THE ROLE OF SOIL TESTING FOR FERTILIZER RECOMMONDATION

It is hard to imagine what the world would look like without the yield increases we have witnessed over the last seven five years. A 50- or 60-year period where yields were flat seems unthinkable, yet this was the case in the latter half of the 19 century into the early 20 century. That is before agronomy organized itself as a scientific discipline and soil testing methods were developed and practiced.

Consequently crop yields increased in industrialised countries in late 1930s and early 1940s due to improved plant nutrition through fertilizer applications, plant breeding for high yielding disease- resistant varieties, and when such efforts were combined with other management practices.

The concept of pH was first introduced in1909 and 20 years later pH meters and glass electrodes became available. That progress provided soil scientists with the single-simple and most informative measurement of a soil property which is pH. Another 20 years passed before flame photometers became available in USA.

Soil testing addressed some important issues facing agronomists such as soil acidity and phosphorus and potassium concentrations in soils. The availability of soil testing as a tool was chosen to make a real difference in many places. Soil test kits were “simple to do” as the starting point toward that effort. The soil test kits used very simple chemistry that still exists today. In the 1920s and 1930s, Truog and others, such as Michael Peech from Cornell University , Roger Bray from the University of Illinois, C.H.Spurway from the Michigan State University, and M.F. Morgan from the University of Connecticut, developed field tests kit procedures to measure soil pH, phosphorus, and potassium.

Most of the soil kits used either some types of pH indicator dye, the Troug test, or thiocyanate test to measure pH or acidity. Phosphorus was measured using dilute acids and potassium was measured by coboltinitrate precipitation.

The use of rapid, microchemical soil tests or “quick soil tests” in the measurement of readily soluble plant nutrients in soils for estimating fertilizer needs and for diagnosing crop failure became a common practice in many USA states after 1940.

Moreover, significant advances were made since 1940 in terms of analytical instruments and the correlation between fertilizer recommendations based on soil tests and crop yields. By 1960 soil testing programs was wide- spread all over the USA states.

Our current knowledge about essential macro and micronutrients of higher plants and the methods of their assessments has expanded remarkably. And with the development of atomic absorption/emissions detection of very low levels of micronutrients as well as toxic levels of heavy metals in soils have been achieved.

It is very important to review the methods used in USA in training county agents and farmers by state, federal and private sectors in using soil tests for fertilizer recommendations that markedly increased productivity of soils during the last 75 years and actually led to surpluses of agricultural products.

There was a Soil Laboratory in Abu-Graib, Baghdad before 1960 but I do not think its mission was soil testing for fertilizer recommendations. It was geared to provide data for soil survey and special Government Projects of land reclamation. However, In Iraq we are still very far behind in using soil tests as a means to provide optimum levels of plant nutrients for increased crop production. On the other hand application of fertilizers to soils without soil tests and plant analysis is not likely to give optimum crop yields and may even have deleterious effects on the crops and on the quality of the environment.

Therefore, there is a great need for initiating a soil testing program in Kurdistan Region as well as in other major regions of the Federal Republic of Iraq. Currently Iraq heavily relies on imports of food for its population because hard currency is available now from oil revenues that accounts for 90% of its gross domestic product (GDP). However, fossil fuel is not a renewable resource but is subject to depletion unlike renewable resources such as soils, plant products and to a great extent solar energy.

Thus, sooner or later Iraq has to make large investments in agriculture to secure adequate food supply for its growing population from its plant and animal products. That means current policy makers of Iraq cannot ignore the eventual need for a strategy of self-sufficiency in agricultural products and should start now rather than later. The task is big but the 100-mile journey begins with the first step forward. To this end we can provide consultancy with other experts of various fields of agriculture to embark on a long term mission equipped with 21 century technology to face realistically the challenge of self-sufficiency in agricultural products in Iraq.

By Mohammed Sa’id Berigari, PhD, Senior Soil and Environmental Scientist-USA. Date: 12/07/2011