The standard method for calculating soil quality index is comprised of three steps; 1. selection of indicators; 2. scoring of indicators; 3. ranking the indicators based on relative importance.  Relative importance of indicators is decided based on the kind of soil function involved. The minimum data set of indicators and their relative importance varies with the type of soil function decided. For ranking or deciding weights there are several methods such as PCA, sensitivity analysis, analytical hierarchy process (AHP) and expert judgement. You may refer to the following paper for further details on soil quality.

Mandal, D., Singh,R, Dhyani,S.K., Dhyani, B.L. 2010. Landscape and land use effects on soil resources in a Himalayan watershed, Catena, 81:203-208.

Hi Sumita

Soil Quality Indexing is a matter with crucial controversy. You can use PCA to find the weighting factor for each indicator and then use it in the calculation. for more information on the method and selected indicators see this paper:

Andrews, S.S., Mitchell, J.P., Mancinelli, R., Karlen, D.L., Hartz, T.K., Horwath, W.R., Pettygrove, G.S., Scow, K.M., Munk, D.S., 2002. On-farm assessment of soil quality in California's central valley. Agronomy Journal 94, 12-23.

simpler ways are also existing. you weigh each indicator using expert opinion. and calculate the index. 

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The standard method for calculating soil quality index is comprised of three steps; 1. selection of indicators; 2. scoring of indicators; 3. ranking the indicators based on relative importance.  Relative importance of indicators is decided based on the kind of soil function involved. The minimum data set of indicators and their relative importance varies with the type of soil function decided. For ranking or deciding weights there are several methods such as PCA, sensitivity analysis, analytical hierarchy process (AHP) and expert judgement. You may refer to the following paper for further details on soil quality.

Mandal, D., Singh,R, Dhyani,S.K., Dhyani, B.L. 2010. Landscape and land use effects on soil resources in a Himalayan watershed, Catena, 81:203-208.

Great. With This complete answer. 

Hi Sumita, from your extended question it seems you are fairly aware of the PCA technique. I totally agree with Dr Mandal on different steps involved in soil quality determination. However, I’m of the opinion that some personal judgement is required at the time of indicators’ selection (MDS). Under the same PC, an easily measureable variable could be selected even though its factor loading might be slightly lower than the best in the PC. That imparts wider and easy applicability to your MDS. For example, if pH and other acidity components (Al and Mn toxicity etc) are falling in the same PC, preference should be given to pH (even with slightly lesser factor loading) based on its easy measurability.

You may refer to the paper attached here which we have published recently.

"Land use impact on soil quality in eastern Himalayan region of India"

Hope it helps.

Thanks.

I appreciate all the answers, and thankful to you all. 

I think Dr Mandals reply completes the answer.

Yes, Sir

Futher, if i need any help i will ask for it.

for improve your research work you add some soil biological properties like particulate organic matter (POM), soil microbial biomass carbon (SMBC), soil respiration and dehydrogenase activity (DHA) and use as a soil quality indicator. Thus use of soil physical, chemical and biological properties as a indicator is best for soil quality. for this you see D.L.N. Rao, 2007 paper on soil biological properties.

 Regarding method of SQI, other than PCA, u can also calculate SQI using concept of relative soil quality index (RSQI) as mention by Karlen and Stott, 1994 and Kundu et al., 2012.

 O'Geen, A.T.,S. Southard, and R.J. Southard. 2008. A revised Storie Index for use with digital soils information. UC-ANR 8000 Ser. Publ. 8335. http://anrcatalog.ucdavis.edu

Soil quality, sometimes referred as soil health, has been accepted as a key factor of sustainable agricultural land management. Soil quality assessment is intended to provide a better understanding and awareness that soil resources are really living bodies with biophysical and chemical properties. The soil quality concept developed in response to increased global importance on sustainable land use and management, stressing that SLM needs more than soil erosion control. Since its inception, several researchers have used different soil indictors to assess soil quality. For more information, please refer the following articles.

Andrews, S.S., Carroll, C.R., 2001. Designing a soil quality assessment tool for sustainable agroecosystem management. Ecological Applications 11, 1573-1585.

Karlen, D., Mausbach, M., Doran, J., Cline, R., Harris, R., Schuman, G., 1997. Soil quality: A concept, definition, and framework for evaluation (a guest editorial). Soil Science Society of America Journal 61, 4-10.

Karlen, D.L., Ditzler, C.A., Andrews, S.S., 2003. Soil quality: why and how? Geoderma 114, 145-156.

Lal, R., 1993. Tillage effects on soil degradation, soil resilience, soil quality, and sustainability. Soil & Tillage Research 27, 1-8.

Lal, R., 2011b. Soil Health and Climate Change: An Overview. In: Singh, B.P., Cowie, A.L. & Chan, K.Y. (Ed.), Soil Health and Climate Change, Soil Biology 29. Springer-Verlag, Berlin pp. 3-24.

Oberholzer, H.-R., Knuchel, R.F., Weisskopf, P., Gaillard, G., 2012. A novel method for soil quality in life cycle assessment using several soil indicators. Agronomy for sustainable development 32, 639-649.

You have to go through our paper on indexing soil quality and production efficiency in rainfed foothill region. It was published in Soil Science. This will hep you in identifying the indicators. 

Sharma, A. and Arora, Sanjay (2010) Soil Quality Indices and Relative Production Efficiency for Maize and Wheat Crops in Different Agro-Climates of North-West India. Soil Science 175 (1): 44-49.

Abstract: Assessment of management-induced changes in soil quality is important to sustaining high crop yield. A large diversity of cultivated soils necessitate identification development of an appropriate soil quality index (SQI) based on relative soil properties and crop yield. Whereas numerous attempts have been made to estimate SQI for major soils across the World, there is no standard method established and thus, a strong need exists for developing a user-friendly and credible SQI through comparison of various available methods. Therefore, the objective of this article is to compare three widely used methods to estimate SQI using the data collected from 72 soil samples from three on-farm study sites in Ohio. Additionally, challenge lies in establishing a correlation between crop yield versus SQI calculated either depth wise or in combination of soil layers as standard methodology is not yet available and was not given much attention to date. Predominant soils of the study included one organic (Mc), and two mineral (CrB, Ko) soils. Three methods used to estimate SQI were: (i) simple additive SQI (SQI-1), (ii) weighted additive SQI (SQI-2), and (iii) statistically modeled SQI (SQI-3) based on principal component analysis (PCA). The SQI varied between treatments and soil types and ranged between 0–0.9 (1 being the maximum SQI). In general, SQIs did not significantly differ at depths under any method suggesting that soil quality did not significantly differ for different depths at the studied sites. Additionally, data indicate that SQI-3 was most strongly correlated with crop yield, the correlation coefficient ranged between 0.74–0.78. All three SQIs were significantly correlated (r = 0.92–0.97) to each other and with crop yield (r = 0.65–0.79). Separate analyses by crop variety revealed that correlation was low indicating that some key aspects of soil quality related to crop response are important requirements for estimating SQI.

Source ; Comparison of Soil Quality Index Using Three Methods by Atanu Mukherjee , Rattan Lal Published: August 22, http://dx.doi.org/10.1371/journal.pone.0105981

Hello, Can anyone answer my quiry? I am planning to conduct soil quality assessment under cassava farming system, I would like to ask what methods should I employ in conducting the test? And how can I able to interpret them?

Dear Samraida

You can select the minimum data set by Principal component analysis using either SPSS or SAS software. There is a lot of literature on assessment of soil quality assessment. I hereby attaching a file you can keep it as a baseline.

Thank you Sumita Chandel, I will read this one.