Search Results

You are looking at 1 - 10 of 17 items for

  • Author or Editor: J. R. Johnson x
  • All content x
Clear All Modify Search
Free access

R.N. Carrow and B.J. Johnson

A turfgrass wear injury study was conducted at Griffin, Ga., on `Tifway' bermudagrass (Cynodon dactylon × C. transvaalensis) using two golf car tires and three golf car types driven in a semicircular pattern to deliver 85 passes over the tread path plot area. Wear injury for the 14 days after wear was applied was assessed by visual quality, percent green coverage, leaf bruising, and verdure. Golf tire × car interactions occurred, but more wear occurred with the low pressure (48 × 103 Pa), dimpled tread tire with flexible sidewalls than the commonly used bias ply (4-ply), V-shaped tread tire with more rigid sidewalls. Significant differences in wear damage occurred for golf car type but were influenced by tire design. Thus, selection of golf car tire and golf car type can influence the degree of wear injury on turfgrass sites.

Free access

Franz J. A. Niederholzer and R. Scott Johnson

Urea foliar sprays may be a more efficient and environmentally sound alternative to soil applied fertilizer N in the postharvest period in tree crop production in California. While tree crop sulfur (S) status can interact with tree N status to affect growth, we know of no study assessing tree crop leaf N and S dynamics following fall (postharvest) foliar urea applications. We conducted a field study to measure temporal dynamics of leaf N and leaf S (% dry weight basis) following postharvest urea sprays on prune (Prunusdomestica) and almond (Prunus dulcis). June-budded nursery stock prune (`French' on Myro 29C) and almond (`Price' on Lovell) trees were sprayed to dripping with 6.5% (w/w) and 10% (w/w) standard urea solutions, respectively. Prunes were sprayed on 1 Oct. 2003 and almonds on 18 Nov. 2003. Leaf samples were taken over a 3-week (almond) or 8-week (prune) period, beginning just before treatment. Foliar urea sprays significantly increased prune (23%) and almond (14%) leaf N compared to untreated control within 8 days of application. This affect was transient, as there were no differences in leaf N concentrations between treated and untreated trees at final leaf sampling. Urea sprays did not affect almond leaf S concentration relative to untreated trees. Prune leaf S was significantly reduced compared to untreated trees 8 days after treatment, but only on that sampling date. Remobilization of S from the leaves of control trees of either species was not apparent.

Free access

S.J. Browning, T.P. Riordan, R.K. Johnson, and J. Johnson-Cicalese

Buffalograss [Buchloë dactyloides (Nutt.) Engelm] is a drought-resistant, dioecious species, native to the Central Great Plains, which shows excellent potential as a low-maintenance turfgrass. Although buffalograss can be propagated vegetatively, there is a need for seeded turf-type cultivars. To assist in developing seeded cultivars, heritabilities of turf characteristics were estimated. Heritabilities from maternal half-sib analyses ranged from h2 = 0.04 ± 0.03 for the 1988 uniformity rating to h2 = 0.62 ± 0.26 for the 1989 spring color rating. Heritability estimates calculated from offspring-parent regression were also variable and generally lower than maternal half-sib analysis. The results suggest that some turf characteristics are highly heritable and that growing conditions markedly affect heritability estimates.

Free access

R. Scott Johnson, Claude J. Phene, and Dale Handley

Generally, water stress reduces yield in annual crops. However, for mature fruit trees, this relationship may not hold in many situations, thus providing the opportunity for saving water without losing production. Indeed, even an increase in productivity may be achieved as we better learn how to manipulate processes within the tree through moderate water stress. Several areas of research have shown promising results. The reduction of irrigation after harvest of early maturing peaches and plums has demonstrated substantial savings of water with no loss of production. Peaches can suffer fruit quality problems such as doubling and deep suturing, but these can be overcome with well-timed irrigations in the previous late summer. Water stress imposed before harvest has also shown some promise. Reports from Australia have demonstrated significant increases in yield and fruit size in peach and pear, although researchers in other locations have generally been unable to replicate these results. The timing and/or rate of stress development appear to be critical factors. Under the right conditions, stress can alter the allocation of resources between vegetative and fruit growth. Before implementation of these practices can be achieved, further research will need to focus on developing good tools for measuring stress in the trees, obtaining a better understanding of adaptation of trees to rapidand slow-developing stress, documenting the effects of stress on vegetative and fruit growth during different times of the season, and understanding the interaction of stress with other factors such as fruit load.

Free access

Billy J. Johnson, Robert N. Carrow, and Tim R. Murphy

Field experiments were conducted to determine the effects of foliar iron (Fe) applied with postemergence herbicides on injury, color, and quality of `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy × Cynodon dactylon (L.) Pers.]. Iron significantly decreased injury and improved quality and color of `Tifway' bermudagrass in conjunction with herbicide treatment. Turf injury was less for 4 to 18 days after the initial MSMA application when Fe was added. Injury was also less from sequential Fe treatment with MSMA + metribuzin (up to 4 days) and MSMA + imazaquin (from 4 to 10 days) compared to the respective herbicides applied alone. There was no difference in turf injury from Fe when imazaquin at 1.3 kg·ha-1 was applied as a single treatment. However, turf treated with Fe and two applications of imazaquin (9- to 10-day interval) recovered from herbicide injury faster than when treated only with the herbicide. Iron did not prevent immediate 2,4-D + mecoprop + dicamba injury to the bermudagrass, but did hasten turf recovery from injury at 26 days after treatment. With a few exceptions, `Tifway' bermudagrass quality was higher and color improved when Fe was added. However, injury expressed as loss of shoot density was not affected by Fe and only injury expressed as color loss was improved by Fe. Chemical names used: 3,6-dichloro-2-methoxybenzoic acid (dicamba), 2-[4,5-dihydro-4-methyl)-4-(1-methylethyl)-5-oxo-1H-imidazol-2yl]-3-quinolinecarboxylic acid (imazaquin), (±)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop), 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one (metribuzin), monosodium salt of MAA (MSMA), and (2,4-dichlorophenoxy)acetic acid (2,4-D).

Free access

David R. Bryla, Elizabeth Dickson, Robert Shenk, R. Scott Johnson, Carlos H. Crisosto, and Thomas J. Trout

A 3-year study was done to determine the effects of furrow, microspray, surface drip, and subsurface drip irrigation on production and fruit quality in mature `Crimson Lady' peach [Prunus persica (L.) Batsch] trees. Furrow and microspray irrigations were scheduled weekly or biweekly, which is common practice in central California, while surface and subsurface drip irrigations were scheduled daily. Trees were maintained at similar water potentials following irrigation by adjusting water applications as needed. Tree size and fruit number were normalized among treatments by pruning and thinning each season. Surface and subsurface drip produced the largest fruit on average and the highest marketable yields among treatments. Drip benefits appeared most related to the ability to apply frequent irrigations. Whether water was applied above or below ground, daily irrigations by drip maintained higher soil water content within the root zone and prevented cycles of water stress found between less-frequent furrow and microspray irrigations. With furrow and microsprays, midday tree water potentials reached as low as –1.4 MPa between weekly irrigations and –1.8 MPa between biweekly irrigations, which likely accounted for smaller fruit and lower yields in these treatments. To reduce water stress, more frequent irrigation is probably impractical with furrow systems but is recommended when irrigating during peak water demands by microspray.

Free access

David R. Bryla, Thomas J. Trout, James E. Ayars, and R. Scott Johnson

A 3-year study was conducted in central California to compare the effects of furrow, microjet, surface drip, and sub surface drip irrigation on vegetative growth and early production of newly planted `Crimson Lady' peach [Prunus persica (L.) Batsch] trees. Furrow treatments were irrigated every 7, 14, or 21 days; microjet treatments were irrigated every 2-3, 7, or 14 days; and surface and subsurface drip (with one, two, or three buried laterals per row) treatments were irrigated when accumulated crop evapotranspiration reached 2.5 mm. The overall performance showed that trees irrigated by surface and subsurface drip were significantly larger, produced higher yields, and had higher water use efficiency than trees irrigated by microjets. In fact, more than twice as much water had to be applied to trees with microjets than to trees with drip systems in order to achieve the same amount of vegetative growth and yield. Yield and water use efficiency were also higher under surface and subsurface drip irrigation than under furrow irrigation, although tree size was similar among the treatments. Little difference was found between trees irrigated by surface and subsurface drip, except that trees irrigated with only one subsurface drip lateral were less vigorous, but not less productive, than trees irrigated by one surface drip lateral, or by two or three subsurface drip laterals. Within furrow and microjet treatments, irrigation frequency had little effect on tree development and performance with the exception that furrow irrigation every 3 weeks produced smaller trees than furrow irrigation every 1 or 2 weeks.

Free access

H. Friedrich, C.R. Rom, D. Johnson, J. Popp, B. Bellows, M. Savin, and D. Miller

A multidisciplinary effort has been initiated between the University of Arkansas and the National Center for Appropriate Technology to identify production barriers, research and outreach needs, and market opportunities for sustainable and organic fruit in the Southern region. The goals of the project are to identify barriers of the organic system through focus group meetings with producers, processors and marketers, and to develop regional research and outreach projects to overcome these obstacles. Market development, organic fertilizer knowledge and organic pest management have been identified as areas that need research and outreach activities. Long-term outcomes are expected to increase sustainable and organic fruit production, provide opportunities for growers and consumers, and encourage local economic development in the Southern region.

Free access

Curt R. Rom, H. Friedrich, D. Johnson, J. Popp, B. Bellows, M. Savin, and D. Miller

Fruit production in the Southern region has declined in the last several decades. Further, although certified organic fruit production has increased significantly in other regions of the US in the past decade, there has been very little growth of that industry in this region. It is presumed that the lack of production is based upon the lack of research, out-reach, and science-based information available to growers which make organic production possible. Based on planning grant funding from the Southern IPM Center program and the Sustainable Agriculture Research and Education program a Southern Organic Fruit Working Group is being formed. The projects are collaborative efforts of horticulturists, entomologists, plant pathologists, soil scientists, and agricultural economists in Arkansas, Georgia, Kentucky, North Carolina, South Carolina, and Tennessee. In each state, a coordinator is hosting stake-holder focus groups of producers, marketers, processors, extension workers, consultants, organic certifiers, etc. The purpose of focus group meetings is to identify challenges and opportunities in production and marketing organic fruit, especially apples, blackberries, blueberries, and peaches, in the Southern Region. Coordinators are combining findings from state focus group meetings to establish priorities for research and outreach to support organic production, and will work collaborative to addresses those priorities. Because of the similarity in climate, geography and demographics of growers and markets among the states of the region, this is a project best addressed as a regionally collaborative effort.

Free access

Kenneth A. Shackel, R. Scott Johnson, Charles K. Medawar, and Claude J. Phene

The heat balance method was used to estimate transpirational sap flow through 60- to 75-mm-diameter stems (trunks) of 3-year-old peach [Prunus persica (L.) Batsch. cv. O'Henry] trees under field conditions. On rare occasions, heat balance estimates agreed well with independent lysimetric measurements, but on most occasions, heat balance estimates of sap flow were unrealistic in both direction and magnitude. In some cases, the errors in sap flow approached two orders of magnitude and were always the result of a calculation involving division by a very small and sometimes negative temperature differential between the stem surface temperature above and below the gauge heater. The occurrence of negative temperature differentials under positive transpiration conditions may be inconsistent with a fundamental assumption in the heat balance model, namely that temperature differentials are solely a consequence of the dissipation of energy supplied to the gauge heater. In the absence of heating power applied to the gauge, temperature differentials exceeding - 1C were correlated with the rate of change in stem temperature, indicating that ambient conditions themselves can impose a bias in gauge signals and, hence, influence gauge accuracy. Our results suggest that the effect of ambient conditions on gauge signals should be critically evaluated before considering heat balance estimates of sap flow as reliable under any given conditions.