Stolon production by strawberry plants in Florida fruiting fields is highly undesirable. Stolons (runners) act as a sink for photosynthates and nutrients, reducing the amount of resources available for fruit production in an annual hill production system. Stolon removal has shown negative or neutral effects on marketable fruit yields of strawberry plants grown in matted row culture (Pritts and Worden, 1988; Buckley and Moore, 1982). However, stolon removal increased yields per plant in matted row culture without increasing per plot yields for twelve cultivars (Hancock et al., 1982). In annual hill production in Florida, stolon removal twice monthly increased the early and total yields of ‘Tufts’ while not affecting yields of ‘Dover’ (Albregts and Howard, 1986). The presence of stolons makes it more difficult for pickers to find berries among the excess vegetation. Hence, manual labor must be used to remove runners in the fruiting field at a cost of $96 to $144 per hectare. If a low cost chemical means could be found to reduce or eliminate runner production in the fruiting field, producers would benefit greatly.

Mepiquat chloride (N, N-dimethylpiperidinium chloride, Pix^®, Ponnax^®, BASF Corp.) has long been used in the production of cotton (Gossypium hirsutum L.) to slow or reduce vegetative growth and increase yield and quality of harvested cotton fibers (Biles and Cothren, 2001; Reddy et al.,1996; McConnell et al., 1992; Reddy et al., 1992; Zhao and Oosterhuis, 2000). The effectiveness of mepiquat chloride in reducing vegetative growth and improving reproductive growth has shown mixed results in experimentation. This variation has been attributed to environmental, water, and nutrient factors (Reddy et al. 1992).

Prohexidione-calcium, a relatively new agricultural chemical produced by the BASF Corp. under the trade name Apogee^®, is a gibberellic acid inhibitor. Currently prohexidione-calcium is registered for use in apples (Malus pumila L.) to control fire blight (Erwinia amylova). In addition, it has shown to have several benefits for apple producers including reduced terminal growth, increased red color and fruit set (Greene and Autio, 2002). It has also been shown to reduced fire blight and increase average fruit weight in pear (Pyrus communis L.) (Costa et al., 2001). In sorghum (Sorghum bicolor L.) ( Lee et al., 1998), plant growth was retarded by applications of prohexidione-calcium but floral initiation was not delayed in comparison to other growth regulators (CCC, uniconazol, and ancymidol). These results suggest that these products may be useful for control of stolons on the 2900 hectares of strawberry production in Florida.

The purpose of this study was to determine the effectiveness of mepiquat chloride and prohexidione-calcium in suppressing runner production of strawberry plants in fruiting fields and the effect of these compounds on yield. Ideally, a suitable chemical would totally control stolon growth, thereby eliminating the need to remove them manually while maintaining or possibly increasing marketable yield.

• Yield - The variety selected should have the potential to produce crops at least equivalent to varieties already grown.  The average yield in Florida is currently about 1400 25-pound cartons per acre.  The potential yield of varieties in use should be much higher than average.

• Disease Resistance - Varieties selected for use in Florida must have resistance to Fusarium wilt, race 1, race 2 and in some areas race 3; Verticillium wilt (race 1); gray leaf spot; and some tolerance to bacterial soft rot.  Available resistance to other diseases may be important in certain situations, such as Tomato Spotted Wilt resistance in northwest Florida.

•  Horticultural Quality - Plant habit, stem type and fruit size, shape, color, smoothness and resistance to defects should all be considered in variety selection.

• Adaptability - Successful tomato varieties must perform well under the range of environmental conditions usually encountered in the district or on the individual farm.

• Market Acceptability - The tomato produced must have characteristics acceptable to the packer, shipper, wholesaler, retailer and consumer.  Included among these qualities are pack out, fruit shape, ripening ability, firmness, and flavor.

Current Variety Situation

 Seed Sources:
            Agrisales:  Agriset 761.
            BHN:  BHN 444, BHN 543, BHN 577, BHN 586, BHN 591, BHN 640.
            Harris Moran:  HMX 1803.
            Seminis:  Florida 47, Florida 91, Sanibel, Sunpac, PX 150535, EX 1405037, SVR 1432427.
            Sakata: XTM 0227
            Syngenta:  RFT 0417, RFT 0849
            University of Florida: Fla. 7810, Fla. 7926, Fla. 7973. 

 Seed Sources:
            Agrisales:  Lucky 13
            BHN:  BHN 640, BHN 650.
            Harris Moran: HMX 1803.
            Sakata: XTM 0227, XTM 0230, XTM 0231.
            Seminis: Florida 47, Florida 91, Sanibel, Solar Set, SVR 1405037.
            University of Florida: Solar Fire, Fla.. 7810, Fla. 7885 B.

The nitrogen (N) cycle is a set of transformations that affect N in the biosphere. Through a series of microbial transformations in the soil, N is made available to vegetables. Thus, knowledge of this cycle by which N passes from air to soil to organisms and back to air, and how the components of the cycle are affected by human activities, is required to design effective strategies for decreasing undesirable losses of N from vegetable production to the environment.

Adequate management of fertilization and irrigation has always been recognized as one of the keys to successful vegetable production in Florida. Thus, fertilization and irrigation practices have aimed at supplying enough nutrients and water to ensure economical yields. Since up to 200lbs/A of exogenous N are recommended for vegetable production in Florida, and fertilizer use efficiency seldom exceeds 75%, it is likely that fertilization affects the N cycle. Best Management Practices (BMPs) aim at reconciling the needs of economical vegetable crop production with those of environmental protection. Efficient BMP implementation, therefore, requires an understanding of how current cultural practices affect the N cycle in commercial vegetable fields.  It is likely that a complete understanding of these issues by farmers and vegetable professionals will be a prerequisite for the success of the BMP program.

The goal of this article is to present the N cycle as it relates to crop production.  A description of (1) how fertilization and irrigation practices affect the N cycle, and (2) how the proposed BMPs may help reduce the environmental impact of these cultural practices will be provided in the next issue of the Vegetarian.

Because the N cycle is a “cycle”, it has no clear beginning and no end. Hence, for the sake of presentation, this description of the cycle starts with N in the soil organic matter where N is in the form of amino acid, proteins, and nucleic acids (Fig. 1). In the soil, N found in decomposing organic matter may be converted into inorganic N forms by soil microorganisms (bacteria and fungi) in a process called mineralization (step 1). Those bacteria and fungi, also called decomposers, may be found in the upper soil layer. They chemically transform the N found in organic matter from amino-N (NH₂) to ammonium (NH₄⁺).
            Step 1: Organic matter à Ammonium
                    R-NH₂  à NH₄⁺ 

Nitrogen in the form of NH₄⁺ can then be adsorbed (step 2) onto the surfaces of clay particles in the soil. The NH₄ ion that has a positive charge may be held by soil colloids because they have a negative charge. This process is called micelle fixation.
            Step 2: Ammonium in solution à adsorbed ammonium à ammonium back into solution
                    NH₄⁺ aqueous à NH₄^{+ … -} soil colloid à NH₄⁺ aqueous

As this fixation is reversible, NH₄⁺ may be released from the colloids by way of cation exchange. When released, NH₄⁺may be chemically altered into nitrite (NO2^-) by a specific type of autotrophic bacteria belonging to the genus Nitrosomonas. Nitrosomonas are autotrophic bacteria that can synthesize their own organic N compounds from inorganic N sources (step 3a). Then, NO2^- may be quickly converted into nitrate (NO3^-) by another type of bacteria belonging to the genus Nitrobacter (step 3b). Both of these processes involve chemical oxidation