what is soil ph in agriculture



pH is usually measured on a scale of 1-14:

  • A pH of 7 indicates neutral soil
  • A pH above 7 indicates alkaline soil
  • A pH below 7 indicates acidic soil

A pH range of 6 to 7 is generally most favorable for plant growth because most plant nutrients are readily available in this range. However, some plants have soil pH require- ments above or below this range. Soils that have a pH below 5.5 generally have a low availability of calcium, magnesium, and phosphorus.


What affects pH in soil?

Soil pH is a measurement of the alkalinity or acidity of soil. Soil pH is measured on a scale of 1-14, with 7 as the neutral mark. The ideal range for most plants is between 6–7. Most plants prefer a somewhat neutral pH, anything from 6.2 to 7.0.

What is the best pH for garden soil?

 · Soil pH Importance – Soils which have a pH between 6.8 and 7.2 is considered neutral and is the best soil for the most of horticultural crops. In fact many microelements can be absorbed optimally in this type of soil, while this does not happen in strongly acid or strongly alkaline ones, except for few microelements. Soil pH Scale.

How do you determine the pH of soil?

 · Most plants do well when the soil pH is between 6.2 and 6.8. pH is a measure of the acidity and alkalinity of a material. The pH range is 0 (extremely acid) to 14 (extremely alkaline) with 7 being neutral. When acidic soil is neutralized by liming, soil nutrients are made more available for the plants to absorb through their roots.

What is the ideal pH of soil?

First, know what soil pH is. It measures relative acidity or alkalinity of the soil solution, according to DuPont Pioneer literature. It is expressed on a 14-point scale. Soil acidity increases as pH drops below 7 (neutral pH), and soil alkalinity increases as pH rises above 7. If your soil pH is 6.5 or above, don’t worry.


What is the pH of agricultural soil?

between 5.5 and 7.5Though soil pH generally ranges from 1 to 14, the optimum range for most agricultural crops is between 5.5 and 7.5. However, some crops have adapted to thrive at soil pH values outside this optimum range.

What does pH mean in soil?

Soil pH is a measure of the acidity or alkalinity of the soil. A pH value is actually a measure of hydrogen ion concentration. Because hydrogen ion concentration varies over a wide range, a logarithmic scale (pH) is used: for a pH decrease of 1, the acidity increases by a factor of 10.

Why is the pH of a soil important in agriculture?

The pH is important because it influences the availability of essential nutrients. Most horticultural crops will grow satisfactorily in soils having a pH between 6 (slightly acid) and 7.5 (slightly alkaline). Since most garden soils in Iowa are in this range, most gardeners experience few problems with soil pH.

What is a good pH level?

The human body is built to naturally maintain a healthy balance of acidity and alkalinity. The lungs and kidneys play a key role in this process. A normal blood pH level is 7.35 to 7.45 on a scale of 0 to 14, where 0 is the most acidic and 14 is the most basic. This value can vary slightly in either direction.

What pH is best for plants?

In general, most plants grow best in a neutral soil pH, although there are important exceptions. For example, blueberries, azaleas and rhododendrons do well in an acidic soil between 4.5 and 5.5. Lawns favor a pH of 5.5 to 6. Roses do best in soils with a neutral pH of 6.5 to 7.

How soil pH affect crop production?

The lower the pH of soil, the greater the acidity. A well maintained soil pH will maintain the value of the soil resource, maximize crop and pasture choice and avoid production losses due to low pH.

How does pH affect crops?

Soil pH is important because it influences several soil factors affecting plant growth, such as (1) soil bacteria, (2) nutrient leaching, (3) nutrient availability, (4) toxic elements, and (5) soil structure.

How do farmers adjust soil pH?

To make soils less acidic, the common practice is to apply a material that contains some form of lime. Ground agricultural limestone is most frequently used. The finer the limestone particles, the more rapidly it becomes effective. Different soils will require a different amount of lime to adjust the soil pH value.


What is the pH of soil?

Soil pH Scale. Soil pH Importance – Soils which have an acid pH – between 5.4 and 5.9 – are generally not very fertile; such conditions usually also inhibit bacterial and fungal activity, which are fundamental to decompose organic substances. Moreover, elements like calcium (or) magnesium are insoluble and thus unusable by all plants.

How to reduce pH in soil?

Soil pH Importance – Instead if we need to reduce the pH in a too alkaline soil, we can try to remedy administering both organic substances and gypsum. Among the organic substances, manure can be successfully used to this purpose, thanks to its slightly acid pH, as well as other benefits that usually brings to soils. Correcting alkaline soils through gypsum, namely calcium sulphate, is often suggested because this substance – if added in a solution – brings sulfuric acid ions . We need to keep in mind that – due to its calcium content – gypsum shows effects similar to lime on soils, namely it quickens organic matter mineralization, increasing productions, but also quickening the depletion of organic reserves.

Does lime help acid soil?

Besides positively modify pH in too acid soils, lime also brings other benefits.

What are the elements that are scarcely present in acid soil?

Other elements scarcely present in an acid soil are boron and phosphorus. Instead, elements highly available and soluble are aluminum, iron and manganese which, if present in too large quantity, could lead to nutritional imbalances and plants problems.

What is the best soil for horticultural crops?

Soil pH Importance – Soils which have a pH between 6.8 and 7.2 is considered neutral and is the best soil for the most of horticultural crops. In fact many microelements can be absorbed optimally in this type of soil, while this does not happen in strongly acid or strongly alkaline ones, except for few microelements.

What is the most important element in soil fertility?

The most known and important case for soil fertility is the one of phosphorus; in the soil it can be found in the form of poorly soluble phosphates. Their solubility depends on pH: if the reaction is acid it means there are iron and aluminum phosphates, the availability of which increases as pH increases; instead if the reaction is alkaline there …

Why is pH important for plants?

Soil pH Importance – Soil pH strongly influences microbiological activity, mineral elements availability and, ultimately, the adaptability of the different plant species. The most of bacteria – from which nitrogen fixation, nitrification, …

What is the pH of soil?

Liming an acid soil creates a favorable soil environment where plants can thrive. Most plants do well when the soil pH is between 6.2 and 6.8. pH is a measure of the acidity and alkalinity of a material. The pH range is 0 (extremely acid) to 14 (extremely alkaline) with 7 being neutral.

What is the organic portion of soil?

The organic portion is composed of plant and animal remains in various stages of decomposition. How much water and air a soil contains depends on the soil’s texture and structure. Soil is composed of three differently sized mineral particles: sand, silt, and clay.

Why is soil fertility important?

The information from a soil fertility test is particularly valuable if the ground is being planted for the first time. A soil test is also beneficial if you are developing a permanent landscape. The information it provides allows you to incorporate needed materials before planting.

What is the ideal soil texture?

The ideal soil texture, called loam, consists of equal parts of sand, silt, and clay. The more intensive the gardening, especially in vegetable plots or flower beds, the more important it is to understand the soil.

What is dirt in gardening?

Dirt is that stuff we vacuum from our carpets and wash off our cars. A gardener distinguishes dirt from soil, that wonderful earth where we grow our plants. Soil is essential for plant development. Understanding soil is essential to a gardener’s success. Although plants tolerate a wide range of soils, a gardener benefits from learning about …

How much does it cost to get a soil fertility test at Penn State?

You can obtain Penn State Agricultural Analytical Services Laboratory soil fertility test kits from your local Penn State Extension office. There is a $9.00 fee for the analysis and for fertilizer recommendations. The kit contains an information sheet for each soil sample, which is necessary for the lab to make lime and fertilizer recommendations. You can go to Penn State’s Agricultural Analytical Services Lab website to find out more and download the information sheet. You will receive the soil test results and recommendations in about 10 days.

What is the role of pH in soil?

Soil pH plays an important role in availability of nutrients essential for plant growth. In general, optimum availability occurs between a soil pH of 6.0 and 7.0 (Brady, 1990 ). Low pH results in lower rates of N mineralization, a process dependent on active, viable microbial populations in the soil. Thus, ammonium accumulation has been shown at low soil pH ( Cornfield, 1952 ). Rhizobium populations usually increase after liming ( Pearson and Hoveland, 1974; Van Keuren, 1980 ).

What is the pH of soil before planting?

Soil pH ranged from 4.41 to 4.63 before planting, having the highest (4.63) in Cu2 and the lowest (4.41) in Cu 3. There was no significant difference ( p ≤ 0.05) between Cu levels in soil pH before planting; however, a significant difference ( p ≤ 0.05) was observed between Cu levels in pH after harvest, ranging from 4.44 to 4.76, having the highest (4.76) in Cu 1 and the lowest (4.44) in control media ( Table 7.5 ). However, there were no significant differences ( p ≤ 0.05) between Cu levels added to the growth media in soil pH after harvest. Soil pH increased at harvest compared to before planting, with the highest increase (4.41 to 4.73) in Cu 3.

Why does soil pH change?

Most soils used for crop cultivation are likely to experience pH changes due to the use of fertilizers, rainwater and irrigation, organic matter decay, and harvesting of high yielding crops. In general, soil pH is decreased by fertilizer application (particularly NH 4+ forming and SO 42 − containing fertilizers), and the acidity increases with increasing rate of fertilization application ( Bolan et al., 1991; Malhi et al., 2000; Tang et al., 2011 ). Bolan and Hedley (2003) reported that, under managed farming systems, soil acidity is increased with increasing nutrient inputs such as N, P, and S into soils. Russell et al. (2005) reported that soil pH (0–15 cm depth) was deceased in continuous corn and corn-corn-oat-alfalfa cropping systems in Midwestern Mollisols due to application of N-fertilizer, because nitrification released protons and decreased soil pH. Therefore, it is expected that fertilizer application in high pH soil may enhance biomass production by lowering the soil pH, although Malkonen and Kukkola (1991) did not observe any decrease in soil pH by adding N-fertilizer with P over a 26–30-year study period in their study of the effect of repeated fertilization on soil properties and biomass production.

How does soil pH affect glucosinolate hydrolysis?

Soil pH influences the formation and disappearance of glucosinolate hydrolysis products although effects on disappearance are not dramatic. Greater amounts of methyl ITC were trapped in headspace from soils adjusted to a higher rather than to a lower pH (Munnecke and Martin, 1964 ), and additions of lime to three soils tended to shorten residence times of methyl ITC in soil ( Ashley et al, 1963 ). No correlation between soil pH and allyl ITC or allyl CN disappearance was observed for six soils ranging in pH from 4.35 to 9.10 ( Borek et al, 1995a ). Typical pH values of agricultural soils are thus not expected to greatly alter allelochemical residence times.

How to determine the amount of lime needed for a soil?

The relationship between soil pH and base saturation was considered to be linear between pH 4 and 7. Measurement of the soil pH provided an estimate of the base saturation. To determine the amount of lime to raise the soil to the desired soil pH requires information about the CEC of the soil which can be estimated based on soil texture and organic matter content. As an example, the amount of lime to bring the pH to 6 (90% base saturation) for a soil which had an initial pH of 5 (50% base saturation) and a CEC of 10 cmol kg−1 soil would be 10 cmol kg −1 soil × 40% = 4 cmol lime kg −1 soil, which is equal to 4000 kg lime ha −1. One of the limitations of this approach is in estimating the CEC of the soil. If the estimate of the CEC is off, this will result in recommendations which are either too much or too little of the required amount of lime.

What is the minimum pH of Fe?

Iron oxides are dominant in governing Fe solubility in soils. Minimum Fe solubility occurs between pH 7.5 and 8.5, which is the pH range of most calcareous soils ( Lindsay, 1991 ). Increases in soil pH or Eh (oxidizing conditions) shift Fe from exchangeable and organic forms to water-soluble and Fe oxide forms.

What micronutrients are available in soil?

Boron is the only micronutrient to exist in solution as a nonionized molecule over soil pH ranges suitable for growth of most plants. Increasing soil pH decreases B availability by increasing B adsorption onto clay and Al and Fe hydroxyl surfaces, especially at a high soil pH ( Keren and Bingham, 1985 ). The highest availability of B was at pH 5.5–7.5, and decreased below or above this pH range. In other studies, B adsorption increased from pH 3 to 8 on kaolinite, montmorillonite, and two zone soils with peak adsorption at pH 8–10, and decreases from pH 10 to 12 ( Goldberg et al., 1996 ). Reduced B availability occurs from liming (called “B fixation,” Fleming, 1980) as Ca carbonate acts as an adsorption surface. As such, B deficiency may occur in plants grown in limed acid soils. Considerable soil Cu is specifically adsorbed as the pH increases. For example, increasing the pH from 4 to 7 increased Cu adsorption ( Cavallaro and McBride, 1984 ), and Cu was adsorbed on inorganic soil components and occluded by soil hydroxide and oxides ( Martens and Westermann, 1991 ). Increases in soil pH >6.0 induces the hydrolysis of hydrated Cu, which can lead to stronger Cu adsorption to clay minerals and Organic Matter (OM). Readily soluble sources of Cu (exchangeable or sorbed) was highly toxic to citrus and Cu concentrations decreased considerably with soil pH increases >6.5 ( Fageria, 2014 ). Overliming acid soils may also lead to Cu deficiency. Soil OM is a primary constituent for Cu adsorption and readily complexes Cu. As pH increases, sizes of organic colloids of high molecular weight diminish to increase surfaces where Cu can be adsorbed ( Geering and Hodgson, 1969 ).

What is the pH of soil?

Though soil pH generally ranges from 1 to 14, the optimum range for most agricultural crops is between 5.5 and 7.5. However, some crops have adapted to thrive at soil pH values outside this optimum range.

Why is soil pH important?

The study of soil pH is very important in agriculture due to the fact that soil pH regulates plant nutrient availability by controlling the chemical forms of the different nutrients and also influences their chemical reactions. As a result, soil and crop productivities are linked …

How to increase pH of acidic soil?

The pH of acidic soil can be increased by using finely ground agricultural lime (limestone or chalk). The buffering capacity of the soil determines the amount of lime needed to increase pH of acidic soil. The buffering capacity of the soil largely depends on the amount of clay and organic matter present.

Why is soil pH 5.5 not good for soybeans?

For instance, soil pH 5.5 is not suitable for soybean plants when molybdenum is low in the soil , but the same pH 5.5 becomes optimum for soybean when molybdenum is sufficient in the soil.

What is the most soluble form of aluminum in soil?

Aluminum toxicity, which is the most widely spread problem of acid soils, occurs when aluminum is present in ionic Al 3+ form. Aluminum ion Al 3+ is the most soluble of all forms of aluminum at soil pH less than 5.0 (acidic condition).

What is the purpose of H+ ions in soil?

H + ions are released by root crops to compensate for the extra positive charges resulting to acid soils. 2.3. Use of fertilizers. Some fertilizers such as ammonium (NH 4+) fertilizers undergo nitrification process to form nitrate (NO 3− ), and during this process, H + ions are released leading to acid soils. 2.4.

Why is rain water acidic?

This is because rainwater is slightly acidic (about 5.7) due to a reaction with CO 2 in the atmosphere that forms carbonic acid. As this rainwater passes through soil pores, it leaches basic cations from the soil as bicarbonates, which increases the percentage of AI 3+ and H + relative to other cations in the soil.

What is the function of pH in soil?

pH is a measure of the acidity vs the alkalinity of the soil, and determines the capacity of that soil to exchange nutrients with plants growing in it. As well as affecting the ability of plants to uptake nutrient by both chemical and biological processes, the pH also affects the diversity and species of soil microbiology. …

Why is it important to balance soil pH?

Once you’re on your way with good soil pH, it’s much easier to treat mineral deficiencies if they crop up in your plants. Because now, you’ve created a soil environment where the plants can suck up the goodness they need, once you give it to them.

What is the best way to change pH?

Add organic matter in the form of a well balanced, pH neutral compost… adding humus is the best way of changing pH… let the biology do the work!!

How long does it take to increase pH?

It will take a while to increase the pH this way – you should see a change in the pH within 6 months. Be careful not to over apply. Add Dolomite – BUT it contains Magnesium, which if it is already present in large quantities, could block other minerals. Again, a total mineral test is a good idea before doing this.

How long does it take for soil to change color?

Wait about 30 seconds for the colour change to take effect. You will get a more accurate result if you wait a few minutes. Use the colour chart to match the colour of your soil samples. Each color indicates what level pH your soil is. If in doubt, wait 2 minutes and check again the resulting color.

How much does a Kelway pH meter cost?

We recommend the dye & powder system (scroll down the page) developed by the CSIRO ($29) , or Kelway Soil pH & Moisture Meter ($175 ) for broader areas.

Is soil science a big topic?

Soil science and the nature and intricacies of the soil food web is a VERY BIG topic. And an awesome one, too. But for now, let’s leave it at that.

What is the pH of soil?

It is an indicator of the soil’s current condition, and is a primary factor controlling nutrient availability, microbial processes, and plant growth. A pH of 7.0 is neutral, less than 7.0 is acidic, and greater than 7.0 is alkaline.

How to raise pH in soil?

To effectively raise the soil pH, both active and exchangeable acidity must be neutralized. The lab determines buffering capacity and lime requirement by estimating the exchangeable acidity. Exchangeable acidity is directly related to the quantity of lime required to increase the pH from its current level to the target level determined by the desired crop.

How long does it take to lower pH in soil?

The chemical reaction needed to lower soil pH takes time. Re-test in 4-6 months before applying additional sulfur.

How to determine the amount of sulfur needed to lower pH?

First, you must know the texture of your soil. To get a rough estimation of soil texture, place about two teaspoons of soil in the palm of your hand and moisten.

What is the name of the acidity that is neutralized by limestone?

As active acidity is neutralized by limestone, hydrogen and aluminum ions held on soil particle surfaces are released, lowering pH further and requiring more limestone to neutralize that acidity. This is called exchangeable acidity.

How to control acidity in soil?

The most effective way to manage soil acidity is to apply agricultural limestone. The quantity of lime required is determined by the target pH (based on what you are growing) and the soil’s buffering capacity. Buffering capacity refers to a soil’s tendency to resist change in pH.

How does acidic soil affect microbes?

Soil acidity also influences soil microbes. For example, when soil pH is low (below 6.0), bacterial activity is significantly reduced. Acidic soil conditions also reduce the effectiveness of some herbicides.

Why is pH important for soil?

Importance of soil pH: It is major factor in determining which trees, shrubs or grasses will dominate the land under natural conditions. pH influences the processes involved in the formation and development of soils. Most minerals are soluble in acid soils than in alkaline soils thus releasing ions toxic to plants e.g. Al.

How does pH affect plant growth?

The soil pH also affects plant growth by influencing the activity of beneficial soil microbes. Most N-fixing bacteria are not very active in strongly acidic soils. Bacteria that decompose soil organic matter and thus release nitrogen and other nutrients for plant use are depressed by strong acidity.

Where is the Institute of Soil and Environmental Sciences?

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan

Why do fungi grow in high pH?

Fungi usually tolerate acidity better than do other microbes. Plant growth is also affected at high pH due to an excess of sodium ions both in soil exchange complex and solution, which actually deteriorate soil’s physical conditions for plant growth.

What is the pH of a solution?

Where (H +) represents the hydrogen ion activity in mol L -1. The pH scale is the logarithm to the base 10 of the reciprocal of the hydrogen ion activity. As the pH of a solution goes from 7 to 6, the hydrogen concentration increases 10 times and OH ions decrease by 10 times. The pH scale extends from 1 to 14, with pH 7 as being the neutral point. Soils with pH less than 7 are acidic and those with a pH above 7 are alkaline or basic. This means that at pH 7, hydrogen and hydroxyl ion concentrations are equal at 10 -7 moles per liter (e.g. water).

Does acid soil have soluble minerals?

Most minerals are soluble in acid soils than in alkaline soils thus releasing ions toxic to plants e.g. Al. It affects the availability of nutrients to the plants. Alkaline pH reduces the solubility of all the micronutrients (particularly Fe, Zn, Cu & Mn) except Mo and Cl.

What is the pH of soil?

Unfortunately, the meanings of these terms and their relationship to plant growth are not clearly understood by some gardeners. The relative acidity or alkalinity of soil is indicated by its pH. The pH scale runs from 0 to 14.

What does a pH of 7 mean?

The pH scale runs from 0 to 14. Any pH reading below 7 is acidic and any pH above 7 is alkaline. A pH of 7 indicates a neutral soil. The pH is important because it influences the availability of essential nutrients.

What plants need a pH of 4.5?

There are a few plants that require a soil pH of 4.5 to 5.5. These “acid-loving” plants include azaleas, rhododendrons, and blueberries. The soil pH for these plants can be lowered by incorporating elemental sulfur (S) into the soil.

What materials are needed to raise pH?

Strongly acid soils need to be limed to raise the pH to near neutral levels. Liming materials include ground limestone which is mainly calcium carbon ate (CaCO3) and dolomitic limestone which contains CaCO3 and some magnesium carbonate ( MgCO3).

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