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Greg D. Hoyt

A no-till sweetcorn strip-till tomato rotation was established to determine whether a grass or legume winter cover crop would provide greater summer mulch and more soil inorganic nitrogen from residue decomposition. Sweetcorn yields improved as N rate increased in rye residue and bare soil, but only increased at the 50 kg N/ha rate in vetch residue. Strip-till tomato yields improved with all N rates for all covers. Total soil N and C were greater in both the vetch and rye residue treatments than the bare soil. Fertilizer N addition did not affect changes in total N or C percentages. Greater soil nitrate was measured beneath vetch residue at spring planting than in the rye residue or bare soil surface.

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M. Marutani, R. Quitugua, C. Simpson, and R. Crisostomo

A demonstration vegetable garden was constructed for students in elementary, middle and high schools to expose them to agricultural science. On Charter Day, a University-wide celebration, students were invited to the garden on the University campus. The purpose of this project was twofold: (1) for participants to learn how to make a garden and (2) for visitors to see a variety of available crops and cultural techniques. Approximately 30 vegetable crops were grown. The garden also presented some cultural practices to improve plant development, which included weed control by solarization, mulching, a drip irrigation system, staking, shading and crop cover. Different types of compost bins were shown and various nitrogen-fixing legumes were displayed as useful hedge plants for the garden.

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Daniel Schellenberg, Ronald Morse, and Gregory Welbaum

Weed suppression and nitrogen (N) management present the greatest challenges to organic growers. Cover crops, the strategic use of tillage, and multiple nitrogen sources are being investigated in order to develop integrated management practices. Combinations of legume and grass cover crops are being utilized as alternative N sources and as tools for weed suppression. Another objective is to compare conventional and no-till practices to determine when the strategic use of tillage is most beneficial for N management and weed control. The last objective is to evaluate the fate of applied N and N released from cover decomposition on crop development. The best combinations of cover crop species, the frequency and intensity of tillage, and optimum N rates will be determined for the production of organic broccoli. This project will aid growers interested in transitioning to organic farming. In addition, integrated management practices that balance the short-term needs for crop productivity and the long-term interests of sustainable production will be reported.

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Michael W. Smith

Several new management tools and management practices are being developed for pecan. Major insect pests of pecan are pecan nut casebearer, hickory shuckworm, and pecan weevil. Sex pheromone attractants are being developed for each of these pests that improve monitoring. Also, a pecan weevil trap (Tedder's trap) was introduced recently that is more sensitive to weevil emergence than the previous trap. New models that predict critical periods for pecan scab infection are being tested. Certain legume ground covers are being tested to increase beneficial arthropods in the orchard for aphid control, and to supply N. Mulches are being investigated as an alternative to herbicide management for young trees. A mechanical fruit thinning method has been developed that increases fruit quality and reduces alternate bearing as well as stress-related disorders.

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Charles R. Clement and Joseph DeFrank

Pejibaye (Bactris gasipaes Kunth) is being evaluated in Hawaii for production of fresh heart-of-palm. Yields and offshoot (sucker) production were evaluated in response to woven black polypropylene mat (control), three legumes [Arachis pintoi Krap. & Greg., Cassia rotundifolia Pers., and Desmodium heterocarpon (L.) DC], and a grass (Chloris gayana Kunth) used as ground covers. D. heterocarpon and C. gayana formed closed canopies quickly and controlled weeds well, but required more frequent mowing. A. pintoi formed a closed canopy slowly and only controlled weeds after forming a thick canopy, but required less mowing. Cassia rotundifolia died out after flowering and setting seed. All vegetative ground covers delayed heart-of-palm harvest and had reduced yields 1.5 years after planting. A combination of polypropylene (adjacent to plants) and vegetative ground covers (in service rows) may provide the best solution to minimizing labor for vegetative management in this orchard crop.

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J.R. Heckman

In-season soil nitrate testing is most useful when there is reason to believe, based on field history, that N availability may be adequate. These reasons may include soil organic matter content, applied manure, compost, legumes in the rotation, or residual N fertilizer. Soil nitrate testing is not helpful when crops are grown on sandy, low organic matter content soils that are known from experience to be N deficient. Soil nitrate testing is useful for annual crops such as vegetables or corn for which supplemental N fertilization is a concern. Soil nitrate tests must be performed at critical crop growth stages, and the results must be obtained rapidly to make important decisions about the need for N fertilization. Soil nitrate-N (NO3-N) concentrations in the range of 25 to 30 mg·kg-1 (ppm) indicate sufficiency for most crops, but N fertilizer practice should be adjusted based on local extension recommendations.

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Charles R. Clement and Joseph DeFrank

Pejibaye (Bactris gasipaes Kunth) is being evaluated in Hawaii for production of fresh heart-of-palm. Yields and offshoot (sucker) production were evaluated in response to woven black polypropylene mat (control), three legumes [Arachis pintoi Krap. & Greg., Cassia rotundifolia Pers., and Desmodium heterocarpon (L.) DC], and a grass (Chloris gayana Kunth) used as ground covers. D. heterocarpon and C. gayana formed closed canopies quickly and controlled weeds well, but required more frequent mowing. A. pintoi formed a closed canopy slowly and only controlled weeds after forming a thick canopy, but required less mowing. Cassia rotundifolia died out after flowering and setting seed. All vegetative ground covers delayed heart-of-palm harvest and had reduced yields 1.5 years after planting. A combination of polypropylene (adjacent to plants) and vegetative ground covers (in service rows) may provide the best solution to minimizing labor for vegetative management in this orchard crop.

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Harry T. Horner, David J. Hannapel, William R. Graves, Carol M. Foster, David J. Hannapel, William R. Graves, Carol M. Foster, Harry T. Horner, and Carol M. Foster

Early nodulin genes, such as ENOD2, play a role in the first stages of nodulation. Although ENOD2 is conserved among nodulating legumes studied to date, its occurrence and activity have not been studied among woody legumes such as Maackia amurensis Rupr. & Maxim. Our objective was to localize MaENOD2 transcripts during nodule development and describe the anatomy of nodules formed on the roots of M. amurensis in relation to ENOD2 mRNA accumulation. Nodules (<1 mm, 1-2 mm, >2 mm in diameter, and mature) were prepared for light microscopy, sectioned, and stained with safranin and fast green for structural contrast or with the periodic acid Schiff's reaction for starch. The location of ENOD2 transcripts was determined by using in situ hybridization with DIG-labeled sense and antisense RNAs transcribed from a 602-bp fragment of the coding region of MaENOD2. Mature nodules from M. amurensis possessed peripheral tissues, a distal meristem, and a central infected region characteristic of indeterminant development. In situ hybridization showed that MaENOD2 transcripts accumulated in the distribution layer and uninfected cells of the central symbiotic region. Amyloplasts that contained starch grains were identified in these tissues and in the inner parenchyma of the nodule. Throughout nodule development, transcripts were restricted to areas with high levels of stored starch that surrounded cells actively fixing N2. Our results suggest that ENOD2 in M. amurensis may be a cell wall component of tissues that regulate nutrient flow to and from sinks, such as symbiotic regions of a nodule. These data may lead to a better understanding of the role of the ENOD2 gene family during nodulation.

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Kyle E. Bair, Robert G. Stevens, and Joan R. Davenport

Concord grape (Vitis labrusca L.) accounts for a majority of juice grapes produced in Washington State. Because synthetic nutrients are not permissible in USDA organically-certified production systems, legume cover crops are used to supply nitrogen (N) to the crop. In order to supply a sufficient amount of N, the cover crop must successfully establish and produce large quantities of biomass. This study evaluates how the planting date influences emergence and biomass production of hairy vetch (Vicia villosa subsp. villosa L.) and yellow sweet clover [Melilotus officinalis (L.) Lam.] when used as legume green manures. The research was conducted on a commercial vineyard and a research vineyard from 2003–05. Treatments for the study consisted of yellow sweet clover and hairy vetch planted in both the spring and fall. Plots receiving soluble N sources were planted with wheat (Triticum aestivum L.) or rye (Secale cereale L.). Because of the large relative seed sizes of rye, wheat, and hairy vetch compared to yellow sweet clover, these treatments established faster with good stands in 2004. In 2005, clover plots had high emergence and biomass production because of water management modifications. Biomass data from the commercial vineyard in May 2005 indicates that fall-planted vetch produced more biomass than spring-planted vetch. Fall-planted hairy vetch and yellow sweet clover in the research vineyard showed higher biomass production than spring- and fall-planted hairy vetch and yellow sweet clover. When hairy vetch and yellow sweet clover are planted in the fall, they generally have better seedling emergence and biomass production due to the heightened aggressiveness exhibited by competing weed species during late spring and summer.

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N.M. Madden, J.P. Mitchell, W.T. Lanini, M.D. Cahn, E.V. Herrero, S. Park, S.R. Temple, and M. Van Horn

Field experiments were conducted in 2000 and 2001 in Meridian, Calif. to evaluate the effects of cover crop mixtures and reduced tillage on yield, soil nitrogen (N), weed growth, and soil moisture content in organic processing tomato (Lycopersicum esculentum) production. The trial was set up as a randomized complete-block design with eight treatments consisting of a 2 × 3 (cover crop × tillage) factorial design, a fallow control (F) and a single strip-till (ST) treatment. Cover crop mixtures were either legumes (L), common vetch (Vicia sativa), field pea (Pisum sativum) and bell bean (Vicia faba), or those legumes with grasses (GL), annual ryegrass/triticale (Lolium multiflorum/xTriticosecale) in 2000; cereal rye (Secale cereale)/triticale in 2001. Tillage treatments included an incorporation of the cover crop at planting (IP), a delayed incorporation (DI) (17 to 19 days after planting), and no-till (NT). Due to regrowth of the annual ryegrass in 2000, tomato fruit yields in 2000 were reduced by 50% to 97% within all GL treatments. However, regrowth of the cover crop was not a problem in 2001 and yields were not different among treatments. Total percent weed cover was 1.6 to 12.5 times higher in NT than IP treatments in 2000 and 2.4 to 7.4 times higher in 2001 as weed pressure was mainly affected by tillage practices and less by cover crop type. In 2000, available soil N was 1.7 to 9.4 times higher in L than GL treatments and was significantly influenced by tillage, but there were no treatment effects in 2001 due to a 60% reduction in weed pressure and minimal or no cover crop regrowth. Soil moisture content did not differ between treatments in either year. These results demonstrate the importance of appropriate selection and termination of cover crops for their successful adoption in organic conservation tillage systems.