Grafting of vegetable seedlings is a unique horticultural technology practiced for many years in East Asia to overcome issues associated with intensive cultivation using limited arable land. This technology was introduced to Europe and other countries in the late 20th century along with improved grafting methods suitable for commercial production of grafted vegetable seedlings. Later, grafting was introduced to North America from Europe and it is now attracting growing interest, both from greenhouse growers and organic producers. Grafting onto specific rootstocks generally provides resistance to soilborne diseases and nematodes and increases yield. Grafting is an effective technology for use in combination with more sustainable crop production practices, including reduced rates and overall use of soil fumigants in many other countries. Currently, over 40 million grafted tomato seedlings are estimated to be used annually in North American greenhouses, and several commercial trials have been conducted for promoting use of grafted melon seedlings in open fields. Nevertheless, there are issues identified that currently limit adoption of grafted seedlings in North America. One issue unique to North America is the large number of seedlings needed in a single shipment for large-scale, open-field production systems. Semi- or fully-automated grafting robots were invented by several agricultural machine industries in the 1990s, yet the available models are limited. The lack of flexibility of the existing robots also limits their wider use. Strategies to resolve these issues are discussed, including the use of a highly controlled environment to promote the standardized seedlings suitable for automation and better storage techniques. To use this technology widely in North American fresh vegetable production, more information and locally collected scientific and technical data are needed.
Field studies were conducted in three Florida locations (Bradenton, Gainesville, and Quincy) during 1998-99 and 1999-2000 to: 1) compare the performance of two transplant systems under diverse MBr alternative programs in `Chandler' strawberry (Fragaria ×ananassa), and 2) determine the efficacy of these treatments on soilborne pest control in strawberry. Fumigant treatments were: 1) nonfumigated control, 2) methyl bromide plus chloropicrin (MBr + Pic) at a rate of 350 lb/acre, 3) Pic at 300 lb/acre and napropamide at 4 lb/acre, 4) 1,3-dichloropropene (1,3-D) plus Pic at 35 gal/acre and napropamide at 4 lb/acre, 5) metam sodium (MNa) at 60 gal/acre and napropamide at 4 lb/acre, and 6) MNa followed by 1,3-D at 60 and 12 gal/acre and napropamide at 4 lb/acre, respectively. Strawberry transplants were either bare-root or containerized plugs. There were no significant fumigant by transplant type interactions for strawberry plant vigor and root weight per plant, whereas ring nematode (Criconema spp.) and nutsedge (Cyperus rotundus and C. esculentus) populations, and total marketable fruit weight were only infl uenced by fumigant application. The nonfumigated plots had the lowest strawberry plant vigor and root weight per plant in all three locations. In most cases, plant vigor and root biomass per plant increased as a response to any fumigant application. With regard to the transplant type, bare-root transplants had similar plant vigor as plugs in two of the three locations. Fumigation improved nutsedge and ring nematode control. All fumigants had higher early and total marketable yield than the nonfumigated control, whereas transplant type had no effect on total fruit weight.
Anaerobic soil disinfestation (ASD) is considered a promising sustainable alternative to chemical soil fumigation (CSF), and has been shown to be effective against soilborne diseases, plant-parasitic nematodes, and weeds in several crop production systems. Nevertheless, limited information is available on the effects of ASD on crop yield and quality. Therefore, a field study was conducted on fresh-market tomato (Solanum lycopersicum L.) in two different locations in Florida (Immokalee and Citra), to evaluate and compare the ASD and CSF performances on weed and nematodes control, and on fruit yield and quality. In Immokalee, Pic-Clor 60 (1,3-dichloropropene + chloropicrin) was used as the CSF, whereas in Citra, the CSF was Paldin™ [dimethyl disulfide (DMDS) + chloropicrin]. Anaerobic soil disinfestation treatments were applied using a mix of composted poultry litter (CPL) at the rate of 22 Mg·ha−1, and two rates of molasses [13.9 (ASD1) and 27.7 m3·ha−1 (ASD2)] as a carbon (C) source. In both locations, soil subjected to ASD reached highly anaerobic conditions, and cumulative soil anaerobiosis was 167% and 116% higher in ASD2 plots than in ASD1 plots, in Immokalee and Citra, respectively. In Immokalee, the CSF provided the most significant weed control, but ASD treatments also suppressed weeds enough to prevent an impact on yield. In Citra, all treatments, including the CSF, provided poor weed control relative to the Immokalee site. In both locations, the application of ASD provided a level of root-knot nematode (Meloidogyne sp.) control equivalent to, or more effective than the CSF. In Immokalee, ASD2 and ASD1 plots provided 26.7% and 19.7% higher total marketable yield as compared with CSF plots, respectively. However, in Citra, total marketable yield was unaffected by soil treatments. Tomato fruit quality parameters were not influenced by soil treatments, except for fruit firmness in Immokalee, which was significantly higher in fruits from ASD treatments than in those from CSF soil. Fruit mineral content was similar or higher in ASD plots as compared with CSF. In fresh-market tomato, ASD applied using a mixture of CPL and molasses may be a sustainable alternative to CSF for maintaining or even improving marketable yield and fruit quality.