Gas exchange (assimilation, transpiration, water use efficiency, and conductance) of `Shawnee' blackberry were measured under field conditions with a portable system (ADC-IRGA with Parkinson Leaf Chamber). Gas exchange primocane pentifoliate leaflets were similar. Gas exchange rates of leaves along a cane exhibited a quadratic function of leaf position with leaves in lower-mid sections (relative position 0.3 - 0.5) having higher A, TR, WUE, gs than either basal or apical leaves. Leaves subtending fruiting laterals on fruiticanes had higher assimilation than similar age leaves on primocanes but did not differ in Tr, WUE, or gs. Primocanes had estimated dark respiration rates of 0.33mg·dm-1.hr-1, estimated light compensation at 14-20 mol.m-2.s-1, estimated light saturation at 1000-1100 mol.m-2.s-1 with maximum A rates ranging from 24-30 mg CO2.dm-1.hr-1. Measurements were made at field temperatures ranging from 24-35 C. Although temperature response was not measured, correlation indicated that Tr, WUE, and gs were more closely related to temperature than A. Similarly, Tr and WUE were more closely related to gs than A (r = 0.6 to 0.8).
Curt R. Rom and John R. Clark
Mark A. DenHerder and Curt R. Rom
Defoliation by pests was simulated with potted tree model systems and field-grown trees. `Redchief'/M.7 apple trees were grown in 10 1 pots as a single shoot. Forty-five days after 25%, 50%, or 75% removal of apical or basal leaf number, new leaf dry weight (produced after treatment) was 23%, 53%, and 45% higher, respectively, for apically treated trees, and -7%, 61%, and 64% higher for basally treated trees, than control trees. Root dry weight was reduced by as much as 59% (apical 75% removed). Photosynthesis following 75% leaf removal was inhibited 1 day after treatment, but increased above the control within 3 days. However, by 35 days after treatment photosynthesis had declined to 53% of control. Leaf removal (50%) June 15 (1990) of 4-year old `Early Granny'/Mark increased net photosynthesis by 40% within 8 days of treatment. Trunk cross-sectional area increase of June- and twice-(June 15 and July 30) defoliated trees was 35% of control trees. Leaf nitrogen content (% dry wt.) in September was 1.75 for twice-defoliated trees compared to 1.58 for control trees.
Ray Allen, Curt Rom, and John Aselage
Summer pruning effects on apple tree canopy microclimate, fruit quality, and summer disease were studied in a commercial orchard in eastern Arkansas. Eighteen lo-year-old trees of `Golde n Delicious'/M111 were treated as follows: 1) non-pruned control, 2) moderate pruned, thinning cuts in the canopy, and 3) heavy pruned, thinning cuts in the canopy and heading shoots on the canopy periphery. Treatments were applied on 23-June, 1992. All trees were dormant pruned. PPFD and relative evaporation (RE), measured with Livingston atmometers, were measured at time of treatment, on 15-July, and at Harvest, 9-Sept. PPFD and RE were immediately increased by summer pruning but by harvest had returned to levels near the non-pruned control. Fruit firmness, titratable acidity, starch, and color were not significantly affected while soluble solids were inconsistently affected. Weight was decreased insignificantly by moderate pruning and decreased slightly by heavy pruning. Summer fruit rot incidence was similar among all treatments. PPFD and RE were significantly higher in upper positions of the canopy as compared to lower positions.
Curt R. Rom and Renae E. Moran
Trunk cross-sectional area (TCA) has been used to estimate leaf area (LA) and yield efficiency but variation in LA and TCA relationships have been unexplored. LA and TCA of 10-yr-old 'Starkspur Supreme Delicious' on 9 rootstocks (STKs) were measured in 1989. LA and TCA of 2-yr-old trees of 3 cultivars (CVs) on 5 STKs were measured in 1991. Regression of LA and TCA was performed for each CV, STK and each CV/STK. On mature trees, LA varied significantly with STK. The number and LA of shoot leaves (LVS) and spur LVS varied with STK but the % of total was not significantly different (approx. 52% spur LVS). The relationships of LA and TCA were linear for mature (r2=.94) and young (r2=.44) trees. On young trees, TCA varied with CV, but LA did not. Both LA and TCA were significantly different among STKs. The linear relationships of LA and TCA had unique intercepts with each CV, STK and CV/STK combination but slopes were not significantly different. Leaf area of Jonagold' and 'Gala' tended to increase more with increasing TCA than 'Empire'.
Renae E. Moran and Curt R. Rom
The relationship of variability in flowering and fruiting habit to canopy position and changing diurnal light and photosynthetic pattern was examined in 7 mature spur-type `Red Delicious'/MM106 apple trees. A .5×.5m column was placed in the north, south, east and west sections of tree canopies. Columns were subdivided by height with 3 study areas located at .25-.5m, 1.0-1.25m and 1.75-2.0m from the top of the canopy. In each, section, flowering index, fruit set, individual fruit weight and size, skin coloration, fruit soluble solids content, spur leaf area and spur bud diameter were determined. Photosynthetically active radiation and photosynthesis were measured from bloom through harvest correlated with variability in flowering, fruiting, spur quality and distribution of growth.
Curt R. Rom, B. Blackburn, and R. Bourne
The growth and productivity of `Redhaven'/Lovell peach during the first 3 years in a replant site was evaluated after planting in one of five preplant treatments. Treatments (trt) were 1) nontreated control (CK), 2) killed fescue (F), 3) soybean rotation (L), 4) summer solarization (SOL), and 5) methyl bromide fumigation (FUM). An orchard was removed from the experimental site in Spring 1991 before establishments of treatments. In June 1991, a tall fescue (K-31), soybeans, or mustard, and cabbage were sown in trt plots 2, 3, and 4, respectively. In July, trt 4 was covered with clear, 4-mil plastic sheeting for 90 days. In October, trt 5 was fumigated with methyl bromide under a 4-mil plastic sheet. Trees were planted in Spring 1992. Soil characteristics, weed populations, and tree growth and productivity were measured in the first three seasons after planting. FUM significantly reduced weed density into the third season. SOL plots had the highest weed density in years 2 and 3. TCSA, yield, and yield efficiency of FUM trees were significantly larger than CK. Trees in F or SOL had significantly lower yields.
Hyun-Sug Choi, Curt Rom, and Jason McAfee
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.
Curt R. Rom, Jason McAfee, and Donn Johnson
Apple cultivar development is an important program necessary to sustain the existing fruit industry and stimulate new production systems for Arkansas and the region. The cultivar development program has two parts. First, currently available cultivars are tested with multiple trees for multiple years. Second, about 150 advanced selections from the Arkansas apple breeding program are evaluated in trials with multiple trees (2nd test) and in replicated trials (3rd test). The goal of both programs is to identify cultivars that have potential in the local production systems and for Arkansas' markets, and to identify those cultivars which are not adapted to the region. All cultivars and advanced selections are evaluated for ∂35 qualitative and quantitative characteristics, including time of bloom, time of harvest, length of harvest season, fruit aesthetic and internal quality, environmental adaptability especially to heat and high light, and insect and disease susceptibility. Primary diseases for which cultivars and selections are screened include fireblight, cedar apple rust, powdery mildew, black rot, white rot and bitter rot. Primary insect pests include mites, codling moth, plum curculio and Japanese beetle. Cultivars are evaluated in the field, under standard management conditions for five to seven years of production before summary evaluation. The program has identified cultivars including traditional cultivars, new cultivars, and heritage cultivars adaptable to the local and regional climates and suitable for those markets.
Kristen Harper, Curt R. Rom, and Jason McAfee
As funding directed toward research has diminished, it has become vital seek other avenues of support to maintain long term field projects. To meet this need, the University of Arkansas Horticulture Department began the Friends of Fruit (FOF) program during 2004 engaging volunteers in conducting tree fruit field research. Volunteers were graduates of the Master Gardener program and executed tasks including data collection and plot maintenance. Objectives of this study were to evaluate the experiences and benefits to the volunteers and horticulture department, and to assess the success of the FOF program in providing assistance and support to research. All volunteers and facilitators were interviewed. Interview questions were designed to understand the motivation and level of volunteer activity, determine if training and supervision was adequate, and determine if ample recognition occurred. Volunteers sought experience and knowledge with fruit crops. Costs to volunteers included time and travel, conversely benefits included knowledge, experience and fellowship. Volunteers planned to repeat the program and were pleased with the recognition they received. Facilitators noted that volunteers had basic horticultural knowledge and the desire to learn. The program did call for improved task management and increased planning time by facilitators. The program succeeded in benefiting volunteers and horticultural research. The FOF volunteers contributed to fruit research by harvesting ≈4,000 kg of fruit samples and providing >200 hours of time.
Curt R. Rom and R. Andy Allen
`Empire', `Smoothee', `Jonagold', and `Rome Beauty' apple cultivars (CV) on five size-controlling rootstocks, Bud.9, M.9 EMLA, M.26 EMLA, Mark, and Ott.3, were planted in Fayetteville, Ark., in 1990 as a complete block design with six replications. Although interactions for several growth variables were observed in 1990–93, there were no cultivar–rootstock interactions in 1994, 1995, or for cumulative yield. After six seasons' growth, CV did not significantly affect any growth variable. Trees on M.26 and M.9 were the largest, while trees on Mark were significantly smaller for both tree height and TCA; trees on Ott.3 and Bud.9 were intermediate. `Smoothee' had the greatest cumulative yield, while both `Jonagold' and `Rome Beauty' had significantly less; `Empire' yield was intermediate. Trees on Ott.3 and M.26 had larger cumulative yields than other stocks, which were all similar. Trees on Mark had the greatest yield/TCA, while M.9 and M.26 had the least yield/TCA; Ott.3 and B.9 were intermediate. Trees on Mark had very high levels of foliar Mn and exhibited symptoms of Mn-induced internal bark necrosis.