Robert J. Dufault

Heat units to predict tomato harvest in the southeast USA

Abstract Planting and first harvest dates of tomato ( Lycopersicon esculentum Mill.) from 2 seasons in 3 years at eight locations in Georgia, North Carolina and South Carolina formed 38 environments which were used to determine the most reliable method to predict fast harvest date of tomato based on daily maximum and minimum air temperature. Eleven methods of calculating heat units were chosen for comparison based on their performance as described in the literature. The most reliable method was defined as the one with the smallest coefficient of variation (CV). CVs were calculated for each method over both seasons and locations, for each season over all locations, each location over all seasons, and for each season at each location. All heat unit summation methods had smaller coefficients of variation (CV) than the standard method of counting days from planting to first harvest. Heat unit summation methods improved harvest date prediction accuracy compared with the counting day method for tomatoes in the South Atlantic Coast (SAC) region. Prediction using location/season specific models were less variable than the models over all seasons and locations. Incorporating daylength improved model prediction accuracy when applied over all locations and seasons, all locations by season, and all seasons by location. Based on the results of this study, the heat unit summation technique recommended for this region (where the location and season specific models are not available) is the reduced ceiling method multiplied by daylength.

Bemisia argentifolii (Homoptera: Aleyrodidae) Attacking Species of Medicinal Herbal Plants

Abstract Research was conducted on the production potential of selected medicinal herbal plant species as new crops suitable for cultivation in South Carolina. Whiteflies (Bemisia argentifolii Bellows & Perring) were found in an experimental production field infesting five perennial species of medicinal herbal plants [feverfew, Tanacetum parthenium (L.) Schultz-Bipontinus; St. John’s wort, Hypericum perforatum L.; purple coneflower, Echinacea pallida (Nuttall) Nuttall and E. purpurea (L.) Moench; and common valerian, Valeriana officinalis L.]. This article reports on whiteflies attacking and developing on these plant species. Density of whitefly nymphs was highest (mean = 2.3/cm2) on the second fully expanded leaf on the apical meristem of E. purpurea as compared with the same leaf position on the other plant species where average whitefly density ranged from 0.1 to 0.6 nymphs per square centimeter from late November 1998 through January 1999. Similarly, adult capture on sticky cards was high (mean = 123 whiteflies per card) in plots of E. purpurea compared with plots of the other four species (mean = 8 to 20 whiteflies per card per species), and adult counts were elevated in the highest (440 kg N/ha) of three fertility rates in E. purpurea. Moreover, laboratory tests agreed with the observation of a higher population of B. argentifolii on E. purpurea compared with the other four plant species. The whitefly completed development on all five plant species, and whitefly-associated parasitoids emerged from field-leaf samples of each plant species.

Potential of biosolids from shrimp aquaculture as a fertilizer in bell pepper production.

Shrimp biosolids (SB) have value as a fertilizer for bell pepper production, but maximum yields cannot be expected when SB is used alone. Although bell pepper marketable yield increased linearly with SB rate and also with Osmocote (OSM, a slow release encapsulated fertilizer) rate, yield at the highest OSM rate was 92% higher than yield at the highest SB rate. The cultural system that enhanced yield included both the highest rates of SB and OSM which delivered a combined total of 633 N - 253 P - 303 K kg/ha. The sodium in SB needs to be considered carefully whenever this material is used with plants. Apparently, SB persisted in the soil to benefit deeply-rooted crops months after initial application, but it is unknown if continued use of SB may eventually improve soil structure and physical properties.

Potential of Biosolids from Shrimp Aquaculture as a Fertilizer for Broccoli Production

Shrimp biosolids (SB) are composed of shrimp fecal matter and decomposed shrimp feed and remain as debris in the bottoms of drained ponds used to culture shrimp. These biosolids are considered waste and usually disposed of in landfills. SB is a valuable source of N, P, K and a variety of other useful plants nutrients; however, SB contains high levels of Na. Field research was conducted to evaluate the potential of SB as a fertilizer source used with and without an inorganic fertilizer source (Osmocote 14N - 6P - 12K) to grow broccoli (Brassica oleracea italica). Yield of marketable heads/ha varied with SB/Osmocote (OSM) ratios. OSM at 75 kg/ha in combination with 9.0 MT SB/ha increased heads/ha significantly compared to lesser rates of each fertilizer source. This SB/OSM fertilizer regime contained a total of 263N - 116P - 99K - 99Na/ha. The biological yield increased 13% with OSM at 150 kg/ha and SB at 9.0 MT/ha, but if OSM was increased to 300 kg/ha, yield decreased significantly by 21% probably due to excessive fertilizer salts from both sources restricting plant growth. Lettuce field bioassays after broccoli production did not indicate that either fertilizer source persisted in the soil. The sodium in SB needs to be considered carefully whenever this material is used and SB should be evaluated in experimental trials before commercial use on other crops.

Influence of Organic and Synthetic Fertility on Nitrate Runoff and Leaching, Soil Fertility, and Sweet Corn Yield and Quality

Abstract Organic farming practices have been reported to reduce agricultural pollution and improve yield and quality compared to conventional practices. Frequently, research has involved comparing completely conventional and organic farming systems over many years. This study was conducted to test whether the use of organic fertilizers versus synthetic fertilizers improved soil fertility and sweet corn (Zea mays L. var rugosa Bonaf.) vigor, yield, size, and nutrient content and minimized nitrate (NO3) leaching and runoff after a single growing season. Sweet corn vigor, yield, and nutrient content were superior for synthetically fertilized sweet corn compared to organically fertilized corn. Runoff NO3 levels were similar regardless of fertilizer type. The use of organic fertilizers neither improved crop yield and quality nor reduced NO3 loss after a single season. These findings are consistent with previous research that reports that more than a single season of organic management is needed to improve soil properties and increase yields.

Heat units, solar radiation and daylength as pepper harvest predictors

Abstract Daily maximum and minimum air temperature, total solar radiation and daylength data from seven locations during three seasons of 3 years were used to compare 52 heat unit accumulation models with counting days as a harvest prediction method for pepper. The best model was defined as the one with the least variation, i.e. smallest coefficient of variation (CV). CVs were calculated for each method over all seasons and locations, for each method over all locations for each season, and for each method in each season at each location. In all cases heat unit accumulation methods were better than counting days. The location and season specific model was the most accurate, but the analysis over all seasons and locations did result in smaller CVs than counting days, so improved harvest prediction can be achieved by using regionally developed models.

Enhancing the Productivity and Fruit Quality of Forced “Sweet Charlie” Strawberries Through Manipulation of Light Quality in High Tunnels

In winter months, the U.S. domestic strawberry supply is low, demand is high, and unit price for strawberries is at its highest point during the year. Forcing strawberries in high tunnels during this time might capture this niche market. ‘Sweet Charlie’ plugs were conditioned from 24 Aug. to 12 Sept. at 24 oC on a 12-hour day/night cycle, and were planted on 12 Sept. in fertilized plots in a high tunnel (29.3 m long × 4.3 m wide × 3.1 m high). Conditioned plants were also planted outside on mulched, drip-irrigated beds as a control. Red, yellow, and pearl ChromatiNets (24% shade factor: lowest intensity possible) were installed over the top of the high tunnel in 7.3 m wide swathes, and a no-net control plot was included. Plants were fertigated weekly with about 3.2 kg N/hectare per week from 15 N–30 P2O4–15 K2O. High tunnels were vented to maintain day temperatures in the range of 25 to 30 oC. Runners were removed and counted beginning 24 Sept. until 17 Nov. when runnering stopped. Runner production was 59% greater with yellow and pearl nets compared with the no-net controls. In contrast, the red nets produced 38% fewer total runners and runners per plant than the yellow and pearl nets, but red nets produced 34% more runners than the no-net controls. Runner production of no-net plants in high tunnels was 20% greater in contrast to the plants growing outside. Yield data from fall/winter forcing and residual spring harvests did not show any great advantage to marketable weight and numbers with ChromatiNets. Marketable berry production began on 31 Oct., with berry production slowing in November and missing the Thanksgiving market window, with negligible production in December. The plants began to produce heavily in January, with greater yields with red nets and no-net controls along with significant reductions with yellow and pearl nets. In February, all three ChromatiNets yielded less than the no-net controls. In March, plants appeared exhausted; therefore, the high tunnel was opened and plants were allowed to acclimate to outside temperatures. By April, the outside plots were in full production, yielding more than any high tunnel treatments. In the high tunnel, however, yields resumed with the no-net control and yellow net yielding similarly, but red and pearl nets yielding less than the no-net controls. In May, all high tunnel treatments yielded less than the outside plots. The no-net control produced greater total yields of all net treatments and apparently, the ChromatiNets suppressed overall yield. It is probable that in winter, the ChromatiNet shading factor overwhelmed any light quality enhancement and in longer, warmer, and brighter days, the ChromatiNets may show an advantage.

Revival of Herbalism and Its Roots in Medicine

ABSTRACT The proper use of phytomedicines in human health care may add a dimension currently lacking in the United States in the treatment of certain diseases and syndromes. Sales of botanicals have been rising for the past few years and are expected to increase 12% to 16% annually for the next few years. As agriculturists, we are developing production techniques using good management practices to grow and process these new crops. However, a fundamental understanding of the genesis of this “new” industry is needed to appreciate the historic use of herbs and significance in society.

Dilemma of regulating dietary supplements.

ABSTRACT The manufacturing of herbal preparations or dietary supplements, has become a multibillion dollar industry in the United States. Presently, dietary supplements are not considered drugs by the government, but are classified as food supplements. The Dietary Supplement Health and Education Act of 1994 (DSHEA) has defined dietary supplements as a product intended to supplement the diet that contains one or more of a vitamin, mineral, an herb or other botanical, an amino acid or a dietary substance to supplement the diet by increasing the total dietary intake, or concentrates, metabolites, constituents, extracts or combinations of any ingredients described above. The main limitation of DSHEA is that it deals only with herbs as dietary supplements, i.e., as foods and not as drugs. A quandary still exists among: (1) the consumers who want to use these products safely; (2) the government that wishes to protect its citizens from potential hazards; and (3) the conventional medical community still questioning the safety and efficacy of these products. DSHEA does not appear to be the final verdict on herbal regulation, but just the first step in a long process of interpretation, evaluation, and decision-making required in the U.S. for regulation of any new class of such products. This paper reviews the current status facing the consumer, medical industry, and government in regards to herbal use.

Further Attempts to Enhance Forced ‘Sweet Charlie’ Strawberry Yield Through Manipulation of Light Quality in High Tunnels

In winter months, U.S. domestic strawberry supply is low and demand is high, and unit price for strawberries is at its highest point during the year. Forcing strawberries in high tunnels during this time might capture this niche market. Since yields are much lower in forced systems, enhancing the light environment to increase yield with colored nets (ChromatiNets; distributed by Polysack, Inc., San Diego, CA) was attempted in 2007–2008 (previously published) without success. In the second year of field experiments in 2008–2009, the experiment was repeated with some modifications. ‘Sweet Charlie’ plugs were conditioned from September 5 to September 26 at 24°C on a 12-hr day/night cycle and were planted September 28 in fertilized plots in a high tunnel (29.3-m long × 4.3-m wide × 3.1-m high). Conditioned plants were also planted outside on mulched, drip-irrigated beds as a control. Red, yellow, and pearl ChromatiNets (24% shade factor, lowest intensity possible) were installed over the top of the high tunnel in 7.3-m wide swathes and a nonnetted plot included. Plants were fertigated weekly with about 3.2 kg N/hectare per week from 15 N–30 P2O4–15 K2O. High tunnels were vented to maintain day temperatures in the range of 25 to 30°C. In the second years work, marketable berry production began November 21, 2008, and continued until February 27, 2009, without any yield advantage for ChromatiNets. In March, plants appeared exhausted; therefore, the high tunnel was opened and plants were allowed to acclimate to outside temperatures. By April, the outside plots were in full production, yielding more than any high tunnel treatments. In the high tunnel, however, yields resumed, with the red nets tending to yield more than the pearl; no-net control and yellow net yielded similarly, but slightly less, than red. In May, all high tunnel treatments and outside berries yielded similarly. Over all harvest periods, there were no differences in total yields with nets in the second year, similar to the first year. It is probable that in winter, the ChromatiNet shading factor overwhelmed any light quality enhancement, and in longer, warmer, and brighter days, the ChromatiNets may show an advantage.