Limited root development of nursery stock in root-control bags facilitates harvest but without irrigation may predispose stock to water stress. The effect of bags and irrigation on growth and water relations of field-grown Malus sieboldii var. zumi were investigated following transplanting as large liners into a silty-clay soil. Predawn leaf water potential (ψ), and midday stomatal conductance (gs) and ψ, were measured periodically through the season. Late-season osmotic potential (ψπ), caliper, leaf area, and root growth were also measured. Non-irrigated treatments exhibited water stress during an extended mid-summer drought, as predawn ψ and particularly gs were less than irrigated treatments, resulting in lower vegetative growth and ψπ. For combined bagged treatments water relations did not differ, but leaf area, root growth, and ψπ, but not caliper, were less than non-bagged trees. Growth measurements and ψπ of non-irrigated bagged trees, however, were consistently lower but nonsignificant than the other treatments. Bag-induced root reduction can limit some top growth even with optimum soil water. Moreover, in terms of potential Type-II errors extrapolated over a conventional production cycle, trees grown in root-control bags in normally non-irrigated soils may be more susceptible to water stress and subjected to further cumulative growth limitation.
Roger Kjelgren and Craig Spihlman
Bhim B. Khatri, Janak D. Shakya, and James H. Lorenzen
Potato (Solarium tuberosum L.) is a major food crop for farmers of higher elevations (> 2000 m) in Nepal. Farmers plant potatoes in early spring after snow melt, utilizing residual winter moisture and occasional pre-monsoon rains for crop growth. The growing season is usually ended by late blight (LB, Phytophthora infestans) after the onset of the monsoon. However, drier areas of the interior of W. Nepal regularly experience drought and impaired plant growth before the monsoon, and the lesser duration and intensity of the monsoon there should result in lower LB pressure with a June/July planting.
Planting just prior to the monsoon in highland areas with annual rainfall < 1000 mm has given outstanding yields with cvs Achirrana Inta and I-1124. On-station and farmers' field trials have produced over 40 and 30 T ha-1, respectively, more than 4x the national average yield and nearly 2x the equivalent yield for a normal season planting in the same site. The LB resistant cultivars and the new cropping pattern may be extended to similar sites. (Supported by Swiss Devel. Assistance & Humanitarian Aid, Bern, Switzerland)
Xin Zhao and Edward E. Carey
High tunnels, unheated greenhouses, have been shown to be a profitable season-extending production tool for many horticultural crops. Production of cool-season vegetables during hot summer months can be achieved using shaded high tunnels. Microclimate in high tunnels and open field was monitored during summer trials of leaf lettuce, in which unshaded tunnels and shaded tunnels (39% PAK white shadecloth) were used, respectively, in 2002 and 2003. Wind speed was consistently lower in high tunnels. Compared to open field, daily air temperature was about 0.7 °C higher in unshaded high tunnels, and 0.5 °C lower in shaded high tunnels. Relative humidity was slightly lower in unshaded tunnels, but tended to increase in shaded tunnels, in comparison to the open field. When using shadecloth, soil temperature was lowered by 1∼3 °C and the leaf surface temperature was significantly reduced by 1.5∼2.5 °C. In shaded high tunnels, PAR light dropped by at least 50% relative to the outside, where the maximum PAR light intensity reached 1800 μmol·m-2·s-1. Overall, shaded high tunnels resulted in higher quality lettuce, with less bolting and bitterness. Reference crop evapotranspiration (ET0) was estimated from meteorological data on a daily basis using the FAO-56 method. ET0 was lowest in shaded high tunnels, and highest in the open field. Relatively lower ET0 in high tunnels indicated a likely lower water requirement and therefore improved water use efficiency compared with the open field.
Duane W. Greene
AVG was applied as the ReTain formulation over three harvest seasons to determine the influence of time of application on drop control efficacy and its influence on fruit maturity of 'McIntosh' apples. Effective drop control was achieved through the commercial harvest season with application of AVG made from 1 to 6 weeks before the anticipated start of harvest for untreated fruit. Drop control extended beyond the normal harvest period when application was made either 2 weeks or 1 week before anticipated harvest. Application made between 6 and 4 weeks before anticipated harvest generally delayed parameters associated with ripening, such as softening, degradation of starch, and development of red color, more than applications made on later dates. While AVG consistently and effectively retarded abscission, the length of time it controlled drop varied from year to year, even when used on similar trees in the same block. Once applied, it required 10 to 14 days before AVG started to retard fruit abscission. AVG controlled drop linearly with increasing concentration. AVG was a superior drop control compound than NAA. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA).
J.M. Kemble, P. Sanders, W. Foshee, and D. Fields
High tunnels (HT) can reduce negative environmental strains on crop production and have been shown to extend the growing season for many small fruits and vegetables. Because HTs require relatively low initial investment compared with standard greenhouse structures, they are well suited for the small to mid-size grower. HTs provide a practical means of entry into intensive crop production for farmers who direct market their produce. By using HTs, direct market farmers may create a special marketing niche which set's them apart by offering locally grown vegetables, cut flowers, small fruits, and herbs earlier in the growing season and into the fall after frost. This project examined 1) the potential use of HTs for the production of fresh-market tomatoes (Lycopersicon esculentum Mill.) and strawberries (Fragaria spp.) and 2) the seasonal market potential for these crops in Alabama. Viable markets were determined by conducting surveys at regional locations throughout Alabama, such as farmers markets, grocery stores, shopping centers, etc. Upscale restaurants were also surveyed to determine the demand for locally grown herbs. These surveys were used to determine target markets by asking demographic questions and determining spending habits. Justification for establishing a direct farmer-to-consumer market or a direct farmer to restaurant market for HT products was determined.
Michael W. Smith and Bruce W. Wood
Allometric equations were developed for orchard-grown pecan [Carya illinoinensis (Wangenh.) C. Koch] trees. Trees, ranging in size from 22 to 33 cm in trunk diameter 1.4 m above the ground, were destructively harvested from two sites. The entire aboveground portion of each tree was harvested and then divided into leaves, current season's shoots, and branches ≥1 year old plus trunk. Roots were sampled by digging a trench beginning beneath the trunk and extending to one-half the distance to an adjacent tree, then separating the roots from the soil. Roots were then divided into those less than 1 cm in diameter and those ≥1 cm in diameter. Equations in the form Y = eaXb were developed to estimate dry biomass of most tree components and the whole tree, where Y is the dry weight, e is the base of the natural logarithm, X is the trunk diameter at 1.4 m above the ground, and a and b are coefficients. A linear equation provided the best fit for estimating the weight of the current season's growth. Power equations were also developed to estimate the weights of inner bark and wood for different size trunks or branches.
Christopher A. Proctor, Matt D. Sousek, Aaron J. Patton, Daniel V. Weisenberger, and Zachary J. Reicher
; Hinton et al., 2001 ) and are commercially available. The objectives of our study were to determine if changing a.i. in initial and sequential applications affects season-long crabgrass control and if single spring applications of PRE tank mixtures
Zachary J. Reicher and Glenn A. Hardebeck
Converting cool-season golf course fairways to creeping bentgrass (Agrostis palustris Huds.) is desirable because it affords excellent playability, enhanced recuperative potential, and enhanced disease tolerance compared to annual bluegrass (Poa annua sp. Timm.) or perennial ryegrass (Lolium perenne), which are common species in fairways. However, converting current golf course fairways to creeping bentgrass with nonselective herbicides is problematic because it disrupts play and decreases revenue, as fairways must be closed for an extended period of time. The objective of our study was to quantify the effect of trinexapac-ethyl (TE), overseeding date, and overseeding rate on the success on the gradual conversion of cool-season fairways to creeping bentgrass over 3 years. `Penneagle' creeping bentgrass was overseeded at 0, 49, or 98 kg·ha-1 in fall, spring, or fall+spring after aerification, and application of TE at 0.0, 0.2, or 0.4 kg·ha-1. Gradual conversion to creeping bentgrass was effective, on perennial ryegrass fairways, with up to 36% cover of creeping bentgrass after 3 years of overseeding. However, only a maximum of 3% creeping bentgrass cover was obtained after the third year of overseeding into primarily annual bluegrass fairways. Fall overseeding with bentgrass at 49 or 98 kg·ha-1 was equally effective and additional spring overseeding did not improve establishment. Applications of TE prior to overseeding did not enhance the conversion. Chemical name used: 4-cyclopropyl-a-hydroxy-methylene-3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).
Timothy Spann, Robert H. Beede, Steven A. Weinbaum, and Theodore M. DeJong
Rootstock significantly alters the pattern of shoot growth of pistachio (Pistacia vera) cv. Kerman. Trees grown on P. atlantica typically produce a single flush of spring growth, whereas trees on P. integerrima selection PGI and P. atlantica × P. integerrima selection UCB-1 can produce multiple flushes during the season. We have shown that the spring flush is entirely preformed in the dormant bud for all three rootstocks, but later flushes are neoformed, that is, nodes are initiated and extended during the same season. Shoots producing both preformed and neoformed growth have lower yield efficiency than those producing only preformed growth. Additionally, yield components of the crop from shoots with both preformed and neoformed growth was different than for shoots producing only preformed growth. However, these differences do not appear to be significant at the whole tree level. These data suggest that neoformed growth can both compete with fruit growth for available resources (lower yield efficiency) and act as an additional source (altered yield components), depending on the factor being measured. Controlling neoformed growth may potentially increase pistachio yield through a shift to the more efficient preformed shoots while at the same time lowering orchard maintenance costs by reducing required pruning. We have data to indicate that regulated deficit irrigation and new pruning techniques may be viable methods for controlling neoformed growth in pistachio without affecting yield.
Ted E. Bilderback, Stuart L. Warren, James S. Owen Jr., and Joseph P. Albano
Many research studies have evaluated potential organic and mineral container substrate components for use in commercial potting substrates. Most studies report results of plant growth over a single production season and only a few include physical properties of the substrates tested. Furthermore, substrates containing predominantly organic components decompose during crop production cycles producing changes in air and water ratios. In the commercial nursery industry, crops frequently remain in containers for longer periods than one growing season (18 to 24 months). Changes in air and water retention characteristics over extended periods can have significant effect on the health and vigor of crops held in containers for 1 year or more. Decomposition of organic components can create an overabundance of small particles that hold excessive amounts of water, thus creating limited air porosity. Mineral aggregates such as perlite, pumice, coarse sand, and calcined clays do not decompose, or breakdown slowly, when used in potting substrates. Blending aggregates with organic components can decrease changes in physical properties over time by dilution of organic components and preserving large pore spaces, thus helping to maintain structural integrity. Research is needed to evaluate changes in container substrates from initial physical properties to changes in air and water characteristics after a production cycle.