Nutrient Loss

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Introduction

Nutrients are needed by organisms for their normal growth and development. Most of the organisms obtain nutrients from the surrounding environment. Animals get most of the nutrients in the form of food and air. Plants obtain nutrients present in the soil as well as air.

The conservation of nutrients in the environment is essential for the maintenance of life in an ecosystem. Soil is the major source of nutrients in any ecosystem. All the nutrients enter the food chain of an ecosystem through plants that get them from the soil. The conservation of nutrients in soil ensures that nutrients remain conserved in an ecosystem. 

Unfortunately, in this age of modernization, nutrients are continuously being lost from soil due to several reasons. In this article, we will mainly focus on the ways by which nutrients are lost from the soil. We will talk about the causes of nutrient loss and its consequences. In the end, we will also mention ways to conserve soil nutrients and improve the fertility of the soil.

Major Nutrients in Soil

Before going into the discussion of nutrient loss, let us first talk about the important nutrients present in the soil.

They are divided into two categories;

  • Major elements
  • Trace elements

Major Elements

These are the nutrients that are required by plants in major amounts. These include the following;

  • Nitrogen: It is the key nutrient for making proteins, nucleic acids, and chlorophyll. Plants absorb nitrogen in the form of nitrates that are made from atmospheric nitrogen via nitrogen fixation.
  • Phosphorus: It is needed to make ATP and other nucleotides as well as nucleic acids. Plants take up phosphorus from the soil in the form of orthophosphate or some organic phosphates.
  • Potassium: It provides immunity to plants. Potassium is also used to make certain compounds and maintain homeostasis in plants. It is absorbed from soil in the form of potassium salts.
  • Calcium: it is needed for the growth of roots and leaves as well as the eruption of new root hairs. It is also absorbed from soil as calcium salts.
  • Magnesium: It is the key mineral present in chlorophyll. Plants need magnesium to make chlorophyll. It is absorbed from the soil along with other minerals.
  • Sulphur: it is needed to make amino acids and proteins. It is absorbed by plants in the form of sulphate ions present in the soil.

Trace Elements

These are the nutrients that are required only in trace quantities by the plants. The important trace elements are listed below.

  • Iron
  • Manganese
  • Copper
  • Zinc
  • Boron
  • Molybdenum

Ways of Nutrient Loss

Nutrients can be lost from the soil in a number of ways. We will discuss only the following methods of nutrient loss in our article.

  • Leaching
  • Soil erosion
  • Monocropping
  • Continuous cropping
  • Change in pH
  • Burning of crops

A brief detail of all these processes is given below.

Leaching

Leaching is the process by which water-soluble nutrients like nitrates, phosphates, and other salts are lost from the soil. It is one of the major causes of soil infertility.

Mechanism

Leaching occurs when excess water flows over soil due to heavy rainfall or excessive irrigation. Water takes away the water-soluble salts and dumps them into the streams, rivers, and other water bodies. Loss of nitrates and phosphate ions present in the soil mainly occurs via leaching. Water also takes away other minerals present in the soil like calcium, sulphur, potassium, magnesium, etc. 

Impacts

Leaching has harmful impacts on crop production and overall yield as well as on the environment.

  • Nitrates, phosphates, and other important nutrients are lost from the soil. It causes abnormal growth of plants. The plants grown in such soil will have thick brittle leaves, short stems with shrunken appearance, and weak growing points, etc. Plants will show stunted growth.
  • Leaching decreases soil fertility. The crop yield is much reduced. Continuous leaching makes the soil unfit for cultivation.
  • Leaching imposes serious threats to the environment. It is the process by which excess salts and minerals get added to the water bodies. Water takes away all the water-soluble minerals from the soil and dumps them into freshwater bodies. This water causes some serious health issues when consumed by livestock animals and humans.
  • Leaching also disturbs the groundwater. Water not only carries minerals to freshwater bodies but also deep in the earth. The minerals are lost from soil and get added to the groundwater contaminating it. nitrates, phosphates, sulphates and other such contaminants get added to the groundwater via leaching. Several health issues may arise if this water is consumed without proper filtration and processing.

Soil Erosion

It is the displacement of the upper layers of soils. Erosion is one of the major causes of soil degradation throughout the world. It causes the rapid loss of nutrients from the soil.

Mechanisms

Soil erosion is caused by certain factors called erosive agents. Erosion can occur by the following mechanisms.

  • Rainfall and runoff causes soil erosion in four ways;
  • Splash erosion: It is the first stage that occurs when a raindrop falls on the soil surface. A small hole is created in soil by ejecting the soil particles.
  • Sheet erosion: It occurs when the rainfall is greater than the capacity of water to infiltrate. Water flows over soil and takes away the loose soil particles along with it.
  • Rill erosion: It occurs when small water flow paths are formed by displacing the top layer of soil.
  • Gully erosion: It occurs when rapid flowing water paths are created by removing soil to a considerable depth.
  • Rivers and streams create soil erosion when water rapidly flows in a linear fashion. The soil is continuously removed from the bed as well as sides of the water flow.
  • Floods also cause soil erosion and nutrient loss. Extremely high flows of large water volumes during floods erode the soil to the bedrock level. They cause extreme local erosions as seen in the flood regions.
  • Wind erosion is important in arid and semi-arid areas. Wind removes the top layer of soil and causes nutrient loss. It is a major problem in arid areas during droughts.
  • The mass movement of the rocks due to gravity also affects the nutrients present in the soil.

Impacts

The impacts of soil erosion on plants as well as the environment are as follows.

  • It is the major cause of land degradation. The previously agriculture land becomes unfit for any type of plant growth due to soil erosion. Wind and water erosion are the major culprits involved.
  • It not only affects the plant growth also disturbs life in the aquatic environment. The soil sediments flowing in water bodies due to erosion are the major cause of water pollution.
  • The soil particles are taken along with the air during wind erosion cause air pollution. These particles may become contaminated and cause serious health effects when inspired.

Monocropping

Monocropping is referred to the condition when only one type of crop is cultivated again and again on the same agricultural land. A single crop is grown every year without rotation with the other crops.

It is an economically very efficient system that allows farmers to have a consistent crop every year. They can cultivate only the most profitable crop every time and have the same yield without many efforts.

However, monocropping disturbs the normal ecology of soil. The same crop utilizes one or more specific nutrients from the soil that becomes exhausted in that particular farm. Moreover, it also creates a disturbed ecosystem in soil that harbors more pests. The land becomes less fertile and more dependent on pesticides and insecticides.

Continuous Cropping

Another reason for nutrient loss from the soil is continuous cropping. It is the phenomenon of growing crops on the same agriculture land without any break between two crops. The land is not prepared properly for the next crop.

It greatly exhausts the soil and deprives it of the natural nutrients. Continuous cropping causes degradation of the organic matter present in the soil. The soil structure also becomes degraded and the land loses its fertility over time.

Changes in Soil pH

The pH of soil affects the water solubility of various nutrients present in the soil. It can change the ionic forms of nutrients. Any change in soil pH can affect nutrient availability by changing their ionic forms.

Nutrients are lost when the pH of the soil changes due to the use of acidic or basic fertilizers. Extreme pH values result in a deficiency of nutrients in the soil. Very low pH decreases the availability of trace elements while very high pH decreases the presence of major elements in the soil.

Burning of Crops

In many under-developed countries of the world, it is a traditional practice to burn the remains of the previous crop before cultivating the next one. The fields are set on fire. These fires not only cause air pollution but also decrease the availability of nutrients in the soil.

The burning of crop residues is another cause of nutrients loss from the soil. The combustion process consumes most of the organic nutrients present in the soil. It also decreases the activity of different microbes. As a result, various nutrients provided by these microbes become unavailable for plants such as nitrates.

Ways to Prevent Nutrient Loss

Human activities and influences are the major cause of nutrient loss from soil. It can be prevented by adopting the following measures.

  • Nutrients can be added to the soil by using appropriate fertilizers in adequate amounts. The use of too much fertilizer will affect the soil pH resulting in further nutrient loss.
  • The fertilizers should be added when heavy rains are not expected. Otherwise, rainfall will result in leaching of the nutrients.
  • Make wetlands or filter beds to recover nutrients from runoff or drainage water.
  • Always apply fertilizers according to the need of the soil.
  • Get your soil tested for pH and nutrients to have a better idea of which type of fertilizer you need.

The list of necessary measures to prevent nutrient loss is long and never-ending.

Summary

Soil is the major source of nutrients in any ecosystem. Plants obtain nutrients directly from the soil. The growth of producers in any ecosystem is directly linked to the availability of nutrients in the soil.

Nutrients are lost from soil due to natural causes as well as human activities.

Major elements present in the soil are nitrogen, phosphorus, potassium, calcium, sulphur, and magnesium.

The trace elements include iron, copper, zinc, manganese, etc.

Leaching runoff is the process by which nutrients present in the soil are carried away by water.

  • Water carries the nutrients into the freshwater bodies or to groundwater.
  • The water causes health effects when consumed by animals of humans.
  • The soil becomes unfit for crops.

Soil erosion causes nutrient loss by disturbing the upper layers. The major nutrients are carried away from the land along with the superficial soil layers. Different agents that cause erosion are:

  • Rainfalls
  • Winds
  • Rivers and streams
  • Floods
  • Mass movements of rocks

Soil erosion disturbs plant growth by causing land degradation, affects aquatic life by causing water pollution, and causes respiratory problems in humans due to air pollution.

Monocropping results in the loss of certain nutrients from the soil that are used by the same crop cultivated every year on the same land. It makes the land more dependent on pesticides.

Continuous cropping without any break exhausts the soil making it unfit for cultivation after continuous cycles.

Any change in the pH of soil affects the availability of the nutrients by changing their water-solubility. Extreme pH changes are the major causes of nutrient loss.

Burning the remains of previous crops consumes all the organic nutrients present in the soil. It also stops the microbial activity causing considerable nutrient loss.

Most of the causes of nutrient loss are preventable by adopting an environment friendly behavior by humans.

References

  1. “WQ262 Nitrogen in the Environment: Leaching | University of Missouri Extension”. Extension.missouri.edu. Retrieved 2013-03-08.
  2. Blanco, Humberto & Lal, Rattan (2010). “Soil and water conservation”. Principles of Soil Conservation and Management. Springer. p. 2. ISBN 978-90-481-8529-0.
  3. Toy, Terrence J.; et al. (2002). Soil Erosion: Processes, Prediction, Measurement, and Control. John Wiley & Sons. p. 1. ISBN 978-0-471-38369-7.
  4.  Poly- and Monocultures: The Good, the Bad, and the Ugly