Nitrogen (N) is the most growth-limiting for vegetable production in sandy soils. In Florida, current recommendations for preplanting N applications (100 lb/acre of N) in `Crookneck' summer squash (Cucurbita pepo) differ from those used by the growers (>200 lb/acre). Therefore, two field studies were conducted in Ruskin and Balm, Fla., to examine the effect of 50, 100, 150, 200, 250, and 300 lb/acre of N on summer squash growth and yield. Variables collected during this study were plant vigor (0–10 scale, where 0 = dead plant) at 3 and 7 weeks after planting (WAP), petiole sap nitrate-nitrogen (NO3-N) at 4 and 8 WAS, and marketable yield starting on 4 WAS (13 and 10 harvests in Ruskin and Balm, respectively). In Ruskin, plant vigor increased linearly with N rates, whereas there was no significant N effect in Balm. No differences in petiole sap NO3-N were observed in either location. In Ruskin, there was a rapid marketable yield increase (§25%) between 50 and 100 lb/acre of N, followed by no change afterwards. In contrast, there was no yield response in Balm. In the latter location, no crop had been established in the previous 3 years, enabling the soil to maximize its organic N accumulation (>40 lb/acre organic-N), whereas in Ruskin the experimental location had been continuously planted during the last three seasons (§25 lb/acre organic-N). The data demonstrated that organic N is an important source of the nutrient to complement preplant applications in summer squash.
Camille E. Esmel, Bielinski M. Santos and James P. Gilreath
Camille E. Esmel, Bielinski M. Santos, Eric H. Simonne, Jack E. Rechcigl and Joseph W. Noling
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.
Camille Esmel*, John R. Duval, E.H. Simonne and Steven A. Sargent
Strawberries are a high value commodity with a short shelf life. Florida is the largest producer of winter strawberries in the United States with 2,790 hectares of production, 90% are located in Hillsborough County. Many Florida growers apply additional calcium (Ca) as a foliar spray despite the lack of conclusive evidence of an increase in fruit quality or yield. It is believed that additional Ca will improve cell wall integrity through Ca linkages with pectins with in the cell wall and increase fruit firmness. Preharvest applications of calcium chloride have shown to delay the ripening of strawberry fruit and mold development. The objectives of this two year study were to determine the effects of Ca on yield, growth, and postharvest quality of strawberry when applied to the soil or as a foliar spray. `Sweet Charlie' strawberry plants were grown on a Seffner fine sand in Dover, Fla. The experimental design was a split-block replicated four times with soil and foliar Ca applications. Main plots consisted of a broadcast preplant incorporation of gypsum (calcium sulfate) 0 kg·ha-1, 36.7 kg·ha-1, and 73.4 kg·ha-1. Sub-plots consisted of foliar applications of 400 mg·L-1 Ca from calcium sulfate, 400 and 800 mg·L-1 Ca from calcium chloride and a water control applied weekly throughout the 2002-03 and 2003-04 growing season. Yield data was collected twice weekly through out the growing season. Fruits were graded for quality based upon size, visual appearance of pathogens degradation, frost/water damage, and misshapen form. Calcium content was determined for leaves, fruit, and calyxes in January and March. Postharvest quality evaluations of pH, titratable acidy, soluble solids, and firmness (Instron 4411) were determined in January and March.
Bielinski M. Santos, James P. Gilreath, Camille E. Esmel and Myriam N. Siham
Field trials were conducted to determine the effect of yellow nutsedge (Cyperus esculentus) and purple nutsedge (C. rotundus) time of establishment on their distance of influence on bell pepper (Capsicum annuum). A single seedling of each weed species was transplanted 1, 2, 3, 4, and 5 weeks after transplanting (WAT) bell pepper. Each weed was separately established in the center of plots within double rows of bell peppers. Crop height and yield were determined from bell pepper plants located at 6, 13.4, 24.7, and 36.5 inches away from each weed. Bell pepper height was unaffected by weed species, time of establishment, or the interaction between these factors. Marketable yield data indicate that yellow nutsedge was more aggressive than purple nutsedge interfering with bell pepper. When yellow nutsedge was established at 1 WAT, bell pepper yield reduction was between 57% and 32% for plants at 6 and 13.4 inches away from the weed respectively, which represents a density of ≈0.14 plant/ft2. One purple nutsedge plant growing since 1 WAT at 6 inches along the row from two bell pepper plants (0.43 plant/ft2) produced a yield reduction of 31%. These results indicate that low nutsedge densities, which are commonly believed to be unimportant, can cause significant bell pepper yield reductions.
Bielinski M. Santos, James P. Gilreath, Myriam N. Siham and Camille E. Esmel
In Florida, nutsedge (Cyperus spp.) is a major weed problem in mulched-vegetable production. As methyl bromide (MBr) is phased out, alternatives are essential for growers. However, because of critical use exemptions, growers will still be able to use restricted amounts of MBr. Therefore, using highly-retentive mulch, such as virtually impermeable film (VIF), can reduce fumigant loss and may allow rate reduction without compromising efficacy. Preliminary studies have shown that metalized mulches can be an alternative to VIF. However, further studies are needed to compare MBr retention properties and nutsedge control of high density polyethylene (HDPE) mulch, VIF, and metalized mulch. Two field studies were conducted in spring 2005, in Ruskin, Florida. Metalized and HDPE mulches, and VIF were combined with the following rates of MBr + chloropicrin (Pic) (67/33, w/w): 175 and 350 lb/acre. Methyl bromide retention was evaluated in soil air samples at 1, 2, 4, and 6 days after treatment (DAT). Nutsedge plants were counted at 2, 4, 7, 9, and 12 weeks after treatment (WAT). Data were examined with regression analysis to establish the relationship between the time and both MBr concentration and nutsedge densities. Concentration of MBr + Pic under either the metalized mulch or VIF was about 6 times higher than under HDPE at 5 DAT, regardless of the MBr + Pic rate. At 12 WAT, nutsedge population was <1 plant/50 ft row with metalized and VIF and 175 lb/acre of MBr + Pic, whereas about 25 plants/50 ft row were present with 350 lb/acre of the fumigant and HPDE. The weed population reached >100 plants/50 ft row with 175 lb/acre of MBr + Pic. These findings demonstrate that metalized and VIF mulches can provide effective control of nutsedge with one-half of the commercially used MBr + Pic rate.
Bielinski M. Santos, Camille E. Esmel, Silvia Slamova and Elizabeth A. Golden
Three separate field trials were conducted to determine the most appropriate planting dates for intercropping cucumber (Cucumis sativus), summer squash (Cucurbita pepo), and muskmelon (Cucumis melo) with strawberry (Fragaria ×ananassa), and their effect on ‘Strawberry Festival’ strawberry yields. ‘Straight Eight’ cucumber, ‘Crookneck’ summer squash, and ‘Athena’ muskmelon were planted every 15 days from 25 Jan. to 23 March. None of the three intercropped species affected strawberry yield up to 60 days before the end of the season on 25 March. Cucumber yield responded quadratically to planting dates, rapidly increasing from 25 Jan. to 23 Feb. and declining afterward. Warmer temperatures favored summer squash yield, with the highest yields when planted on 23 Feb. or later. Muskmelon yields decreased as air temperatures increased, and the best planting dates were between 25 Jan. and 9 Feb. In summary, cucumber and summer squash seemed to be favored by planting under warmer temperatures, whereas muskmelon thrives under cooler weather.