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By collecting rain from a roof during rain events and storing it in a barrel or cistern, homeowners can create an alternative water supply to irrigate their home gardens and landscaping that will not overpump the groundwater or increase the water bill. In this example, a typical home garden would be 400 ft2 on which the homeowner plans to irrigate using a 55-gal heavy-duty plastic barrel with a spigot located near the bottom of the tank. The objective of this study was to develop a spreadsheet-based model using daily data to determine how the watering habits of home gardeners affect the amount of available supplemental irrigation water and cost savings using a typical 55-gal rain barrel, thus resulting in a more realistic cost-benefit analysis. The model allows for multiple, user-selected criteria such as the size of the barrel, number of barrels, harvest efficiency of the guttering system, size of the garden, the catchment area, and the watering habits of the homeowner (such as how many days without precipitation have occurred before they feel the need to water), which were used to develop seven different scenarios. To optimize rainwater use and cost benefits, the following parameters are recommended: catchment area of 600 ft2, 90% harvest efficiency by reducing leaks and other problems with guttering and rain barrel, threshold of 0.10 inch for a wet day, minimum of only 2 dry days before using the water in the barrel, and one overflow barrel. In this case, a homeowner in Knoxville, TN, can harvest an average of 1570 gal per season (range of 1076–2076 gal), at an average cost savings of $22, and thus recover the cost of the two barrels in 3–6 years.

The daily light integral (DLI) is a measurement of the total amount of photosynthetically active radiation delivered over a 24-hour period and is an important factor influencing plant growth over weeks and months. Contour maps were developed to demonstrate the mean DLI for each month of the year across the contiguous United States. The maps are based on 30 years of solar radiation data for 216 sites compiled and reported by the National Renewable Energy Lab in radiometric units (watt-hours per m-2·d-1, from 300 to 3,000 nm) that we converted to quantum units (mol·m-2·d-1, 400 to 700 nm). The mean DLI ranges from 5 to 10 mol·m-2·d-1 across the northern U.S. in December to 55 to 60 mol·m-2·d-1 in the southwestern U.S. in May through July. From October through February, the differences in DLI primarily occur between the northern and southern U.S., while from May through August the differences in DLI primarily occur between the eastern and western U.S. The DLI changes rapidly during the months before and after the vernal and autumnal equinoxes, e.g., increasing by more than 60% from February to April in many locations. The contour maps provide a means of estimating the typical DLI received across the U.S. throughout the year.

Peach [Prunus persica (L.) Batsch.] production in the southeastern United States. has suffered a decline in the past several decades due to late and severe spring freezes. Much of the peach production in Tennessee is located on topographically diverse sites. Peach producers do not have adequate information about the effects of microclimates within their orchards on peach bud development and subsequent freeze risk. Such information may help them select the best adapted cultivars based on microclimate. The objectives of this study were to use a `Redhaven' peach bud development model to compare and contrast the phenology and freeze risks at five sites within the orchard, and to study the freeze characteristics (advective vs. radiative) of these same sites. Automated weather stations were located in topoclimatically different areas of a peach orchard in Dandridge, Tenn., from October 1990 to April 1992. Hourly weather data included average air temperature, chill units (CUs), growing degree hours (GDHs), and wind speed. The data show that the microclimatic factors that affect peach bud development and freeze risk, such as CUs, GDHs, and minimum temperatures, can vary in a topographically diverse orchard, but the effects are not as straightforward as previously reported. For instance, peach buds at a site at a lower elevation may break dormancy later due to slower accumulation of CUs, which could be beneficial to the grower. Then the buds may develop more slowly due to cold air drainage to the lower elevations, which would also be desirable. However, the lower temperatures due to cold air drainage could be damaging to the bud and cause more problems with injuries. Over the two seasons, there were more radiative freezes than advective freezes, but the advective freezes were more severe. Small differences in wind speed can account for surprisingly different freeze conditions during radiative situations. Any improvement in cold air drainage should help decrease the duration and severity of radiative freezes.

Peach [Prunus persica (L.) Batsch] production in Tennessee has declined since 1985 due to the occurrence of freezing temperatures that kill the buds, usually in the spring. Analyses of long-term (1951-89) daily temperature data from four locations in Tennessee were used to evaluate the freeze risks for `Redhaven' peach tree buds at those sites. A model using daily accumulated chill units and growing degree hours (base 4.4C air temperature) was used to estimate the dates to begin and end chill unit accumulations and the dates of full bloom of `Redhaven' peach trees for each year in the climatological record. The actual dates of freezes with air temperatures at or below –2.2C and the estimated bud developmental stage on the date of each freeze also were determined. The model was tested using peach orchard records and was found to be an improvement over using only freeze data. The model indicated that Spring Hill had the highest risk for peach production and Jackson the lowest. Recent problems with spring freezes at Knoxville and Spring Hill were due to later than normal freeze dates rather than earlier development of the `Redhaven' peach tree buds. At Springfield, the recent freeze problems were due to earlier breaking of rest, earlier full bloom, and later freezes.

Tennessee is located in an area of diverse topography, ranging in elevation from

Vegetable production has become a multi-million dollar activity in Tennessee. The large number of options of planting dates and maturity classes of different vegetable species and cultivars result in a flexible, yet confusing, situation for the grower. A plentiful supply of vegetables for the processor, fresh market, or family table can be assured by the proper scheduling of planting and harvest of different crops and cultivars. Growers have very limited access to climatic data oriented to vegetable production in their locations. For the most part, they depend on planting maps on the backs of seed packets, or on extension bulletins with very general planting and harvest date recommendations. Tennessee consists of 4 climatic divisions that do not adequately describe the multitude of climates due to the diverse topography. The objective of this research was to create GIS maps of climatic variables important to vegetable production. Maps of temperatures, growing degree days, and rainfall, freeze and heat stress probabilities based on data from 72 locations in Tennessee were used to characterize the growing seasons for different vegetables.

To investigate effects of temperatures in the preceding developmental stage on the following developmental stage, `Sunny' tomatoes were seeded in the greenhouse at six dates and three temperature levels. Plants were rotated among temperature levels so that all plants received approximately the same temperature accumulation at the time of field transplanting. Developmental stages defined were: emergence, 1st, 2nd, 3rd, 4th, 5th, and 6th leaf appearance. Temperature and solar radiation were recorded hourly. Results indicated a significant effect of temperature in the preceding stage on the following stage. Coefficients of variation (CV) in growing degree days (GDD) calculated from the 1st to the ith stage were significantly smaller than those calculated from the (i-1)th to ith stage. When Ri, defined as the reciprocal of the number of days from the 1st to the ith stage, was regressed to Ri-1 and the daily average temperature was regressed from the (i-1)th to the ith stage, all coefficients of Ri-1 were significant at the 1% level. This model was superior to one in which Ri was regressed to the daily average temperature from the 1st to the ith stage.

Peach production in Tennessee has suffered a decline in the past decade due to late and severe spring freezes. East Tennessee is an area of diverse topography. It may be possible to use topoclimate exposure to ameliorate the low temperatures in spring and therefore lessen the damage to peach buds. Exposure also may also influence the accumulation of chill units and growing degrees, therefore affecting the stage of peach bud development when the freeze occurs. Five automated weather stations were located in topoclimatically different areas of a peach orchard in Dandridge, Tennessee, from September, 1990 to May, 1991. Hourly chill units (base 6.1 °C) and growing degrees (base4.4 °C) were calculated. Twigs from peach trees close to each weather station were forced every three days to determine the date of completion of rest. Hourly freeze data were collected from each weather station. Preliminary results on the effects of topoclimate on spring freeze characteristics, accumulation of chill units and growing degrees, and peach phenology will be presented.