAH is days after hilling (DAH = 0 on 14 May), ASW is available soil water (0.13 mm/mm), D is soil water deficit (mm), R is rainfall (mm) and I is irrigation (mm). Root depth expanded at a rate of 13 mm/day to a maximum depth of 305 mm. Root depth at hilling was 191 mm. Controlled levels of water application ranging between 0% and 161% of the model rate were created with drip tapes. The model scheduled irrigations on 35, 39, 43 and 49 DAH. On 85 DAH, potatoes were harvested and graded. Irrigation influenced total yield, marketable yield, and combined US #1 grades (P < 0.01; R2 > 0.85). Mean marketable yields were 19, 28, and 21 t/ha for the 0%, 100%, and 160% irrigation rates, respectively. These results suggest that supplementing rainfall with irrigation and controlling the amount of water applied by adjusting irrigation to actual weather conditions could increase potato yields. Excessive water, as well as limiting water, reduced potato yields.
The efficacy of garlic spray (GS; Garlic Barrier™) as an alternative to conventional chemical control of disease and insect pests was evaluated on bell pepper and lettuce. Treatments consisted of a recommended chemical spray as needed (Treat. 1), GS applied once (Treat. 2) or twice (Treat. 3) a week, and water spray applied twice a week (Treat. 4). Because of no pest pressure during the test, no chemical sprays were used in Treat. 1. Differences among bell pepper yields were not significant (P > 0.50). For lettuce, Treat. 2 resulted in significantly (P = 0.02) higher head yield. Differences among treatments were not visually detectable in the field. These results suggested that GB applied at the manufacturer's rate (Treat. 2) did not adversely affect bell pepper and lettuce growth and yield. Garlic smell was not detectable on either vegetables, even after Treat. 3. Due to a low pest pressure, this study failed to identify beneficial effects of the GS. Without more scientific reports, relying only on GS to control pests of bell pepper and lettuce may involve uncontrolled risks.
An irrigation scheduling model represented by 12.7 DAT * 0.5 * ASW = D(DAT – 1) + [Ep(DAT) * CF(DAT) – R – I] was tested in central Alabama for Spring-grown bell pepper (Capsicum annuum L.). In the model, DAT (days after transplanting) is crop age; effective root depth is 12.7 DAT with a maximum of 250 mm; usable water (mm3·mm–3) is 0.5 ASW; deficit on the previous day is D(DAT–1); evapotranspiration is pan evaporation [Ep(DAT)] times a crop factor value [CF(DAT) = 0.15 + 0.018 DAT – 0.0001 DAT * DAT]; rainfall (R) and irrigation (I) are in mm. The model called for 13 irrigations between 17 and 85 DAT. Under the current N recommendation rate for bell pepper (112 kg/ha), marketable yield increased quadratically from 36% to 148% of the model rate. Highest marketable yields occurred near the model rate. Under a N rate of 170 kg/ha, yields increased linearly. These results suggests that the model provided adequate moisture to maximize bell pepper marketable yields under the recommended N rate.
The effect of irrigation scheduling method (variable crop factor, 1; constant crop factor, 2; empirical, 3), soil water tension (25, 50, 75kPa SWT), tillage (disc arrow, DA, moldboard plow, MP) and planting dates (PD) on total irrigation (TI), number of irrigations (NI), useful (UR) and lost rainfall (LR) was studied using a Pascal program that simulated water budgets of 720 crops of snap bean over 10 years. NI and TI were significantly (p<0.01) lower with met.1. Met.3 had the lowest LR and highest UR, but did not allow the complete calculation of the water balance. TI was significantly higher at 25kPa. MP tillage requested fewer NI and less TI, had lower LR and higher UR. Early PD requested fewer NI and TI, and had higher LR. Hence, when water supply was not limiting and weather data were available, a combination of Met.1, MP at any PD provided a continuous supply of water to the crop while controlling water deficit.