This material addresses aspects of the following syllabus outcomes:
H1.1 explains the influence of the physical,
biological, social, historical and economic factors on sustainable
H2.1 describes the inputs, processes and interactions of plant production systems.
The work presented in the following section contributes towards understanding the following syllabus content areas:
Students learn about:
Soil, nutrients and water
Extract from Stage 6 Agriculture Syllabus NSW Board of Studies Amended 2009
Nitrogen is one of the most important nutrients for crop growth, second only to water, and is the major nutrient the producer can control. Nitrogen exists in many different chemical forms and passes around natural and agricultural ecosystems in a cycle. The various forms of nitrogen determine its availability to plants or whether nitrogen escapes and is no longer available to plants. The supply of useable nitrogen and the rate of losses from the soil affects the sustainability of production. Mismanaged, it can result in economic loss to the producer and have environmental repercussions, or both.
Nitrogen is one of the main chemical elements required for plant growth and reproduction. Nitrogen is a component of chlorophyll and therefore essential for photosynthesis. It is also the basic element of plant and animal proteins, including the genetic material DNA and RNA, and is important in periods of rapid plant growth.
Plants use nitrogen by absorbing either nitrate or ammonium ions through the roots. Most of the nitrogen is used by the plant to produce protein (in the form of enzymes) and nucleic acids. Nitrogen is readily transported through the plant from older tissue to younger tissues. Therefore, a plant deficient in nitrogen will show yellowing in the older leaves first due to the underdevelopment or destruction of chloroplasts and an absence of the green pigmented chlorophyll.
All of these above forms of nitrogen are known as inorganic forms of nitrogen.
Organic nitrogen compounds are complex and unavailable to plants. They are the end products of immobilisation.
Below is diagram showing the nitrogen cycle, the various forms of nitrogen, the processes that convert one form of nitrogen to another and the part of the environment in which these processes occur. There are many variations of this basic nitrogen cycle diagram
Nitrogen may be found in air, water or land; nitrogen may exist in several different chemical forms; it will undergo many changes in form and location throughout the cycle due to processes which occur as a result of weather, plants, animals and humans. In some cases nitrogen may be lost to the soil nitrogen cycle. It is important to determine whether human activity has accelerated the rate of natural losses and whether these losses pose an environmental threat.
Visit the University of Western Australia/Soil health-Nitrogen cycle web site and complete the following.
Farm managers manipulate the nitrogen cycle to maximise the availability of nitrogen and hence improve production. To complete an activity about manipulation of the nitrogen cycle go to the tutorial Manipulating the nitrogen cycle to maximise production.