Enhancing nitrogen and water use efficiency in tomato production by using grafting technique

View the project final report

• 2011 annual report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: fertigation, irrigation, nutrient cycling, tissue analysis
• Farm Business Management: budgets/cost and returns, feasibility study
• Production Systems: holistic management
• Soil Management: nutrient mineralization

A two-year field study demonstrated that tomato plants grafted onto vigorous interspecific hybrid rootstocks produced significantly higher total and marketable yields in comparison with non-grafted plants. Grafting also significantly improved irrigation water use efficiency and nitrogen use efficiency based on marketable fruit yields. Fruit quality assessment did not reveal any major consistent changes as a result of grafting with interspecific rootstocks. Although use of grafted transplants increased the total production and harvest costs, the yield improvement generated significant gross returns to offset these costs and led to higher net returns compared to the non-grafted tomato production.

Introduction

The purpose of this project was to evaluate the potential of grafting as an economically viable approach to optimizing irrigation and nitrogen (N) management in tomato production in Florida. Tomato is widely grown in the U.S., with Florida being a leading producer. Like other vegetable crops grown commercially, tomato production in Florida is intensively managed with relatively high inputs of fertilizers and irrigation water which may contribute to pollution of water resources due to nutrient leaching and runoff. Vegetable grafting may provide an environmental-friendly approach to optimizing water and nitrogen management. In effect, vegetable grafting has been shown to enhance yield and improve crop tolerance to abiotic stresses like drought, salinity, flooding, and low soil temperatures (Davis et al., 2008; Lee et al., 2010; Rivero et al., 2003). It is suggested that underlying mechanisms for increased plant vigor and yield in grafted plants may be attributed to increased water and nutrient uptake by using vigorous rootstocks. Nutrient and water uptake as well as plant hormone status can be influenced by rootstocks (Aloni et al., 2010; Lee et al., 2010). It was pointed out that fertilization programs should be modified accordingly to reflect the improvement of nutrient use when growing grafted tomato plants (Leonardi and Giuffrida, 2006).

Owing to its multifaceted benefits, grafting has been widely used in the production of solanaceous and cucurbit vegetables in Asia and Mediterranean countries for disease control, plant vigor, and yield increase (Davis et al., 2008; Lee, 1994; Lee and Oda, 2003). In the U.S., grafted plants have been employed in hydroponic tomato production, while grafting has just emerged as an alternative practice for field tomato cultivation (Kubota et al., 2008). The research projects funded previously by SARE (O’Connell, 2008; Rivard, 2006) were focused on heirloom tomatoes grown organically in North Carolina. These projects provided preliminary information on grafting performance to manage soilborne diseases and improve nutrient uptake in heirloom tomatoes; however, water use and its interaction with nutrient management was not addressed, particularly within a broad context of crop production. In addition, quality attributes of fruit from grafted tomato and the economic feasibility of the grafted tomato cropping systems were not well elucidated. While quality attributes of tomato fruit such as titratable acidity, soluble solid content, fruit color, fruit firmness did not show any significant difference between grafted and self-rooted tomato plants (Khah et al., 2006), grafting has been shown in some instances to increase levels of lycopene, ß-carotene, vitamin C, and antioxidant activity in tomato fruit (Davis et al., 2008; Dorais et al., 2008; Fernandez-Garcia et al., 2004). Furthermore, it is also critical to evaluate the economic feasibility of grafted vegetable systems. Efficient management strategies can only be fully integrated into agricultural management practices when farmers can also sustain long term profitability of their operations (Baggs et al., 2000). Given the increasing interest from growers, in-depth research is needed to demonstrate successful integration of the grafting technology into site-specific tomato production systems in Florida.

1. Examine the effects of grafting with vigorous rootstocks on plant growth, fruit yield, and water and N use efficiency in field production under different combinations of irrigation regimes and N fertilization rates;

2. Determine whether grafting can alter the nutritional quality attributes of tomato fruit;

3. Assess the economic feasibility of the grafted tomato production systems.