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Rebecca Nelson Brown and Josef H. Gorres

Highway rights-of-way are routinely planted with turfgrasses to prevent erosion, filter runoff, and improve aesthetics. However, the roadside is a harsh environment, and perennial grasses often die within the first year, leading to bare ground and annual weeds, which do not prevent erosion during the winter. To improve the survival of perennial vegetation on the roadside, it is necessary to identify the factors limiting vegetation growth and then to either identify plants that can tolerate those factors or identify ways to ameliorate the stresses while still maintaining safety. This study was designed to evaluate the effects of improved cultivars, salt tolerance, and organic matter amendments on perennial grass survival along two highways in Rhode Island. The amendments tested were processed biosolids and composted yard waste, each applied in a 50:50 mixture by volume with existing roadside soil; plain soil was included as a control. We tested 20 improved turfgrass cultivars and one seed mixture with common creeping red fescue (Festuca rubra L.) as the standard. Turfgrass species tested were perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.), red fescue, alkali grass [Puccinellia distans (Jacq.) Parl.], idaho bentgrass (Agrostis idahoensis Nash), tufted hairgrass [Deschampsia cespitosa (L.) P. Beauv.], and kentucky bluegrass (Poa pratensis L.). We found that soil amendment was more effective than either improved genetics or salt tolerance. Establishment, vertical growth, and persistence of vegetation cover were significantly improved by amendment with organic matter, particularly biosolids. In Summer 2009 (the second growing season), turf cover exceeded 50% in the biosolids plots but was below 20% in the plain soil plots with complete loss of cover in the plain soil plots at one location. Kentucky bluegrass, tall fescue, red fescue, and idaho bentgrass showed the best persistence at the species level, and there were no consistent differences among cultivars.

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Rawia El-Motaium and Patrick H. Brown

Boron toxicity is a wide spread problem especially in arid and semiarid areas of the world. Boron toxicity can result in yield loss of many crop plants, especially stone fruits which are sensitive to high boron concentration. This study was designed to follow the effect of Ca+2 supplementation on partitioning of B at the plant organ level (leaves, stem, roots) and the subcellular level (the cell wall) using the stable isotope 10B.

Results demonstrate that calcium supplementation reduced B accumulation in plum and peach leaves by 31% at the low level (0.25 mM) and by 12% at the high B level (0.50 mM). Results indicate an effect of Ca on the uptake and distribution of 10B between plant organs.

Symptoms of B toxicity in peach (Lovell) include stem die back, necrotic brown spots on the stem and gum formation on the nodes, whereas in plum (Mariana), stem die back and gum formation, as droplets, on the lower leave's surface were the main symptoms.

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Kimberly H. Brown, John C. Bouwkamp, and Francis R. Gouin

Optimum conditions for composting encourage and maintain the growth of microorganisms. Aerobic conditions must be maintained along with a 30 C: 1 N ratio and appropriate moisture levels. Our research found that P along with C and N are primary nutrients required by the microorganisms involved in composting. Phosphorus is a very important component of ATP and ADP, which drive most biochemical processes and are therefore necessary to all energy-driven processes. Results of this experiment show that MSW treatments with a minimum of 120 C: 1 P result in significantly higher temperatures during the composting process; lower final C: N ratios; greater volume reduction; and more available N in the final product. Emphasis of ongoing research is to determine appropriate C: P levels.

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Richard C. Rosecrance, Steve A. Weinbaum, and Patrick H. Brown

The interrelationships between crop load, root growth, and nutrient uptake in mature, pistachio trees were examined in this study. Nutrient uptake was determined during the spring, summer, and fall using labeled nitrogen (15N) and boron (10B) and by differences in whole-tree accumulation between tree harvests for other nutrients (e.g., P, K, Ca, Zn). Nitrogen and boron uptake were double in fruiting compared with nonfruiting trees in the spring. Most of the labeled N was found in the developing fruits and leaves. Total labeled N recovery during the spring flush period, however, was low, indicating that much of the N in the fruit came from N reserves from within the tree rather than uptake from the soil. In contrast, significant amounts of N were taken up from the soil during the summer uptake period. Thus, our data support the hypothesis that sink demand (i.e., fruit development) conditions N uptake in pistachio. The relationship between root growth and N uptake was also examined in this study. Root observation chambers were constructed, and root growth determined by tracing roots growing up against the glass windows. Root length, root growth rate, relative root growth rate, and total tree fine root weight were all greater in nonfruiting compared to fruiting trees during the fruit development period (late May to mid-July). Surprisingly, fruiting trees had less root growth, but greater N uptake than nonfruiting trees during this period. This evidence suggests that N uptake is decoupled from root growth in mature pistachio trees.

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Oswaldo A. Rubio, Patrick H. Brown, and Steven A. Weinbaum

Leaf N concentrations (% dry wt) appear relatively insensitive to high levels of applied fertilizer N (Weinbaum et al, HortTechnology 1992). This insensitivity may be attributable to growth dilation, lack of additional tree N uptake, a finite capacity of leaves to accumulate additional N or our inhability to resolve a limited increment. Our objective was to asses the relative accumulation of mobile forms of N (NO3, NH4 and amino acids) relative to a total N over a range of fertilizer N application rates in 3 year old, field-grown “Fantasia” nectarine trees. Between 0 and 136 Kg N/Ha/Yr we observed a linear relationship between N supply and all N fractions. Above 136 Kg N/Ha/Yr leaf concentrations of amino acids and total N remined constant, but NO3 and NH4 accumulation continued. These results suggest that leaf concentration of NO3 and NH4 are more sensitive indicators of soil N availability and tree N uptake than was total leaf N concentration.

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Richard C. Rosecrance, Steve A. Weinbaum, and Patrick H. Brown

Contributions of nitrogen (N) fertilizer applications to nitrate pollution of groundwater is an increasing public health concern. In an effort to improve N fertilizer efficiency, a study was initiated to determine periods of tree N demand in mature, alternate bearing pistachio trees. Seasonal patterns of nitrogen accumulation in the branches (i.e. fruit, current year wood, one year old wood, and leaves) and roots were monitored monthly.

Branches from heavily fruiting trees contained almost six times more nitrogen than branches from light fruiting trees by September; a result of the large amount of N accumulated in the fruit. Nitrogen accumulated in the branches during the Spring growth flush and nut fill periods in both heavy and light fruiting trees. Root nitrate and total N concentrations, however, peaked during the Spring growth flush and subsequently decreased during nut fill. The relationship between tree N demand and the capacity for N uptake is discussed.

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Qiupeng Zeng, Patrick H. Brown, and Brent A. Holtz

A field experiment was conducted from 1996 to 1998 to examine the effects of K fertilization on leaf K, nut yield, and quality in pistachio (Pistacia vera L.). There were six treatments, including four annual rates of K application (0, 110, 220, and 330 kg·ha-1) and three K sources (K2SO4, KCl, and KNO3). Pistachio trees exhibited highly fluctuating seasonal leaf K levels. Leaf K concentration was low (<10 g·kg-1) during spring flush, increased dramatically during fruit development, and declined rapidly after harvest. Leaf K concentration increased following K fertilization. Potassium fertilization at the rate of 110 to 220 kg·ha-1 K significantly increased nut yield and quality, but nut yield tended to decrease when the annual rate exceeded 220 kg·ha-1 K. There were no significant differences among the K sources in their effects on leaf K concentration, nut yield, and quality. The use of KCl as a K source for 3 years did not increase leaf Cl concentration. There was a significant, positive correlation between nut yield and leaf K concentration during nut fill. The critical leaf K value for optimal pistachio production determined from 3 years' cumulative data was 16.9 g·kg-1. For sustained production in highly productive pistachio orchards, we recommend annual application rates of 110 to 220 kg·ha-1 K, using K2SO4, KCl, or KNO3.

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H.C. Bittenbender, N.V. Hue, Kent Fleming, and Hilary Brown

A fertilization experiment, started in 1989, evaluated the merits of macadamia husk-manure compost as fertilizer for the production of macadamia. Three fertilization treatments were compared at four sites over 4 years on the MacFarms of Hawaii Honomalino orchard. The treatments were conventional fertilization, a combination of solid and liquid mineral fertilizers annually adjusted by the orchard manager based on leaf and soil analysis; compost only as 5 tons of a macadamia husk-cattle manure compost applied annually between July and October; and compost plus supplemental mineral fertilizers deemed needed by the orchard manager based on leaf and soil analysis. In-shell nut and kernel yield and quality was not significantly different between treatments. Change in leaf nutrient values appears minimum except for slightly lower N at two sites for the compost treatment. Higher Mg was noted for the compost but not the compost plus treatments at the irrigated sites. The effect of compost on the soil nutrient levels was more distinct and may have a delayed and longer term effect. Total exchange capacity of the soil increased, as did soil pH, Ca, Mg, K, and Na. Organic matter increased only at the site with least soil. Extractable soil Fe decreased, this maybe related to the change in pH, but had no consistent effect on leaf Fe. Compost fertilization was not considered sustainable as the cost of compost and its application exceeded conventional fertilization.

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Richard C. Rosecrance, Steven A. Weinbaum, and Patrick H. Brown

The effect of crop load on nutrient and starch storage in mature, alternate-bearing pistachio trees was examined. Tree storage pools were estimated from the differences in nutrient and starch contents of perennial tree parts between dormancy (the period of highest nutrient and starch content) and following spring flush (the period of lowest nutrient and starch content). Following a lightly cropping (off) year, trees contained significantly larger N, P, and K storage pools than following a heavily cropping (on) year. The relative contribution of leaf nutrient resorption to tree nutrient storage pools varied depending on the crop load. Nutrient storage is a function of net leaf nutrient resorption and current uptake from the soil. Leaf nutrient (N, P, and K) resorption was a more significant component of nutrient storage in on-year than off-year trees. The contribution of nutrient storage to shoot (i.e., leaves, fruit, current-year wood) nutrient contents was evaluated following the spring flush (May) and nut fill (September) periods. Nutrient storage pools are an important source of nutrients during the spring flush of growth, but nutrient demands during nut fill are met primarily by current nutrient uptake from the soil. The relationships between nutrient storage and uptake are discussed.

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Maurus V. Brown, James N. Moore, and Fens H. Huang

`Saturn', `Mars', and `Reliance' were compared based on their different Vitis vinifera and V. labrusca compositions. Disks (10 mm) from young leaves were placed abaxial side down on a standard media containing NAA or 2,4-D at 0.0, 1.0, and 2.0 mg/L with BAP at 0.0, 0.1, and 0.2 mg/L. Each treatment was replicated in 10 culture tubes and incubated at 25 ± 1C under cool-white fluorescent light for 10h photoperiods. Calli were compared by size, color, and occurrence of morphogenesis. NAA generally produced a larger callus by cultivar than 2,4-D. A greater quantity of callus was generally produced with the increase of the V. labrusca component. Callus produced on 2,4-D medium was round, compact and light to dark green in color. However, callus produced on NAA medium was amorphous, friable, and ranged in colors. Rooting occurred on some calli produced on NAA media.