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D.M. Glenn and W.V. Welker

Planting sod beneath peach trees (Prunus persica) to control excessive vegetative growth was evaluated from 1987 to 1993 in three field studies. Peach trees were established and maintained in 2.5-m-wide vegetation-free strips for 3 years, and then sod was planted beneath the trees and maintained for 5 to 7 years. Reducing the vegetation-free area beneath established peach trees to a 30- or 60-cm-wide herbicide strip with three grass species (Festuca arundinacae, Festuca rubra, Poa trivialis), reduced total pruning weight/tree in 5 of 16 study-years and weight of canopy suckers in 6 of 7 study-years, while increasing light penetration into the canopy. Fruit yield was reduced by planting sod beneath peach trees in 5 of 18 study-years; however, yield efficiency of total fruit and large fruit (kg yield/cm2 trunk area) were not reduced in one study and in only 1 year in the other two studies. Planting sod beneath peach trees increased available soil water content in all years, and yield efficiency based on evapotranspiration (kg yield/cm soil water use plus precipitation) was the same or greater for trees with sod compared to the 2.5-m-wide herbicide strip. Planting sod beneath peach trees has the potential to increase light penetration into the canopy and may be appropriate for high-density peach production systems where small, efficient trees are needed.

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Tara A. O'Brien and Allen V. Barker

This research evaluated production of wildflower sods in soil and composts of mixed municipal solid waste, biosolids and woodchips, fall leaves, and mixed agricultural wastes. Soil or composts were laid on plastic sheeting in outdoor plots, and a mixture of wildflower seeds was sown in July and in September in separate experiments. Quality of sods was assessed in two growing seasons. Best sods with respect to seed germination, stand establishment, and intensity and diversity of bloom over two seasons occurred in mature biosolids compost and in agricultural waste compost. These composts were low in ammonium but rich in total N. Germination and growth of wildflowers were limited by high ammonium concentrations in immature biosolids composts. Nitrogen deficiency limited sod growth and quality in leaf composts. Poor N nutrition and weed competition restricted sod production in soil. Fertilization of soil promoted unacceptably large weed growth. Summer seeding or fall seeding resulted in good sods, but many annual flowers that appeared in the summer seeding were absent in the fall-seeded planting. Using plastic-lined plots was a convenient system for evaluating composts and other media in outdoor culture.

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Maxim J. Schlossberg and William P. Miller

Coal combustion by-products (CCB) are produced nationwide, generating 108 Mg of waste annually. Though varied, the majority of CCB are crystalline alumino-silicate minerals. Both disposal costs of CCB and interest in alternative horticultural/agricultural production systems have increased recently. Field studies assessed the benefit of CCB and organic waste/product mixtures as supplemental soil/growth media for production of hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] sod. Growth media were applied at depths of 2 to 4 cm (200 to 400 m3·ha-1) and vegetatively established by sprigging. Cultural practices typical of commercial methods were employed over 99- or 114-day growth periods. Sod was monitored during these propagation cycles, then harvested, evaluated, and installed offsite in a typical lawn-establishment method. Results showed mixtures of CCB and biosolids as growth media increased yield of biomass, with both media and tissue having greater nutrient content than the control media. Volumetric water content of CCB-containing media significantly exceeded that of control media and soil included with a purchased bermudagrass sod. Once installed, sod grown on CCB-media did not differ in rooting strength from control or purchased sod. When applied as described, physicochemical characteristics of CCB-media are favorable and pose little environmental risk to soil or water resources.

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Bruce R. Roberts, Henry F. Decker, Kenneth J. Bagstad, and Kathleen A. Peterson

Two biosolid-containing waste media [sewage sludge compost and incinerated biosolids (flume sand)] were tested individually, together, and in combination with a commercial growing medium for growing wildflower sod in greenhouse trials over a 3-year period. A medium composed of flume sand and Metromix (7:3 weight/weight) in 7.5 {XtimesX} 10.5 {XtimesX} 2-inch deep (19 {XtimesX} 27 {XtimesX} 5-cm) plastic trays seeded at 20 oz/1000ft2 (6.1 g·m-2) with cosmos (Cosmos bipinnatus), cornflower (Centaurea cyannis), plains coreopsis (Coreopsis tinctoria), white yarrow (Achillea millefolium) and purple coneflower (Echinacea purpurea) produced a suitable wildflower sod in 10 to 12 weeks. A single application of slow release fertilizer (Osmocote 14-14-14, 14N-4.2P-11.6K) applied as a top dressing had no significant effect on sod development; however, a 4-mil [0.004-inch (0.10-mm)] polyethylene barrier placed in the base of each container resulted in increased dry weight accumulation and a higher root to shoot ratio relative to sod grown without plastic.

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Charles A. Sanchez and Jeffrey. C. Silvertooth

About 33% of all irrigated lands worldwide are affected by varying degrees of salinity and sodicity. Soil with an electrical conductivity (EC) of the saturated extract >4 dS·m−1 is considered saline, but some horticultural crops are negatively affected if salt concentrations in the rooting zone exceed 2 dS·m−1. Salinity effects on plant growth are generally osmotic in nature, but specific toxicities and nutritional balances are known to occur. In addition to the direct toxic effects of Na salts, Na can negatively impact soil structure. Soil with exchangeable sodium percentages (ESPs) or saturated extract sodium absorption ratios (SARs) > 15 are considered sodic. Sodic soils tend to deflocculate, become impermeable to water and air, and puddle. Many horticultural crops are sensitive to the deterioration of soil physical properties associated with Na in soil and irrigation water. This review summarizes important considerations in managing saline and sodic soils for producing horticultural crops. Economically viable management practices may simply involve a minor, inexpensive modification of cultural practices under conditions of low to moderate salinity or a more costly reclamation under conditions of high Na.

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Lance Stott, Lisa Rew, and Tracy Dougher

The California Department of Transportation (Caltrans) has used hydroseeding, imprinting, and drill seeding methods to revegetate highway construction sites, with varying degrees of success. Ecological concerns, particularly in areas with high erosion potential, have led Caltrans to search for more-reliable plant establishment methods. One possibility is native sod, which should reduce erosion potential, and, the species would also be better suited to local environments, require less maintenance, and pose no invasive threat to adjacent ecosystems. In addition, the use of native sod may also reduce or prevent weed establishment. Our project aims to evaluate different native grass species mixes to determine the best species combinations for sod. We selected 21 species of native grasses in order to determine their suitability for sod production in six Californian ecoregions. Grasses were grown in six growth chambers that mimic the climate of the six ecoregions. Mixtures of varying species included either one rhizomatous species with three bunch grasses, one rhizomatous species and five bunch grasses, two rhizomatous species with three bunch grasses, or two rhizomatous species with five bunch grasses for each ecoregion. The mixtures were grown and tested for yield, species composition, and percentage of cover over time. At the end of the 6-month production time, a final harvest evaluated root depth and biomass as well as sod strength. Rhizomatous grasses, if planted with Bromus sp., were quickly overwhelmed. At the first harvest ground coverage was between 10% and 15% for all species mixes. Ground coverage increased over the production cycle, but maximum ground coverage remained less than 80% overall.

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Mouna Benmbarek, Y. Desiardins, and R.R. Simard

Landfiling and incineration constitute the most commonly used methods of biosolid disposal. To minimize the environmental risk, their chemical and biological characteristics have been the subject of several investigations.

The present research was undertaken to evaluate the agronomic value of municipal solid wastes (MSW) and composted de-inked sludge (CDS) in a field experiment for sod production. Four variables in a split factorial design, were investigated at two sod farms: compost (MSW and CDS), soil (sandy loam and clay loam), application method (surface applied 6cm and incorporated 20cm), and the application rate (50-100 and 150t/ha). Controls consisted of unfertilized and unamended but fertilized plots. Both experimental sites were seeded with kentucky bluegrass.

Preliminary data indicate that the two biosolids promoted the sod growth at the rates applied. However, a better plot cover was observed if composts were rototilled at a depth of 6cm as compared to the conventional treated plots. Measurements of root and foliar weights revealed that the turf growth was enhanced with increasing rates, which is probably caused by additional soil macronutrients showed by the analysis. Seed germination and seedling emergence were not delayed as indicated by the observed increase in the water retention capacity of the soil especially at higher compost rates.

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Bruce R. Roberts, Henry F. Decker, Lindsey M. Ganahl, and Elizabeth Yarmark

Two biosolid-containing waste media [composted sewage sludge (Com-Til) and incinerated biosolids (flume sand)] were evaluated as soilless media for growing `Crenshaw', `Penncross', and `ProCup' creeping bentgrass sod (Agrostis palustris). The media were combined with sand and either sphagnum peat or a commercial growing mix (Metromix) and leached with 5.1 fl oz (150 mL) tap water either zero, one or three times before seeding. Leaching with tap water to remove soluble salts had no beneficial effect on germination or dry mass accumulation. Flume sand was not a particularly good rootzone component for growing creeping bentgrass sod; however, a sieved [0.08-inch (2-mm)] medium consisting of sand, Com-Til and Metromix (8:1:1, by weight) seeded with `ProCup' creeping bentgrass at 2 lb/1000 ft2 (9.8 g·m-2) and grown over 4-mil (0.004-inch, 0.10-mm) plastic in 3.5 × 7.5 × 2-inch deep (9 × 19 × 5-cm) trays produced good sod in about 6 weeks.

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A. Graifenberg, M. Lipucci di Paola, L. Giustiniani, and O. Temperini

`Terom' globe artichoke (Cynara scolymus L.) plants were propagated vegetatively and grown for 2 years in soil-filled pots in the greenhouse under saline-sodic conditions. Plants were irrigated with water containing from 1 to 10 g NaCl/liter. Growth and yield responses were evaluated with a two-line response model. The aim of this work was to determine the salt tolerance threshold and slope for artichoke yield and growth expressed in terms of electrical conductivity (EC) of irrigation water (ECi) and saturated-soil extract (ECe). The thresholds for yield and plant fresh weight (PFW) were the same—2.7 and 4.8 dS·m-1 for ECi and ECe, respectively. The slopes for yield—14.4% and 10.7% per dS·m-1 for ECi, and ECe—were greater than those for PFW. These data indicate that PFW was less sensitive to soil and water salinity than yield. Plants survived and produced suckers at an ECe of 21.8 dS·m-1, but `Terom' yield was much more sensitive to saline-sodic conditions.

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J.W. Boyd, M.D. Richardson, and J.H. McCalla

Zoysiagass (Zoysia japonica) use continues to expand on golf courses, home lawns, and sports fields in the transition zone. Unfortunately, the slow growth rate of the species and long establishment period have limited its use to those sites that can afford zoysiagrass sod. The development of sprig-planting techniques that can produce a zoysiagrass turf in a single season would considerably increase the use of this desirable species. A study was conducted over 2 years at two different regions in Arkansas to evaluate the efficacy of a new zoysiagrass net-planting technique (ZNET) on establishment of zoysiagrass from vegetative sprigs. The technique involves rolling the sprigs onto the site in cotton netting and top-dressing the sprigs with 1.0 cm (0.4 inch) of native soil. This technique was compared to a standard sprig-planting technique and a standard sprig planting that was also top-dressed with 1.0 cm of native soil. The standard treatments were planted according to established methods using freshly-harvested sprigs applied at a rate of 70.0 m3·ha-1 [800 bushels (1000 ft3) per acre]. Rate of turfgrass cover was monitored throughout the growing season. The ZNET planting technique significantly improved establishment over the traditional sprigging technique and the turf reached about 85% cover by the end of the growing season (120 days). Top-dressing a traditionally sprigged area with native soil also improvedestablishment compared to traditional sprigging and was comparable to the ZNET technique. It was concluded that the ZNET technique did improve establishment rates of zoysiagrass, but the same results could be attained by top-dressing sprigs that were planted with a standard planter.