Orchard Groundcover Management Systems Research Articles

Long-term orchard groundcover management systems affect soil microbial communities and apple replant disease severity

Apple replant disease (ARD) is a soil-disease syndrome of complex etiology that affects apple tree roots in replanted orchards, resulting in stunted tree growth and reduced yields. To investigate whether different groundcover management systems (GMSs) influence subsequent ARD severity, we grew apple seedlings in an outdoor nursery in pots containing orchard soil from field plots where four GMSs had been maintained for 14 years in an orchard near Ithaca, NY, USA. The GMS treatments were: (1) pre-emergence herbicide (Pre-H), bare soil strips maintained by applying tank-mixed glyphosate, norflurazon and diuron herbicides annually; (2) post-emergence herbicide (Post-H), sparse weed cover maintained by applying glyphosate in May and July each year; (3) mowed sod grass (Mowed Sod); and (4) bark mulch (Mulch). Soils were also sampled from the grass drive lane maintained between the trees in the orchard (Grass Lane). Sampled soils (Orchard soil) were either pasteurized or left untreated, placed into 4-L pots, and planted with one apple seedling per pot. After 3 months of growth, soil (Bioassay soil) and apple tree roots (Bioassay roots) were sampled from each pot and microbial populations colonizing samples were characterized. Seedling growth was reduced in soils sampled from all four GMS treatments compared to the Grass Lane soils. Among the GMS treatments, seedling biomass was greater in Pre-H than in the Post-H soil. Soil microbial communities and nutrient availability differed among all four GMS treatments and the Grass Lane. Root-lesion (Pratylenchus sp.) nematode populations were higher in the Mowed Sod than in the other GMS treatments. Soil bacterial and fungal community composition was assessed in Orchard and Bioassay soils and Bioassay roots with a DNA fingerprinting method (T-RFLP). Redundancy analysis indicated that soils sampled from the different GMS treatments differentially influenced seedling biomass. A clone library of 267 soil bacteria was developed from sampled Orchard soils and Bioassay roots. These communities were dominated by Acidobacteria (25% of sequences), Actinobacteria (19%), δ-Proteobacteria (12%), β-Proteobacteria (10%), and these ratios differed among the GMS soils. Members of the family Comamonadaceae were detected only in tree-row soil, not in the Grass Lanes. The dominant sequences among 145 cloned fungi associated with apple seedling roots were Fusarium oxysporum (16% of sequences), an uncultured soil fungus submitted under DQ420986 (12%), and Rhodotorula mucilaginosa (9%). In a redundancy analysis, factors including fungal and oomycete community compositions, soil respiration rates, population sizes of culturable bacteria and fungi, soil organic matter content, and nutrient availability, were not significant predictors of apple seedling biomass in these soils. Different GMS treatments used by apple growers may influence subsequent ARD severity in replanted trees, but edaphic factors commonly associated with soil fertility may not reliably predict tree-root health and successful establishment of replanted orchards.

Groundcover Management Systems Influence Soil Microbial Community Composition in an Apple Orchard

An apple (Malus domestica cv. Empire on M9/MM111 rootstock) orchard groundcover management systems (GMSs) study has been underway since 1992 in Ithaca, N.Y. Four GMS treatments are applied each year in 2-m wide tree-row strips: Pre-emergence herbicides (Pre-H: diuron + norflurazon + glyphosate); Post-emergence herbicide (Post-H: glyphosate); mowed-sod (Grass); and composted hardwood bark mulch (Mulch) treatment. The soil (silty clay loam) physical and chemical conditions have been monitored continuously. In May and Sept. 2003, we sampled topsoil beneath trees in each GMS and used PCR-DGGE combined with sequencing to characterize soil microbial community composition. Mulch had more culturable soil bacteria than the Pre-H treatment. Soil in Grass plots had the most culturable soil fungi. Soil microbial respiration rates were higher in Mulch than Grass and herbicide GMSs. Surface vegetation in the Grass and Post-H plots strongly influenced soil bacterial community composition. In Principal Component Analyses, Post-H and Grass treatments comprised one variance cluster, and Pre-H and Mulch treatments another. The soil fungal community was less diverse (fewer DGGE bands) than the bacterial community, and was less affected by GMS. Treatments with more surface vegetation (Post-H and Grass) also had more free-living and phytonematodes than Pre-H and Mulch. A total of 47 clones from 12 DGGE bands yielded 31 unique DNA sequences. Of these, 15 were novel sequences with no matches in the GenBank (NCBI) database. Another 10 (27 clones) could be matched with known fungal species at 96-100% identity. The primer pair used, ITS1F/ITS2, amplified a considerable number of Basidiomycetes and Ascomycetes, but there was no amplification for Zygomycetes and Oomycetes.

Orchard Groundcover Management Systems Affect Meadow Vole Populations and Damage to Apple Trees

Meadow vole (Microtus pennsylvanicus Ord) populations, feeding activity and damage to young apple (Malus ×domestica Borkh.) trees were monitored for several years in a New York orchard by direct observation, trap counts, and a feeding activity index in various groundcover management systems (GMSs). Meadow vole population density differed among GMSs, with consistently higher densities and more trees damaged in crown vetch (Coronilla varia L.), hay-straw mulch, and red fescue (Festuca rubra L.) turfgrass tree-row strips. Vole densities were high in autumn and low in spring each year. Anticoagulant rodenticides and natural predation did not adequately control voles in GMSs providing favorable habitat. Groundcover biomass per m2 was weakly correlated with vole densities in 2 of 3 years, while the percentage of soil surface covered by vegetation was not significantly correlated with vole populations. Applications of thiram fungicide in white latex paint were better than no protection, but less effective than 40-cm-high plastic-mesh guards for preventing vole damage to tree trunks. A combination of late-autumn trapping, close and consistent mowing of the orchard floor, trunk protection with mesh guards, contiguous habitat for vole predators, and herbicide applications within the tree rows provided effective control of meadow-vole damage to trees at this orchard during 3 years without applications of rodenticide baits. Chemical names used: Tetramethylthiuram disulfide (thiram)

Compost Mulch, Canola Cover Crops, and Herbicides affect soil Fertility, Apple Tree Yield, and Nutrition

Three orchard groundcover management systems (GMSs) were established in a newly planted apple (Malus domestica cvs. Liberty, Nova Easygro, and NY84828-12 on Malling 9 rootstock) orchard on a silty-clay loam soil (Aeric Ochraqualf). The GMSs were applied in 2-m-wide strips within tree rows as follows: 1) a 6-cm-thick mulch layer of composed manure, straw, sawdust, and vegetable plant wastes applied in May 1992 and 1994; 2) a “green manure” cover crop of canola (Brassica campestris cv. Humus) seeded in mid-August each year and tilled under the following May; and 3) Post-emergence applications of N-(phosphonomethyl) glycine (glyphosate) herbicide (2.0 kg a.i./ha) in mid-May and July each year. After 3 years of GMS treatments, apple tree growth and trunk cross-sectional area were similar in all three systems. Fruit yield and yield efficiency were greater in glyphosate and compost than in canola GMSs, and `Liberty' was the most productive cultivar. Topsoil N, P, K, Ca, Mg, Zn, and organic matter content were all substantially greater in the compost GMS. Leaf N, K, and P concentrations were consistently greater in trees in compost plots; leaf Ca, Mg, Cu, and Zn concentrations were lower in compost GMS. Weed growth was rank and difficult to control in the compost mulch, but this GMS substantially enhanced orchard soil fertility.

Orchard Groundcover Management Systems Influence Surface Runoff and Subsoil Leaching of Agrichemicals

Non-point source water pollution by agrichemicals is a recognized problem that has been studied in agronomic crop systems, and simulated using computer models or artificial soil columns, but rarely measured at field scale in orchards. For three growing seasons, we monitored the movement of nitrate and pesticide analogs and a widely used fungicide (benomyl) in two apple orchards under four different groundcover management systems (GMSs), including turfgrass, wood-chip mulch, residual pre-emergence herbicides, and post-emergence herbicide treatments. In subsoil lysimeter samplers at one orchard, we observed that nitrate and pesticide analogs leached more rapidly and in higher concentrations under herbicide plots compared with turfgrass plots. At another orchard where subsoil leaching and surface runoff of benomyl and nitrate-N were monitored in replicated GMS plots, we observed higher concentrations of benomyl (up to 30 μg·liter–1) and nitrate-N up to 50 μg·liter–1) leaching under herbicide GMS. The highest benomyl concentrations (375 μg·liter–1) and most frequent runoff of this pesticide were observed in the residual pre-emergence herbicide plots. Yearly weather patterns, irrigation, and development of different soil physical conditions under the four GMSs determined the relative magnitude and frequency of agrichemical leaching and runoff in both orchards. The agrichemicals apparently leached by mass flow in preferential flowpaths such as old root channels and soil cracks, while surface chemical runoff occurred mostly adsorbed on eroding soil sediment. These observations indicate that orchard GMSs can have a significant impact on leaching and runoff of pesticides and nutrients.

Comparing Mulches, Herbicides, and Cultivation as Orchard Groundcover Management Systems

Natural (hay, wood chips, recycled paper pulp) and synthetic (polypropylene film and polyester fabric) mulches were compared with mechanical tillage and residual herbicides as orchard groundcover management systems (GMSS). In two New York orchards-the Clarke farm and Hudson Valley Lab (HVL—GMSS were applied from 1990 to 1993 in 1.8-m-wide strips under newly planted apple (Malus domestica; `Liberty', `Empire', `Freedom', and advanced numbered selections from the disease-resistant apple breeding program at Geneva, N.Y.) trees. GMS impacts on soil fertility, tree nutrition and growth, yields, crop value, and vole (Microtus spp.) populations were evaluated. After 3 years at the Clarke orchard, extractable NO3, Mn, Fe, B, and Zn concentrations were greater in soil with herbicides than synthetic mulches; soil K and P concentrations were greater with herbicides and wood chips than synthetic mulches. At the HVL orchard, topsoil NO3, K, and Mg concentrations were greater with hay mulch than herbicides or other mulches; Mg, Fe, and B concentrations were lower in soil with wood chips than other GMSs. Soil organic matter content was not affected by GMS. Apple leaf N, K, Cu, and Zn concentrations were greater with herbicides, hay mulch, and polypropylene mulch than cultivation or recycled paper mulch at the HVL orchard during hot, dry Summer 1991. Despite transient differences among GMSS during the initial years, after 4 years of treatments there were no consistent GMS trends in cumulative tree growth or gross yields. The higher establishment and maintenance costs of several mulches were offset by their prolonged efficacy over successive years; crop market values from 1992 to 1994 were considerably greater for trees with polypropylene film, polyester fabric, and hay mulches than herbicides, cultivation, or other mulches. Voles caused more serious damage to trees in synthetic and hay mulches, despite the use of mesh trunk guards and rodenticide bait.

073 A COMPARISON OF NATURAL AND SYNTHETIC MULCHES WITH CONVENTIONAL ORCHARD-FLOOR MANAGEMENT SYSTEMS

In several northeastern USDA Low-Input Sustainable Agriculture (LISA) projects, we compared natural (hay-straw, wood-chips, recycled newspaper pulp) and synthetic (polypropylene films and polyester fabrics) mulch materials with mowed sodgrass, tillage, and residual herbicides, as orchard groundcover management systems (GMS). Treatments were applied in 2m-wide strips under newly planted apple (Malus domestica cvs. Liberty, Empire, Freedom. and others) trees on MARK rootstock, planted at 3 by 5m spacing, in 1990. Edaphic, economic, tree nutritional and fruit yield impacts of these GMS were evaluated for four years in five Hudson Valley orchards. All the mulches cost more to establish and maintain ($450 to 4500/ha) than mowed sod ($150/ha), tillage ($120/ha), or residual herbicide ($50/ha) systems. There were few differences in soil water or nutrient availability, leaf nutrient content, tree growth or fruit yield in the mulch systems compared with herbicide or tillage GMS. Meadow voles (Microtus spp.) caused considerable damage to trees in the synthetic and straw mulches, despite the use of trunk guards. Wood-chips were the most enduring, least expensive, and most effective natural mulch. There were insufficient short-term benefits to offset the greater costs of synthetic mulch fabrics or films, in comparison with conventional herbicide snip systems for orchard floor management.

Orchard Groundcover Management Impacts on Soil Physical Properties

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.

Orchard Groundcover Management Impacts on Apple Tree Growth and Yield, and Nutrient Availability and Uptake

This study compared various conventional and alternative 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 postemergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage (tilled)—during 6 years in a newly established apple (Malus domestica Borkh.) planting. Trunk cross-sectional area and fruit yield were higher in STMCH, GLY, and NDPQT, intermediate in tilled, and lower in GRSOD, MWSOD, and CNVCH treatments after 5 years. Despite N and K fertilizer applications, extractable soil N and leaf N concentrations were reduced under MWSOD and GRSOD, and soil K, P, and B concentrations were greater under STMCH. Leaf K concentrations were usually highest in STMCH trees, even when heavily cropped; leaf K declined below the sufficiency range in GLY, NDPQT, and tilled trees as they began to bear fruit. Leaf Ca was marginally deficient in all trees and was unaffected by GMS. Foliar Mn, Zn, and B concentrations declined rapidly in all treatments during 2 years without micronutrient fertilizers. Leaf Cu was higher in herbicide and tilled treatments where seasonal soil water content was intermediate (22% to 27%) and lower where soil was very wet or dry for most of the 1988 growing season. Multiple regression analysis indicated that leaf N and B and soil organic matter in 1990, and mean soil water content during the unusually dry Summer 1988, were the best predictors of fruit yield in 1990. Phytophthora root rot and meadow vole depredation were serious problems in STMCH and CNVCH trees. GMSs greatly affected tree establishment, nutrition, and yield; each system involves tradeoffs among important short- and long-term impacts on the orchard agroecosystem.

A comparison of herbicide-controlled orchard ground cover management systems on the vigour and yield of apples

SummaryThe effects of eight orchard ground cover management systems on the growth, number of flower clusters and fruit set per tree, leaf NPK levels, fruit number and size, and yield of cvs Cox’s Orange Pippin and Golden Delicious apple trees, both on MM. 106, were compared over a nine-year period. For three years following planting, both cultivars grown in overall grass controlled by applications of MH plus 2,4-D were smaller and yielded less than those in all other treatments. When grown in the weed-free row alleyway system with grass controlled with MH plus 2,4-D both cultivars grew and yielded as well as those in mown grassed alleyway treatments. In the overall weed-free treatments, six years without N fertilizer application did not reduce yield, growth or leaf N levels. In both cultivars trees grown in overall unmown strawberry clover swards outyielded those in white clover swards, but trees in both clover swards were as vigorous and productive as those in mown grassed alleyway treatments. The compar...