This lesson focuses on the process of eutrophication; the relationship between land application of manure and soil phosphorus (P) dynamics on P delivery to surface waters; and on the P dynamics in water bodies that result in increased P available to aquatic vegetation.
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Soils - Part 9 addressed how soil testing works and the proper method of taking soil samples. The purpose of soil testing is to provide a rational basis for making fertilizer recommendations. The impact of not having the optimum crop nutrition can be yield loss, economic expense and environmental contamination. For many years, it has been widely known that fertilizer recommendations for a given crop often vary widely, depending on who is making the recommendation. With the development of site- specific nutrient management, more emphasis is being placed on soil sampling as a basis for predicting response to applied fertilizer. This lesson will explain several approaches to making fertilizer recommendations and will discuss why recommendations may vary widely when different approaches are used to interpret soil tests.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Nitrogen (N) is one of the most abundant elements on earth, and after carbon (C), hydrogen (H), and oxygen (O), it’s the element living creatures need most. The atmosphere over each square foot of the earth’s surface — which is 78 percent dinitrogen (N2) gas — contains approximately 6,000 pounds of nitrogen. However, most of the earth’s nitrogen (98 percent) is in rock, sediment, and soils. The amount of nitrogen in rocks is about 50 times more than that in the atmosphere, and the amount in the atmosphere is approximately 5,000 times more than in soils (Stevenson, 1982).
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Phosphorus fertilizers are second only to nitrogen in importance for growing crops in Nebraska; however, the principles affecting efficient phosphorus use are totally different. Nitrogen is a mobile nutrient, both in the plant and in the soil, while phosphorus moves very little in the soil. Additionally, total plant requirements are much lower for phosphorus than for nitrogen. For example, leaves commonly contain 10 times more nitrogen than phosphorus. However, phosphorus is concentrated in the grain so that only about 2.5 times more nitrogen is removed in harvested grain compared to phosphorus.
Potassium (K) is an essential plant nutrient. Next to nitrogen, crops absorb potassium in greater amounts than any other nutrient. It is a vital component of numerous plant functions including nutrient absorption, respiration, transpiration, and enzyme activity. Potassium is unique because it does not become part of plant compounds, but remains in ionic form in the plant. Potassium remaining in plant residues after harvest and in manure are quickly returned to the soil when water leaches through the plant residue.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Sixteen elements are known to be essential for plant growth. These are divided into two groups: macronutrients — those elements used in relatively large quantities and micronutrients — those needed in very small amounts.
Macronutrients | ||
Carbon (C) | Nitrogen (N) | Calcium (Ca) |
Hydrogen (H) | Phosphorus (P) | Magnesium (Mg) |
Sulfur (S) | Potassium (K) | Oxygen (O) |
Micronutrients | ||
Zinc (Zn) | Copper (Cu) | Boron (B) |
Iron (Fe) | Manganese (Mn) | Molybdenum (Mo) |
Chlorine (Cl) |
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[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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During the first seven lessons, we have discussed a variety of topics related to soils, ranging from their formation to how nitrogen reacts in the soil. In Soils - Part 8, we are going to shift gears and discuss some common fertilizers and their characteristics. These will include the common nitrogen and phosphorus fertilizers, as well as many fertilizers that provide micronutrients to the soil. In this chapter, no attempt is made to judge the value of each type of fertilizer.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Soil tests are part of a four-step process of determining and providing nutrients to agronomic crops. The four steps are:
1) soil sampling,
2) soil analysis,
3) result interpretation and decision making, and
4) fertilizer application.
This chapter will focus on Steps 1 and 3 — soil sampling and result interpretation and decision making. It will not examine specific laboratory procedures or address fertilizer application issues. Until very recently, soil testing was conducted on a field basis. Site-specific management and the associated technologies of fertilizer application and yield monitoring are enabling agriculture management to reduce the area associated with each soil test to the subfield level. The article, "Soil Testing and Nutrient Recommendations," from Nutrient Management for Agronomic Crops in Nebraska, includes further information on soil testing.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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