How can you tell the difference between a wheat crop and barley crop in the field?
build these competencies
using growth staging guides
A growth staging guide is like a reference or key for crop growth. These guides provide farmers, scientists and researchers with a common reference that allows them to monitor the development of a crop. Understanding growth stages also lets farmers determine when to use inputs like fertilizers and water.
Click here to explore the Canola Growth Stages guide from the Canola Council. Find more details on the Canola Encyclopedia by clicking here.
In what ways do these growth staging guides depend on knowledge of a plant’s life cycle?
How do these guides help farmers determine when to seed their crops and when to harvest them?
Click here to explore the Cereal Staging Guide from Alberta Agriculture, Forestry and Rural Development.
Click here to explore the Field Pea Growth Staging Guide. Find more detailed information on this crop and other pulses on the Alberta Pulse Growers website in Growing Pulses.
growth factors
In order to grow, plants need light, heat, air, water and nutrients. These are called growth factors.
These growth factors are not always equal. Plant growth is limited by the factor in the least supply. In other words, growth cannot be greater than that allowed by the most limiting factor.
In the prairie region, growth is most often limited by water. That is why irrigation almost always increases yields. After water, plant nutrients are most likely to be limiting factors.
Plant nutrients are made up of the fourteen essential elements that plants obtain from the soil. Some are required in relatively large quantities. Others are needed only in very small amounts.
In soils, the nutrients most likely to be limiting are nitrogen and phosphorus. When soil nutrients cannot produce a good crop yield, additional nutrients must be added. Applying too little nutrient will limit yield. Applying too much does not make economic sense and can impact the crop yield and harm the environment.
This can be illustrated by looking at a barrel filled with water. The level of water in the barrel represents the growth of the plant.
Even though the other growth factors are present in more than adequate amounts, the plant can not grow higher than allowed by the shortest plank in the barrel. In this example, water is the limiting factor.
Agriculture and Agri-Food Canada. Nutrient management planning. Government of Canada: Online. https://agriculture.canada.ca/en/agriculture-and-environment/soil-and-land/soil-nutrients/nutrient-management-planning
Liebig’s law of the minimum is a principle developed by Carl Sprengel, a botanist, and later made popular by Justus von Liebig, a scientist. Liebig used an image of a barrel with unequal planks to explain how plant growth is limited by the factor that is in the shortest supply – just like the level of water in the barrel is limited by the shortest plank.
Image: Public Domain via Wikimedia
farming stories
Farmers across the world – including those across Alberta – apply a practice called 4R Nutrient Stewardship. This practice focuses on where, when, what and how fertilizer is used on crops – applying the right type of fertilizer at the right rate, at the right time and in the right place.
Consider these other examples of the practices that Alberta farmers use.
Watch this original project AGRICULTURE video interview to understand more about some of the practices that Alberta farmers can use to grow healthy crops.
Watch this original project AGRICULTURE video interview to find out about the practices that two Alberta farmers use to make decisions about managing bugs and weeds.
growth decisions
Farmers make decisions every day that affect the crops they grow, livestock they raise and food they produce. Many of these decisions consider the growth factors that affect the yield of their crops. Practices that allow farmers to know their soil, what kind of nutrients they may be lacking and when to plant seeds increase plant growth and health as well as crop yields.
Consider the following example of decision-making from an Alberta grain farmer in an excerpt from the article Pay Dirt.
In what ways is the farmer in the article describing limiting growth factors?
You might just think of it as dirt, or you might not think about it at all. But in the agricultural industry, soil takes on a very different meaning – as one of the building blocks for all the life on Earth.
“In terms of a living entity, there is more life in soil than you would see anywhere on the planet,” said Len Kryzanowski, [a director] with Alberta Agriculture and Forestry. “For a farmer and for society in general, soil is definitely the foundation for our food system.”
Soil is a reservoir for nutrients and water. The material contains millions of living organisms. The micro-organisms in the soil include fungi, bacteria, insects and earthworms that all play vital parts in the health of the soil and in soil processes. For the soil to function at its best, these organisms need to be fed and balanced.
Like people, soils need balanced nutrition to be able to grow crops. In a closed-loop system, the plants die and return their nutrients to the soil, enabling the soil to grow more plants.
“In farming, because we’re actually removing parts of the crops, whether it’s vegetables from gardening or the seeds from grain we grow in the field, we’re removing the nutrients that make those components,” said Daryl Tuck, a farmer from Vegreville. And that’s why farmers often need to add fertilizer back into the soil to supply the nutrients that plants need….
Applying fertilizer helps farmers get the best production out of their land and the biggest crop possible. But in order to determine how much fertilizer they need, farmers need to test their soil.
“I take a sample of the soil from my field to get it analyzed for its nutrient content,” said Tuck. “This tells me how much available nutrient is in the soil before I decide how much I need to fertilize.”
Once he has his soil analysis, Tuck, who farms canola, peas and wheat on land settled by his great-grandfather, can crunch the numbers and make some decisions about how to balance the nutrients in his soil. It’s a delicate decision. Adding more fertilizer than the crop needs isn’t just a waste of money, it’s also a poor environmental decision because the unused fertilizer can leach off or seep into a waterway.
But there are also problems if Tuck doesn’t add enough fertilizer. If the crops don’t have enough nutrients, they might not grow as well as they could. “In different growing areas, the biggest factor that influences our fertilizer use is our average or expected rainfall. Crops require moisture to grow, and the more moisture we have (to a point), the more our crops will yield, and the more nutrients are needed to produce that crop and use that moisture,” he said.
…Different crops need different amounts of fertilizer.
“If I’m growing canola, in addition to the nitrogen, phosphate and potash fertilizer that I would put, I would also add sulphur fertilizer because canola uses a lot of it,” said Tuck. “On my farm, I have some poor-quality land and it’s not capable of producing a high-yielding crop. On those fields, I use less fertilizer because I can’t produce a crop and so it gets too costly to produce a crop where I am applying excessive amounts of fertilizer.”
Kienlen, A. (October 4, 2016). Pay Dirt. Grains West: Online. https://grainswest.com/2016/06/pay-dirt/
fertilizer choices
Some of the nutrients used by plants to support healthy growth come from fertilizers. These nutrients are the same, whether they come from organic or conventional fertilizers. Explore these SnapAG fact sheets from Agriculture in the Classroom Canada.
Find more information and references on fertilizer from Agriculture in the Classroom Canada by clicking here.
Find more information and references on the use of conventional and organic fertilizers from Agriculture in the Classroom Canada by clicking here.
resisting weeds
Herbicides kill unwanted plants — weeds — so crops can flourish. Weeds and other invasive plants are actually the most damaging pests for many agricultural crops because they compete for vital nutrients, space, water and sunlight.
Herbicide-resistant canola varieties allow farmers to treat fields with certain herbicides that would damage conventional canola. That means better weed control, less tillage, earlier seeding, higher yields and a cleaner crop at harvest.
Herbicide-resistant canola varieties also help farmers grow more on their farmland. This provides important benefits for the environment. The fields do not have to be tilled with a tractor to remove the weeds, which means that the soil is not disturbed. Soils that are not disturbed have more organic matter, more moisture and less erosion.
Consider what one farmer says about the benefits of herbicide-resistant canola.
“Weed control is essential in canola production,” says Alberta farmer, Jay Schultz. “Because if weeds take over they can take up a lot of yield by robbing canola of nutrients, space and sunlight.”
“Having access to different types of herbicide-tolerant canola is important because it allows us to rotate the herbicides we use and stay ahead of resistance,” Schultz points out.
