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Jae H. Han, George L. Good* and Harold M. Van Es

Field experiments were conducted in 1998 and 1999 to determine the effect of soil-incorporated, composted municipal biosolids on the growth and nutrient content of 30.8 cm-38.5 cm Rhododendron × `PJM' grown as containerized plants. Biosolid compost produced in Endicott, N.Y., was incorporated in May 1998 and 1999 at rates of 0, 9.8 Mg/ha and 19.7 megag/ha to a depth of 23 cm. Each treatment was replicated six times in a randomized block design. Plants were planted 10 June 1998 and 8 June 1999. Plants were harvested 10 June, 19 Aug., and 22 Oct. 1998 and 8 June and 22 Sept.1999 after which they were dried, weighed, and analyzed. During 1998, there was little difference in dry weight or nutrient content in plants harvested at the August harvest date, however, dry weight and most nutrient levels increased with increasing rates of compost application in plants harvested at the October harvest date. In 1999, no statistical differences were noted at the September harvest date in plant dry weight or nutrient content. In 1999, measured soil physical properties (water retention, bulk density, water content, and soil strength) did not differ significantly between treatments. Excellent soil structure and drainage, relatively low rates of compost application and a severe drought may have contributed to the lack of any conclusive results noted in 1999 though some positive plant responses to the treatments were evident in 1998.

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Ian A. Merwin, Warren C. Stiles and Harold M. van Es

This study was conducted to compare various orchard groundcover management systems (GMSs)—including a crownvetch “living mulch” (CNVCH), close-mowed (MWSOD) and chemically growth-regulated (GRSOD) sodgrasses, pre-emergence (NDPQT) and two widths of post-emergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage (tilled)—during the first 6 years in a newly established apple (Malus domestica Borkh.) planting. Mean soil water potential at 5 to 35 cm deep varied substantially among treatments each summer, and treatment × year interactions were observed. During most growing seasons from 1986 to 1991, soil water availability trends were STMCH > NDPQT > GLY2.5 > GLY1.5 > tilled > GRSOD > MWSOD > CNVCH. Soil organic matter content increased under STMCH, CNVCH, and MWSOD and decreased under NDPQT and tilled treatments. Water infiltration and saturated hydraulic conductivity after 4 years were lower under NDPQT and tilled, and soil under STMCH and GRSOD retained more water per unit volume at applied pressures approximating field water capacity. Mid-summer soil temperatures at 5 cm deep were highest (25 to 28C) in tilled and NDPQT plots, intermediate (22 to 24C) under GRSOD, and lowest (16 to 20C) under CNVCH and STMCH. These observations indicate that long-term soil fertility and orchard productivity may be diminished under pre-emergence herbicides and mechanical cultivation in comparison with certain other GMSs.

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Jae H. Han, George L. Good, Eric B. Nelson and Harold M. Van Es

Composts vary in their ability to suppress disease activity when incorporated into growing media. Bioassays that enable a reliable and quick assessment of compost's ability to suppress disease activity can save time, funds and space. A bioassay using Lupinu× `Russell Hybrid' seedlings was evaluated as a short-term test for gauging the ability of three composts to suppress activity of P. cinnamomi. Colonized millet seeds were prepared via the V-8 agar method. The colonized millet seed were incorporated into the potting media at 0, 50, 100, 200, and 400 colonized millet seed/200 cc of the media used. Three composts, including composted sewage sludge, brewer's waste and cow manure, were incorporated into the media (50% sand: 50% sphagnum peat, by volume) at rates of 0%, 10%, 25%, and 50%, by volume. The media, including the inoculated millet seed, were placed in small plastic pots (7.6-cm-diameter and 6.7 cm high), after which 10 Lupine seeds were sowed in each pot. Percentage of seedling loss was determined after 43 days of observation. The composted sewage sludge and the cow manure proved suppressive at the 50% incorporation rate and the 10% and 25% rate of the latter compost. The brewer's waste compost proved ineffective in this regard; thus, research with this product was discontinued. In a greenhouse study the same inoculation and compost incorporation rates were used, but rooted cuttings of Rhododendro × PJM `Elite' were plotted into the various treatments. Suppression of disease activity by the composts was significant 2 and 4 months after initiation of treatments. Significance in disease suppression noted between these treatments decreased significantly during the fifth month of the experiment.

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Jae H. Han, George L. Good, Eric B. Nelson and Harold M. Van Es

Composted municipal biosolids were incorporated into a potting mix containing sphagnum peat and sand (1:1 by volume) at rates of 0%, 25%, and 50%, by volume. A second medium was prepared by mixing cow manure compost in the same basic mix at rates of 0%, 10%, and 25% by volume. Each mix was inoculated with P. cinnamomi colonized millet seed at a rate of 200/200 cc of compost-amended media. The potted plants were placed outdoors under nursery conditions 14 July 2003. One half of the plants were irrigated every day, except when natural precipitation occurred; the other half was watered once each week. Soil water potential of all treatments was measured daily with tensiometers. Plants were harvested on 18 Aug. and 21 Oct. 2003, when the experiment was terminated. Frequent rainfall during the period prior to the first harvest masked any impact that the irrigation treatments may have had on disease suppression. Even so, three compost treatments proved successful in suppressing disease activity. Between the first and second harvest dates rainfall was significantly less frequent; thus, differences in P. cinnamomi activity between the wet and dry regimes was noted at the 21 Oct. harvest. Under the dry regime, all inoculated compost treatments, except the 25% municipal biosolid compost, exhibited disease suppression based on root symptom severity and percentage of root infection. Suppression based on shoot symptoms and percentage of shoot loss was evident only in the 50% and 25% biosolid and cow manure composts, respectively. Under the wet regime, only one treatment exhibited suppression of disease activity. All compost treatments held more water particularly at lower moisture tensions. The presence of more water would tend to favor more disease activity and not suppression.

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Maren J. Mochizuki, Anusuya Rangarajan, Robin R. Bellinder, Harold M. van Es and Thomas Björkman

If benefits of conservation tillage can be quantified even in the transition year from conventional tillage, growers will more likely integrate practices that maintain or enhance soil quality and productivity. The management of surface residue is an important component of conservation tillage, especially in cool, rainy climates where vegetable growth and yield reductions have been observed when heavy residue is present. Cereal rye (Secale cereale L.), grown until flowering, was killed with glyphosate and was then cut and removed (stubble treatment) or rolled or chopped to form a surface mulch (mulched treatment) before transplanting cabbage. Rolled mulch increased soil wet aggregate stability by 4% and reduced soil penetrometer resistance by up to 0.5 MPa compared with rye stubble treatments in 2003. In 2004, frequent rains saturated soils and may have accelerated the decomposition of chopped mulch, minimizing treatment effects. Rolled mulch reduced soil temperatures by up to 2 °C in 2003, but June transplanting of cabbage probably minimized the impact of soil temperature. Mulched treatments did not delay cabbage maturity or affect head quality characteristics such as color or uniformity. Although rolled mulch reduced cabbage growth by as much as 30% and yield by 21% in 2003, chopped mulch did not affect growth or yield in 2004. Yield reduction may be overcome by killing the rye relatively early in the spring or retaining only the surface stubble; these strategies may maintain or measurably improve soil quality even in the transition year to conservation tillage.

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Maren J. Mochizuki, Anusuya Rangarajan, Robin R. Bellinder, Thomas Björkman and Harold M. van Es

Vegetable producers are increasingly interested in adopting conservation tillage practices to maintain or enhance productivity and soil health, but reducing tillage may reduce yields in cool climates. Strategies to transition from full-width tillage to zone tillage systems for cabbage (Brassica oleracea L. Group capitata) were tested with the goals of overcoming soil temperature and compaction limitations and producing crop yield and quality equivalent to conventionally tilled. Designed to achieve differential soil temperature and compaction levels, the treatments were factorial combinations of two widths of zone tillage (15 and 30 cm) and two depths of zone tillage (10 and 30 cm) plus a conventional rototilled treatment (full width and 20-cm depth) as a control. To assess the effect of treatments in the transitional year to reduced tillage, the experiment was conducted in 2003 and 2004 at different fields that were previously conventionally tilled. Increasing tillage width from 15 cm to 30 cm increased soil temperature by 1 °C in both years but had a limited effect on cabbage growth and no effect on yield. Tillage width and soil temperature may have greater impact on an earlier planting. By contrast, increasing tillage depth from 10 cm to 30 cm reduced soil penetrometer resistance by up to 1 MPa, increased plant growth by 28%, and increased yield by 22%. Growth and yield in 30-cm depth treatments were similar to conventional tillage, indicating the undisturbed, between-row areas in zone tillage treatments did not restrict growth. Zone tillage did not affect cabbage maturity or quality. Tillage depth was more important to the success of this system than tillage width; vertical tillage to 30-cm depth left between 60% and 80% of the soil surface area undisturbed and can be an effective transition to conservation tillage for transplanted cabbage.