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Victorine Alleyne and John R. Clark

An investigation was conducted over 2 years to evaluate the effect of N rate and time of application on fruit composition of `Arapaho' thornless erect blackberry (Rubus L., subgenus Eubatus). N from ammonium nitrate was applied at 56 or 112 kg·ha-1 in single applications, or at 112 kg·ha-1 as a split application with 0 kg·ha-1 as the control. Increasing N rates increased fruit N and pH but did not affect soluble solids concentration, titratable acidity, sugar-acid ratio, and total solids. Timing of N application had no effect on the fruit characteristics measured.

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Victorine Alleyne and John R. Clark

An investigation was conducted in 1994 and 1995 to evaluate the effect of N rate and timing of application on postharvest performance of `Arapaho' thornless blackberry fruit. Treatments were 0 kg N/ha, 56 kg N/ha, 112 kg N/ha single application, and 112 kg N/ha split application. The N source was ammonium nitrate. Fruit samples were hand-harvested and stored for 0–8 days. In general, `Arapaho' fruit quality was not affected by N applications. Increasing N rates increased soluble solids content but had no effect on pH, titratable acidity, sugar: acid ratio, total solids, firmness, and weight loss. Nitrogen applications increased fruit N content.

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J.G. Clapp Jr.

Urea-triazone-based nitrogen (N) solutions were evaluated for potential leaf injury on agronomic and horticultural crops at 61 commercial grower sites throughout the United States. Poliar spray solutions containing triazone N were used at concentrations ranging from 1.5% to 15.7%. Safe N concentrations for urea-triazone-based N products ranged from 1.5% for crops such as sweet corn, apple, cherry, and pear, and up to 15.7% for nursery root stocks. Urea-triazone-based N solutions were found to be much safer on crop foliage than ammonium-, nitrate-, and/or all urea-based foliar fertilizer products than reported in the literature.

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Wlodzimierz Bres and Leslie A. Weston

Experiments were conducted to evaluate the effect of incorporated hydrogel amendments to a soilless growth medium on ammonium, nitrate, and water retention and tomato (Lycopersicon esculentum Mill.) seedling growth. HydroSource and Agri-gel were incorporated into a 1 peat: 1 perlite: 1 vermiculite soilless medium at rates of 1, 2, or 3 g·liter-1 with 0.88 g of ammonium nitrate fertilizer. Water retention by the growth medium increased linearly with gel application; HydroSource generally was more effective than Agri-gel. Between 90% and 96% of the applied nitrate-N was recovered in the resulting leachate of the gel-amended media, while 33% to 55% of the ammonium-N was recovered. Nitrate-N and ammonium-N retention was higher when 3 g·liter-1 of either gel was added to the growth medium than when lower amounts or no gel was added. Gel amendment did not affect tomato seedling growth. Total foliar N concentration in tomato leaves was significantly higher in the HydroSource treatments than in the control or Agri-gel treatments.

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Jianjun Chen, Yingfeng Huang, Zhen Yang, Russell D. Caldwell, and Cynthia A. Robinson

Containerized ornamental plant production represents extremely intensive agricultural production. An average of 200,000 containers may occupy 1 acre of surface area, to which a large amount of chemical fertilizers will be applied. Because of the use of high-drainage soilless potting mixes coupled with excessive fertigation, a great amount of nutrients, particularly nitrogen and phosphorus, are leached, which increases the potential for ground and surface water contamination. Over the past 2 decades, research has been centered on developing fertigation delivery systems such as nutrient film techniques, ebb-and-flow and capillary mat systems, for reducing leaching. Relatively limited research has been conducted on improving potting medium substrates to minimize nutrient leaching. The objectives of this study were to determine the adsorption isotherm of six different zeolites to ammonium, nitrate and phosphorus, identify and incorporate desired zeolites in a peat/bark-based medium for reducing nutrient leaching in ornamental plant production. Results indicated that the zeolites possess great holding capacities for ammonium, nitrate, and phosphorus. Compared to control, ammonium leaching was reduced 70% to 90%, phosphorus 30% to 80% and nitrate 0% to 60% depending on zeolite species and quantity used per pot. Zeolite amended media caused no adverse effects on plant growth. Conversely, biomass increased significantly when compared to that of the control.

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Kent E. Cushman and Thomas E. Horgan

Mississippi growers produce southernpea for the fresh market on raised beds using 20 to 30 lb/acre nitrogen. This study compared conventional production practices to alternative approaches in a 3 × 2 × 2 factorial arrangement in a randomized complete-block design with four replications. Three cultivars of southernpea, `Quickpick' (QP), `Texas Pinkeye' (T × PE), and `Mississippi Pinkeye' (MsPE), were planted into either raised or flat beds using either 30 lb/acre ammonium nitrate without seed inoculation or no ammonium nitrate with Rhizobium seed inoculation. QP and T × PE were harvested with a one-row Pixall harvester and MsPE was hand harvested. All plots were harvested at the mature-green stage. Yields were reduced due to drought conditions during pod fill. MsPE was hand harvested only once due to dry conditions and less-than-ideal yields. QP produced significantly greater yield (1208 lb/acre) than T × PE (962 lb/acre) or MsPE (981 lb/acre). The two nitrogen treatments were not significantly different. QP and T × PE were not affected by bed architecture, but MsPE on raised beds yielded significantly more than on flat beds. As with a similar study in 1998, also under nonirrigated conditions, MsPE had a significantly greater shellout than QP or T × PE. There were no significant interactions for yield or percent shellout.

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Senay Ozgen, Mustafa Ozgen, and Jiwan P. Palta

Several recent studies, including from our laboratory, have provided evidence that by improving tuber calcium level, we can improve tuber quality such as low internal defects and better storability. The purpose of this study was to be determine the influence of supplemental calcium fertilization on tuber size and tuber number. For this purpose, plantlets of Solanum tuberosum cv. Russet Burbank raised in tissue culture were planted in 20-L pots filled with sandy loam soil with pH of 6.9 and soil calcium level of 350 ppm. All treatments received same total amount of nitrogen (at the rate of 280 kg·ha–1). Five treatments were evaluated: i) nonsplit nitrogen (from ammonium nitrate), ii) split nitrogen (from ammonium nitrate), iii) split nitrogen + gypsum, iv) split nitrogen (from liquid nitrogen) + calcium chloride, and v) split nitrogen (from calcium nitrate). The total calcium was applied at the rate of 168 kg·ha–1. Gypsum application was made at 4 weeks after planting, and other sources of calcium were applied on a split schedule (equally split at 4, 6, 8 weeks after planting). Four months after planting, tubers were harvested and evaluated. In general, all calcium treatments had lower tuber number and greater tuber size compared to the nonsplit nitrogen control. The percentage of total A-grade tubers as well as the percentage yield from A-grade tubers was increased by all calcium applications. These results suggest that calcium content I the soil can influence both potato tuber number and tuber size.

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James E. Brown, Daniel W. Porch, Ronald L. Shumack, Charles H. Gilliam, and Larry Curtis

In sweet corn field plots in Alabama, urea-ammonia nitrogen was applied to the soil through underground and aboveground drip fertigation systems. Dry nitrogen in the form of ammonium nitrate was surface band-applied as a control. Nitrogen rates of 67 kg/ha and 135 kg/ha were applied in either 2 or 4 applications by each of the 3 methods. P and K fertilizers were applied to all treatments in a dry form according to soil test recommendations. The underground drip pipe was placed 23 cm beneath the soil surface in each row. Nitrogen (wet or dry) rate of 135 kg/ha produced greater sweet corn yield than the 67 kg/ha rate with no effect of application number on yield in 1988, when rainfall was less than adequate. In 1987 and 1989, when rainfall was adequate, no differences occurred in yields regardless of number, rate, or method of application of nitrogen.

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R.P. Bracy, R.L. Parish, P.E. Bergeron, and E.B. Moser

A precision cultural system proved successful for growing broccoli in multiple rows of plants on narrow or wide beds. Higher production obtained from planting in the multiple-row configurations, however, was not proportional to the increase in number of rows. To quantify the optimum rate of fertilization on multiple rows per bed, broccoli was grown during the spring and fall, 1990, in one row/1-m beds, two rows/1-m beds, or six rows/2-m beds with fertilizer rates ranging from 448 to 1,680 kg·ha-1 of 9N-12P-22K and 150 to 560 kg·hg-1 of ammonium nitrate. During both seasons, fertilizer rate had an overall linear effect on the yield but did not affect average head weight. Response to fertilizer rates was greatest when broccoli was grown in six rows/2-m beds. Broccoli grown during the spring showed a greater response to fertilizer rates than did broccoli grown in the fall.

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Kalala Mwamba, E.G. Rhoden, R.O. Ankumah, and V. Khan

Amaranth (Amaranthus sp.) is a vegetable crop with grains and leaves high in protein, especially, lysine and the sulfur-containing amino acids which are limiting in many vegetables and grains. These nutritional qualities and the ease of growth make it a suitable alternate crop for limited resource farmers. A study was conducted to determine the effect of nitrogen sources and fertilization rates on amaranth production in Alabama and other Southeastern States. The experiment was set up as a complete randomized block design in Norfolk sandy loam (Fine silicoeus, thermic, Typic Paleudult). Four nitrogen sources (urea, sodium nitrate, ammonium sulfate, and ammonium nitrate) were used at three different levels (0, 40, and 80 Kg/ha) one week after transplanting. Sources of nitrogen did not have any significant effect on both fresh and dry vegetable yield (p 0.05). However, fertilization brought significant increases in both yield and total nitrogen content of vegetable amaranth (p 0.05).