PROBLEM: How can we effectively
kill weeds with the lowest concentration of salt
without affecting the surrounding environment?
Sunlight - PRIORITISED FACTOR 1
Temperature
Soil
Water
Cost
"All things need energy to grow" (GardeningKnowHow, 2018).
Photosynthesis is how light can affect the growth of a plant.
Without light, a plant will not be able to produce energy to grow.
However, trees that grow in the shade often tend to grow taller and the taller plants receive enough light to survive and reproduce.
Sunlight is a key factor required for the growth of weeds and needs to be eliminated to kill them.
High temperatures
Low temperatures
Effects the heat on photosynthesis and when temperatures rise, so do photosynthesis and respiration.
The two processes become unbalanced when high temperatures are reached.
Extreme heat slows down plant growth.
Low temperatures triggers the plant to reduce growth and store energy.
As temperatures approach freezing, the plant growth stops and becomes dormant.
The plant is better able to withstand cold temperatures when dormant which stumps its plant growth.
Therefore, room temperature is the best option.
Salt raises soil salinity which dehydrate the roots of plants and keeps them from absorbing nutrients if too much salt is added or the concentration is too high.
The soil must be consistent.
Environmental Impact
On soil
On plants
“The accumulation of dissolved salts in the soil water inhibits plant growth” (Munns, CSIRO).
Therefore, increased amounts of salt in the soil can affect the ability of plants to effectively germinate and grow.
Salt in the soil can cause “reduced infiltration, [the process in which water enters the soil], affects the rate which water flows through the soil and can cause the blockage of avenues for water and roots to move through the soil” (Pearson, Montana State University, 2003)
Over time, the salt can cause extensive damage to the soil, making it unusable for farming and other uses, as most plants are unable to survive in these conditions.
“Salt poising is costing the world $27.3 billion (USD) in lost crop production” (Stallard, 2014).
This issue is leading to major problems including decreased employment opportunities, increased health problems in humans and animals, infrastructure deterioration and the reduction of a farms property value if it contains degraded land.
Not to over-water because that is the common death of plants.
If the weeds are around plants with large or thin leaves than they need more water than succulent plants.
We must consider the weather and environment conditions such as rain fall because if the rainfall levels are high, we cannot use a lot of water. But if rainfall levels are low then we must use a substantial amount of water.
Investigation of Factor
Conduct the experiment in shade as research states that it is the most effective in growing plants and killing weeds.
Other Factors
Controllable Factors
Salt - PRIORITISED FACTOR 2
Salt concentration
Mentions that it should be watered down with a large amount of water because too much salt will kill plants.
There is a size that is recommended which is Rock Salt because it is large and will cover a larger area, it is less expensive than table salt.
There is no exact concentration mentioned online for what is most effective to kill weeds.
Salt considerations
Salt stays in soil so it can affect it long-term.
It can kill flowers and crops.
Investigation of Factor
The salt concentration will act as the independent variable in the practical. Each garden bed with existing plants and weeds will have different amounts of salt and the most effective concentration will be presented.
Ineffectively Controlled Factors
The amount of water poured within each bed plant will be kept the same in order to allow the results to be reliable.
The experiment will be conducted inside at room temperature and applies to every garden bed being utilised.
The type of soil will be kept the same and must be consistent for reliable results.
Cost cannot be effectively controlled and is considered as a limitation to the practical as the same type of soil and salt is being used. Therefore, the results will only be specific and applicable to those specific brands and does not provide information as to whether or not a cheaper or more expensive brand is effective.