inely prepared seed bed. The
crop requires supplemental irrigation. Both overhead and furrow irrigation
should be available. The soil surface must be kept moist for uniform
germination and emergence; irrigation by sprinkler is advised to enhance
seedling establishment and minimize soil crusting. After the stand is
established, water is best applied by furrow irrigation.
Marigolds are usually grown in double rows on 75- or 100-cm beds. The crop is
sown as early as possible, for an early start promotes flowering. Final stands
in the row should be 15 to 25 cm. Under optimal germination rates, the seeding
level should be 0.37 kg/ha.
Phosphorus is required to promote flowering. Nitrogen should be applied two or
three times during the growing season. The effects of nutrients, growth
regulators, planting time, and plant density on plant growth, flower yield and
quality, and seed yield have been reported elsewhere (Parmar and Singh 1983;
Arora and Khanna 1986; Gowda and Jayanthi 1986; Ravindran et al. 1986; Shedeed
et al. 1986; Anuradha et al. 1988a, 1988b, 1990; Yadav and Bose 1988;
Arulmozhiyan and Pappaiah 1989; Girwani et al. 1990; Tolman et al. 1990).
Marigold is often intercropped with other plants. Rotation with marigolds
reduces diseases of other crops (Medhane et al. 1985; Ijani and Mmbaga 1988;
Perwez et al. 1988; Abid and Maqbool 1990), and reduces nematode populations
(Prasad and Haque 1982; Baghel and Gupta 1986; Reddy et al. 1986; Alam et al.
1988). No pesticides are registered in the United States for use on marigolds
grown for xanthophyll production, so proper site selection to minimize pest
problems is important. Marigolds are susceptible to root diseases, but risk
can be minimized by not planting marigolds in fields previously planted to
peppers and by avoiding fields that are prone to standing water. Mites can be
a severe problem on marigolds, but miticides are not registered for use on
marigolds grown for xanthophyll production or feed use.
Cultivation to control weeds is advised until the crop canopy has closed
because as no herbicides are reg-istered for use on marigolds grown for direct
use in poultry feed or for xanthophyll production. Flowers are harvested by
hand when plants have, on the average, two or three fully developed flowers
(about 90 days after planting). Subsequent harvests (up to two) can be made at
intervals of 3 to 5 weeks, depending on plant vigor. Mechanical harvesters are
also used; they generally limit the number of harvests to one because of plant
MFP can be extracted from the meal with warm (50° to 55°C) water
(BeMiller et al. 1989). MFP was determined to be a protein-polysaccharide.
One purified fraction of the polysaccharide portion was found to contain 3.75%
galacturonic acid and neutral sugars in the molar ratio: galactose (15):
glucose (7): arabinose (3). Methylation analysis indicates a highly branched,
acidic arabinoglucogalactan. Partial characterization of the protein part
indicated the presence of at least two very hydrophobic polypeptide
constituents (Wickramasingha 1990).
The crude extract was dark, and a procedure involving an oxidative pretreatment
of the meal prior to extraction of the gum was worked out to give preparations
of minimal color (BeMiller et al. 1989). Both the crude-extract and the
bleached MFP had emulsifying and emulsion stabilization powers for limonene
equivalent to those of gum arabic at equal concentrations (1 and 2.5%) and
slightly less than those of gum arabic for olive and castor oils (BeMiller et
al. 1989). It was not, however, possible to prepare high-solids, low-viscosity
solutions of MFP and, hence, not possible to prepare concentrated emulsions.
It was hypothesized that the difference in negative charge on the two molecules
(ca. 16% uronic acid in gum arabic vs. 3.75% uronic acid in MFP) might be the
reason for their different rheological behaviors. A project was undertaken to
increase the negative charge on MFP by sulfation. The net negative charge was
increased to 14.3 mole% without decreasing its emulsion-stabilizing properties.
The reduct