Search Results

You are looking at 1 - 10 of 22 items for

  • Author or Editor: Lincoln Zotarelli x
Clear All Modify Search

Poor water- and nutrient-holding capacity of sandy soils, combined with intense leaching rainfall events, may result in excessive N-fertilizers losses from vegetable production systems. Three cover cropping (CC) systems were used to assess supplemental N-fertilizer requirements for optimal yields of selected vegetable crops. Fertilizer N-rates were 0, 67, 133, 200, and 267; 0, 131, and 196; and 0, 84, 126,168, and 210 kg N/h for sweet corn (Zea mays var. rugosa), broccoli (Brassica oleracea), and watermelon (Citrullus lanatus), respectively. Crop rotations consisted of sunn hemp (Crotalaria juncea) in Fall 2003 followed by hairy vetch (Vicia villosa), and rye (Secale cereale) intercrop or a fallow. During Spring 2004, all plots were planted with sweet corn, followed by either cowpea (Vigna unguiculata) or pearl millet (Pennisetum glaucum), which preceded a winter broccoli crop. Hairy vetch and rye mix benefited from residual N from a previous SH crop. This cropping system provided a 5.4 Mg/ha yield increment for sweet corn receiving 67 kg N/ha compared to the conventional system. For the 133 N-rate, CC-based systems produced similar yields compared to conventional systems amended with 200 kg N/ha. Pearl millet accumulated 8.8 Mg/ha—but only 69 kg N/ha—and potential yields with this system were 16% lower compared to cowpea system. For a subsequent watermelon crop, trends were reversed, possibly due to a delay in mineralization for pearl millet. Because of its persistent growth after mowing, hairy vetch hampered initial growth and shading also delayed fruit development. Although CC may accumulate up to 131 kg N/ha actual N benefits, N-fertilizer benefits were only 67 kg N/ha, which may be related to a lack of synchronization between N release and actual crop demand.

Free access

Major horticultural crops in Florida are vegetables, small fruit, melons, and tree fruit crops. Approximately half of the agricultural area and nearly all of the horticultural crop land is irrigated. Irrigation systems include low-volume microirrigation, sprinkler systems, and subsurface irrigation. The present review was divided into two papers, in which the first part focuses on vegetable crop irrigation and the second part focuses on fruit tree crop irrigation. This first part also provides an overview of irrigation methods used in Florida. Factors affecting irrigation efficiency and uniformity such as design and maintenance are discussed. A wide range of soil moisture sensors (e.g., tensiometers, granular matrix, and capacitance) are currently being used in the state for soil moisture monitoring. Current examples of scheduling tools and automated control systems being used on selected crops in Florida are provided. Research data on the effect of irrigation scheduling and fertigation on nutrient movement, particularly nitrate, are reviewed. Concluding this review is a discussion of potential for adoption of irrigation scheduling and control systems for vegetable crops by Florida growers and future research priorities.

Full access

Florida is the most important center of processed citrus (Citrus spp.) production in the United States, and all of the crop is irrigated. Irrigation systems include low-volume microirrigation, sprinkler systems, and subsurface irrigation. This review details the relative irrigation efficiencies and factors affecting irrigation uniformity such as design and maintenance. A wide range of soil moisture sensors (e.g., tensiometers, granular matrix, and capacitance) are currently being used for citrus in the state. The use of these sensors and crop evapotranspiration estimation using weather information from the Florida Automated Weather Network in irrigation scheduling are discussed. Current examples of scheduling tools and automated control systems being used on selected fruit crops in Florida are provided. Research data on the effect of irrigation scheduling, soluble fertilizer injection, and soil nutrient movement, particularly nitrate and the use of reclaimed water in Florida, are also reviewed. Concluding this review is a discussion of the potential for adoption of irrigation scheduling and control systems for citrus by Florida growers and future research priorities.

Full access

Most strategies used to determine crop N fertilizer recommendations do not address potential environmental issues associated with agricul-tural production. Thus, a more holistic approach is required to reduce N loading associated with vegetable crops production on soils that are prone to N leaching. By linking fertilizer N uptake efficiency (FUE) with irrigation management, root interception capacity, and N uptake dynamics, we aim to improve FUE. Nitrogen uptake for peppers, tomato, potato, and sweet corn followed a logistic N accumulation patterns. Up to 80-85% of N uptake occurred between 4 to 7 weeks (sweet corn) vs. 6 to 12 weeks (other crops), while N uptake during initial growth and crop maturation was relatively low. Maximum daily N accumulation rates occurred at 5 weeks (sweet corn) vs. 8-10 weeks (other crops) and maximum daily N uptake rates were 4-8 kg N/ha. Overall FUE for most vegetables may range between 23% and 71%, depending on production practices, soil type, and environmental conditions. Maximum root interception capacity was typically attained 3 to 5 weeks prior to crop maturity. It is concluded that, during initial growth, root interception may the most limiting factor for efficient N use. Although recent uptake studies have shown that FUE may be highest toward the end of the growing season, this may not coincide with the greatest crop demand for N, which occurs during the onset of the linear growth phase. As a result, yield responses to N applied later in the season may be limited. Integration of these results into best management practices and expert systems for vegetable production can minimize the externalities associated with commercial vegetable production on vulnerable soils in the southeastern United States.

Free access

Growth and yield typically increase when tomato plants are grafted to selected interspecific hybrid rootstocks from which distinctive root system morphologies are envisioned to aid nutrient uptake. We assessed these relationships using a range of exogenous nitrogen (N) supplies under field production conditions. This study analyzed the impact of N on growth, root distribution, N uptake, and N use of determinate ‘Florida 47’ tomato plants grafted onto vigorous, interspecific, hybrid tomato rootstocks ‘Multifort’ and ‘Beaufort’. Six N rates, 56, 112, 168, 224, 280, and 336 kg·ha−1, were applied to sandy soil in Live Oak, FL, during Spring 2010 and 2011. During both years, the leaf area index, aboveground biomass, and N accumulation (leaf blade, petiole, stem, and fruit) responded quadratically to the increase in N fertilizer rates. Averaged over the two seasons, the aboveground biomass, N accumulation, N use efficiency (NUE), and N uptake efficiency (NUpE) were ≈29%, 31%, 30%, and 33% greater in grafted plants than in nongrafted controls, respectively. More prominent increases occurred in the root length density (RLD) in the uppermost 15 cm of soil; for grafted plants, RLD values in this upper 15-cm layer were significantly greater than those of nongrafted plants during both years with an average increase of 69% over the two seasons. Across all the grafted and nongrafted plants, the RLD decreased along the soil profile, with ≈60% of the total RLD concentrated in the uppermost 0 to 15 cm of the soil layer. These results demonstrated a clear association between enhanced RLD, especially in the upper 15 cm of soil, and improvements in tomato plant growth, N uptake, and N accumulation with grafting onto vigorous rootstocks.

Free access

Consumer demand for specialty market potatoes has been growing. Cultivated South American diploid potatoes possess great variation for skin and flesh colors, shape, and taste. A long-day adapted population of Solanum tuberosum groups Phureja and Stenotomum (phu-stn) was evaluated for characteristics associated with the type known as papa criolla or papa amarilla in South America. Tubers have intense yellow flesh and may be fried or roasted and eaten whole. A U.S. northern location (Maine), representative of a seed growing region, and two southern locations (Florida and New Mexico), representative of potato growing regions near large Hispanic populations, evaluated yellow-fleshed clones selected within a phu-stn population. Agreement between selectors at two locations was greater than 50%. Tuber skin color and shape were highly correlated between locations; flesh color and tuber dormancy moderately so; eye depth had low correlation between locations; and appearance and skin texture had low or no correlation between locations. Tuber dormancy was generally short, but a few longer dormant clones were identified. There were significant differences among clones for yields, with the highest yields occurring in Maine. More intense evaluations are planned for a subset of these clones before possible release as new varieties. Future breeding efforts will be undertaken to lengthen tuber dormancy in this population.

Free access

Muscadine grape is a perennial crop that is highly responsive to local environmental factors and viticulture practices. Biochar is a promising soil amendment used to improve soil water and nutrient retention and promote plant growth. The present study aimed to assess the effects of different pinewood biochar rates on nutrient status and vegetative parameters of muscadine grape cv. Alachua grown on a nutrient-poor sandy soil, Ultisols (97.2% sand, 2.4% silt, and 0.4% clay), and mixed with five different rates (0%, 5%, 10%, 15%, and 20%) of biochar based on weight. Variations in soil moisture, temperature, and leaf greenness value [soil plant analysis development (SPAD) reading], net photosynthesis rate, and plant root and shoot dry weights were measured. In addition, the nutrient status of the soil, plant root, and shoot were determined. The results indicated that the higher rate of biochar could significantly (P < 0.05) improve soil moisture. Biochar can also decrease soil temperature, although there were no significant differences among treatments. Regarding the nutrient status, the biochar amendment increased the nutrient content of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca), as well as the soil organic matter content and cation exchange capacity. Higher nutrient contents in soil lead to increased P and Mg in both aboveground and belowground muscadine plant tissues and decreased nitrogen (N), iron (Fe), and copper (Cu) in the root part. There were no significant differences observed in SPAD values, net photosynthesis, or dry weights of the root and shoot. This study demonstrates that the addition of biochar may enhance the soil water and nutrient status as well as improve plant P and Mg uptake; however, it showed no significant differences in the physiological performance of muscadine grape plants.

Open Access

The majority of strawberry (Fragaria ×ananassa) production in Florida, USA, uses bare-root transplants that require large volumes of water via sprinkler irrigation for establishment. Although plug transplants can be established without sprinkler irrigation, they generally are more than double the cost of bare-root transplants. We hypothesized that the use of early-planted (September) plug transplants on white-on-black mulch without impact sprinkler irrigation (WP system) would be more profitable and conserve water compared with the typical grower standard practice of black plastic mulch and bare-root transplants planted in mid-October that were established using impact sprinkler irrigation for heat mitigation for 12 d after transplanting (BB system). ‘Florida Radiance’ plug transplants and bare-root transplants were used in the 2-year study that was conducted at Citra and Balm, FL, USA. Water use and early and total strawberry yield of the two systems were compared. Water use in both locations was lower with the WP system than the BB system. Early yield was higher by 683 and 346 8-lb flats/acre with the WP system at Citra and Balm, respectively, compared with the BB system. The total marketable yield with the WP system was 2062 flats/acre and 1917 flats/acre greater at Citra and Balm, respectively, than with the BB system. Partial budget analysis indicated that the WP system at Citra increased the net profit by $14,657/acre, whereas a net profit of $13,765/acre was obtained at Balm. These results will inform decision-making about cropping system modification that can be adopted by Florida strawberry growers to considerably reduce water use in an economically feasible manner.

Open Access

Seepage is characterized as an inefficient irrigation method with regard to water and nutrient use. There is a need for an economically viable irrigation alternative to seepage, which increases crop productivity and profitability in Florida. The use of plastic mulch and drip irrigation for cabbage (Brassica oleracea var. capitata) production increases plant population per area and reduces the irrigation water requirement. However, plasticulture has a high capital investment and operating cost. The objectives of this study were to compare the profitability of plasticulture cabbage production and traditional seepage bare ground irrigation systems for Florida cabbage production, and to determine the breakeven point for cabbage grown under plasticulture given a range of market prices. The preharvest cost per acre for the plasticulture system was significantly higher than the cost for the seepage system ($4726 and $3035 per acre, respectively). However, for all planting dates considered in this study, the plasticulture system resulted in a significant increase in marketable yields when compared with the seepage system. The resulting increase in potential revenue offset the increase in preharvest costs and assured a positive net return on investment over the whole range market prices. It was also observed that low air temperatures combined with reduced solar radiation can prevent optimum plant development for cabbage transplanted between November and mid-December. Therefore, the return on investment may be reduced during less favorable climatic conditions for cabbage growth, making the plasticulture system less economically desirable for certain planting dates.

Full access

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.

Free access