June 20, 2019 posted by

The reciprocal yield approach was preferred for the partitioning of interspecific and intraspecific competition effects and the measurement of interactions between density and proportion. Overall density is held constant for the series. In the spring of , N concentrations were influenced by duration of weed interference Table 3. It has been shown, however, that when fertilizer P is applied in a band below the crop row, optimum yields can be obtained with substantially reduced rates of P fertilizer on a field basis Sanchez et al. In another study the effect of interruptions in the supplies of N, P and K to lettuce during early growth following transplanting was assessed Burns, Hoeing also results in damage to lettuce plants Dusky and Stall,

Lettuce is particularly sensitive to phosphorus supply during early growth. Phosphorus application by each of the methods resulted in increased yields at all durations of weed interference. Studies have been conducted to compare some of the alternative approaches to competition analysis when applied to specific situations Rejmanek et al. This suggests that spiny amaranth may have been competing with lettuce for P; the more intense competition under the higher spiny amaranth density resulting in lowered P concentrations in lettuce. Actual means and regressions of yield on duration of weed interference are shown. This was demonstrated in greenhouse experiments where P was applied simultaneously by 2 methods Costigan,

Lettuce heads of these samples were cut up, dried and stored at 60 C. This can be accomplished by the selection of a suitable combination of density and experiment duration. For the duration of weed interference of 6 days, P concentrations were found to be greater for hybriduus broadcast applied P than for the other treatments. In the study by Roush et al. Only a limited amount of information is available on the effects of weed interference on lettuce.

Literature review on amaranthus hybridus

Water is one below-ground factor for which competition between weeds and crops can occur Aldrich, ; Griffin et al. The results obtained in competition studies can be influenced by a number of factors Aldrich, and basic methods are found to be biased with certain mixtures Connolly, This was shown by measuring uptake of dual isotopes of P.


This was 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. Studies on nutrients as limiting factors for which plants compete have most often considered N although any nutrient could conceivably be important in this context Zimdahl, hybrieus The purpose of these studies was to establish P fertility rates to be used in the competition studies. Other definitions for the luterature interference and competition are also found in the literature e.

Data for monocultures of a density of one plant per pot were excluded from this analysis. The levelling and tapping procedures were then repeated. While vegetable amaranth is used as a delicacy or a food staple in many parts of the world, use in the United States is limited to canned imports for ethnic uses, primarily in the New York City area.

Studies in chapter IV concern the determination of how P fertility influences the growth of each of the weed and the crop when grown in the presence of one another. Calcium concentrations in lettuce ranged from as literrature as 1.

literature review on amaranthus hybridus

Nutrient addition can indeed llterature the competitive interactions in plant mixtures Hall, b; Siddiqi et al. Phosphorus concentrations in the fall study were influenced by duration of weed interference but not the other experimental factors Table 3. While lettuce growth was dependent on P fertilization, this was not found to be the case for spiny amaranth.

These studies showed that elimination of weeds by hand at 3 weeks after emergence of the crop, with no additional weed removal, was sufficient to prevent yield loss. This study corroborates the findings of Sanchez et al. Interpretation of altered nutrient status of crops due to weed competition is probably dependent on the nature of competition. Direct comparison of yields for the two spring studies cannot be made due to differences in the degree of trimming used at harvest in the two experiments.


The crop responds to each of P and K amendment in a predictable manner on these soils Sanchez and Burdine, This response was attributed to the slow early growth of lettuce roots.

Literature review on amaranthus hybridus – Don’t have time to do homework

Their data also suggest that growth rate sensitivity to withholding N and K was not as great as for P deprivation, which resulted in abrupt cessation of growth once the nutrient was withheld for 9 days. Falseflax thus competed more strongly for P than flax, both interspecifically and intraspecifically. In each of the spring studies Tables 3.

literature review on amaranthus hybridus

These extended to 30 cm above the pot surface. In general, the principle factors affecting spiny amaranth biomass were the length of time it was grown DWI and the density at which it was grown.

Livid amaranth Amaranthus lividus L. Temperature may influence growth rates and competitive ability of weed species differentially Aldrich, Amarqnthus potential for nutrient addition to influence competitive relations between plants can be not only species dependent but also, for crops, cultivar dependent Siddiqi et al. Once this value is obtained a corresponding fertilizer P rate can be determined from a calibration curve Sanchez and Burdine, Competition was assessed based on analyses of individual plant weight, relative yields, relative crowding coefficients RCC and relative mixture response.

Using this approach, intraspecific competition is quantified by comparison of actual monoculture yields with projected yields.