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  • Author or Editor: Eric Simonne x
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Several practices have been adopted to minimize water use and potential N leaching of vegetable production systems, including use of drip irrigation, plastic mulch, and fertigation. However, these practices may not be adequate on sandy soils with poor water and nutrient retention capacities. The objectives of this study were to evaluate the interactive effects of irrigation practices and fertilizer rates on yield, fertilizer requirements, and N-leaching of pepper and tomato production systems. Bell pepper and tomato were planted on plastic mulched to evaluate the effects of three nitrogen (N) fertilizer rates (154, 192, 288 kg·ha -1 N for pepper vs. 166, 208, and 312 kg·ha-1 N for tomato) and three irrigation scheduling methods were evaluated. Depending on sensor readings, soil moisture sensor (SMS) irrigation treatments allowed up to five watering events per day where as for the fixed duration treatment irrigation was applied once a day. For tomato, the effect of subsurface drip irrigation (SDI) was also evaluated. Compared to TIME, use of SMS control system reduced water use by 29& to 44% and 37% to 66% for tomato and pepper, respectively. Tomato yield was significantly higher on SMS and SDI treatments compared to TIME treatments. For pepper yield and biomass accumulation were not affected by irrigation treatments. The average yields were 24.6 and 27.8 Mg·ha-1 of fresh marketable fruits for pepper and tomato, respectively. Nitrogen rate did not affect yield and optimal yield N rate did not affect yield for either crop. On average, SMS treatments increased irrigation water use efficiency 2–3 times compared to TIME treatments for both tomato and pepper.

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Vegetable producers in south Florida suffered the effects of four major hurricanes during 2004 and two during 2005, causing damage to crops and farms estimated at well over 1 billion dollars each year. Producers were quick to respond by replanting or nursing damaged crops back to health. Green beans and leafy crops appeared least likely to recover or produce acceptable yields after exposure to high winds and driving rains. Young tomato plants up to the second or third string were at times completely stripped of leaf material, yet recovered surprisingly quickly. A replant study showed no benefit in replanting compared to keeping damaged plants in the field. Older tomato plants were marginal in their ability to recover with 10% to 60% reductions in yield for first and second harvests when compared to yields common in the region. As much as 100% of Palm Beach County's 2005 early fall bell pepper planting was destroyed by storms. Other peppers in the region were affected by flooding and subsequent development of root diseases such as phytophthora. Damaged eggplant recovered slowly. Research plantings located in commercial fields and at Research and Education Centers were devastated. In addition to loss of crops, costs to vegetable growers included labor to remove damaged plastic and reset stakes, installation of replacement plastic mulches, replanting, and structural damage to buildings and packing facilities. Some transplant houses and greenhouses for specialty peppers were completely destroyed. Removing plastic coverings before a storm's arrival saved structures and crops. Transplants of all crops were in short supply. Labor was lacking due to reconstruction efforts in New Orleans and the Gulf Coast. Successful and not-so-successful recovery efforts will be shown.

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On sandy soils, potential N contamination of groundwater resources associated with intensively managed vegetables may hamper the sustainability of these systems. The objective of this study was to evaluate the interaction between irrigation system design/scheduling and N fertilization rates on zucchini production and potential N leaching. Zucchini was planted during Fall 2005 using three N fertilizer rates (73, 145, 217 kg/ha) and four different irrigation approaches. Irrigation scheduling included surface-applied drip irrigation and fertigation: SUR1 (141 mm applied) and SUR2 (266 mm) using irrigation control system (QIC) that allowed time-based irrigation (up to five events per day) and a threshold setting of 13% and 15% volumetric water content (VWC), respectively; Subsurface drip irrigation (SDI) using a QIC setting of 10% VWC (116 mm) combined with surface applied fertigation; and a control treatment with irrigation applied once daily (424 mm). Leacheate volumes were measured by drainage lysimeters. Nitrate leaching increased with irrigation rate and N rate and measured values ranged from 4 to 42 kg N/ha. Use of SDI greatly reduced nitrate leaching compared to other treatments. SDI and SUR1 treatments had no effect on yields (29 Mg/ha). However, SDI had a 15% and 479% higher water use efficiency (WUE) compared to SUR1 and the fixed irrigation duration treatment. Application of N in excess of intermediate N-rate (standard recommendation) did not increase yield but yield was reduced at the lowest N-rate. It is concluded that combining sensor-based SDI with surface applied fertigation resulted similar or higher yields while it reduced both water use and potential N leaching because of improved nutrient retention in the active root zone.

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Collecting leachate from lysimeters installed in the field below vegetable fields may be used to quantify the amount of nitrogen released into the environment. Because limited information exists on the optimal design type and on the effect of design components on lysimeter performance, the objective of this study were to identify existing designs and their limits, assess cost of design, and test selected designs. Ideally, lysimeters should be wide enough to collect all the water draining, long enough to reflect the plant-to-plant variability, durable enough to resist degradation, deep enough to allow for cultural practices and prevent root intrusion, have a simple design, be made of widely available materials, and be cost-effective. Also, lysimeters should not restrict gravity flow thereby resulting in a perched water table. Previous study done with a group of free-drainage lysimeters (1-m-long, 45-cm-wide, installed 45-cm-deep) under a tomato-pumpkin-rye cropping sequence resulted in variable frequency of collection and volume of leachate collected (CV of load = 170%). Improving existing design may be done by increasing the length of collection, lining the lysimeter with gravel, limiting the depth of installation, and/or breaking water tension with a fiberglass wick. Individual lysimeter cost was estimated between $56 to $84 and required 9 to 14 manhours. for construction and installation. Costs on labor may be reduced when large numbers of lysimeters are built. Labor needed for sampling 24 lysimeters was 8 man-hr/sampling date. Because load may occur after a crop, lysimeter monitoring and sampling should be done year round.

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With increasing environmental concerns, the sharp cost increase of fertilizer and the absence of a soil test to predict nitrogen (N) needs of tomato (Solanum lycopersicon L.) grown on Florida’s sandy soils, a partnership was created with growers, state agencies, and the University of Florida, Institution of Food and Agricultural Sciences (UF/IFAS). The objectives of this study were to identify a range of N rates that would result in highest yields and postharvest quality, and maximum economical return for tomato, grown with subsurface irrigation (management of a perched water table above an impermeable soil layer or hard pan) during the spring season (low probability of leaching rain events). The study was conducted in Spring 2007 and 2008 in Palmetto, FL, with N rates ranging from 22 to 470 kg·ha−1 at pre-plant as ammonium nitrate (NH4NO3). Weather conditions were typical of a dry spring season in central Florida with no leaching rain events recorded in either year; however, rain patterns were different between the 2 years. In the absence of leaching rain and frost protection (either may raise the water table), petiole sap NO3-N decreased over time and the rate of decline depended on the N fertilizer rate. Extra-large and total marketable fruits yields showed a quadratic plateau response to N rates with maximum yields at two harvests (97% of the yields) grown with 172 and 298 kg N/ha in 2007 and 2008, respectively. During subsequent ripening, N rate did not correlate consistently to fruit ripening rate, fruit firmness, nor compositional quality at table-ripe stage. The high value of tomatoes relative to the cost of N fertilizer created a situation in which the profit-maximizing rate of N was not significantly different from the production-maximizing N rate. Whether the profit-maximizing level of N was higher or lower than the UF/IFAS-recommended rate depended on the growing season. With favorable growing conditions (i.e., conditions in 2008), a grower’s net return would have decreased between $1000 and $2000 per hectare by using UF/IFAS-recommended rates depending on market conditions. However, if the UF/IFAS-recommended rate of 224 kg·ha−1 resulted in the highest yield, applying upwards of 300 kg·ha−1 would have increased grower production costs by at least $67/ha. Although fertilizer costs are known before the crop is grown, tomato prices are realized only at the end of the growing season and profit margins can only be calculated after the fact.

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In addition to managing soilborne diseases, grafting with vigorous rootstocks has been shown to improve yield in tomato (Solanum lycopersicum L.) production. However, the influence of different levels of nitrogen (N) and irrigation supplies on grafted tomato plants has not been fully examined in comparison with non-grafted plants, especially under field conditions. The objective of this two-year study was to determine the effects of different irrigation regimes and N rates on yield, irrigation water use efficiency (iWUE), and N use efficiency (NUE) of grafted tomato plants grown with drip irrigation in sandy soils of north Florida. The determinate tomato cultivar Florida 47 was grafted onto two interspecific hybrid rootstocks, ‘Beaufort’ and ‘Multifort’ (S. lycopersicum × S. habrochaites S. Knapp & D.M. Spooner). Non-grafted ‘Florida 47’ was used as a control. Plants were grown in a fumigated field under 12 combinations of two drip irrigation regimes (50% and 100% of commonly used irrigation regime) and six N rates (56, 112, 168, 224, 280, and 336 kg·ha−1). The field experiments were arranged in a split-plot design with four replications. The whole plots consisted of the irrigation regime and N rate combination treatments, whereas the subplots represented the two grafting treatments and the non-grafted plants. Self-grafted ‘Florida 47’ was also included in the 100% irrigation and 224 kg N/ha fertilization treatment as a control. In 2010, the 50% irrigation regime resulted in higher total and marketable yields than the 100% irrigation regime. Tomato yield was significantly influenced by N rates, but similar yields were achieved at 168 kg·ha−1 and above. Plants grafted onto ‘Beaufort’ and ‘Multifort’ showed an average increase of 27% and 30% in total and marketable fruit yields, respectively, relative to non-grafted plants. In 2011, fruit yields were affected by a significant irrigation by N rate interaction. Grafting significantly increased tomato yields, whereas grafted plants showed greater potential for yield improvement with increasing N rates compared with non-grafted plants. Self-grafting did not affect tomato yields. More fruit per plant and higher average fruit weight as a result of grafting were observed in both years. Grafting with the two rootstocks significantly improved the irrigation water and N use efficiency in tomato production. Results from this study suggested the need for developing irrigation and N fertilization recommendations for grafted tomato production in sandy soils.

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Turnip (Brassica rapa L.) and mustard (Brassica juncea L.) were grown in drainage lysimeters under controlled soil water regimes during 2 years. Irrigation regimes consisted of water applications when the soil water tension at a 10-cm depth exceeded 25,50, or 75 kPa throughout growth of the two crops on two soil types during spring and fall production seasons. Leaf yield and water use were highest when irrigation was applied at 25 kPa soil water tension. Regression equations are presented to describe the relationships of daily pan evaporation and water use to plant age, and to compute daily evapotranspiration: pan evaporation ratios (crop factors) during spring and fall production seasons.

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Florida had the largest fresh-market tomato (Solanum lycopersicum L.) production in the United States, with a value of $437 million and 13,355 ha harvested in 2014. Despite the development of Best Management Practices (BMPs) and University of Florida/Institute of Food and Agricultural Sciences (UF/IFAS) fertilizer recommendations, tomato growers often use fertilizer rates above the recommended ones, especially when seepage irrigation is used and a longer growing season is foreseen. If a mass balance of N–P–K partitioning could be made in field conditions, a better understanding of nutrition applications could be reached. Therefore, a field study was conducted on seepage-irrigated tomato on a commercial farm in southwest Florida, during the spring and winter season of 2006 to evaluate the nitrogen (N) rate and season effects on tomato plant growth, fruit yield, N, phosphorous (P), and potassium (K) accumulation and use efficiency. The UF/IFAS N-recommended rate (224 kg·ha−1) was compared with a commercial grower (CG) rate (358 kg·ha−1). Both N rates were incorporated at bedding with 61 and 553 kg·ha−1 of P and K, respectively. Fruit yield and plant growth were measured and roots, stems, leaves, and fruit samples were analyzed to determine total N, P, and K content and accumulation in different plant parts. Nutrient recovery (REC) and the partial factor of productivity of applied nutrients (PFP) were calculated for each N rate. In the spring, 120 days after transplanting, plants dry biomass was 11.5% higher (P = 0.01) in the CG N rate than with UF/IFAS N rate, while no significant differences were observed in the winter season. In the spring, N, P, and K accumulation were 250, 56, and 285 kg·ha−1 in plants grown with CG N rate and were significantly lower (23%, 5%, and 23%, respectively) with the UF/IFAS N rate, respectively. In the winter, total N accumulation was 231 kg·ha−1 in plants fertilized at CG N rate and significantly lower (16%) with the UF/IFAS N rate. N rate did not significantly affect P and K accumulation, which were on average 64 and 312 kg·ha−1, respectively. Marketable fruit yield was significantly higher (P = 0.03) with CG N rate than with UF/IFAS N rate (91.1 vs. 81.5 Mg·ha−1), and was significantly higher (P = 0.03) in the spring than in the winter (100.8 vs. 71.8 Mg·ha−1). The NREC was significantly higher (P = 0.01) with the UF/IFAS N rate than with CG N rate and was not significantly affected (P = 0.94) by seasons. The PFPN was significantly higher (P = 0.001) with the UF/IFAS N-rate than with CG N-rate, and was significantly higher (P = 0.04) in the spring than in the winter season. These results suggest that current UF/IFAS N recommendations are more conservative of N and this should lead to reduced leaching potential but, UF/IFAS recommendations must be season specific due to the difference in environmental conditions of fruit maturation in cooler weather of the winter season compared with a warmer environment of the spring season.

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For shallow-rooted vegetables grown in sandy soils with low water-holding capacity (volumetric water content <10%), irrigation water application rate needs to provide sufficient water to meet plant needs, to avoid water movement below the root zone, and to reduce leaching risk. Because most current drip tapes have flow rates (FRs) greater than soil hydraulic conductivity, reducing irrigation operating pressure (OP) as a means to reduce drip emitter FR may allow management of irrigation water application rate. The objectives of this study were to determine the effect of using a reduced system OP (6 and 12 psi) on the FRs, uniformity, and soil wetted depth and width by using three commercially available drip tapes differing in emitter FR at 12 psi (Tape A = 0.19 gal/h, Tape B = 0.22 gal/h, and Tape C = 0.25 gal/h). Reducing OP reduced FRs (Tape A = 0.13 gal/h, Tape B = 0.17 gal/h, and Tape C = 0.16 gal/h) without affecting uniformity of irrigation at 100 and 300 ft lateral runs. Flow rate was also reduced at 300-ft lateral length compared with 100 ft for all three tapes. Uniformity was reduced [“moderate” to “unacceptable” emitter flow variation (q var) and “moderate” coefficient of variation (cv)] at 300 ft for Tape B and C compared with “good” q var and “moderate” to “excellent” cv at 100 ft. Using soluble dye as a tracer, depth (D) of the waterfront response to irrigated volume (V) was quadratic, D = 4.42 + 0.21V − 0.001V 2 (P < 0.01, R 2 = 0.72), at 6 psi, with a similar response at 12 psi, suggesting that depth of the wetted zone was more affected by total volume applied rather than by OP itself. The depth of the wetted zone went below 12 inches when V was ≈45 gal/100 ft, which represented ≈3 h of irrigation at 6 psi and 1.8 h of irrigation at 12 psi for a typical drip tape with FR of 0.24 gal/h at 12 psi. These results show that, for the same volume of water applied, reduced OP allowed extended irrigation time without increasing the wetted depth. OP also did not affect the width (W) of the wetted front, which was quadratic, W = 6.97 + 0.25V − 0.002V 2 (P < 0.01, R 2 = 0.70), at 6 psi. As the maximum wetted width at reduced OP was 53% of the 28-inch-wide bed, reduced OP should be used for two-row planting or drip-injected fumigation only if two drip tapes were used to ensure good coverage and uniform application. Reducing OP offers growers a simple method to reduce FR and apply water at rates that match more closely the hourly evapotranspiration, minimizing the risk of leaching losses.

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A renewed interest in sulfur (S) deficiency has occurred because of reductions in atmospheric depositions of S caused by implementation of clean air regulations around the world. In vegetable production systems, other sources of S exist, such as soil S, fertilizers, and irrigation water. While soil testing and fertilizer labels impart information on quantity of S, it is unknown how much S within the irrigation water contributes to the total crop requirement. Two studies were conducted to determine the influence of elemental S fertilization rates and irrigation programs on tomato (Solanum lycopersicum) growth and yield. Irrigation volumes were 3528, 5292, and 7056 gal/acre per day and preplant S rates were 0, 25, 50, 100, 150, and 200 lb/acre. Data showed that neither plant height, leaf greenness, soil pH nor total soil S content was consistently affected by preplant S rates. During both seasons, early marketable fruit weight increased sharply when plots were treated with at least 25 lb/acre of preplant S in comparison with the nontreated control. Early fruit weight of extralarge and all marketable grades increased by 1.5 and 1.7 tons/acre, respectively, with the application of 25 lb/acre of S. There were no early fruit weight differences, regardless of marketable fruit grade, among preplant S rates from 25 to 200 lb/acre. Based upon this result, adding preplant S to the fertilization programs in sandy soils improves tomato yield and fall within the current recommended application range of S (30 lb/acre) for vegetables in Florida. At the same time, irrigation volumes did not consistently influence soil S concentration, soil pH, leaf S concentrations or tomato yield, which suggested that irrigation water with levels of S similar to this location [58 mg·L−1 of sulfate (SO4) or 19 mg·L−1 of S] may not meet tomato S requirement during a short cropping seasons of 12 weeks, possibly because microbes need longer periods of time to oxidize the current S species in the water to the absorbed SO4 form.

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