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Carolyn DeMoranville, Brian Howes, David White, and Daniel Shumaker

Although cranberry production typically requires a low fertilization rate compared to many crops, bog waters are generally discharged through surface water flow directly to streams, ponds or lakes and indirectly to coastal waters. Since discharge is primarily to fresh water bodies, and since such waters are generally phosphorus-limited, P is the fertilizer element of most environmental concern in Massachusetts cranberry production. This study was designed to determine how much P enters and leaves cranberry bog systems on an annual basis, what activities contribute to nutrient releases, and what management changes can reduce P discharges. On a total budget basis, including fertilizer applications as inputs and crop and other biomass (leaves) removal as outputs, the bogs were generally net importers of total N and total P. However, total P in outgoing waters was greater than that in source water. Net TP fluvial output averaged 2.08 kg·ha–1·yr–1 in 2002 (range 0.01 to 4.15); 1.66 kg·ha–1·yr–1 in 2003 (range –0.63 to 3.62) and 1.22 kg·ha–1·yr–1 in 2004 (range –1.24 to 4.30). The primary path of nutrient discharge from the bogs was through surface water. Flooding events were the primary source of total P output from the cranberry bogs. Gross total P export from the cranberry bogs was within the range of that for other reported agricultural land uses but greater than that for forested lands. When fertilizer P input was reduced (20% to 35%) at cranberry bog sites for two consecutive seasons, crop yield was not adversely affected and P discharge was reduced compared to that in the initial (prereduction) year.

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E.V. Herrero, J.P. Mitchell, W.T. Lanini, S.R. Temple, E.M. Miyao, R.D. Morse, and E. Campiglia

No-till processing tomato (Lycopersicum esculentum Mill.) production in four winter cover crop-derived mulches was evaluated in 1997 and 1998 in Five Points, Calif. The effectiveness of two medics, `Sava' snail medic (Medicago scutellata Mill.) (sava), and `Sephi' barrel medic (Medicago truncatula Gaertn.) (sephi), and two cereal/legume cover crop mixtures, triticale/`Lana' woolypod vetch (X Triticosecale Wittm./Vicia dasycarpa Ten.) (triticale/vetch) and rye/`Lana' woolypod vetch (Secale cereale L./V. dasycarpa) (rye/vetch), was compared with two conventionally tilled fallow controls (with and without herbicide) (fallow+h and fallow-h) in suppressing weeds and maintaining yields with reduced fertilizer inputs. The comparison was conducted as a split plot, with three N fertilization rates (0, 100, and 200 lb/acre; 0, 112, and 224 kg·ha-1) as main plots and cover crops and fallow controls as subplots. Tomato seedlings were transplanted 3 weeks after the cover crops had been mowed and sprayed with herbicide. There were no significant differences in weed cover in the no-till cover crop treatments relative to the fallow controls in 1997. Early season weed suppression in rye/vetch and triticale/vetch plots was similar to herbicide-treated fallow (fallow+h) in 1998, however, later in the 1998 season weed suppression was best in the fallow+h. Tissue N was highest in the fallow treatments in both 1997 and 1998. Yields were highest in the triticale/vetch and fallow and lowest in sephi treatments in 1997, but there were no differences among treatments in 1998. These results demonstrate the feasibility of no-till mulch production of furrow irrigated processing tomatoes and identify opportunities for further optimization of the system.

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Lincoln Zotarelli, Johannes Scholberg, Michael Dukes, Hannah Snyder, Eric Simonne, and Michael Munoz-Carpena

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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Yan Chen, Regina Bracy, and Roger Rosendale

While herbaceous perennials continuously gain popularity in southern landscape plantings, the nutrient requirements of many species in this group are still unknown. The business goal of lawn and garden care companies emphasizes aesthetic value of the urban landscape. Improper nutrient management, such as the overapplication of fertilizers, is inefficient and may result in increased pest problems and risks of contaminating ground and surface waters by nutrient runoff. Seven herbaceous perennials (lantana, rudbeckia, purple cone flower, daylily, mexican heather, cigar plant, and guara) were planted in simulated landscape beds. Fertilizers applied included one or two OsmocotePlus 16-8-12 tablets (7.5 g), OsmocotePlus 15-9-12 (5 months) at 0, 33, 66, and 131 g/m2 at planting, or applying OsmocotePlus 15-9-12 (5 months) 33 g/m2 or one OsmocotePlus tablet at the time of planting plus another 33 g/m2 topdressing after flowering. Plant growth of rudbeckis, purple cone flower, and lantana were highest at 131 g/m2 applied at planting, but resulted in similar overall plant quality as with 33 or 66 g/m2 treatments. Daylily growth was similar across fertilization treatments, and overall quality decreased at high fertilization rates with more severe daylily rust observed on these plants. Applying one OsmocotePlus 7.5-g tablet resulted in similar plant quality with applying OsmocotePlus 33 and 66 g/m2, but significantly reduced the amount of fertilizer used. Additional topdressing after flowering did not further increase plant quality in fall, but may affect the overwintering survival of perennial plants.

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T.K. Hartz, C. Giannini, E.M. Miyao, and J.G. Valencia

The effect of transplant production and handling practices on processing tomato growth, yield, and fruit quality were evaluated in five field trials in California. In 1999, processing tomato (Lycopersicon esculentum Mill. cv. Halley) transplants were obtained from a number of commercial transplant producers and taken to the Univ. of California-Davis (UCD) where treatments were imposed for 1 week prior to transplanting. Treatments included N and P fertilization, exposure to lath house or greenhouse temperature, withholding water, and storage in the dark for 2 days to simulate shipment from greenhouse to field. Nine treatments per site were compared in field trials at Yolo, Woodland, and Knights Landing. In 2000, transplants were grown at UCD under varying nutrient regimes, including P fertilization rates ranging from weekly application of 0 to 90 mg·L-1. Two commercial field trials comparing 8 treatments were conducted near Winters and Newman. Although transplant production and handling practices significantly influenced relative growth rate in the 3-4 weeks following transplanting in all 1999 trials, effects on fruit yield were minimal, with only one treatment at Woodland showing significantly lower yield and no treatment differences in crop maturity, fruit soluble solids, or juice color observed at any site. In 2000, plants receiving no weekly P fertilization showed slower growth in the 3 weeks after transplanting, but no treatment differences were observed after 6 weeks. Fruit yield, soluble solids content (°Brix) and juice color were unaffected by transplant treatment. We conclude that transplant production and handling practices tested had minimal differential effect on the subsequent field performance of processing tomato transplants in the Central Valley of California.

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S.J. Breschini and T.K. Hartz

Trials were conducted in 15 commercial fields in the central coast region of California in 1999 and 2000 to evaluate the use of presidedress soil nitrate testing (PSNT) to determine sidedress N requirements for production of iceberg and romaine lettuce (Lactuca sativa L.). In each field a large plot (0.2-1.2 ha) was established in which sidedress N application was based on presidedress soil NO3-N concentration. Prior to each sidedress N application scheduled by the cooperating growers, a composite soil sample (top 30 cm) was collected and analyzed for NO3-N. No fertilizer was applied in the PSNT plot at that sidedressing if NO3-N was >20 mg·kg-1; if NO3-N was lower than that threshold, only enough N was applied to increase soil available N to ≈20 mg·kg-1. The productivity and N status of PSNT plots were compared to adjacent plots receiving the growers' standard N fertilization. Cooperating growers applied a seasonal average of 257 kg·ha-1 N, including one to three sidedressings containing 194 kg·ha-1 N. Sidedressing based on PSNT decreased total seasonal and sidedress N application by an average of 43% and 57%, respectively. The majority of the N savings achieved with PSNT occurred at the first sidedressing. There was no significant difference between PSNT and grower N management across fields in lettuce yield or postharvest quality, and only small differences in crop N uptake. At harvest, PSNT plots had on average 8 mg·kg-1 lower residual NO3-N in the top 90 cm of soil than the grower fertilization rate plots, indicating a substantial reduction in subsequent NO3-N leaching hazard. We conclude that PSNT is a reliable management tool that can substantially reduce unnecessary N fertilization in lettuce production.

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G. Hochmuth, S. Locascio, R. Hochmuth, Jennifer Hornsby, D. Haman, B. McNeal, and J. Kidder

Nitrate concentrations in the springs and rivers in northern Florida have been increasing, and several state agencies are interested in implementing nitrogen management programs on farms to reduce N entering the groundwater. Watermelon was grown in the first season of a six-season project under various cultural and fertilization programs to investigate the relationship of N management with N leaching. Treatments were a factorial arrangement of two cultural systems (polyethylene mulch with drip-irrigated beds and unmulched, overhead irrigated beds) and three N fertilization programs [N at the extension-recommended rate, N at the commercial-watermelon-producer rate (1.5 times recommended), or N at the recommended rate with 50% of N from poultry manure]. Nitrate in the soil beneath the watermelon crop was monitored at the 2-m depth with porous-crop suction lysimeters and soil sampling. Yields were greater with the mulch/drip irrigation system compared with the unmulched/sprinkler cultural system; however, fertilization program had no effect on yield. Nitrate-N concentrations in the soil solution at the 2-m depth with all fertilizer treatments were only slightly elevated (3 to 5 mg·L-1) above that in the unfertilized soil (< 1.0 mg·L-1) early in the season when no rain fell. Later in the season, soil solution nitrate-N concentrations at the 2-m depth increased to >50 mg·L -1 with the unmulched treatment and with the greater fertilization rate. Polyethylene mulch, drip irrigation, and recommended N rate combined to maintain groundwater nitrate-N concentration below 10 mg·L-1 for most of the production season and only slightly above 10 mg·L-1 during the summer off-season when rainfall was frequent.

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Carmen Feller and Matthias Fink

The nitrogen requirement of broccoli (Brassica oleracea var. italica) ranges from 300 to 465 kg·ha–1. Recommendations for N fertilization are accordingly high. High fertilizer rates applied at planting result in a high soil mineral N content that remains high for weeks because the N requirement of the crop is low at early growth stages. Therefore, the risk of leaching is high for several weeks until the available N is finally taken up by the crop. Our study had two objectives: 1) to quantify yield responses to preplant fertilization, and 2) to test our hypothesis that the preplant fertilization rate could be reduced without yield losses by increasing the N content in the transplants and improving crop establishment. Field experiments were carried out on transplants with four levels of N content in dry matter (0.018 to 0.038 g·g–1 dry weight), which were tested in all combinations with four fertilization timings. All treatments received the same amount of N fertilizer (270 and 272 kg·ha–1 in 2001 and 2002, respectively), but with different rates of supply at the time of planting (0 to 90 kg·ha–1 N fertilizer plus 30 and 28 kg·ha–1 soil mineral N in 2001 and 2002, respectively). Total and marketable yields increased significantly with an increasing N supply at time of planting. In our experiments, in which topdressing was applied 25 days after planting, an N supply at planting of 80 to 118 kg·ha–1 was required to obtain maximum marketable yields. The N content in transplants had little effect on growth and yield, and there were no significant interactions between the N content in the transplant and fertilizer timing.

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Adamson D. Wang, John M. Swiader, and John A. Juvik

Dimethyl sulfide (DMS) has been identified as the compound responsible for the characteristic aroma of cooked sweet corn (Zea mays L.) and, along with sugar and water-soluble polysaccharides, is one of the main flavor components in the kernels. Because of the close relationship between DMS and its amino acid precursor S-methylmethionine, the premise was formulated that it might be possible to improve sweet corn aroma and overall eating quality through enhanced production of DMS from increased application of N and S to the crop in the field. Studies were conducted on a Plainfield sand and a Flanagan silt loam to evaluate the effects of N and S fertilization on kernel DMS production in several commercial sh2 hybrids; in the process, the effect of N and S fertilization on various yield and yield component parameters was also determined. Hybrid was the main factor affecting kernel DMS production, although in both soils kernel DMS levels were influenced by significant interactions between hybrid and fertilizer treatments. Kernel DMS content, in response to increasing N fertilization rates, increased by an average of 85% in three of six hybrids in the Plainfield sand and by 60% in two of three hybrids in the Flanagan silt loam. The effect of S fertilization on kernel DMS production was small, with only one hybrid on the sandy soil showing a positive response (38%) to S application, and then in combination with high N rates. Irrespective of N-S fertilization regime, kernel DMS concentrations decreased at both locations by an average of ≈8.5% per day as kernel maturity increased. The results showed that kernel DMS production may be enhanced by N nutrition, independent of N fertilization effects on ear and kernel yields.

Open access

Alberto Sánchez-Estrada and Julián Cuevas

In countries new to producing ‘Manzanillo’ olive trees (Olea europaea), free cross-pollination is often insufficient to obtain high levels of fruit set. An appropriate pollination design is therefore essential to ensure a timely, abundant, and compatible pollen supply. With a view to determining whether a pollination deficit exists in a nontraditional olive area such as the northern Mexico, pollination experiments were carried out in two consecutive seasons in both a monovarietal and a multivarietal Manzanillo orchard, where Sevillano, Barouni, Picual, Pendolino, Mission, Nevadillo, and Frantoio trees were growing nearby. The pollination treatments were self-, open, and cross-pollination with ‘Barouni’ and ‘Sevillano’ pollen, the latter only in the multivarietal orchard. The results confirmed the full self-incompatible condition of ‘Manzanillo’. Open-pollination did not improve fruit set in the monovarietal orchard, but it did so significantly in the multivarietal plot, where fruit set levels under open-pollination matched those of cross-pollination. Lower pollen adhesion, as well as occasional decreased germination, and reduced and delayed pollen tube growth were observed under self-pollination, highlighting self-incompatibility reactions. The reduction in fertilization rates led to low fruit set under self-pollination. Positive effects of open- and cross-pollination treatments were also noted on fruit weight (despite higher crop loads) and pulp-to-pit ratios. A strategic plantation design, including appropriate pollinizers in the right number and position, is therefore suggested for increasing ‘Manzanillo’ fruit quality and yield in Mexico. Both ‘Barouni’ and ‘Sevillano’ served as efficient pollinizers for ‘Manzanillo’, although we recommend ‘Barouni’ as a more efficient because the bloom periods of them matched that of ‘Manzanillo’