Search Results

You are looking at 1 - 10 of 2,955 items for :

  • N fertilization x
  • All content x
Clear All
Free access

Habib Khemira, T. L. Righetti, David Sugar, and A. N. Azarenko

Current N fertilization practices, where high spring applications are utilized, may lead to excessive vegetative growth. However, high rates may not be required to maximize fruit yield and quality. Therefore, alternative strategies to minimize shoot growth while still providing the N needs of the tree were investigated. Mature `Comice' and `Bosc' pear trees were given one of the following treatments: a spring soil (SS) application of NH4NO3 nitrate at 112.5 kg/ha rate, a similar application in the fall after harvest (FS), a fall foliar (FF) spray of a 7.5% urea solution after harvest (FF), or no N (Control). Trees that received a FF application had the same leaf and fruit N content as control trees, but they yielded more fruit The SS application gave more vigorous trees than FF application. Yield, however, was not different.

A 15N enriched urea solution was applied at harvest as either a foliar spray, soil application, or combination of both treatments to mature `Comice' trees. Flower buds from trees that previously received a foliar treatment had 37% of their N derived from the foliar N application. No labeled N was detected in buds from the soil treatment These results indicate that vegetative and reproductive N requirements of fruit trees may be managed separately.

Free access

George J. Hochmuth, Earl E. Albregts, and Craig K. Chandler

During the 1992-93 fruiting season, strawberries were fertigated weekly with 0.28, 0.56, 0.84, 1.12, or 1.40 kg N/ha/day from ammonium nitrate. K was applied uniformly at 0.84 kg/ha/day by fertigation. Irrigation maintained soil moisture tension in the beds between -10 and -15 kPa. Fruit yields responded positively to N fertilization with yields maximized at 0.56 kg N/ha/day. Leaf N and petiole sap nitrate N concentrations increased with N rate with leaf-N for the plants receiving 0.28 kg N/ha/day remaining below 25 g·kg-1 most of the season. Sufficiency ranges for petiole sap nitrate-N quick testing were developed.

Free access

C.A. Sanchez, H.Y. Ozaki, K. Schuler, and M. Lockhart

Experiments were conducted from 1985 to 1989 to evaluate the response of radishes (Raphanus sativus L.) to N fertilization on Histosols. Three of these experiments used 15N-labeled fertilizer to evaluate the recovery of N by radishes. There was no response to N fertilization in seven of the eight experiments, even though some of them were conducted under conditions of high rainfall. The one experiment in which radish yields increased with N was conducted in a poorly drained, waterlogged field that was atypical of normal radish production fields. Recoveries of fertilizer N in the marketable radish roots averaged 19%. The results of N and 15N analysis showed that although fertilizer N was available for uptake, so was an ample amount of soil mineralized N. These results indicate that under typical growing conditions, radishes produced on Florida Histosols do not respond to N fertilization.

Free access

Anthony F. Silvernail and Gary R. Cline

The effects of cover crop, tillage, and N fertilization on yields of `Paladin' watermelon (Citrullus lanatus) were analyzed by determining available soil N levels, foliar N content, and relative greenness with a SPAD-502 chlorophyll meter. Analyses from all three analytical procedures identified N deficiencies in watermelon with their respected measurements. Available soil N analyses indicated that soil N levels below 40 mg·kg–1 at vining caused dramatic decreases in yields, while the level needed to ensure maximal yields during the same period was 100 mg·kg–1. Results from foliar and SPAD tests indicated that plants with foliar N levels below 42 g·kg–1 and SPAD readings below 40 SPAD units at anthesis will have suppressed yields. Optimal foliar N levels and SPAD readings required for maximum yields were 50 g·kg –1 and 48 SPAD units, respectively. The main difference among all three N testing procedures was that available soil N analysis was able to detect possible deficiencies two to three weeks before either the foliar or SPAD analysis. Differences in yield between plants from conventionally tilled plots and no-till plots were not significant. However, inorganic N fertilization significantly increased yields in watermelon following both rye (Secale cereale) and mix cover crop treatments. Watermelon yields of plants following the hairy vetch (Vicia villosa) cover crop treatment showed no response to inorganic N fertilization. Of the three cover crop treatments, the addition of N fertilizer had the most effect in the rye treatment.

Free access

Mohammed Z. Alam, Calvin Chong, Jennifer Llewellyn, and Glen P. Lumis

Toronto, Canada Rathier, T.M. Frink, C.R. 1989 Nitrate in runoff from container grown juniper and Alberta spruce under different irrigation and N fertilization regimes J. Environ. Hort. 7 32 35 Richards

Free access

Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth, and Peter J. Stoffella

Journal Series No. N-01914. We thank Speedling, Sun City, Fla., for partial support of this project. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked

Free access

Joseph Naraguma and John R. Clark

Applications of N to blackberry plantings are a common practice in Arkansas, but fertilizer recommendations are largely based on those of other states. The need for information on fertility of a new blackberry from the Arkansas breeding program motivated this study. A three-year-old `Arapaho' blackberry planting at the University of Arkansas Fruit Substation was used for this study. Treatments which began in 1994 and continued through 1996 were: 1) control—no N applied, 2) 56 Kg N/ha applied in a single application in early spring, 3) 112 Kg N/ha applied in a single early spring application, and 4) 112 Kg/ha applied in a split application with one-half applied in the early spring and one-half applied immediately after harvest. Fruit was harvested from the plots in June and total yield and average berry weight determined. Foliar samples were collected in August and elemental analysis conducted. Primocanes in each plot were counted at the end of the growing season. Over the three years, there was no significant treatment effect on yield, berry weight, or primocane number. A trend toward higher primocane number where N was applied was seen, however. Foliar levels of N, P, K, Ca, S, and Mn were affected by either N rate or time of application. The foliar N levels were influenced by N rate and the split application gave the highest concentration. Calcium was higher when no N was applied, Mn was greater at higher N rates while the control had the lowest foliar N level in each year.

Free access

Barbara Cohea Pitman, D.C. Sanders, and W.H. Swallow

of the N.C. Agricultural Research Service, Raleigh, NC 27695–7901. Partial funding provided by Joan of Arc Co., Turkey, N.C. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper

Free access

M. Pilar Bañados, Bernadine C. Strik, David R. Bryla, and Timothy L. Righetti

, personal observation). Various studies have been completed on the effect of rate of N fertilization on the growth and yield of mature blueberry plants. In a 5-year study on ‘Bluecrop’ blueberry, plants fertilized with a split application of 75 kg·ha −1 of

Full access

Fang Xiao, Zaiqiang Yang, Haijing Huang, Fei Yang, Liyun Zhu, and Dong Han

indirectly by influencing chlorophyll content ( Berges et al., 1996 ; Rufty et al., 1988 ). Moreover, there is a significant positive correlation between N fertilization contents and photosynthetic rate of plant leaves. Some researchers found that N can