Such studies indicate that substantial weed losses will occur if weeds are not controlled. Durations of weed interference 1, 2, 3, 4 and 5 correspond to numbers of days after plot establishment of 0, 7, 21, 35 and 49 , 0, 7, 39 Table 3. Hoeing also results in damage to lettuce plants Dusky and Stall, Environmental concerns, among others, call for reduced fertilizer application due to its potential adverse effect on wetland ecosystems which are closely linked to agricultural lands. With this approach, mixtures of two or more components can be studied Rejmanek et al. Substantially greater biomass was achieved in the spring Table 3. The effect of the duration of weed interference was assessed at 2 weed densities that fall within the range of what might be encountered under commercial production conditions.
As density is increased, indices that quantify competition in replacement series tend to become less density dependent Cousens, Plant competition studies provide a means of evaluating the effects that certain management practices have on weed and crop interactions Conolly, Wilson reviewed literature concerning studies in which attempts were made to separate competitive interactions occurring between shoots from those arising in the root environment. Competition refers to situations in which the growth of plants interacting with one another is limited due to consumable resources being quantitatively inadequate Goldberg, ; Radosevich and Holt, Common purslane Portulaca oleracea L.
These differences occurred regardless of whether one half or one third of the broadcast rate was used in the band application and, therefore, may be due to more than optimization of rate.
Although the crop was affected by spiny amaranth interference, the immediate cause of yield loss to the weed does not appear to be due to interference with the P nutrition of the crop.
Under low weed density there was no significant effect of duration of weed interference on lettuce yields. This gybridus because soil P in the root 83 microenvironment was not altered by P uptake for a distance greater than 1 mm away from the root.
litsrature Fertilizer P application resulted in higher spiny amaranth P concentrations, which were also greater with the broadcast than the band application. This is in contrast to another weedy amaranthus species, redroot Table 3.
Literature review on amaranthus hybridus – Don’t have time to do homework
In the spring ofN concentrations reciew influenced by duration of weed interference Table 3. Field studies in England showed that weed densities of 65 per m2 resulted in complete loss of marketable yield when weeds were allowed to remain present in the crop Roberts et al. In portions of the study conducted at low N, ryegrass negatively affected red clover at low P and K fertility but not when P and K levels were increased.
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: Lettuce in the spring experiment was only partially trimmed in contrast to the trimmed lettuce of the study.
In the spring experiment Ca concentrations showed a negative response to P application but did not differ for the two P application methods Table 3.
Thus, under the low P fertility conditions of these experiments, spiny amaranth growth, as literture in per plant biomass, was similar with or without the addition of fertilizer P. Harvest involved excising shoots just above the soil surface. In the fall experiment Mg concentrations showed a response to duration of weed interference but not to the other oiterature factors Table 3. The replacement design is used for determining which of two components of a binary mixture is the better competitor.
Spiny amaranth plants removed from plots were dried at 60 C. Each of these methods is useful for answering a unique set of questions Cousens, Barley was sown at 7, 21 and 31 days after lambsquarters and three harvests were made for each sowing. The sensitivity to shading which would occur in competition for light could be expected to vary with plant species. Using the same procedure as in the initial filling, additional soil was added to again fill the pots.
Yield differences for the P application treatments would therefore have occurred as a result of the nutritional status that prevailed early in the season, when a response to P was evident.
Aldrich cites that environmental conditions would preclude competition for CO2 and In light of this situation, modifications or extensions of these basic methods of analysis of plant competition have been proposed.
However, Glauninger and Holzner consider space to be just the combined effects of competition for light, nutrients and water.
Literature review on amaranthus hybridus
Harvest dates are given in Table 3. For lettuce, Roberts et al.
Consequently, competition for mobile resources could begin sooner than for less mobile ones. Soil moisture levels can also influence the nature of competition that occurs between plant species. Pots in which plants were grown were plastic containers, measuring 12 cm in diameter and 21 cm deep and having 4 amarajthus of 0. Lettuce is particularly sensitive to phosphorus supply during early growth.
Its herbicidal activity at a given use rate was found to be less on histosols than on mineral soil Braverman, Locasio, Dusky and Hornsby, On the other hand, relatively immobile resources, such as phosphorus, would only be taken up from soil in close proximity to roots of the individual plants. Comparison of spring yields with those of the more thoroughly trimmed lettuce of spring does suggest, however, that the yields of the latter were greater Table 3.
Samples were thoroughly mixed following grinding and a subsample of the ground material was used for analysis. Spiny amaranth generally grew as well with or without the addition of P ln.