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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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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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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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Misty J. Moore, Mohanjeet S. Brar, Jameel M. Al-Khayri, Teddy E. Morelock, and Edwin J. Anderson

Cowpea (Vigna unguiculata L.) is an important grain legume that is grown extensively in Africa, South America, India, and in the United States. This study investigated the effects of silver nitrate (AgNO3) on regeneration of cowpea cotyledon explants. Silver nitrate at 50 μm significantly increased percent regeneration in comparison to the control. The effect of duration of exposure was also determined with the ethylene inhibitor AgNO3. By exposing explants to 59 μm AgNO3 during different stages of culture, significant increases were actualized in percent regeneration and shoot number. The greatest percent regeneration was obtained when 59 μm AgNO3 was augmented to both the initiation and regeneration media or to only the regeneration media. These results indicate that the low percentage of regeneration of this genotype may be related to ethylene biosynthesis or metabolism. This study resulted in an improved regeneration system for the commercial cowpea cultivar Early Scarlet, and will be useful in developing a cowpea transformation system.

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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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Michelle Hadawi-Broeske and Helen C. Harrison

Renewed interest in soil conservation over the past decade has led to greater research efforts in the area of living mulch cropping systems. However, crop/mulch competition continues to present challenges. The objective of this study was to determine what effect two types of chemical growth suppressants (Mycogen 6121—an herbicidal soap, and Royal Slo-grow—a soil plant growth regulator) had on the water-use efficiency, nutrient use, and soil-shading ability of two annual living mulches, ryegrass (Lolium multiflorum) and crimson clover (Trifolium incarnatum). Two greenhouse experiments were performed in sand culture using a modified Hoagland's soap, one rate of growth regulator, and a mechanical treatment of mowing. Significant differences in nutrient use and soil-shading ability were obtained. The second experiment (69 days) replicated the ryegrass treatments less one rate of soap and included the legume crimson clover with one rate of soap and one rate of growth regulator. Results from both experiments will be discussed.

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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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Roland E. Roberts, Kenneth Gray, and Joseph J. Bryant

Breedlove Dehydrated Foods (BDF), the largest charitable dehydration plant in the world, is capable of dehydrating 6,000 lb. raw product/hr. BDF dehydrates and distributes nutritious fruits, vegetables, and legumes to charitable organizations which feed hungry people. At least 35,617 people die from hunger in our world every day! Thousands of tons of nutritious but slightly imperfect horticultural products are wasted yearly in the United States. Donations totaling $7.8 million funded construction of BDF. Texas A&M and Texas Tech Universities provided expertise to plan and operate BDF. BDF dehydrated over 30 million lb. of fruits and vegetables in the initial two years of operation. BDF is a model of people focused on an unusually high goal and working together.

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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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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.