The Importance of Chemistry in Policy Formulation, National and County Planning: Some reflections on soil pH and its importance in planning the utilization of land resources.

By Timothy W. Mwangi

11th May,2017

*The   author is a physical planner in the Ministry of Lands and Physical Planning. The views expressed in this article are personal and do not reflect  the position of the National Executive .



“In a statement to the Senate delivered on 2nd April 2015 the Chairman of the Standing Committee on Agriculture Livestock and Fisheries stated “The Government procured 18750 tons of DAP in 2015. The Ministry is aware that no DAP fertilizer was supplied to Kitale National Cereals Produce Board (NCPB) depot in Trans Nzoia County.  This is because according to soil tests conducted in 2013 and launched by His Excellency the President in February 2014, DAP was not recommended for Trans Nzoia unless accompanied by agricultural lime.  The reason for this being this county is largely acidic.[1]The Soil Suitability Evaluation for Maize Products Report 2014 on page 226 States, “In Trans Nzoia East Sub County the soil pH ranges from strongly acidic (4.53) to slightly acidic (5.81).None acidifying fertilizers are recommended.” By glancing the reports’ findings in 141 sub counties, one can safely infer that chemical characteristics of soils have a spatial temporal dimension. This article demonstrates the importance of Chemistry in policy formulation and  Physical Planning at national, regional, county and sub county levels .



Physical Planning is the discipline that organizes activities on space in urban and rural areas to ensure public health, morality, efficiency, economy, suitability and aesthetics within the context of principles of land policy in Article 60 of the Constitution.  Physical planners make pre-development decisions.

In  his inaugural lecture at the University of Port Harcout Prof  Bieluonwa Augustus Uzoukwu (2011)   had this to say  “Chemistry is the scientific study of the changes that occur when substances interact with one another (Manilla, et al 2001). Put in a layman’s language: A + B → C Where A and B  are the interacting substances symbolized by the symbol + to give a substance(s) C that is totally different from both A and B physically and chemically.” Chemistry is a discipline that sees the world “from a molecules point of view.”  We our bodies and world are all made of chemicals.  So if we can understand even a bit of the physical underpinnings of the behavior of these chemicals, we will have learned some very fundamental and broadly applicable things about ourselves and our world”.

Soil comprises of minerals, organic matter, gases, liquids and organisms.  These are part of the definition of land under Article 260 of the Constitution.  Elements (metallic and non-metallic) in the soil are either positively (cation) or negatively (anion) charged.  Ions interact in the same way opposite poles of magnets attract each other.  This is referred to as cation exchange.  Soil pH is an important determinant of cation exchange.

Soil acidity and alkalinity are among the most analyzed characteristics of soils.  Acidity or alkalinity is measured in pH units.  pH is defined as the negative 10g or base 10 value of hydrogen ion[H+] concentration.  The pH scale ranges between 1-14 with pH of 7 as the neutral point (think   back to Chemistry lesson 101).  Any value below 7 signifies acidity while above 7 is alkalinity.  Alkaline conditions are characterized by an increase in hydroxyl [OH] ions. Hence, on pH scale of 1-14, [OH] and [H+] have an inverse relationship.



In Trans Nzoia East Sub County the slightly acidic soil have a pH of 5.81.  What would be the change in acidity [H+] the pH over time reduces to 4.81? pH of a solution is calculated using the formula :

pH = – log10 [H+]

where [H+] is hydrogen ion concentration

We need to calculate the hydrogen ion concentration at these two levels

pH = – log10 [H+]

note logxy = z  implies that xz= y

therefore to get [H+] = 10(-pH)

Hydrogen ion concentration at pH 5.8 can be calculated as

[H+] = 10(-pH)



Hydrogen ion concentration at pH 4.8 can be calculated as

[H+] = 10(-pH)




 Note   that1.584893192*10-5/1.584893192*10-6 =10( tenfold)

 From the above calculation, it is evident that, a change of pH   from 5.8 to 4.8 results in a tenfold  and not  a single digit increase in acidity of   the  soil . This should attract the attention of policy makers and planners.



In natural ecosystems acidification is largely as a result of carbon dioxide.  However the pH remains constant at 5.6.[2]

H20 + CO2                 H2C03                     H+ + HC03

(l)      (g)            (l)                (aq)    (aq)

The [H+]is the cause of acidity. The more [H+]ions  a soil  reaction produces, the more acidic the soil becomes . However, this equilibrium (pH 5.6) is disturbed when ammonical fertilizers are applied to soils.  The most popular ammonical fertilizer is Diammonium Phosphate – (NH4)2HPOwith a Nitrogen  Ammonical fertilizers commonly use ammonium (NH4+) ion as the source of Nitrogen.  Nitrogen is useful in formation of Chlorophyll (required for photosynthesis), formation of enzymes (catalysts of all biochemical reactions) and is basic element in nucleic acids (DNA and RNA).  Incidentally, the ammonium (NH4+) ionic form is one that plants utilize less energy for uptake compared to the Nitrate (N03) ion.[3]  In addition, it is less likely to be leached.  It is therefore not surprising that commercial fertilizers have the (NH4+) ion. Conversion of ammonium to nitrate   through the process of nitrification is accompanied by release of hydrogen ions.

(NH4)2HP                                  2NH4+ + HPO42-……equation  1


NH4 ++202                          NO3 + H20 + 2H+

(aq)     (g)            (aq)    (l)      (aq)


Note that two hydrogen ions are produced for every ammonium ion converted to nitrate. The two ammonium ions in one molecule of DAP will release four hydrogen ions. This inevitably leads to increased soil acidity. Therefore it is the release of [H+] that results in an increase of acidity.  At pH levels below 5.5, hydrolysis of aluminum compounds through hydrolysis release aluminum and hydrogen ions. The effects of the release of aluminum into the soil and its eventual entry into the food chain are not difficult to postulate. In addition, the process results in the formation of insoluble compounds which further reduce uptake of nutrients, a double tragedy.


Al+3 + H20 Al(0H)2+ H

(aq)    (l)           (s)     (aq)

Uptake of most nutrients by plants is optimal at pH close to 7.  Availability of Nitrogen, Potassium, Phosphorus, Sulfur, Molybdenum and Calcium is limited under acidic conditions as the diagram below depicts.

Source: soilacidity.htm

When soil acidity is not properly controlled, reduced fertility use efficiency and crop performance is expected.5  Therefore, It is no wonder that the County Government of Trans Nzoia made the drastic decision to ban the sale and application of DAP in the county (The Star Newspaper 9thApril , 2014 ).

Continuous mining of soil nutrients accompanied by excessive applications of ammoniacal fertilizers results in loss of Nitrogen, Phosphorus, Potassium, Copper, Selenium and Zinc.  Negative nutrient balances have resulted in situations in which inputs exceed outputs.  In Mumias Nucleus Sugarcane Estate, yields have dropped from 90 tonnes/hectare in 1995 to 40 tonnes / hectare in 2014 because of severe deficiency of available Potassium (KALRO,2014). This is not worthy because  the Nucleus Estate did not experience land sub division that is a characteristic of out grower small scale farms. This explains low agricultural productivity of soils in Kakamega and Bungoma Counties in spite of  reliable  precipitation in  a zone  characterized   by  a modified equatorial climate.

Liming mitigates against  soil acidity through application of  limestone (CaCO3 ) , Ca (OH)2 or lime ( CaO )  which  contain Calcium as follows :

Caco3(s) + H2O                           Ca+2 + 2OH + CO2 —— equation 2

(s)          (l)               (aq)  +(aq)    (g)

The Ca+2 are higher in the electrochemical series and displace

Al+3 and H+

Ca+2 + [soil positive + Al+3 and H+]                         [soil particle + Ca+2] + Al+3+ H+

(aq)                          (aq)                                                               (aq)

The OH in equation 1 reacts with Al+3 to form Al(OH)3 (solid) liming hence neutralizing the toxic Al+3 to form Al(OH)3.  In addition, liming increases concentration of Calcium in the soil and since pH increases with liming, the “excess” Calcium is more readily available to plants.  However, wanton application of lime without calculating the amount required based on analytical analysis   risks enhancing alkalinity as a result of excessive accumulation of OH in the soil.

It is within this context that the Chairman of the Senate Standing Committee on Agriculture, Livestock and Fisheries pronounced himself thus ; “DAP was not recommended for Trans Nzoia unless accompanied by agricultural lime.



Four months after  the His Excellency the  President launched   the soil  suitability report, the  State  Department of  Agriculture invited bids  for supply  and delivery of various  types of fertilizer as indicated below .






1. Diammonium Phosphate (DAP) 18:46:0 5,000 9.1
2. Chemically Compound NPK


7,000 12.74
3. Urea (46%N) 5,000 9.1
4. Muriate of Potash (MOP) 3,950 7.2
5. Blend 1, NPKCaMgS;12:30:7:7:2:1 3,126 5.7
6. Blend 2, NPKCaMs;26:0:20:0:3:1 3,126 5.7
7. Blend3 , NPKCaMgS;10:26:10;10:4:5 16000 29.1
8. Blend 4,NPKCaMgS:26:0:0;10:0:5 11,748 21.4
    54,950 100


Source: TENDER REF No. MOALF/SCMD/AGRIB/12/2014-2015



The Preamble  to the advertisement  read in part  “ fertilizer is a major input in crop production and hence food security but its use by farmers in Kenya is limited by its high cost.  In an effort to make fertilizer affordable and accessible to farmers, the National Government subsidizes the price of fertilizer…………………    …………..The Government of Kenya through the Ministry of Agriculture Livestock and Fisheries now invites fertilizer dealers operating in Kenya to quote for direct supply of various types of fertilizer to Kenyans at the designated National Cereals and Produce B Board depots all over the country.”

It is not in doubt that the National Government is responsible for policy formulation and setting standards (Part 1 of the Fourth Schedule as read   with Articles 186 and 191 (b) of the Constitution). This was affirmed by Supreme Court of Kenyan the Constitutional Application No. 2 of 2011.The Court pronounced itself thus “Policy making function regarding the strategies adopted by the Executive and the Legislature, belong   to the Executive.’

From the  matrix above, it is clear that lime was omitted, yet KALRO recommended in its Report   that soils in Rift Valley   and former   Western Province were alarmingly acidic and required mitigating   against that condition by applying lime. This is a classic example of one arm of government making critical decision in total disregard of the other. This is even more preposterous because KALRO is the scientific arm of the Ministry of Agriculture, Livestock and Fisheries. In addition, the advertisement implies that fertilizers will be distributed across the country irrespective of prevailing local soil characteristics. This is fortified by the concerns raised by the Trans Nzoia County Government Senate deliberations. Time is ripe for the fertilizer industry to be regulated with the same rigor the National Government regulates chemists, pharmacists and medical facilities. In any event as demonstrated by   equations 1 and 2 fertilizers   like  drugs  are   complex chemical compounds   that should be handled with  care as required  by Article 43 (1 ) ( a) (b)  and (d)  of   the Constitution .



The challenges we face today are complex. Policy makers and planners need to go beyond analysis of climate, topography and demography, agro climatic zones  and migrate  to  the realm of understanding elements which are the building  blocks of  natural resources   whose utilization  the  National and  county governments endeavor  to plan for: this  is the  meeting of the discipline of Chemistry and  Physical Planning .

Albert Einstein the German Physicist and Nobel Prize winner in Physics stated “You cannot solve a problem at the same level it was created.”Could inability   of  policy makers including  national and county  planners to address some of the problems that face our nation be as a result of failure to embrace science? Probably yes.

Policy makers   and planners need chemists to analyze the chemical traits of land resources in the context of Article 260  in order to make informed decisions. This is the coming together of two disciplines.

In order to  ensure  that decisions  are sustainable, planners  and policy makers require scientists to provide sound solutions to mitigate against actions that negatively affect equilibrium of  natural  and man made  ecosystems ( human settlements ).

Chemists on the   other hand should  tap on  the planners’ expertise  with respect to identifying  the most appropriate sites  for location of  observatories to monitor phenomena which  will in  turn inform  planners’  future decisions   in addition  to  validating scientists’ recommendations. Soil   pH has   spatial temporal dimensions and  physical planners’ training in  nearest neighbor index, center of  gravity computations may assist in determining the most appropriate locations for  observatories . This  will subsequently guide  the  Eldoret fertilizer plant to  formulate fertilizer brands based on acidity or alkalinity of soils in various   parts of Kenya. The  upshot is by  understanding site specific pH conditions policy makers and planners will prepare action plans to guide land use activities in urban and rural areas that are realistic within the context of Articles 60  and 174.

We posit  that  fertilizer industry   is  highly scientific and  should be informed by science. Policy makers need scientific advice on  the amount and  type  of fertilizers including  mitigating agents such as lime that should be procured for various areas – see equations 1 and 2, because  soil chemistry has spatial temporal characteristics .

It is common sense that policy makers and planners need to tap from the discipline of Chemistry in order to make informed decisions   that will pass the test. This is   the philosophy of “coming together of disciplines”.



  2. The Senate Hansard – Thursday 2nd April 2015
  3. J. Mesho 2004 – Survey of Organic and Biological Chemistry
  4. Nduwumuremyi A.  2013 Effects of Different limes on soil properties and Yield of Irish Potatoes in Burera District Rwanda Msc  Kenyatta University
  1. Malcom E. Sumner – Land Use and Soil Science – Vol. VII