Goals of Modern Nutrient Management

The objective of this web resource is to assist you in making decisions, as well as taking action, in accordance with the goals of modern nutrient management. Furthermore, we aim to help you identify, prevent, minimize, and solve the most crucial nutrient management problems on Maui that may lead to economic and environmental loss.

• Apply nutrients in a way that optimizes profitability
• Minimizes the risk of environmental harm

Researchers in the College of Tropical Agriculture and Human Resources (CTAHR) have stated that the goal of a sound nutrient management plan is “to ensure the availability of adequate nutrients for crop production with minimal nutrient loss in runoff or leaching from the root zone” (Silva and Uchida, 2000).

Nutrient Management plan recommended by CTAHR

According to this plan, the farmer would take action in four ways:

• Assess environmental concerns of your field/property
• Evaluate the current status of plant-available nutrients
  • One such method is soil testing
• Calculate appropriate rates of applied nutrients after considering available soil nutrients and practical yields
• Implement the correct method of nutrient applicatio
  
  

Law of the Minimum

The Law of the Minimum is an important concept in any nutrient management strategy. It states that crop yield will be limited by any essential component of plant growth which is insufficiently present. Since plant nutrients are essential to plant growth, any deficiencies in any one nutrient can limit crop yield. For example, even if nitrogen is sufficiently supplied, a phosphorous deficiency will cause yields to be much less than if both were adequately present.

Critical Nutrient Levels

There are 12 essential elements which plants obtain from the soil that are commonly managed by growers. In addition, plants require carbon, hydrogen, and oxygen to grow.

What makes an element essential to plant growth?

• An element is essential if the plant cannot complete its life cycle without the element.
• It is essential if the element is directly or indirectly involved in the metabolic processes of the plant (i.e. photosynthesis or respiration).
• A deficiency in an essential nutrient will result in the development of a characteristic, visual symptom.

Table 1. The essential elements for plant growth

Figure 1. Periodic Table
Source: http://can-do.com/uci/lessons98/index.html

The relative nutrient status of a plant may be easily described using the following terms:

Deficiency range
Nutrient deficiencies occur in plants when an essential element is not taken up by the plant in sufficient amounts. As a result, yield will be limited by the element which is deficient. While slight to moderate deficiencies do not always result in visual deficiency symptoms, distinct visual symptoms appear in severe cases.

Critical range
Below the critical range of nutrients, an addition of the essential element will trigger an increase in yield. Above the critical range, the levels of essential nutrients are considered sufficient.

Sufficiency range
Within this range, additions of the essential nutrient will not result in any increase in yield. However, uptake of the nutrient may continue. Thus, the concentration of that essential nutrient in plant tissue will also increase. We refer to the uptake of an essential nutrient within the sufficiency range as luxury consumption.

Toxicity range
Toxicities occur when an essential (or nonessential) element is taken up in great enough quantities to actually reduce plant growth. As a result, toxicities can severely limit yield.