Hundreds of books have been published on soil fertility and I am only able to share just a little in the area of soil fertility. In this broadcast I would like to focus on phosphorus fertilizer. Before I jump into the subject matter I would like to share a few exerts from a portion of a book titled ‘Soil Fertility-Past and Present.’
“During most of our existence on earth, food has been procured by hunting and gathering. However, as agricultural systems improved in the past the global population has grown. Agriculture has not progressed evenly across the globe. Presently there is starvation in large areas where food production or food distribution is inadequate. In contrast, countries utilizing improved agricultural practices such as: improved seed varieties, fertilizers, and pesticides are generally self-sufficient in food production.”
By 1975 the world’s population reached 4 billion, and by the year 2000 the world’s population has grown to over 6 billion. It is estimated that the world’s population will continue to grow to 11 billion by the year 2050, where it is believed to stabilize. Can you imagine about twice as many people as there are now? With cultivated land only estimated to increase by 20%, it will be necessary to intensify agricultural production, wherein phosphorus fertilizer will play a vital role.
Phosphorous is an interesting element in the soil. Unlike nitrogen, it is very stable in the soil and as long as there is not any significant erosion, the only phosphorous loss will be what the crop removes. One excellent source of phosphorous is animal or human waste. I work in an area where there is a great deal of animal agriculture. Some of the fields I have worked with have had soil test performed to determine the level of phosphorous in the soil. The fields that have had a long history of animal waste applied also had extremely high levels of phosphorous, and the fields that had no history of animal waste applications had low levels of phosphorous in the soil.
I can remember working with one landowner that farmed a particular farm for more than 20 years. This farmer had never applied any animal waste and he knew that his soil phosphorous would be low. However, when we tested the soil the phosphorus levels were very high. I explained to him that once your soil is high in soil phosphorous it will remain high until the crops remove the phosphorous from the soil. If the plants do not remove any phosphorous, and there is not any soil erosion the phosphorous will be there forever. Well, forever may be an exaggeration. There is only one thing that will last forever, and that is your eternal destination.
The Bible talks a great deal about eternal life. Did you know that you can have eternal life? The Bible says that “He who believes in the Son has eternal life; but he who does not obey the Son shall not see life…(John 3:36). And the witness is this, that God has given us eternal life, and this life is in His Son. He who has the Son has the life; he who does not have the Son of God does not have the life. These things I have written to you who believe in the name of the Son of God, in order that you may know that you have eternal life. (1 John 5:11-13) In all of these verses the Son is referring to God’s only son Jesus.
When I think about the future it gives me great comfort to know that I have eternal life through Jesus. Unfortunately, not all have this assurance. People often lack assurance because they cannot remember or point to a specific time when they received Jesus. There is a specific point in time when eternal life begins. I can remember a specific point in my life that I received Jesus as my personal Lord and Savior. At one time in my life I thought that you had to live a good life in order to go to Heaven. Then I came to learn that it is impossible to live a life good enough to deserve Heaven, and that is why God sent his Son Jesus. The Bible says that “for by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works”…(Ephesians 2:8-9). When I think about eternal life being a gift from God I sometimes view Jesus as the invitation. You have to accept the invitation (Jesus) before you can enter into eternal life.
Do you know what God’s word has to say about how to accept Jesus and entering into eternal life? The Bible is very clear. There is one verse that stands out to me. It says “if you confess with your mouth lord Jesus and believe in your heart that God raised him from the dead you will be saved (Romans 10.9,10).” I can remember when I made this confession with my mouth the Lord Jesus and believed in my heart that God raised Him from the dead. Ever since that time I have been able to live with the comfort of knowing where my future eternal destination will be.
I now want to give some specific information and recommendations on phosphorous fertilizer. I want to do that by answering three specific questions: Why is Phosphorous important and what does it do?; How much should I apply?; and Are there any visual symptoms of phosphorous deficiencies?
Why is Phosphorous important and what does it do? Phosphorous occurs in most plants in concentrations between 0.1% and 0.4%, which is considerably lower than those typically found for Nitrogen or Potassium. The most essential function of phosphorous in plants is in energy storage and transfer. Energy obtained from photosynthesis and metabolism of sugars is stored in phosphorous compounds for later growth and reproductive processes.
An adequate supply of phosphorous early in the plants life is important in the development of its reproductive parts. Large amounts of phosphorous are found in seed and fruit, and it is considered essential for seed formation. A good supply of phosphorous is also associated with increased root growth. Several other effects on plant growth are attributed to phosphorous fertilization. It is associated with early maturity of crops, particularly grain crops. An adequate supply of phosphorous is associated with greater straw strength in cereal crops such as wheat. The quality of certain fruit, forage, vegetable, and grain crops is improved and disease resistance increased when these crops have satisfactory phosphorous nutrition. Lastly, the risk of winter damage to small grains can be substantially lowered by applications of phosphorous.
How much should I apply? Earlier I told you how phosphorous does not move in the soil. Therefore, if you already have high levels of soil phosphorous you probably do not need any additional phosphorous. The only way to know how much phosphorous is in the soil is to test it. However, soil testing is not always possible. When I make recommendations on how much phosphorous to apply when no soil testing is available I base the recommendation on how much phosphorus is removed by the crop grown. But I also include a little extra phosphorous to improve the soil for future crops.
I know of farmers who apply 20% more phosphorous than is actually needed by the crop being grown. They do this for two reasons. First they want to improve their soils for future crops. This is a good management practice, especially on poor soils. The second reason is farmers do this is that they realize how important phosphorous fertilizer is and they want to make sure that the plants have plenty of phosphorous available.
I would like to give you some information about how much phosphorous is removed by some major crops. The first example is corn. Corn removes about 3.4 grams of phosphorous for every kilogram of corn harvested. Therefore, a 10,000 kilogram/hectare corn crop will remove 33.6 kilograms of phosphorous from the soil. But this does not take into account all of the phosphorous needed to grow the leaves, stalk, and roots of the corn plant. Therefore, to truly put enough phosphorous on the field which yields 10,000 kilograms of corn per hectare you would need to apply 61 kilograms of phosphorous per hectare.
Soybeans need even more phosphorous than corn for every kilogram produced. Soybeans remove 6.1 grams of phosphorous for every kilogram of beans raised. This will be similar for all kinds of beans grown. In order for there to be enough phosphorous in the soil for the beans and the leaves, stems, and roots you should apply 44 kilograms of phosphorous to produce 3300 kilograms of soybeans. If you are growing soybeans and rice in a rotation with one another I would recommend putting an additional 18 kilograms of phosphorous on the soybeans and this will be enough for the following rice crop.
The last crop I want to talk about is wheat. The phosphorous fertilizer should be applied in the fall of the year before planting the crop. Wheat removes 4.5 grams of phosphorous for every kilogram of wheat grown. Therefore, a 3,600 kilograms per hectare wheat crop will remove 16 kilograms of Phosphorous from the soil. But this does not take into account all of the phosphorous needed to grow the leaves, stalk, and roots of the wheat plant. Therefore, to truly put enough phosphorous on the field which yields 3,600 kilograms of wheat per hectare you would need to apply 33 kilograms of phosphorous per hectare.
In my area most of the farmers who raise wheat also grow soybeans in the summer. Therefore, many of them apply enough phosphorous fertilizer to grow to grow both crops. This phosphorous is all applied in the fall of the year before the wheat is planted. It takes about 76 kilograms of phosphorous to raise both crops. This is one of the nice features about phosphorous, it can be applied far in advance of the crop and it will not be lost.
Are there any visual symptoms of phosphorous deficiencies? Phosphorous is mobile in plants, and when deficiencies occurs, it moves from older leaves to the actively growing parts of the plant. Because phosphorous is used in so many processes in the plant there is seldom any visual symptom other than stunted growth. In corn and other grass species, phosphorous deficiency symptoms also are expressed by purple discoloration of the leaves or leaf edges.
I have told you a great deal of how much phosphorous to apply per hectare, but it can be hard to determine how much you are actually applying. Let me tell you a way of determining just how much phosphorous you are applying. Place a sheet on the ground and measure how many square meters the sheet is. Then apply phosphorous on the sheet at the rate you are trying to achieve. Then all you have to do is weigh the phosphorous on the sheet and divide it by the square meters on the sheet. This will tell you the kilograms of phosphorous that were applied per square meter. The last step is to multiply the results by 10,000 to convert to kilograms per hectare. I also need to clarify one point. The fertilizer you are applying as phosphorous is not pure phosphorous. Therefore, you need to find out what percent of the fertilizer is actually phosphorous and base your application on this percentage.
In summary phosphorous is an essential nutrient needed by all plants, and this nutrient is involved in countless functions within the plant. Compared to nitrogen, phosphorous is need is relatively small quantities, but is every bit as important. However, phosphorous is much more easily managed because it is not mobile in the soil. Phosphorous can even be applied a year in advance of the crop being grown and it will still be there. God is also there, he is everywhere and he has invited you into a relationship with him through his son Jesus.
Did you know that there is salvation in no one else; for there is no other name under heaven that has been given among men, by which we must be saved (Acts 4:12). He who did not spare His own Son, but delivered Him up for us all, how will He not also with Him freely give us all things? (Romans 8:32). These two verses from the Bible clearly show just how much God desires us to come to know Him. If you do not know God through his Son Jesus, you can come to know him right now. Remember what I told you earlier about what the Bible said “if you confess with your mouth lord Jesus and believe in your heart that God raised him from the dead you will be saved.” If you make this confession and truly believe, you will have a never-ending relationship with God.