Understanding Soil Acidification Process Using Animation and Text: An Empirical User Evaluation With Eye Tracking

Abstract

This chapter presents a user study in which the participant performance is comparatively measured using two ways of presenting information: animation and text. The stimuli contain equivalent information, but use fundamentally different ways of communicating this information. We designed a workplace to simulate the process as it may occur in the real world. First, a representative task from an actual website was selected (i.e., understanding the soil acidification process). 50 participants first took part in a short ‘study session’, where they were told to remember as much as possible. Then they took a multiple choice test using either the animation or the text in an “open book” setting. The tested media have been assessed through the classical measures of effectiveness (error rate), and efficiency (time to complete the multiple choice test). Text users achieved a slightly higher score in the multiple choice test and required less time compared to animation users. In contrast, more of the animation users considered the questions “easy”. Thus, against all intuition (yet in agreement with some of the previous findings in literature) animation does not appear to perform better for the tasks in this experiment. To further strengthen the experiment, an eye tracking study was also conducted with the animated displays for a more in-depth effort to explore user strategies when asked to ‘remember as much as possible’.

Appendices

Appendix 1: Text Used in the Experiment

Soil Acidification

The pH of soil indicates the strength of acidity or alkalinity in the soil solution which bathes soil constituents, plant roots and soil micro-organisms. The more hydrogen ions (H⁺) in the soil the more acidic it is. The more hydroxyl ions (OH⁻) in the soil the more alkaline it is. While pH is measured on a scale of 1–14, most agricultural soils are found between the range 4 and 10 (when measured in water). For practical purposes, soil is neutral when pH is between 6 and 8, depending on plant requirements, and it is acidic when pH is less than 6 and alkaline when it is greater than 8. A pH of 9 denotes a very strongly alkaline soil, and a pH of 4 denotes a very strongly acidic soil. Agriculture can change the pH of soil. Ammonium-based fertilisers, urea or the urea from the urine of animals can acidify the soil in the longer-term by producing ammonium (NH₄ ⁺). The transformation of ammonium (NH₄ ⁺) to nitrite (NO₂ ⁻) to nitrate (NO₃ ⁻) releases three hydrogen ions (H⁺) into the soil. The presence of a greater number of H⁺ ions than OH⁻ ions causes the soil pH to drop.

Nitrate leaching, where NO₃ ⁻ moves below the root zone and cannot be used by plants is a significant source of agricultural acidification. Furthermore if the ammonium (NH₄ ⁺) living in nodules on legume roots is not all used up by the crop or pasture the soil can become more acidic. Agriculture can also accelerate acidification by removing alkaline products such as wool, milk, cereal grain, legumes and hay. The reverse is also true, where the introduction of manure, decaying animals, silage and stockfeeds can add alkalinity back into the soil and therefore increase soil pH.

Plant production can be constraint on strongly acid soils by aluminium toxicity and manganese toxicity. Both are more soluble at low pH, for example, aluminium dissolves into the soil solution as Al³⁺ that is taken up by the plant causing root deformation and stunted plant growth.

If a soil continues to acidify until it becomes very strongly acidic, biological activity, soil structure and nutrient toxicity and deficiency can become significant challenges to productive agriculture. One way to combat acidification is to apply lime (CaCO₃) to the soil. The breakdown of lime (CaCO₃) in the soil produces oxygen (O₂ ⁻)·and water (H₂O). This reaction consumes H⁺ ions and increases soil pH.

Appendix 2: Multiple Choice Test

Put an X next to the correct statement:

Question 1: A soil is denoted…
(a)	... Very strongly alkaline with a pH-value of 9. ... Very strongly acidic with a pH-value of 4.
(b)	... Very strongly acidic with a pH-value of 9. ... Very strongly alkaline with a pH-value of 4.
(c)	... Very strongly alkaline with a pH-value of 8. ... Very strongly acidic with a pH-value of 5.

Question 2
(a)	The more hydrogen ions (H+) in the soil the more acidic is the soil. The more hydroxyl ions (OH−) in the soil the more alkaline is the soil.
(b)	The more H+ in the soil the less acidic is the soil. The more OH− in the soil the less alkaline is the soil.
(c)	The more OH−in the soil the more acidic is the soil. The more H+ in the soil the more alkaline is the soil.

Question 3
(a)	The use of fertilisers and urea increase soil pH.
(b)	The use of fertilisers and urea decrease soil pH.
(c)	The use of fertilisers and urea decrease soil pH if air temperature is higher than 20 °C.

Question 4
(a)	By harvesting hay, grain and legumes alkaline products are removed which decreases the pH-value.
(b)	By harvesting hay, grain and legumes alkaline products are removed which increases the pH-value.
(c)	By harvesting hay, grain and legumes acidic products are removed which increases the pH-value.

Question 5
(a)	With the introduction of manure, decaying animals, silage and stockfeeds acidic products are added to soils which increases the pH- value.
(b)	With the introduction of manure, decaying animals, silage and stockfeeds alkaline products are added to soils which increases the pH-value.
(c)	With the introduction of manure, decaying animals, silage and stockfeeds alkaline products are added to soils which decreases the pH- value.

Question 6
(a)	Agriculture has only acidifying effects on the pH of soil.
(b)	Agriculture is an important factor of influence on pH of soil since it can accelerate acidification but also add alkalinity.
(c)	The acidifying and alkaline effects of agriculture on soil compensate in order to not change the pH of soil.

Question 7: The transformation of ammonium (NH4 +) to nitrite (NO2 −) to nitrate (NO3 −)…
(a)	... releases OH− ions raising soil pH.
(b)	... releases H+ ions raising soil pH.
(c)	... releases H+ ions reducing soil pH.

Question 8: NH4 + on Iegurne roots and NO3 − leached below root zone because it is not used by animals and plants
(a)	... can lead to increased soil alkalinity.
(b)	... causes soil acidification.
(c)	... does not change soil pH.

Question 9: Aluminium toxicity dissolves…
(a)	... easier.a.t low pH, The product Al3+ is taken up by the plant constraining it production.
(b)	... easier at high pH, The product Al3+ is taken up by the plant constraining it production.
(c)	... easier at low pH, The product Al3+ defenses plant against lice attacks.

Question 10: The dissolution of lime (CaCO3)
(a)	... comsumes H+ ions resulting in the soil become more alkaline.
(b)	... comsumes H+ ions resulting in the soil become more acidic.
(c)	... comsumes OH− ions resulting in the soil become more alkaline.

Appendix 3: Questionnaire

• 1. Did you use the animation/text to respond to the questions? (Yes/No)

  lf yes:

• 2. How easy was it to find the answers in the animation or in the text (very easy/easy/difficult/very difficult)?

Participant’s background questions:

• 1. Age:

• 2. Gender (m/f):

• 3. Do you have any visual impairment? (If yes, please describe the constraints)

• 4. How much do you know on a scale from 1 (no knowledge) to 6 (high knowledge) about chemical processes in soils?

• 5. Do you study or work in the field(s) of:

  • Agriculture

  • Soil science

  • Chemistry

  • Biology

  • others