The reason for soil amendment is to provide a better environment for roots and plant growth: this includes the improvement of the soil structure and water holding capacity, the availability of nutrients, and the living conditions for soil organisms, which are important for the plants to grow. Furthermore, a better soil texture and better root growth avoids soil degradation during heavy rains or in windy regions. It also supports the nutrient cycle when organic amendments are used (e.g. manure). Beside soil amendment, there are several methods to provide soil moisture conservation such as soil cover and reforestation (living plants), mulching or several tillage techniques. Of course it is also very important that a crop is planted which is suitable for the given climate. Basically, any organic or inorganic material that is added to the soil and improves its quality can be considered as soil amendment. The type of amendment chosen depends entirely on how the soil needs to be changed. By using soil amendment, almost every type of soil can be made fertile (WEST COAST SEEDS 2011).
Inorganic substances are vermiculite, perlite, tire chunks, pea gravel and sand. In general, they must be bought, which makes them more expensive than organic amendments. Additionally, the industrial production process needs a great deal of energy. Therefore, these substances do not have the same degree of sustainability as organic amendments. Most are relatively sterile (with regard to plant pathogens) and many are relatively inert. Inorganic amendments are used to (REED 2007):
Organic growing medium amendments usually are derived from plants or plant products that occur naturally (peat moss from peat bogs), or are the by-products of processing plants or mills (sawdust, cedar chips, bark, bagasse, rice hulls) or waste disposal plants (compost, processed sewage sludge, biosolids). The main purpose of using organic amendments is to loosen the soil and create large pores to increase (REED 2007):
In professional agriculture, the most commonly used organic amendment is peat moss (e.g. sphagnum peat moss which is the highest quality, but also hypanaceous or domestic peat). Other organic amendments include wood chips, grass clippings, straw, compost in general (produced in large or small scale facilities), manure (see also use of compost, use of dehydrated faeces or terra preta), processed sewage sludge (biosolids), sawdust, etc. Normally, there are more organic substances available than inorganic substances and generally they are cheaper (REED 2007; GIZ 2010). Practising good crop rotations and choosing the correct crop improves soil amendment.
Before incorporating into ground beds, most organic amendments, especially sawdust, cedar chips, bark and bagasse, should be composted or aged, and sterilised before use if possible. All of these amendments have a high C:N ratio. Use of amendments which are not composted and have a high C:N ratio will deplete N from the soil, may cause a salt or an ammonia/ammonium burn, or may cause damage due to heat build up.
Amendments with a low C:N ratio will release N upon further decomposition, thus act as an organic fertiliser. However, organic matter with a low C:N ratio also should be composed to avoid rapid ammonia/ammonium release and toxicity (adapted from REED 2007).
Humic acid is a principal component of humic substances, which are the major organic constituent of organic soil amendments. Organic soil amendments (humus) have been known by farmers to be beneficial to plant growth for longer than recorded history. It was supposed that humus was used directly by plants, but it was shown later that plant growth depends upon inorganic compounds. Therefore, many soil scientists held the view that organic matter was useful for fertility only as it was broken down with the release of its constituent nutrient elements into inorganic forms. At the present time, soil scientists hold a more holistic view and at least recognise that humus influences soil fertility through its effect on the water-holding capacity of the soil: the spongy structure of organic matter is able to bind water and some inorganic molecules which act as micro- or macro-nutrients. Consequently, humic acids also slow water evaporation from soils. This is especially important in soils where clay is not present or in a low concentration, in arid areas, and in sandy soils without the capability to hold water. The oxygen end of another water molecule bonds with the hydrogen end of another, until the evaporation rate is reduced by 30% (NUTRANETICS 2000).
(Adapted from DAVIS & WILSON 2005)
There are at least four factors to consider in selecting a soil amendment:
Laboratory tests can determine the salt content, pH and organic matter of organic amendments. The quality of bulk organic amendments for large-scale landscape uses can then be determined. The amendment you choose depends on your goals.
Most inorganic amendments are mined from natural deposits and further processed to yield the final product. Heavy machinery and technical know-how is necessary to produce such amendments. These facts cause higher costs in production. In the other hand, organic amendments have high self-help compatibility, because farmers can produce them on-site. There are numerous methods that help to produce organic amendments and support a sustainable handling of the local nutrient and water cycle. Composting toilets, terra preta toilets, fossa alternas or arborloos, UDDT are toilet systems that generate organic amendments. According to GIZ (2010), there are more organic substances available than inorganic, and they are generally cheaper.
Soil amendments have to be handled carefully. Soil does not have the capacity to bind substances ad infinitum without releasing them. If too many nutrients or organic matter are put into the soil, they can be released and cause an outflow into the groundwater and surrounding rivers and lakes, which can cause water pollution (GIZ 2010).
Organic or inorganic substances are mixed into the soil to improve the physical properties. The goal is a better environment for roots, water infiltration, and holding capacity.
Each soil type has different needs for soil amendments.
Depending on the infrastructure, it can either be more or less expensive to buy inorganic substances than to produce organic substances.
Reliable, old method. Carefully applied, regular soil amendment can improve soil quality immensely.
Even minor improvement of the physical properties of the soil can generate a much better soil condition for plants.
Too much input of substances results in an output mainly in surrounding water bodies, which is an environmental damage.
Soil amendments, if managed carefully, can be applied everywhere. Care has to be taken in choosing the appropriate soil amendment depending on the initial soil conditions. Especially organic amendments can be produced locally. Mixture into the soil can be time consuming
REED, D. (2007): Horticulture Workshops: Plant Propagation, Soil and Soilless Growing Media, Simple Soil and Water Testing. Texas: A&M University. URL [Accessed: 24.04.2012].
AGRESOURCE (Editor) (2012): Protecting Local Water Resources by Amending Soil with Compost. Amesbury: Agresource Inc. URL [Accessed: 12.01.2012]. PDF
Communities can protect water resources by instituting minimum requirements for organic matter in soil. Compost, much of which is generated locally, when incorporated into soil improves water holding capacity and soil quality. By incorporating compost into soil for establishment of lawns and landscape plantings, water used for irrigation is conserved and the potential for groundwater contamination is reduced. Read more about it in this paper.
AGWE, J.; MORRIS, M.; FERNANDES, E. (2007): Africa’s Growing Soil Fertility Crisis: What Role For Fertilizer? . Washington, D.C.: The World Bank. URL [Accessed: 25.04.2012]. PDF
This document draws upon the material prepared for fertiliser strategy as-sessment, summarises the information on the approaches to enhancing fertiliser supply and use in Africa, and identifies some future steps.
This factsheet gives an overview how to choose a soil amendment. It talks about the application rate, organic or inorganic amendments, salt and pH content of the soil and if biosolids are safe to use as an amendment.
World population growth and changing consumption patterns, along with limited capacity to expand arable land and pasture, require the intensification of agriculture. There is much potential for such intensification in developing countries: the soils are often nutrient-poor as a result of both natural conditions (climate, geology) and human activity, while at the same time use of external inputs is limited. One way of improving land productivity is to provide better plant nutrition, for which both organic and inorganic fertilisers are available options.
HUE, H.V.; SILVA, J.A. (2000): Organic Soil Amendments for Sustainable Agriculture: Organic Sources of Nitrogen, Phosphorus, and Potassium. In: SILVA, J.A.; UCHIDA, R. (): Plant Nutrient Management in Hawaii’s Soils, Approaches for Tropical and Subtropical Agriculture. Honolulu, 133-144. URL [Accessed: 25.04.2012]. PDF
Sustainable agriculture, which is characterised by farming profitably while minimising damage to the environment, is not easy to practice. “Conventional” agriculture in the USA is commonly considered to involve practices that have potential to damage the environment. These include tilling the soil excessively, over applying readily soluble inorganic fertilisers (“chemical fertilisers”), and over applying pest-control formulations (herbicides, insecticides, fungicides, etc.). “Sustainable” agriculture attempts to find alternatives to such practices, alternatives that are economically feasible but have less potential to cause environmental damage.
ROY, R.N.; FINCK, A.; BLAIR, G.J.; TANDON, H.L.S. (2006): Plant Nutrition for Food Security: A Guide for Integrated Nutrient Management. Rome: Food and Agriculture Organization of the United Nations (FAO). URL [Accessed: 25.05.2012]. PDF
This guide on integrated plant nutrient management, dealing with various aspects of plant nutrition, is an attempt to provide support to the ongoing efforts directed at enhanced and sustainable agricultural production. It seeks to bridge the scientific knowledge gap, and it presents updated information on plant nutrition with emphasis on INM. In helping stakeholders to improve their ability to identify and resolve constraints relating to plant nutrition – be they of a technical, economic, social or policy nature – and to demonstrate on the field practical ways of increasing production through efficient plant nutrition, the guide should assist in achieving the goal of food security.
This publication covers basic soil properties and management steps toward building and maintaining healthy soils. The publication is divided into three distinct sections, each with its own purpose. Section 1 deals with basic soil principles and provides an understanding of living soils and how they work. In section 1 you will find answers to why soil organisms and organic matter are important. Section 2 covers management steps to build soil quality on your farm. The last section covers farmer stories of people who have successfully built up their soil. A large resource section of other available information concludes the publication.
Fertilisers and soil amendments are a wide array of materials added to soils to improve plant growth. They can be organic, such as bone meal, or inorganic, such as 10-10-10 fertiliser. Some must be purchased, while others are free for the taking from your landscape. Many are dual purpose—they serve as both fertilisers and soil amendments.
U.S. EPA (Editor) (2006): The Use of Soil Amendments for Remediation, Revitalization, and Reuse. Washington DC: United States Environmental Protection Agency (U.S. EPA). URL [Accessed: 12.01.2012]. PDF
This paper is a product of a workshop, which was hosted by the U.S. EPA in 2006. Soil amendments of interest consist of waste residuals such as municipal biosolids, animal manures and litters, sugar beet lime, wood ash, coal combustion products, log yard waste, neutralising lime products, and a variety of composted agricultural by-products, as well as traditional agricultural fertilisers.
A short article about soil amendments and some tips how some different amendments can be used and its benefits.
A corporation located in the United Kingdom focuses on soil organic matter research and practical advices for farmers. There was a case study and a bro-chure released in 2010.
http://www.ext.colostate.edu/ [Accessed: 15.11.2011]
More general information about plants, soil, fertiliser and insect Colorado State University, basic knowledge about garden management
http://www.westcoastseeds.com/ [Accessed: 15.11.2011]
Soil amendments and how to use them; an overview about different soil amendments and their advantages.