biomass and yields of a range of vegetables ( Bumgarner et al., 2011 ; Hunter et al., 2012 ), but also exposes plants to temperatures closer to their maximum which may be harmful to productivity. The addition of soil heating cables generally leads to an
Dan Drost, Taunya Ernst and Brent Black
Takashi Miwa, Kihara and Tonogi
Recently, full-green turf on the sports fields in a winter period is highly required. The negative factor for warm-season grass pitch is its winter dormancy. Winter overseeding (WOS) is one of the successful methods to make them seem green. However, maintenance cost for winter overseeded turf is relatively expensive, and WOS itself involves some difficulties. On the other hand, under-soil heating (USHS) has been used only for cool-season grass pitch, but for warm-season grass pitch for the purpose to make them full green in a winter term. The objectives of this study are: 1) to confirm USHS's effectiveness for warm-season grass, 2) to make the specified system itself, and 3) to estimate the approximate heat demand. The results indicate that USHS can make warm-season grass green and maintain much higher turf quality, even in a severe winter period. The parameters needed to create the system are obtained. Those includes: heating pipe's spacing and depth, initial media temperature, and required soil temperature. In addition, USHS needs plastic cover for insulation, which light, air and water can pass through. Compared with WOS, this method can reduce maintenance fee and procedures such as preparation for WOS in a fall and transition in a spring. Thus, it can prolong total playing period. Moreover, it is easy to maintain the turf quality higher and maintenance cost can be less than WOS. The future subjects are to assess weed invasion, pests and diseases levels induced by USHS or by excess humidity, and to create a special maintenance program for this method.
Takashi Miwa, Hisakazu Kihara and Hideaki Tonogi
Recently, full-green turf on sports fields in the winter is highly desirable. The negative factor for warm-season grass pitch is its winter dormancy. Winter overseeding (WOS) is one successful method to make turf seem green. However, maintenance cost for WOS turf is relatively expensive and brings some difficulties. Undersoil heating (USH) has been used for cool-season grass pitch or warm-season grass pitch to make turf green in winter. Our objectives were 1) to confirm USH effectiveness for warm-season grass, 2) to make the specified system itself, and 3) to estimate the approximate heat demand. The results indicate that USH can make warm-season grass green and maintain much higher turf quality even in severe winter conditions. Weed invasion, pests, and diseases levels are quite low during the test period. The characteristics needed to create the system include heating pipe spacing and depth, initial media temperature, and required soil temperature. In addition, USH needs a plastic cover for insulation that is light and that air and water can penetrate. Compared with WOS, USH can reduce maintenance fees and procedures, such as preparation for WOS in a fall and transition into spring. Thus, UHS can prolong total playing period. Moreover, it is easy to maintain the higher turf quality and lower maintenance cost than WOS. In the future, we should concentrate on creating more concrete maintenance program for this method.
Theo J. Blom and Brian D. Piott
The effect of constant 16C and noncontrolled soil temperature on flowering of four Alstroemeria cultivars grown in a greenhouse was studied over 3 years. Soil temperature regime did not influence either the start or cessation of flowering. During spring/summer, production was 15% lower under constant soil temperature, irrespective of cultivar. During fall/winter, the effect of constant soil temperature was cultivar-dependent; yield of `Red Sunset' was increased by 150%, while that for `Rio' decreased by 2270 relative to the noncontrolled. Annual production was not affected, but the ratio between the production of spring/summer and fail/winter decreased from 3.1 to 2.2 for noncontrolled and constant soil temperature, respectively.
Clauzell Stevens, Victor A. Khan, Theresa Okoronkwo, Ah-Yin Tang, Mack A. Wilson, John Lu and James E. Brown
Soil polarization for 98 days in 1985 resulted in a 91% reduction of weeds present in collard greens (Brassica oleracea acephafa L.) plots during 1986. Soil solarization was more effective in controlling weeds in collard green plots when compared to an application of Dacthal-75W herbicide in nonsolarized plots. Collard green plants grown in solarized soil showed an increase in yield and other growth responses. Soil samples from the rhizosphere of plants grown in solarized soil showed higher population levels of bacteria and thermotolerant fungi than from nonsolarized soil. There were significant negative responses in marketable yield and root growth of collard greens and in soil microflora in solarized soil in response to Dacthal-75W herbicide application. Chemical name used: dimethyltetrachloroterephthalate (Dacthal-75W).
Martin P.N. Gent and Vincent Malerba
The soil within a greenhouse was heated by blowing hot air from a forced-air heater through drainage pipes buried beneath raised beds. This warmed the soil from 50F (10C) to 68F (20C) after 1 week of heating in mid-March. Soil in unheated beds did not warm to this temperature until May. The yield of tomato (Lycopersicon esculentum Mill.) planted in heated beds was higher than in unheated beds by 16% over the season in 1992, and by 14% as of early July 1993. The weight fraction of highest-quality fruit also were 11% greater in 1993. This simple method of soil heating involved negligible additional expense
Royce S. Bringhurst and Jose Godoy F
There is a great deal of interest in the possibility of developing suitable materials or procedures for use in strawberries and other crops in place of methylbromide as a soil fumigant. One such has been soil heating resulting from the bed application of transparent polyethylene. This requires high mid-summer soil temperatures with relatively high soil humidity. We present the results of a solarization experiment. Bed soil temperature were measured regularly at a depth of 12 cm through the 9 weeks of differential treatments. The soil temperature differences were highly significant, averaging ≈7°C higher than the non-solarized treatments. Weed control is one of the results of high interest. The number of weeds were counted twice. The number in the solar plots were not significantly different from the number counted for the methyl-bromide-fumigated plots. Vegetative vigor (asexual response) was also an important measurement. This was measured in two ways: first, the number of runners, and second, the measurement of plant size. The results were identical. The solarized plots and fumigated plots were identical in plant size and identical in runner production, and both were significantly different from the non-solarized and non-fumigated plots. Similar results were obtained for the sexual responses, yield, and fruit size. Solarization should be tested sufficiently in detail as a possible procedure to replace some methyl-bromide fumigation.
The biggest problem may be difficulty getting the temperature high enough to be adequately effective.
Timothy S. Prather, James J. Stapleton, Susan B. Mallek, Tarcisio S. Ruiz and Clyde L. Elmore
A double-tent solarization technique, which accumulates higher soil temperatures than solarization of open fields, was recently approved by the California Department of Food and Agriculture (CDFA) as a nematicidal treatment for container nurseries. Due to the need for broad-spectrum pest control in container nursery settings, this technique was tested to determine its usefulness as an herbicidal treatment. Laboratory-derived thermal death dosages (temperatur × time) for several weed species important in California, including common purslane (Portulaca oleracea), tumble pigweed (Amaranthus albus), and black nightshade (Solanum nigrum), were previously determined and the data were used as guidelines for devising treatment duration in this study. In two field experiments conducted in 1999 and 2000 to validate the laboratory data, moist soil was placed in black polyethylene planting bags [3.8 L (1 gal) volume], artificially infested with seeds of the three test species, and subjected to 0 to 24 hours of double-tent solarization after reaching a threshold temperature of 60 °C (140 °F) (about 1.5 to 2.0 h after initiation of the experiment). In 1999, samples were removed at 2, 4, 20, and 24 hours after reaching the 60 °C threshold, then incubated to ameliorate possible secondary dormancy effects. Seeds failed to germinate in any of the solarized treatments. In 2000, samples were removed at 0, 1, 2, and 6 h after reaching 60 °C. Again, apart from the nonsolarized control treatment, all weed seeds failed to germinate at any of the sampling periods, in accordance with prior laboratory thermal death results. Reference tests to estimate effects of container size on soil heating showed that soil in smaller container sizes (soil volume) reached higher temperatures, and were maintained at high temperature [above 60 °C (140 °F)] for a longer period of time, than larger container sizes. The double-tent solarization technique can be used by commercial growers and household gardeners to effectively and inexpensively produce weed-free soil and potting mixes in warmer climatic areas.
Jay M. Ham, G.J. Kluitenberg and W.J. Lamont
Research was conducted to determine the optical properties of eight plastic mulches and evaluate their effects on soil, mulch, and air temperatures in the field. Optical properties of the mulches were measured in the laboratory in the shortwave (0.3 to 1.1 μm) and longwave (2.5 to 25 μm) wavebands using a spectroradiometer and Fourier transform infrared spectrophotometer, respectively. Additionally, each mulch was installed on a fine sandy loam soil near Manhattan, Kan. Air and soil temperatures were measured 5 cm above and 10 cm below the surface, respectively. Measurements of longwave radiation emitted and reflected from the surface were used to approximate the apparent temperature of the surface. Shortwave transmittance of the mulches ranged from 0.01 to 0.84, and shortwave reflectance ranged from 0.01 to 0.48, with the greatest reflectance from white and aluminized mulches. Infrared transmittance ranged from 0.87 for a black photodegradable mulch to 0.09 for aluminized material. Air temperatures at 5 cm were similar for all mulch treatments, but were typically 3 to 5C higher than the air at 1.5 m during the day. Midday soil temperatures were highest beneath mulches with high shortwave absorptance (black plastics) or those with high shortwave transmittance coupled with low longwave transmittance. Apparent surface temperatures approached 70 to 80C during midday, with the highest temperatures occurring on mulches with high shortwave absorptance. For some mulches, both, shortwave and longwave optical properties of the plastic governed the level of radiative heating. Our results suggest that conduction of heat between the plastic and the soil surface also affects the extent of soil heating in a mulched field.
Daniel Rowley, Brent L. Black, Dan Drost and Dillon Feuz
subplots that were either covered with a low tunnel or left uncovered. In addition, soil heating cables (Mor Electric Heating Assoc., Inc., Comstock Park, MI) were installed in the beds under the low tunnels. Soil heat cables were buried 2 to 3 cm deep