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Gilbert Miller, Ahmad Khalilian, Jeffrey W. Adelberg, Hamid J. Farahani, Richard L. Hassell, and Christina E. Wells

watermelons ( Citrullus lanatus cv. Wrigley) grown under polyethylene mulch; and (2) to quantify root distribution and root length density of grafted and ungrafted watermelons under adequate and deficient soil moisture treatments. We hypothesized that the

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T. Caruso, F.P. Marra, A. Motisi, and D. Giovannini

Length and distribution of the roots of 2-year old cv. `Flordaprince' peach trees grown under polyethylene greenhouse were studied over a two year period. The self-rooted, micropropagated trees were spaced 4.9 m between the row and 70, 52 and 42 cm. along the row to obtain a density of 3000, 4000 and 5000 trees/ha respectively. Orchard was clean cultivated, mulched along the row with black plastic fabric 1 m wide, and drip fertigated. Soon after harvest, for each density, the root system of one tree was totally excavated and root length, distribution, dry weight and nutrients content were determined. Total root length per tree was negatively related to planting density in two-year old trees (470, 380 and 320 m/tree respectively for 3000, 4000 and 5000 trees/ha). The shallowest root systems were found at 5000 trees/ha density and their length was unchanged from year to year. Root length density, ranging from 220 to 250 m/m), was only slightly affected by spacing in the two years. The roots were evenly distributed between the two sides of the rows.

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Maxim J. Schlossberg, Keith J. Karnok, and Gil Landry Jr.

Subjection of intensively managed creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.). Farw., (syn. Agrostis palustris Huds.)] to supraoptimal soil temperatures is deleterious to root viability and longevity. The ability to estimate viable root length would enable creeping bentgrass managers to more accurately schedule certain management practices. The purpose of this rhizotron study was to develop a model, based on an accumulated degree-day (ADD) method, capable of estimating viable root length density of established `Crenshaw' and `L93' creeping bentgrass maintained under putting green conditions. Viable root length density observations were made biweekly and soil temperature data collected April through September 1997, and January through August 1998 and 1999. Relative viable root length density (RVRLD) is defined as the measured viable root length density divided by the maximum density attained that spring. In both years, maximum annual viable root length density for all plots was reached, on average, by 138 days from the beginning of the year (18 May). Cultivar and year effects were nonsignificant (P = 0.67 and 0.20, respectively). Degree-day heat units were calculated using an array of base temperatures by integral and arithmetical methods. Although the two accumulative methods proved suitable, the model regressing arithmetical degree-day accumulations against the bentgrass RVRLD provided a better fit to the data set. Use of the 10 °C base temperature in the arithmetical ADD calculations provided the following model; RVRLD = 0.98 - [1.30 × 10-4 (ADD)], accounting for 83.8% of the experimental variability (P < 0.0001). As several abiotic/edaphic factors have been shown to significantly influence root growth and viability, development of a widely usable model would include additional factors.

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Susan L. Barkley, Sushila Chaudhari, Jonathan R. Schultheis, Katherine M. Jennings, Stephen G. Bullen, and David W. Monks

root density used by commercial farmers. Seed roots were graded according to the USDA and North Carolina Department of Agriculture ( USDA, 2005 ) standard that classify roots into no. 1 (diameter of 1.75 to 3.4 inches and length of 3 to 9 inches

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Betsey Miller, Denny J. Bruck, and Vaughn Walton

, P > 0.04) or for shoot length, shoot weight, and root weight from destructive sampling ( t < 1.7, df = 94, P > 0.10). Hence, for subsequent tests, treatments were grouped into three egg density categories: low (0–5 eggs), medium (10–20 eggs), and

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Claudia Fassio, Ricardo Cautin, Alonso Pérez-Donoso, Claudia Bonomelli, and Mónica Castro

means ± se of nine trees; 1 cm = 0.3937 inch, 1 mm = 0.0394 inch. Table 1. The effect of the propagation technique and grafting on the vertical depth of the root frame, soil volume explored, root length density, and main root growth angle of 2-year

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Ana Fita, Belén Picó, Antonio J. Monforte, and Fernando Nuez

millimeters)]; secondary root number, as the number of each discernible lateral secondary root >1 mm emerging from the PR (SRN); secondary root density, calculated as SRN/PRL [SRDe (SRN per centimeter)]; and the average length of secondary roots, calculated as

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Eric M. Lyons, Peter J. Landschoot, and David R. Huff

it is important to determine the distribution of root length density with soil depth in addition to measuring total root length density to assess differences in rooting between cultivars and nutrient regimes. Annual bluegrass growth and

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Haishan An, Feixiong Luo, Ting Wu, Yi Wang, Xuefeng Xu, Xinzhong Zhang, and Zhenhai Han

is root length density and RND is root number density. Fine root production and mortality. For each rhizo-pit, the RLD-based fine root production was calculated as the sum of the RLD of newly emerged roots, representing the gross increase in the RLD

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Li Ma, Chang Wei Hou, Xin Zhong Zhang, Hong Li Li, De Guo Han, Yi Wang, and Zhen Hai Han

( Actinidia Lindl.) vines ( Gandar and Hughes, 1988 ) are bowl-shaped with the roots centered near the stem, whereas older trees have a more layered structure with a higher root length density (RLD) further away from the trunk ( De Silva et al., 1999