Why do you have to grow a crop on your septage land application site?
There are several reasons. An easy answer is both state and federal laws require a crop to be grown but this avoids
the question. Growing a crop will reduce run off and soil erosion. We want to keep the septage waste on the area
where it was applied. If it moves to another part of the field, that part of the field receives more septage than was
planned and permitted. This may be more than the soil in that part of the field can treat. If the septage waste moves
out of the field, it may enter surface waters. This is a no-no. The goal is to keep the wastes in the part of the field
where they were applied.
The main reason for growing a crop is to remove some nitrogen and phosphorus from the “soil water” if we may call
the liquid part of the septage waste in the soil “soil water”. Soil has a limited capacity to remove nutrients from
wastes. The crop uses some of these nutrients and when the crop is harvested and removed those nutrients are also
removed and the soil in the land application field does not have to continue holding those nutrients. The second
septage is added to the soil either by surface application or injection a large amount of septage is in contact with a
small amount of soil.
There are several reasons. An easy answer is both state and federal laws require a crop to be grown but this avoids
the question. Growing a crop will reduce run off and soil erosion. We want to keep the septage waste on the area
where it was applied. If it moves to another part of the field, that part of the field receives more septage than was
planned and permitted. This may be more than the soil in that part of the field can treat. If the septage waste moves
out of the field, it may enter surface waters. This is a no-no. The goal is to keep the wastes in the part of the field
where they were applied.
The main reason for growing a crop is to remove some nitrogen and phosphorus from the “soil water” if we may call
the liquid part of the septage waste in the soil “soil water”. Soil has a limited capacity to remove nutrients from
wastes. The crop uses some of these nutrients and when the crop is harvested and removed those nutrients are also
removed and the soil in the land application field does not have to continue holding those nutrients. The second
septage is added to the soil either by surface application or injection a large amount of septage is in contact with a
small amount of soil.
This contains more nutrients than that amount of soil can treat.
The “soil water” will move away from that spot. As it moves
through “new” soil, that soil will remove additional nutrients.
As the “soil water” moves through the soil, the soil the septage
has moved through will have removed the maximum amount
of nutrients it can. Crop roots explore the soil for water and
nutrients, and both are components of septage. The roots will
remove some of the nutrients in the soil. As the crop grows,
the roots will remove more of the nutrients that were removed
by the soil from the septage. When the crop is harvested,
those nutrients are taken from the soil in the septage application
The “soil water” will move away from that spot. As it moves
through “new” soil, that soil will remove additional nutrients.
As the “soil water” moves through the soil, the soil the septage
has moved through will have removed the maximum amount
of nutrients it can. Crop roots explore the soil for water and
nutrients, and both are components of septage. The roots will
remove some of the nutrients in the soil. As the crop grows,
the roots will remove more of the nutrients that were removed
by the soil from the septage. When the crop is harvested,
those nutrients are taken from the soil in the septage application
field to another field. The harvested crop is not considered a waste and is not regulated. Each additional crop in that
field will remove more of the nutrients that were removed by the soil from the septage application. Harvesting and
removing the crop will lower the level of nutrients in the soil. If the crop is not harvested, the crop will take up the
nutrients but when the crop dies, the nutrients are added back to the soil. Growing crops, harvesting and removing as
much of the plant as possible will shorten the time until septage can be applied to that field again. The amount of
nutrients in the soil before septage is applied will determine the rate at which you may apply septage. This means you
must not only be a septage hauler but also a crop manager.
The crop you choose to grow, depends on what you want to do with it. You may want to raise a crop that can be
sold. What does the buyer want? If the crop is to be fed to horses, a grass crop is best. If the crop is to be sold to a
grain elevator, the crop will depend on the area of the state the field is located. In large areas of the northern part of
Michigan, corn cannot be grown for grain so you will have to choose another crop. If the crop is to be fed to cows,
you can grow corn for silage. This is actually better than corn for grain because almost the entire crop above the
ground will be removed and more nutrients will be removed.
You do not have to sell the crop. The crop may be harvested and removed and then applied to another field as green
manure. Because the crop is not regulated, the field you add the green manure to is not required to meet the criteria
for a field in which septage is applied.
There are a variety of crops that may be grown in the field where septage waste is applied. Different crops have
different capacities to remove nutrients. You make the decision of which crop to grow. If you can use a crop, choose
that crop. If you wish to use the crop to pay some of your expenses, the buyer will help you make the choice. If you
are independently wealthy (isn’t the goal of all septage haulers to be independently wealthy?), you make the choice.
Remember, the goal os the crop is to reduce soil erosion and to remove as many nutrients from the soil as possible.
Some additional questions to consider. Who will plant the crop? Who will spray the crop if it is required? Who will
harvest the crop? Do you have the necessary equipment? This is an opportunity to broaden your expertise, become a
crop specialist.
If you are considering a new field in which to apply septage waste, consider the amount of nutrients, especially
phosphorous, that the soil may have before you enter an agreement with a land owner to rent or buy that field. Most
farmers do not add excessive amounts of fertilizer. There are some farmers who have spread large amount of animal
manure on fields and the phosphorous levels are so high they may not add more manure. In that case you won’t be
able to add any septage waste. Before you buy or rent a field, soil test!
Dr. Del Mokma is a Soil Scientist and professor at Michigan State University
field will remove more of the nutrients that were removed by the soil from the septage application. Harvesting and
removing the crop will lower the level of nutrients in the soil. If the crop is not harvested, the crop will take up the
nutrients but when the crop dies, the nutrients are added back to the soil. Growing crops, harvesting and removing as
much of the plant as possible will shorten the time until septage can be applied to that field again. The amount of
nutrients in the soil before septage is applied will determine the rate at which you may apply septage. This means you
must not only be a septage hauler but also a crop manager.
The crop you choose to grow, depends on what you want to do with it. You may want to raise a crop that can be
sold. What does the buyer want? If the crop is to be fed to horses, a grass crop is best. If the crop is to be sold to a
grain elevator, the crop will depend on the area of the state the field is located. In large areas of the northern part of
Michigan, corn cannot be grown for grain so you will have to choose another crop. If the crop is to be fed to cows,
you can grow corn for silage. This is actually better than corn for grain because almost the entire crop above the
ground will be removed and more nutrients will be removed.
You do not have to sell the crop. The crop may be harvested and removed and then applied to another field as green
manure. Because the crop is not regulated, the field you add the green manure to is not required to meet the criteria
for a field in which septage is applied.
There are a variety of crops that may be grown in the field where septage waste is applied. Different crops have
different capacities to remove nutrients. You make the decision of which crop to grow. If you can use a crop, choose
that crop. If you wish to use the crop to pay some of your expenses, the buyer will help you make the choice. If you
are independently wealthy (isn’t the goal of all septage haulers to be independently wealthy?), you make the choice.
Remember, the goal os the crop is to reduce soil erosion and to remove as many nutrients from the soil as possible.
Some additional questions to consider. Who will plant the crop? Who will spray the crop if it is required? Who will
harvest the crop? Do you have the necessary equipment? This is an opportunity to broaden your expertise, become a
crop specialist.
If you are considering a new field in which to apply septage waste, consider the amount of nutrients, especially
phosphorous, that the soil may have before you enter an agreement with a land owner to rent or buy that field. Most
farmers do not add excessive amounts of fertilizer. There are some farmers who have spread large amount of animal
manure on fields and the phosphorous levels are so high they may not add more manure. In that case you won’t be
able to add any septage waste. Before you buy or rent a field, soil test!
Dr. Del Mokma is a Soil Scientist and professor at Michigan State University
The Sanitation Journal is a monthly trade publication that caters to the portable restroom industry. Each month
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today and make sure you never miss an issue.
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Considerations For Ground
Application
Application
Dr. Del Mokma
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Serving the American Liquid Waste Industry Since 2002