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Plant Nutrients and Fertilizers 
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I. Topic

This lecture deals with an addition of soil nutrients to enhance crop productivity. Given the problems of maintaining fertility with increased tillage and the resultant depletion of organic matter (O.M.), the addition of plant nutrients to the system becomes a part of crop management.

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II. Learning Objectives
 
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To become aware of the impact of fertilizer addition to crop productivity. 
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To know the basic, primary and secondary micronutrients essential for crop and plant growth and development. 
japanese beatle To introduce the primary materials used in cropping systems to deliver nutrients to the field.
japanese beatle To become aware of different fertilizer combinations and methods of application of these materials
japanese beatle To become aware of different fertilizer combinations and methods of application of these materials
 
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III. Overview

Fertilizer use has led to the ascendance of U.S. agriculture in the world. After World War II, the munition of plants producing Nitrogen were converted to plants that could manufacture fertilizer Nitrogen. Cheap, available Nitrogen was responsible for the substantial increase of corn production.  Fertilizers accounted for about half of the increase in crop yields in the U.S. between 1941 and 1955.

The primary fertilizer elements are called "primary" because they are used in the greatest amount by the plant. These elements are Nitrogen (N), Phosphorus (P), and Potassium (K). A typical corn plant producing 150 bu/a would need 150 lb.. of N, 55 lb.of P, and 65 lb. of K. Nitrogen is especially important in the photosynthetic reaction and the formation of amino acids in DNA/RNA and the cell divisions and growth. Phosphorus is essential in respiration, providing the "P" in the ATP cycle, and in photosynthesis by providing the P energy reaction" for the NADPH2 cycle of photosynthesis. Potassium is essential to the smooth running of plant enzymes into the plant.

These are several common carriers of these elements, and their use is ultimately determined by their cost and the concentration of the essential elements. Application of these materials is often a compromise between economics and plant intake efficiency. Management of fertilizers is a major part of a modern agricultural system, and is an important consideration in a sustainable agricultural system. As fertilizer use becomes more and more expensive, and application methods become critical for both economically sound and environmentally responsible agriculture.
 
In modern agricultural systems, increased emphasis is being made to properly obtain soil samples to estimate fertilizer weeds.  Detailed soil mapping, and state of the art application equipment is being used to prescription feed crop fields.  These systems address crop yield, economic, and environmental concerns.  Uniformity, in many developing countries, the fertilizer technology is very expensive, primitive and, in some places, is nonexistent.  Here lies one of the real differences in agriculture between the developed and developing worlds.

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IV. Introduction
 
1. Fertilizers accounted for about half the increase in crop yields in the U. S. from 1941-1955.
2. Increased use of fertilizers/improved technology are major hope for developing nations.
3. Twenty elements necessary for normal growth of crop plants: General Information About Fertilizers

1. Three figures written - 10-20-10 refer to percentage of N, P2O5 and K2O.
2. Acidity and basically of fertilizers

3.  Cost of fertilizers. Fertilizer Elements and Materials

1.  Nitrogen

2.  Phosphorus
 CONCEPT
Phosphorus availability decreases at both high and low pH's. (diagram)
3.  Potassium
 CONCEPT
Potassium is depleated easily with the rremoval of high yielding crops without retaining residue. (I.E. corn, silace, hay)
4.  Calcium and magnesium and liming. 5.  Micro nutrients Estimating Fertilizer Needs

1.  Soil tests

2.  Plant analysis
  CONCEPT
Soil testing is an estimate of the nutrients availabe for crop uptake, tissue analysis.  It tells what plants could take up.
Mixed Fertilizers

1.  Common practice to mix materials so 2-3 or more elements in fertilizer.

2.  Bulk blending common in major farming areas.

3.  Small farms in developing countries - bagged, granular fertilizer easiest to handle

4.  In U. S. and Europe, N applied as a separate material (at least portion).

 CONCEPT
Nitrogen use efficiency is higher and loss of Nitrogen to the environment is less when Nitrogen is applied when plant demand is greatest.  (I.E. when corn is 12" to tassel.)
 
Fertilizer Application

1.  Usually a compromise between ideal and practical.

2.  In course soil - split applications reduce leaching.
 
3.  In loams and clays - apply before planting.

4.  Best to have a good nitrogen fixing legume crop followed by crop with high N requirements.

5. N usually applied with each crop.

6. P and K frequently made on selected crops in the cropping sequence.

Method of Application

1. Most efficient utilization of fertilizer N is when applied during periods of high plant demand - e.g. tasseling.
 
2.  Best to make nutrients position available to plant roots in early growth stages.
 
3. Banding and size dressing advantageous where soils low in fertility and only limited quantities of fertilizer are used.
 
4. Broadcast applications used - where soils are maintained in high states of fertility.
 
5. Anhydrous ammonia and nitrogen solutions usually injected.

6. Broadcast applications on perennial sods or legume crops.

7. Broadcast where no-till is practiced.

 CONCEPT
Fertility application method is dependent on level of fertility, climate, and available management.
 
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V. Summary
 
Proper use of fertilizer can greatly improve the productivity of crop plants.  Fertilizer can partially overcome the loss of fertility that is usually associated with tillage, and makes up for nutrients lost by the wind and water erosion that accompanies even the best crop systems.  However, fertilizer is an exhaustible resource.  Nitrogen fertilizer is often tied to petrochemicals, Phosphorus and Potassium are both salts that are mined, and deposits will not last forever.  The countries in the world that are using fertilizers heavily, have the cheapest food, and the highest standard of living.  Unfortunately these resources are finite.  In the developing world, atmospheric Nitrogen fixation, soil nutrient recycling and O.M. addition are the primary methods of providing essential plant nutrients to crops.  The irony is, we might all need to look to these methods in the future to supply the nutrients needed to support life on our planet.
 
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VI. Self Assessment
 
japanese beatle Be able to list primary nutrients and descrive why they are primary. 
japanese beatle How do primary elements differ from secondary and micro elements?  Which are more important? 
japanese beatle How would you chose a fertilizer for your crop and how would you determine the proper application? 
japanese beatle Describe what systems the primary elements impact most within crop plants. 
japanese beatle Be able to contrast fertilizer usage in the developed and developing worlds.  What problems do you forsee if this trend continues? 
 
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