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  • Author or Editor: Curt Rom x
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Mulch may affect soil chemistry, soil microclimate, biological communities, and tree performance. The trial was conducted to evaluate the effects of different orchard mulches on leaf nutrition, soil moisture, bulk density, root density, and water infiltration for understanding potential use in organic orchards for weed control and as a nutrient resource. Black plastic, hardwood chips, and shredded white paper were applied to three apple cultivars, `Gala', `Jonagold', and `Braeburn' on M.9 rootstocks. A control was sprayed with contact herbicide. Trees grown in hardwood mulch had the highest foliar P and K in year 3. Trees in other mulches showed no difference of leaf nutrition in year 5. All treatments had consistently higher soil moisture than control in year 1, 2, and 4. Mulch did not affect soil bulk density in year 2. The root density was lowest under black plastic mulch in year 2, but was similar in all treatments in year 3. In year 2, water infiltration was fastest in hardwood mulch and control treatments.

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Influence of photosynthetically active radiation (PAR) microclimate in the canopy of four training systems [open-center with high trunk (OH); open-center with middle trunk (OM); open-center with low trunk (OL); and a traditional round canopy (RC)] on the growth, yield and fruit quality of apple were studied in the Beijing area. The results showed that: 1) the growth and yield potential were affected by canopy light microclimate. The average leaf chlorophyll content from OH, OM and OL systems was 12.3% to 18.1% greater than that from the RC system. Trees from OH, OM, and OL systems produced 84.2% to 89.7% of shoot forming flower clusters compared to only 47.3% to 50.9% of the RC shoots. Training system did not affect total yield of 8-year-old trees, but in 10-year-old trees the RC system had lower yields compared with open-center systems. 2) Fruit quality was also affected by canopy light microclimate. The average anthocyanin content in the skin of fruit from OH, OM, and OL systems was 35.9% to 46.1% higher than that from the RC system, but chlorophyll content from the OL system was higher than in the open-center systems. Meanwhile, the contents of TSS and esters in apple flesh from the open-center systems were significantly higher than that from the RC system. 3) When the relative value of PAR in canopy exceeded 33.8%, the growth index of trees (chlorophyll: return-bloom ratio) exceeded 66.6% and the fruit quality index (TSS × anthocyanin) exceeded 94.7%. When PAR was less than 20.6%, the growth index was under 37.2% and the fruit quality index was under 67.5%. PAR value was significantly correlated with the growth and fruit quality index in the four training systems, and the total canopy volume of higher PAR(exceeding 33.8%, relative value) from OH, OM, and OL systems was 37.1% to 45.0% greater than that from the RC system.

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A strategy of chemical crop load control has been to use chemical desiccants to prevent fertilization and cause fruitlet drop. However, little is known of the solution characteristics that reduce pollen viability, inhibit pollen germination and growth, and cause pistil damage. This project was established to determine the solution characteristics effecting those results. Apple pollen was dispersed on germination media mixed with PEG (MW 10,000) to attain osmotic tensions from 0 to -5.0 MPa to evaluate effect on pollen germination and growth. Similarly, apple pollen was dispersed on germination adjusted to a range of pH from 2.3 to 12.0 with acids and NaOH. Excised apple pistils were place on filter paper supports saturated with solutions with osmotic tension adjusted by PEG in the range of 0 to -5.0 M Pa, and pH from 3.0 to 12.0. Solutions of osmotic tension in the range of 0 to -5.0 M Pa were applied by brush to intact pistils on apple flowers in a greenhouse and under field conditions. Pollen germination decreased with increasing osmotic tension and no pollen germinated at tensions greater than 4.0. Pistils, either excised or intact, had significant desiccation and death when treated with solution osmotic tensions greater than 4.0. Fruit set of individual spurs of the cvs Jonagold, Gala, and Arkansas Black were highly related to pistil survival 48 h after treatment with PEG. When solution osmotic potential exceeded 4.0, fruit set was reduced by more than 80%. Pollen germination was reduced by more than 50% at solution pH below or equal to 4.0 and greater than 10.0 and completely inhibited at solution pH below or equal to 3.0 and greater than 11.0. Similar results were observed for excised pistil and intact viability.

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Leaf gas exchange of six red raspberry (Rubus idaeus L.) and one blackberry (Rubus L. subgenus Rubus Watson) genotypes growing in 12-L containers was measured at four temperatures (20, 25, 30, and 35 °C) once a month for 3 months in growth chambers by infrared gas analysis. Measurements were taken on three successive leaves on the same primocane between the third and seventh nodes (≈75% to 85% of full leaf expansion). The plants were grown in ambient (field) conditions except when measurements were taken. Maximum daily ambient temperatures rose as high as ≈37 °C during this period. Net CO2 assimilation (A), evapotranspiration (ET), and stomatal conductance (gs ) were measured during June, July, and August. Significant differences (P ≤ 0.01) in A were found among the seven genotypes. 'Arapaho' blackberry displayed the highest mean A rate at all temperatures. Only in the raspberry cultivars Nova and Reveille did the rate of A drop significantly when temperature increased from 20 to 30 °C. 'Reveille' was also the only cultivar in which A significantly declined between 30 and 35 °C. The ET increased significantly over the four temperatures in four cultivars ('Arapaho', 'Heritage', 'Nova', and 'Southland'). The ET rate at 35 °C was higher for 'Arapaho' than for all other cultivars. 'Autumn Bliss', 'Dormanred', and 'Reveille' did not change significantly as the temperature rose from 20 to 35 °C. Stomatal conductance of 'Heritage' and 'Arapaho' did not change significantly between 20 and 35 °C, whereas that of 'Autumn Bliss' and 'Reveille' declined almost 50% when temperature increased to 30 or 35 °C.

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Interest IN and conversion to sustainable agriculture practices, such as organic agriculture, integrated pest management or increasing biodiversity, has been increasing for a number of years among farmers and ranchers across the United States In order to meet the needs of producers, university researchers and educators must adapt their program areas to reflect this change toward sustainable agriculture practices. Although consumers, producers, and extension workers have been surveyed regarding their attitudes and interests in sustainable agricultural practices, few surveys have examined sustainable agriculture perceptions among university agriculture professionals. The object of this study was to survey 200 agriculture professionals, including research scientists, classroom educators of the Land-Grant agricultural college and the Cooperative Extension service of a southern state with a traditional agricultural economy in order to determine their perceptions and attitudes toward sustainable agriculture and to gather information on current research and education activities relevant to sustainable agriculture. Seventy-eight questions were asked concerning professional incentives, personal and professional importance of topics under the sustainable agriculture rubric, current research and educational activities, and demographics. By conducting this research we hope to identify factors that are an impedance or assistance to future research and education to support sustainable agriculture. The survey findings will provide a foundation for directing and developing agriculture research and education programs for row crops, fruit, vegetable and livestock production.

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Seven Rubus cultivars were evaluated at two locations in Arkansas, northwest (Fayetteville) and southwest (Hope), to evaluate plant growth differences under high and very high summer temperature conditions. Temperatures during the hottest month (July) averaged 34 °C and 38 °C for Fayetteville and Hope, respectively. Growth; leaf area and number; and fresh and dry weights of leaves, stems, and roots were measured on the containerized raspberry cultivars Autumn Bliss, Dormanred, Heritage, Nova, Reveille, and Southland and the blackberry cultivar Arapaho. Growth measurements included number of canes per plant, number of laterals per cane, cane length, node number, and internode length. Measurements were taken monthly from June through September. Leaf areas were done after all growth measurements were taken at both locations in September. Variation occurred among cultivars and locations for leaf area, fresh and dry weights, growth, and leaf number. Plant death occurred at the Hope location, with `Heritag', `Reveille', and `Southland' all having plant mortality, while `Dormanred' and `Arapaho', both southern-adapted cultivars, had the greatest fresh and dry weights. The Fayetteville location had no plant loss after initial emergence in spring, and this more moderate environment probably contributed to higher plant survival. Our data indicated that only `Dormanred' and `Arapaho' achieved adequate survival and growth in the very high temperatures of the Hope location, whereas other cultivars (Reveille and Southland) with some southern U.S.-adapted germplasm, showed poor adaptation to the environments of our study. Our findings reflect the impact of high heat on non-adapted germplasm and reveal information on adaptation levels needed for parental consideration in breeding for southern conditions.

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The Arkansas tree fruit research program has a history of involvement in rootstock development. The elements of rootstock development are rootstock cultivar testing and rootstock breeding and evaluation. Research is focused on apple and peach rootstocks. Rootstock testing is done in conjunction with the NC-140 cooperative uniform rootstock research project. Currently, there are 10 NC-140 trials in progress for apples, peaches, pears, and cherry rootstocks in Arkansas. The Arkansas rootstock breeding projects were established in the early 1970s as components of the fruit breeding program. The objectives are to develop apple and peach rootstocks which are adaptable to the Arkansas edaphic and adaphic conditions, have size control, have some degree of pest resistance, and are efficient in production. To date, 92 apple rootstock selections have been made and 41 are still in early evaluation for propagation and growth characteristics, while 56 peach rootstocks have been selected and are in early evaluation. Arkansas apple rootstocks selections are sequentially numbered with numbers preceded by AAR (ex: AAR-92). Peach rootstocks selections are numbered with numbers preceded by APR. Data from 2 NC-140 apple rootstock trials were presented and discussed.

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Single leaf gas exchange measurements were taken at a range of light intensities from 20 to 1500 μmol·m-2·s-1 PAR under greenhouse conditions on `Washington Spur'/EMLA seven potted apple trees subjected to either 1500 cumulative mite days (CMD) European Red mite (ERM) damage or no mite damage. 1500 CMD ERM damage significantly reduced assimilation (A) over all light intensities for leaves present during mite damage at 6 days after the mite population had reached the 1500 CMD level and the mites were killed. Mite damage did not significantly affect A of either leaves present during mite damage or leaves produced after the mites were killed on any other sampling date. However, a trend of reduced A of leaves present during mite infestation on the mite-damaged trees was apparent on all sampling dates after the mites were killed. Evapotranspiration (E) was not affected by mite damage. The mite damage by light intensity interaction did not have a significant effect on A or E on any sampling date.

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Seasonal variations of nutrient concentrations in soil and apple leaves, soil properties, weed density, and tree performance were observed for response to four groundcover managements systems: 1) mowed control; 2) plastic woven landscape fabric; 3) wood chip mulch; and 4) shredded commercial paper mulch. Soil sampled below the wood chip and shredded paper mulch treatments had higher NO3-N concentrations during the season. Soil below the shredded paper mulch had greater soil Ca, Na, and Zn than other treatments. Soil sampled below wood chip mulch had higher Mg and B. Leaf K was greater for trees grown with bark chip mulch than the other treatments. Overall, the seasonal patterns of N, P, and K decreased and had similar patterns as previously reported conventionally grown orchards. The leaf Ca and Mg increased during the season for all treatments. The concentration of other microelements had patterns similar among all treatments. Seasonal soil pH decreased during the season and was affected by treatments. During the season, water infiltration was faster into the soil covered with shredded paper mulch. The organic matter was greater in soil under the wood chip mulch at the 15-cm soil depth. Very little weed invasion occurred in the landscape fabric through August. Trees grown with shredded paper and wood chip mulch treatments had greater trunk cross-sectional area compared to trees grown under landscape fabric after 5 years; however, the latter treatment resulted in greater tree height, tree canopy spread, and fruit yield.

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It has been observed that paper birch (Betula papyrifera Marsh.) has significant leaf abscission under mild to severe water stress. One-year-old paper birch seedlings were exposed to water deficit, ethylene, or inhibitors of ethylene action under controlled conditions to study water-stress induced leaf abscission. Exposing well-watered and water-stressed paper birch to 20 ppm of ethylene for 96 hours resulted in more than 50% leaf abscission regardless of plant water status, while water stress alone did not cause leaf abscission. However, the application of 1 ppm ethylene did not cause leaf abscission. Exposure to 1 ppm 1-methylcyclopropene or treatment with 0.1 mM of silver thiosulfate did not affect predawn water potential, gas exchange, and chlorophyll fluorescence. The measured evolved ethylene did not significantly increase in water-stressed paper birch prior to leaf abscission. Based on these observations, ethylene would appear to play a minor role in water-stress induced leaf abscission in paper birch.

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