Search Results

You are looking at 31 - 40 of 65 items for

  • Author or Editor: T.K. Hartz x
Clear All Modify Search

Carrot (Daucus carota L.) root cracking and breakage during harvest and handling operations result in serious losses. The environmental and management factors affecting carrot cracking and breakage susceptibility were investigated in a survey of fields and a series of trials conducted in California from 2000–02. Roots, leaves and soil were collected from a total of 31 commercial fields of `Sugar Snax' carrot, and soil texture and plant and soil fertility status were determined. Soil moisture was monitored in 10 fields to determine whether irrigation management was correlated with root cracking susceptibility; in 4 of these fields roots were harvested both before 0800 hr and at 1300 hr on the same day to directly compare the effects of root water status on cracking. The effect of N fertilization on cracking and breakage was investigated in 5 field trials. The relative susceptibility of 10 cultivars to cracking and breakage was also compared. Cracking susceptibility was determined with an impact test, and breakage with a loading test. Roots were selected by size (18 to 24 mm diameter) and cooled to 5 °C before testing. The percentage of roots cracked in the impact test varied from 7% to 75% among survey fields. Initial root water potential was not correlated with cracking incidence. However, after hydrating roots to minimize differences in water potential among fields, cracking incidence was correlated with turgor potential (r = 0.41). Soil sand content and mean air temperature in the 30 days preceding harvest were also correlated with cracking (r = –0.48 and 0.36, respectively), suggesting that cracking susceptibility may be minimized in cool weather and in light-textured soil. Irrigation management in the final 30 days preceding harvest had no consistent effect on root cracking. Time of day of harvest had a small but significant effect, with roots harvested before 0800 hr being more crack-susceptible. N fertilization in excess of that required to maximize root yield significantly increased cracking susceptibility. Cultivars varied widely in cracking susceptibility, with less variation in tissue strength and stiffness. Removal of the periderm dramatically decreased susceptibility to both cracking and breakage.

Free access

The study was undertaken to determine the physiochemical properties and nutrient supply characteristics of composted green yard and landscape waste (CGW) and to document its performance as a field soil amendment or constituent of potting media. Three CGW samples were collected from each of two composting operations in California from Nov. 1993 to Apr. 1994. Macronutrient content varied widely between operations, and among samples from the same operation, with mean total N, P, and K levels averaging 1.1%, 0.26%, and 0.67%, respectively. Controlled-environment incubation of a moist 1 CGW: 9 soil blend (2 weeks at 30 °C) was conducted to determine net N mineralization from CGW. Despite low C: N ratios (<12), five of six CGW samples showed net immobilization, a characteristic of immature compost. An in-field incubation of soil amended with 1% or 2% CGW (w/w) showed no net N release from CGW over 4 months. In a field trial, bell pepper (Capsicum annuum L.) fruit yield was increased by soil amendment with CGW (17 or 34 t·ha–1) under a low N fertilizer regime (168 kg·ha–1), but was unaffected where sufficient fertilizer N (280 kg·ha–1) was applied. CGW was compared with peat as a constituent of potting media; both were blended 1:1 (v/v) with perlite and used in the production of tomato (Lycopersicon esculentum Mill.) and marigold (Tagetes erecta L.) plants under varying fertigation regimes (constant feed of N at 0, 50, or 100 mg·L–1 as 15N–13P–12K). CGW was equivalent or superior to peat in plant growth; CGW did contribute to crop macronutrient nutrition, but the highest fertigation rate was required for optimum growth.

Free access

Seed germination and crop growth characteristics were determined for Tagetes spp. L. `Lemondrop', marigold; Catharanthus roseus Don. `Little Pinkie', vinca; Petunia hybrida Vilm. `Royalty Cherry', petunia; Dendranthema×grandiflorum (Ramat.) Kitamura `White Diamond', chrysanthemum; Pittosporum tobira Ait. `Wheeleri', sweet mock orange; Photinia ×fraseri Dress., photinia and Juniperus sabina L. `Moon Glow', juniper grown in various size containers containing blends of composted green waste (CGW) and UC Mix. Seed germination, plant height, and stem and root fresh and dry mass were lowest in unamended CGW. For most plants studied, a CGW: UC Mix blend containing at least 25% UC Mix was required for adequate growth and development. Germinating seeds and young seedlings were most adversely affected by unamended CGW. As plants grew and were transplanted into larger containers (10- and 15-cm pots, 530 and 1800 mL), they were better able to grow in media with higher CGW content.

Free access

Cracking of carrot (Daucus carota L.) roots during harvest and handling is a serious problem for the commercial industry, particularly for `cut and peeled' products. Thirty commercial fields of cv. `Sugar Snax' in California were surveyed over the period 2000-03. Soil texture was determined, and soil and crop nutrient status, air temperature and soil moisture were monitored. In 10 fields the effect of excessive N fertilization was investigated; 90-180 kg·ha-1 N was sidedressed in addition to the growers' N regime. At one site a comparison of 10 cultivars was conducted to determine the root cracking sensitivity of commercial cultivars suitable for the cut and peeled market. In all fields roots were hand harvested, with undamaged roots 18-24 mm in diameter selected for study. Roots were cooled to 5 °C and subjected to an impact test to rate cracking sensitivity. Fields varied widely in root cracking sensitivity, with 4% to76% of roots cracked in the impact test. Cracking sensitivity was positively correlated with the % silt and clay in soil, and with air temperature in the final month of growth. Irrigation management had no consistent effect on cracking sensitivity. N application in excess of the growers' N regime did not increase carrot yield, but increased root cracking sensitivity by an average of 30%. Root cracking varied among cultivars from 10% to 49%. However, when the periderm was peeled from roots before impact testing, incidence of cracking declined to 2% or less in all cultivars. Periderm strength or flexibility is apparently the dominant factor in carrot cracking sensitivity, and environmental and management variables that affect cracking sensitivity must do so by affecting the periderm structure.

Free access

Three field trials were conducted in central California in 1999 to assess the effects of transplant production and handling practices on yield, crop maturity, and fruit quality of processing tomato (Lycopersicon esculentum Mill.). For each trial, transplants of `Halley' tomato were obtained from a variety of commercial greenhouse transplant growers and subjected to various conditioning treatments during the week prior to planting. These treatments included N and/or P fertilization, varying temperature exposure or degree of water stress, or storage in the dark for 2 days before transplanting to simulate shipment from greenhouse to field. Nine transplant treatments (combinations of transplant source and conditioning treatment) were evaluated in each trial, with five 30 m long single-row plots per treatment arranged in a randomized complete-block design. Plots were mechanically harvested. Despite large differences among treatments in initial transplant characteristics (plant height, root cell volume, macronutrient content), there were no significant treatment differences in fruit yield in two trials; in the third trial, one treatment had significantly lower yield than the highest yielding treatment. In no trial were treatment differences in crop maturity (percent green fruit) or fruit quality (soluble solids content or juice color) significant. Across trials, the only transplant characteristic positively correlated with relative fruit yield (treatment yield/mean yield of that trial) was shoot P concentration, which varied among treatments from 1.3 to 11.7 g·kg–1.

Free access

The utility of presidedress soil nitrate testing (PSNT) in irrigated lettuce (Lactuca sativa L.) and celery (Apium graveolens L.) production was evaluated in 15 commercial fields in California from 1996 to 1997. Fields were selected in which soil NO3-N (5- to 30-cm depth) was >20 mg·kg–1 at the time the cooperating grower made the first sidedress N application. The grower's N regime was compared with reduced N treatments established by reducing or eliminating one or more sidedress applications. All fields were sprinkler and/or furrow irrigated, with minimal in-season precipitation. Reductions in seasonal N application averaging 143 and 209 kg·ha–1 N in lettuce and celery trials, respectively, had no effect on marketable yield in any field. Crop biomass N at harvest in the lowest N treatment in each field averaged 94% (lettuce) and 88% (celery) of that in plots receiving the full grower N program. Based on controlled-environment aerobic incubation of soil from 30 fields in long-term vegetable rotations, in-season N mineralization averaged 1% to 2% of soil organic N. A soil NO3-N “quick test” procedure utilizing a volumetric extraction of field-moist soil and measurement by nitrate-sensitive colorimetric test strips was evaluated and proved to be a practical on-farm method to estimate soil NO3-N concentration. Lettuce midrib NO3-N concentration at cupping stage was poorly correlated with current soil NO3-N level. We conclude that PSNT can reliably identify fields in which sidedress N application can be delayed or eliminated without affecting crop performance.

Free access

Diagnosis and Recommendation Integrated System (DRIS) norms were derived for processing tomato (Lycopersicon esculentum Mill.) from a 1993-94 survey of >100 fields in the Sacramento and San Joaquin Valleys of California. Relative foliar N, P, K, Ca, Mg, and S concentrations were expressed in ratio form, with DRIS norms calculated as the means of fields with fruit yield ≥90 Mg·ha-1. Norms were developed for three growth stages: first bloom, full bloom, and 10% of fruits ripe. Optimum foliar nutrient concentration ranges were calculated by regression analysis from DRIS nutrient indices of high-yield fields. These optimum ranges were in general agreement with existing empirically derived sufficiency ranges for N and P, higher for Ca, Mg, and S, and much lower for K. The relatively low foliar K levels observed were attributed primarily to the strongly determinate growth habit of currently used cultivars. In the fields sampled, yield-limiting nutrient deficiency appeared to be rare.

Free access

The effect of K fertigation through buried drip irrigation on processing tomato (Lycopersicon esculentum Mill.) was evaluated in two California field trials in 2004, and soil K dynamics was investigated in greenhouse trials. Fertigation trials were conducted in fields with exchangeable soil K of 190 (site 1) and 270 mg·kg-1 (site 2), above the yield response threshold by traditional preplant or sidedress K application established by prior research. Two fertigation strategies were compared to an unfertilized control: continuous fertigation at 100 mg·L-1 K from early fruit set through early fruit color development, and weekly application of 40 kg·ha-1 K over the same period. In both treatments, a total of 200 kg·ha-1 K (from KCl) was applied. K fertigation significantly increased fruit yield at site 2, and improved fruit color at both sites. In the greenhouse experiments, fescue (Festuca arundinacea) was grown for 2 weeks atop columns of eight soils ranging from 120–380 mg·kg-1 exchangeable K; the columns were wetted from the bottom, by capillarity. The fescue roots were separated from the soil by a nylon fabric that prevented root penetration while allowing the penetration of root hairs, creating a two-dimensional root/soil interface. In all soils, fescue K uptake reduced soil exchangeable K only in the top 2 mm of the columns, suggesting that effective K diffusion was very limited. In columns of 200-mm height, applying 100 mg·kg-1 K in the water used to wet the soil had minimal impact on fescue K uptake. In columns of 15-mm height, this method of K application more than doubled fescue K uptake in all soils, suggesting that the effective limit of K movement was between 15-200 mm.

Free access

Abstract

Considerable research on greenhouse energy conservation has been conducted since the escalation of fuel prices began in 1973. A variety of conservation techniques such as air-inflated polyethylene over glass (17) and thermal curtains (8, 24, 25) have been studied. Alternative energy sources such as solar energy (7, 14, 15, 16, 18, 19), waste heat from power plants (26) and deep mine air (23) have been examined. Unfortunately, commercial application of these techniques frequently results in reduced light transmission, growing area or precision of environmental control, offsetting the conservation potential.

Open Access

Abstract

The effect of soil solarization (solar heating of soil using clear plastic during a summer fallow period) on consecutive cropping of bell pepper (Capsicum annuum L.) and muskmelon (Cucumis melo L.) was investigated. Raised beds were mulched with 40 µm clear polyethylene film in July, irrigated, and left undisturbed for one month. The plastic then was either removed or pigmented and left in place as a mulch. Solarization increased marketable yield of fall-grown bell pepper 20% when compared to conventional, nonsolarized culture. Where the solarizing plastic was pigmented and left in place as a mulch, pepper yield was 53% higher than in nonsolarized plots. There was a significant residual solarization effect on marketable yield of muskmelon grown the following spring. Increased pepper and melon yields were attributable to increased fruit number rather than fruit weight. Solarization did not influence earliness.

Open Access