Review: Possibility of Using Ceramic Pots Manufactured Locally in Irrigation Applications (Al-Mohammed, 2015)

Table of Contents

Study
Objective of the study
Overview
Contents
Description of the experiments
Results
Conclusions
Comment

Study

Title: Possibility of Using Ceramic Pots Manufactured Locally in Irrigation Applications
Authors: Al-Mohammed, Fadhil Mohammed
Type of Study: Experimental
Journal: Journal of Kerbala University, Volume 13, Issue 2, 2015, 172-183.
Open Access: Yes
Link: https://www.iasj.net/iasj?func=article&aId=103792

 

Objectives of the study

“The main objectives of this paper are to examine seepage volume through the local manufactured ceramic pot’s walls and surface wetting edge around the pots under different conditions and to study viability of applying ceramic pot irrigation in loamy sand soil.” [173]

 

Overview

Type of experiment: Lab study; On campus field study
Country: Iraq
Place: Technical Institute of Karbala, Al-Furat Al-Awsat Technical University (32˚ 34′ 35” N, 44˚10′ 24” E)
Timespan: 19.12.2013 – 8.4.2014 (winter season)
Crops: Green onion (no more information provided)
Soil Type: Loamy sand
Number of pitchers: 9
Parameters analysed: Seepage volume, surface wetting edge, yield response, root distribution

 

Content

1. Introduction

2. Materials and Methods

3. Test Procedure

4. Results and Discussion
4.1 Seepage
4.2 Radius of Wetting Edge
4.3 Yield Response
4.4 Root Distribution

5. Conclusions

6. Recommendations for Further Studies

7. Acknowledgement

7. References

Note: Acknowledgement and References are both numbered as section 7.

 

Description of the experiments

Nine pitchers purchased from local markets were used in this experiment.

Pitcher characteristics

Pitcher Volume (ml) Height (cm) Average wall thickness (cm) Maximum outside diameter (cm) Neck diameter (cm) Base diameter (cm) Surface area (cm2)
1-9 ~ 3.150 ~ 37 19 10

 

Soil characteristics

Depth (cm) Bulk density (kg/m3) Specific
gravity
Soil moisture content (cm3/cm3) under -10kPa and -1500kPa Moisture
holding
capacity
mm/m
Organic
matter
content
%
pH EC
dS/cm
0-25  1.580 2.59 0.19 0.058  132 0.53 8.08 2.06
25-50 1.550 2.64 0.17 0.056 114 0.15 8.1 1.93
50-75   1.660  2.59 0.169 0.047  122  0.15  7.84 1.2
75-100  1510  2.62    0.172 0.049 123  0.11 8.02 0.96

 

Experimental Set-up
Note: The description of the experimental set-up is incomplete, sometimes incrompehensible and confusing. Information is not fully provided in section 3 labeled “Test Procedure”, instead the reader has to gather information distributed all over the paper to reconstruct the exact experimental set-up. The set-up itself displays several flaws, see comment section.

The plot size of the experiment was 10m x 20m. “Seepage volume and wetting edge experiments were carried out in winter season during the period from 19-12-2013 to 8-4-2014 by using ceramic pots with three replications. Tests for comparison were done for three cases.” [173]

Case 1: The clay pots were exposed to atmospheric pressure.
Case 2: The clay pots were buried in the soil.
Case 3: The clay pots were buried in the soil “with planting the wetted surface soil surrounding the ceramic pots with green onion transplants.” [174]

“Experiments were supplied with water from a main tank which is supplied with water from the city main pipe of potable water supply network.” [173]

In cases 2 and 3 “a planting hole about two times as deep and three times as wide as the ceramic pot was adopted.” [174]

In case 3 “green onion plants were planted in the wetted area surrounding the buried clay pots after three days of the operation of the ceramic pot system as shown in Fig.(3). Green onion plants were arranged with a unicenter circles in a radius 10 cm, 18 cm, and 26 cm in 12, 22, and 32 plants respectively. Crop spacing and cultivation procedure were as per horticultural recommendations (…)” [174]
Note: No details are provided concerning the question if the planting description applies to each of the three pots or if the numbers “12, 22, and 32 plants” relate to individual pots so that 12 plants were planted around pot 1, 22 around pot two and 32 around pot 3. Based on some images it seems that around each of the three pots three plant circels were planted.

The seepage volume was calculated “at any time by multiplying the vertical distance for water falls down by the cross sectional area of the water supply tank.” [174]

“The wetted area that surrounding each ceramic pot was measured in 12 constant radial lines by
using graded ruler, the average value was adopted.” [174]

 

Results

Seepage
Seepage values “vary with the interaction between the ceramic pot and its environment. The average accumulated seepage volume values for the first, second, and third cases are 159.6 l, 239.8 l, and 316.5 l respectively. The difference of accumulated seepage volume between the second and third cases is 76.6 l, which represent the effect of green onion consumptive use during the period from plants to harvest.” [175]

 

Radius of Wetting Edge
This concerns the experimental cases two and three.
“Field observation shows that wetted surface area is surrounded the ceramic pots for the second and third cases. After 38 days it has been noticed that these areas became dry for the second state ceramic pots as shown in Fig. (7). Observation were shown that these wetted areas still continue for the third case ceramic pots which is due to the canopy which is responsible for decreasing the direct sunlight. Radius of wetting Rw may be defined as the horizontal distance between the axial line of the clay pot and wetted edge for the surface wetted area that surrounds the clay pot. Knowing Rw may help us designate the area which is used for planting different crops. The results showed that the average value of Rw after 35 days is 33.6 cm.” [176]

“the average value of Rw [radius wetting edge] after 35 days is 33.6 cm.” [176]

 

Yield Response
This concerns only case three.
“the average yields, water requirements, WUE are 2.9 kg, 316.5 l, and 9.1 kg/m3 respectively.” [176]

 

Root Distribution
“(…) the green onion plants had formed mats of roots all around the ceramic pot without penetrating the wall of the ceramic pots (…). [177]

“Observations have also shown that the green onion have shallow rooting.” [177]

Conclusions

The author provides a list with ten points in the conclusions section of which nine present selected results, no conclusions. Only no. 7 might be regarded as a conclusion, but see the comment section.

“Ceramic pot system is a suitable irrigation system to irrigate green onion in loamy sand soil.” [177]

 

Comment

The study displays several flaws which are discussed in the following.

Measuring Seepage
The author writes: “Daily seepage volume for each clay pot was measured for five depths of water in each ceramic pot. The relationship between the daily seepage volume and depth of water for each ceramic pot was presented. Accordingly the depths of water that give equal daily seepage volume were selected for all ceramic pots. Then the part of the ceramic pot above the selected water depth was painted with white color, to reduce water evaporation.” [174]
While it is good that the author considered a potential variety in seepage volume of the individual pots, the choice of pots and the solution display several problems.

    • The description of this set-up is too unprecise ro reconstruct it. How was the daily seepage volume measured? What were the “five depths of water”?
    • The pots used in this experiment had a handle which influences the water seepage rate and the radius. Clay pots with handles are neither used nor recommended for use in buried clay pot irrigation systems. The author chose this type of pitchers not based on scientific reasons in regards to the experiments but simply because “This type of ceramic pots is the most popular in Iraq.” [173] Most popular for what kind of use? Certainly not for a clay pot irrigation system. “Most popular” is not a valid argument for the choice of a pot used in a scientific study when the objective is “to study viability of applying ceramic pot irrigation in loamy sand soil.” [173]
    • The authors’ solution to control the potential individual seepage volume of each pot is to paint “the part of the ceramic pot above the selected water depth (…) with white color, to reduce water evaporation.” [174]  Fig. 1 shows a photograph of four pitchers prepared in this way and the problems occurring with this solution become straight away apparent: The author painted the necks of the pitchers and in three cases the handles received some roughly painted colour splashes as well. How much sense does a colour splash on a handle make in terms of a controlled, precise reduction of seepage volume? Also, as fig. 2 demonstrates, the necks were at no point filled with water during the experiment to determine the seepage volume. If the necks do not get in contact with water at all the question arises: How much water would have seeped through those necks anyway? And can the seepage volume of a clay pot be precisely reduced by painting those parts of the pot that do not come in contact with water at all?
    • The author does not mention if the pots were hanging in the air with the seeping water able to drip on the ground, or if they were placed in some kind of box collecting the seeping water. Since the pots also seep through the bottom this important feature has to be taken into consideration when calculating the seepage volume correctly.
    • While the author writes that the seepage volume was calculated “at any time” without providing any further details to what that means exactly, fig. 4 shows data for only three to seven measures within a period of 500 hours which is about once in every three days at the most. Also the time intervall between measure points increases with no explanation. The author claims that the “daily seepage volume” [174] was measured but the figure does not show that.

 

Wetting pattern
This concerns the experimental cases two and three.
The author writes: “After 38 days it has been noticed that these areas became dry for the second state ceramic pots as shown in Fig. (7). Observation were shown that these wetted areas still continue for the third case ceramic pots which is due to the canopy which is responsible for decreasing the direct sunlight.” [176]

    • Fig. 7 only displays data for 35 days, not for 38.
    • It seems to display data for all three experimental set-ups but the data for the three cases is represented with the same symbol and colour which makes impossible to contextualize individual numbers with the individual cases 1, 2 and 3. It would have been better to use individual symbols or colours for each set-up.
    • I am not sure what the author means by saying “these areas became dry” after 38 days, since 38 days contain only 912 hours but the previous fig. 6 shows a continous seepage for cases 1 and 2 for about 2.700 hours. Does the author mean that – due to them only monitoring the wetted surface area – this area became dry despite seeping continued?
    • The author claims “Knowing Rw [radius of wetting] may help us designate the area which is used for planting different crops.” [176] This is only partially correct. To designate the area around a clay pot for planting crops it takes not only the horizontal distribution but also the vertical distribution of water.

 

Root Distribution
The author presents in his results section the observation that “the green onion have shallow rooting.” [177] The root characteristics of green onions are well known and information about this is easily available. It is surprising that the author did not acquaint himselve with this fundamental knowledge prior to the experiment.

 

Conclusions
The author presents a list with selected results in the conclusions section. Only one of the ten points in this list, no. 7, actually is qualifies as conclusion: “Ceramic pot system is a suitable irrigation system to irrigate green onion in loamy sand soil.” [177]

The author states under nos. 1 and 2: “The seepage volume for the first case increases gradually per the first 100 hrs, after that seepage volume values becomes relatively stable with oscillation.” “The seepage volume values for the second and third cases increases at the beginning of trial, these values decrease slowly towards the end of the experiments.” [177]

    • The corresponding data is presented in fig. 4 [180] but it does not seem to coincide with the author’s interpretation. The seepage volume of case 1 does not become stable after 100 hours, in fact, it does not become stable at all. The description of the seepage volume of the second and third case is imprecise, too.
    • Instead of providing incorrect descriptions of the data in the conclusions section, the author should have thought about the potential reasons of the multiple seepage peaks, e.g. case 3 displays the highest peaks at  about 250 hours and 700 hours and up until around 1.500 hours all three cases display rather a zig zag line than representing “relatively stable” data “with oscillation”. In the conclusions section the author should have provided answers for this, especially since the author claims that the water level in the pots was kept constant.
    • Fig. 4 displays 29 data points for a period of about 2.700 hours. This means only one data point is given in roughly four days. But the time spans of the data points are not equal, some of them are very close together while others are much further apart. This figure does not reflect regularly observed data and the author does not explain why he chose to display the unregularly data points.

The max. yield variance in “case 3” is 26.5% but the author does not address this significant divergence.

 

Recommendations for Further Studies
The author provides a section called “Recommendations for Further Studies” but leaves this section empty. Obviously there was either no peer review or no peer reviewer recognized this, and nobody from the publisher’s side recognized this either.


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