Chemical Properties of Soils

Have you ever looked at soil and wondered why plants grow so well in some soils and not in other soil?  It may have to do with the chemical properties of the soil.  When I was at the University studying soils I took a class in soil chemistry.  I remember thinking; just how much chemistry could take place in the soil?  I soon learned that the level and complexity of soil chemistry is amazing.  I would like to share several items with you, but I am going to limit this broadcast and tell you about soil acidity. 

Soil acidity is measured on a scale of 0 to 14.  A soil acidity level of 7 is considered neutral.  Any value less than 7 is acidic and all values greater than 7 is considered not acidic, but alkaline.

What is soil acidity?

Soil acidity is simply the amount of Hydrogen ions in the soil.  However, the level of soil acidity plays a huge role in how plants are able to grow.  A soil acidity level of 6.0 to 6.5 is generally best for most crops. As soil acidity drops by one unit (for example, 6.0 to 5.0), acidity increases by 10 times. A soil with an acidity level of 4.0 would be 100 times more acidic than a soil acidity of 6.0.

Much can be learned simply by knowing the acidity of the soil. Most agricultural soils have an acidity range of 4.0 to 9.0. Soils with acidity of near 4.0 probably have free acids in the soil solution from the oxidation of sulfides or aluminum. Soils with an acidity of 5.2 or less have high amounts of aluminum and manganese. They are toxic to many crop plants and thus reduce growth and yield.

Soils with an acidity of 7.8 to 8.2 have calcium carbonates (limestone). These soils generally tie up vast amounts of phosphate fertilizer, holding it back from crops and decreasing available supplies of many micronutrients to the point of deficiency for some crops. A soil acidity greater than 8.5 indicates high exchangeable sodium and very poor structural condition of the soil. When wet, these soils are greasy and get puddled. They are as hard as concrete when dry.

In most situations the concern is with soils being too acidic.  Luckily there are soil amendments, which we can add to bring the acidity level more near neutral.  The most common of these is lime.  Lime is simply limestone, which has been crushed into a fine powder.  Liming acid soils increases yields and provides a number of other benefits. Liming a soil from an acidity level of 4.5 to 6.0 can increase soybean yields by 15 percent.  Benefits from liming come from decreasing the soil acidity to a crop's most favorable range for growth.

Other benefits provided by liming soils include:

Just like adding lime to the soil to improve it we too also have to add things to our lives in order make us happy.  We find friends, enjoy our families, and I enjoy spending time outside.  However, I have learned to have true happiness we must have God in our hearts.  I would like to share with you how the Bible says we can have God in our lives.

According to Romans 5:8, God demonstrated His love for us through the death of His Son. Why did Christ have to die for us? Because Scripture declares all men to be sinful. To “sin” means to miss the mark. The Bible declares, “all have sinned and fall short of the glory (the perfect holiness) of God” (Rom. 3:23). In other words, our sin separates us from God who is perfect holiness (righteousness and justice) and God must therefore judge sinful man.

Scripture also teaches that no amount of human goodness, human works, human morality, or religious activity can gain acceptance with God or get anyone into heaven. The moral man, the religious man, and the immoral and non-religious are all in the same boat. They all fall short of God’s perfect righteousness. After discussing the immoral man, the moral man, and the religious man in Romans 1:18-3:8, the Apostle Paul declares that both Jews and Greeks are under sin, that “there is none righteous, not even one” (Rom. 3:9-10). Added to this are the declarations of the following verses of Scripture:

Ephesians 2:8 For by grace you have been saved through faith; and that not of yourselves, it is the gift of God.

Titus 3:5-7 He saved us, not on the basis of deeds which we have done in righteousness, but according to His mercy, by the washing of regeneration and renewing by the Holy Spirit, 6 whom He poured out upon us richly through Jesus Christ our Savior, 7 that being justified by His grace we might be made heirs according to the hope of eternal life.

No amount of human goodness is as good as God. God is perfect righteousness. Because of this, Habakkuk 1:13 tells us God cannot have fellowship with anyone who does not have perfect righteousness. In order to be accepted by God, we must be as good as God is. Before God, we all stand naked, helpless, and hopeless in ourselves. No amount of good living will get us to heaven or give us eternal life. What then is the solution?

God is not only perfect holiness (whose holy character we can never attain to on our own or by our works of righteousness) but He is also perfect love and full of grace and mercy. Because of His love and grace, He has not left us without hope and a solution.  Romans 5:8 says - But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us.

This is the good news of the Bible, the message of the gospel. It’s the message of the gift of God’s own Son who became man, lived a sinless life, died on the cross for our sin, and was raised from the grave proving both the fact He is God’s Son and the value of His death for us as our substitute.

           Because of what Jesus Christ accomplished for us on the cross, the Bible states, “He that has the Son has life.” We can receive the Son, Jesus Christ, as our Savior by personal faith, by trusting in the person of Christ and His death for our sins.

          This means we must each come to God the same way: (1) as a sinner who recognizes his sinfulness, (2) realizes no human works can result in salvation, and (3) relies totally on Christ alone by faith alone for our salvation.

           If you would like to receive and trust Christ as your personal Savior, you need to express your faith in Christ by a simple prayer acknowledging your sinfulness, accepting His forgiveness and putting your faith in Christ for your salvation.

Just about everything people and nature do to the soil tends to create acidity. Soil acidity develops gradually in soils because:

What is Effective Neutralizing Material?

Effective neutralizing material is a term used to express an amount of agriculture limestone to apply to soil to get the proper acidity level in the soil. A soil test recommendation will call for a given amount of Effective Neutralizing Material to be applied if the soil is acidic. The recommended amount is based on the crops to be grown and the amount of acidity in the soil.

Agricultural limestone should be analyzed for purity and fineness of grind. These two factors determine the Effective Neutralizing Material of the agricultural limestone. You need to only know the Effective Neutralizing Material required by the soil and the Effective Neutralizing Material of the limestone. Simply divide the Effective Neutralizing Material of the agricultural limestone into the Effective Neutralizing Material required by the soil and you will have the metric tons of limestone required per hectare.

For example, say the soil is acid and calls for 1,200 Effective Neutralizing Material. Your agricultural limestone dealer says he has 400 Effective Neutralizing Material lime. Divide 400 into 1,200 and you determine you need 3 metric tons of that limestone per hectare to satisfy the lime requirement. If another ag lime dealer had 600 Effective Neutralizing Material lime, you would only need 2 metric tons per hectare of that lime to satisfy the field requirements.

Adding lime to acid soil

An acid soil reacts slowly with limestone because limestone is not very water-soluble. Grinding limestone finer improves its solubility and speeds up reaction with soil.

When limestone reacts with soil, acidity (or hydrogen ions) is removed. Hydrogen attached to the clay is exchanged with calcium from the soluble limestone. The hydrogen is then in the soil water and reacts with the carbonate, also from the soluble limestone, to form carbonic acid. Carbonic acid is not stable in soils and further breaks down to carbon dioxide gas and water. The hydrogen has then been converted from an acid on the clays to a neutral molecule of water. 

Many people think calcium is the key to reducing acidity. However, without the carbonate, the soil would still contain the acid hydrogen and acidity would not change. Some people wrongly sell gypsum (calcium sulfate) as an acidity reducer for soils. Gypsum will not reduce soil acidity. Calcium from soluble gypsum does replace hydrogen on the clays. The hydrogen then reacts with the sulfate in soil solution to form sulfuric acid. Sulfuric acid is stable in the soil and remains in the system, thus there is no change in acidity. The acid hydrogen ion remains as an acid hydrogen ion.

Numerous products are still sold as acidity adjusters to unknowing farmers and homeowners. Many of these are liquid products containing calcium. These products, like gypsum, have essentially no effect on soil acidity. Always seek research evidence about such products from a reputable source.

Acidity and crop growth

Soil acidity begins to affect nearly all crops adversely when the acidity level falls below 5.5.  However, in my area more than a third of the soil samples tested in 1984 still show severe acidity problems. Yield reductions are likely.

Legumes are sensitive to soil acidity. When seeding legumes, you should be sure the soil acidity is already above 6.0. To achieve this goal, you may need to apply limestone six to 12 months prior to seeding on very acid soils. On established stands, maintain the acidity at 6.0 to 6.5. If you are soil sampling an established stand of legumes, apply limestone if the acidity falls below 5.8. Under very acid conditions where you can only surface apply limestone; apply no more than 3 metric tons of agricultural limestone at one time. Wait one year and apply the remaining lime requirement.

If a soil’s acidity is 5.3 or less and you haven't applied limestone at seeding, success in establishing legumes is unlikely. Under those circumstances, apply the limestone and delay seeding until the next planting season.

Corn, wheat, cotton, and sorghum are more tolerant to soil acidity than are soybeans. Plan limestone applications accordingly. Apply limestone six to 12 months prior to growing soybeans. Corn, wheat, cotton and sorghum will all grow well when soil acidity is at 5.3 or more. However, soybeans do best at soil acidity levels of 5.8 or above. Generally, you should apply limestone to bring the soil acidity to 6.0 to 6.5 range. When a recommended rate of effective neutralizing material equates to 2 or more metric tons of limestone or the soil acidity is below 5.5, lime the row crops.

In pure grass stands, soils may become more acid without a noticeable decrease in production. But if you interseed a legume such as red clover, you will need to lime in most cases. Grass may do well down to an acidity range of 4.8 to 5.0, but clover will probably show reduced growth at an acidity level below 5.5.

This may have been the first time you have ever heard of soil acidity and how important it is to maintain.  This also may have every heard that God loves you.  If you would like to receive and trust Christ as your personal Savior, you need to express your faith in Christ by a simple prayer acknowledging your sinfulness, accepting His forgiveness, and putting your faith in Christ for your salvation.