Data for monocultures of a density of one plant per pot were excluded from this analysis. In the fall experiment lettuce yields were essentially not affected by spiny amaranth Table 3. The methodology used in this study, therefore, was chosen to enable some comparison of methods for use in the assessment of competition as influenced by P fertility. A replacement study design at a series of densities was used for these studies. Nevertheless, it has been demonstrated that nutrients can be important in influencing the outcome of interspecific plant competition in agricultural settings Hall, b; Siddiqi et al. In anticipation of the adoption of a banded fertilizer P application practice, studies were carried out to determine how this might influence the impact of weed interference on lettuce. Conventional analysis of replacement series studies uses expected yields as a reference from which inferences about competition are made Jolliffe et al.

While weed control is commonly employed in commercial lettuce production, detailed documentation of the effects of uncontrolled weed growth on lettuce is scarce. Current environmental and economic issues, however, compel growers to reduce fertilizer P use Alvarez and Sanchez, ; Sanchez et al. Following removal of spiny amaranth, these plots were maintained free of all weeds. Yields decreased in a linear fashion with duration of weed interference in the spring of , suggesting that weeds began to affect yields beginning with the earliest durations of weed interference. Several methods can be used to assess interference between different plant species when grown in mixture Cousens, The 21 day planting resulted in weed and crop coexisting with neither becoming dominant.

This was shown by measuring uptake of dual isotopes of P. In amaranthuz fall of trimmed heads were used. The highest rates used were adequate to give optimal yields when this was the only source of P fertilization.

literature review on amaranthus hybridus

Prior to selecting the field location for each experiment, soil was sampled and analyzed for nutrients as described by Sanchez The effect of high weed density was more pronounced than that of low weed density for each of untrimmed and trimmed lettuce yields.


Yields decreased in a linear fashion with duration of weed interference amarantyus the spring ofsuggesting that weeds began to affect yields beginning with the literaature durations of weed interference. Concentrations of P in lettuce ranged from 0.

Samples were thoroughly mixed following grinding and a subsample of the ground material amaraanthus used for analysis. Lettuce tissue P concentrations litrrature the yield response to P fertilization; P being least with no added P, intermediate with banded P and highest with broadcast P.

The effect of P fertility on biomass production by 17 plant species occurring as weeds in southern United States was studied Hoveland et al. Restoration of the supply of each of the nutrients resulted in a rapid increase in plant growth rate.

literature review on amaranthus hybridus

Log transformation was made after addition of 1 to data. Once established, plots were maintained free of unwanted weeds by hand weeding or hoeing. Weeds adversely affect crops due to competition for light, water and nutrients Patterson, Amaranths are recorded as food plants for some Lepidoptera butterfly and moth species including the nutmeg moth and various case-bearer moths of the genus Coleophora: Several studies provide evidence for the occurrence of competition for nutrients other than N between roots Caldwell et al.

I also am greatly indebted to the faculty at the Everglades Research and Education Center at Belle Glade for valuable assistance and encouragement they provided me. Greatest yields were obtained in the spring of Table 3. In lettuce production on south Florida histosols fertilizer P is applied prior to planting the crop Sanchez, Factors for which Plants Compete Of the factors that influence plant growth some are of a consumable nature nutrients, water, CO2, 02 and light while others are conditions, e.

Experiments in this study were therefore designed so that competition between lettuce and spiny amaranth grown under varied P regimes could be assessed using both replacement series analysis techniques Conolly, ; DeWit and Van Den Bergh, ; Rejmanek et al.

Spiny amaranth biomass showed a positive response to P application Table 3.

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However, weeds in the crop row remain uncontrolled with this measure. The study also suggested that proper timing of fertilization, in conjunction with weed control, can be valuable in enhancing the ability of the crop to llterature weeds that survive control measures. Crisphead lettuce ‘Southbay’ Guzman, was direct seeded two rows to a litsrature.


Deionized water was applied to the surface as needed in order to keep the vermiculite moist until seedling emergence was complete. An additional distinction is made that light is available in a fixed amount while water and nutrients, though available in limited amounts, can be manipulated by the grower Glauninger and Holzner, hybridu While weed control is commonly employed in commercial lettuce production, detailed documentation of the effects of uncontrolled weed growth on lettuce is scarce.

Yields were consistent for amaraanthus durations of weed interference of 0 through 28 days and appeared to decrease only when amaranth was present through harvest of the crop 36 days after plot establishment. Foliage of adjacent plants at low density never overlapped but foliage did overlap extensively for plants at revirw high density.

Another application of the study of plant competition in agriculture concerns the case in which crop plants grow in mixture with plants that are not part of the intended crop. Falseflax uptake of P, conversely, was greater in mixture than in monoculture. Cylinders used in Preliminary 1 were constructed of window screen.

Literature review on amaranthus hybridus

Under low weed density there was no significant effect of duration of weed interference on lettuce yields. These competitive interactions were differentially influenced by soil fertility in several ways.

literature review on amaranthus hybridus

Prior to CP addition, soil was fumigated in steel drums ammaranthus methyl bromide, allowed to aerate for at least 3 weeks, and then sieved through a 1 cm mesh galvanized screen.