Soil organic carbon is a measureable component of soil organic matter. It has an important role in the physical, chemical and biological function of agricultural soils. Organic carbon influences many soil characteristics including nutrient and water holding capacity, nutrient cycling and stability, improved water infiltration and aeration.

Water Holding Capacity is the ability of a certain soil texture to physically hold water against the force of gravity.  It does this by soil particles holding water molecules by the force of cohesion. It is important to know the water holding capacity of the soil to determine how much water storage capacity the field has, and to determine how much supplemental irrigation should be applied. 

Objectives :

1.To study the effect of organic carbon on water holding capacity of soil.

2.To study the effect of organic carbon on crop yield.

3.To check the effect of agriculture waste mulching on the crop yield.

Need of project:

The organic carbon of soil is decreased leading to low microbes in soil which causes high demand of fertilizers and low water holding capacity of soil. Hence, the demand of water is increased leading to higher pollution and ecological imbalance.

Hence, use of organic carbon in field will be beneficial to farmers.


Determination of water holding capacity of soil.


  1. 100 gm of dry sample was taken.
  2. The funnel was set with filter paper on measuring cylinder.
  3. The sample was added on the filter paper. Then 200 ml water was added into the sample.
  4. The sample was kept for 20 minutes and the reading of water retained in measuring cylinder was taken.
  5. Then the water holding capacity of soil was determined by using following formula.

Water holding capacity = {(Total water added-Water retained in the measuring cylinder)/Dry weight of sample}×100


  • Weight of soil=100 gm
  • Total water = 200ml
  • Water retained in the measuring cylinder = 140ml


Water holding capacity of red soil = {(200-140)/100}×100


Fig 1. Determination of water hoding capacity of soil


Collection of soil and preparation of beds:

The experiment is to be carried out in beds of 2×2 ft. For this,bricks and red soil was collected from the polyhouse of Vigyan Ashram. Measurements for bed preparation were taken with the help of tape. After that 9 beds were prepared for the experiments.

Fig 2. Collection of soil and bed preparation

Qualitative analysis:

Qualitative Analysis is the determination of non-numerical information of different properties.

Determination of organic carbon by O.C kit.

At first, Organic carbon of the red soil was determined with the help of O.C kit. It is qualitative method. O.C ranged from 0.4-0.6%. But the exact value of O.C was not received.

Fig 3. Determination of O.C by O.C kit

Quantitative analysis:

Quantitative analysis is the measurement of the quantities of particular constituents present in the substance. It is numerical information of different properties. The exact value of O.C, was determined by Walkley-Black method.

Determination of organic carbon by Walkley-black method.


  • 1. 500-ml conical flasks.
  • 2. 10-ml pipette.
  • 3. 10-and 20-ml dispensers.
  • 4. 50-ml burette.
  • 5. Analytical balance.
  • 6. Magnetic stirrer.


  1. H3PO4, 85%
  2. H2SO4, concentrated (96%)
  3. NaCl, solid
  4. Standard 0.167M K2Cr2O7:- Dissolve 49.04 g of dried (105°C) K2Cr2O7 in water and dilute to 1 L.
  5. 0.5M Fe2+ solution: Dissolve 196.1g of Fe (NH4)2(SO4) •6H2O in 800 ml of water containing 20 mL of concentrated H2SO4 and dilute to 1 L. The Fe2+ in this solution oxidizes slowly on exposure to air so it must be standardized against the dichromate.
  6. Ferroine indicator: Slowly dissolve 3.71 g of ophenanthroline and 1.74 g of FeSO4•7H2O in 250 ml of water.

Procedure :

  1. Weighed 1.00 to 2.00g oven dried soil and transfered to a 500-mL conical flask.
  2. Added 10 ml K2Cr2O7 solution by means of pipette.
  3. Added 20 mL. H2SO4 of concentrated by means of a dispenser and swirled gently to mix of the flask out of the solution.
  4. Allowed it to stand for 30 min. The flasks should be placed on an insulation pad during this time to avoid rapid heat loss.
  5. Diluted the suspension with about 200 mL of water to provide a clearer suspension for viewing the endpoint.
  6. Added 10 mL of 85% H3PO4, using a suitable dispenser, and 0.2g of NaCl. The H3PO4 and NaCl is added to complex Fe3+ which would interfere with the titration endpoint.
  7. Added 10 drops of Ferroin indicator.
  8. Titrated with 0.5 M Fe2+ to a burgundy endpoint. The color of the solution at the beginning is yellow-orange to dark green, which shifts to a turbid grey before the endpoint and then changes sharply to a wine red at the endpoint .
  9. Ran a reagent blank using the above procedure without soil. The blank is used to standardize the Fe2+ solution daily.


O.C={(B-S)×M of Fe2+×12×100}/4000


  • B = mL of Fe2+ solution used to titrate blank
  • S = mL of Fe2+ solution used to titrate sample
  • 12/4000 = Mili equivalent weight of Carbon.

Calculations :

The experiment was performed for 4 times to determine the organic carbon of red soil.The calculations were as follows:

Sr.NoBlank titration readingTitration with sample reading% O.C
Table no.1 Calculation of % O.C of soil

There was variations in the O.C of soil. It was due to the differences in procedures. The phosphoric acid was not used in first 3 times . Hence, the value of O.C was inaccurate. The experiment was performed again and proper value of O.C as per range of O.C kit was received. Soil of 0.63% O.C was used to prepare beds.

Fig 4. Determination of O.C by Walkley-Black method

The O.C of compost was determined by Walkley-Black method and it is 22.2%.

After the determination of Organic carbon of soil and compost,to increase the O.C of soil theoretical calculations were done by following formula:

O.C={[weight of soil×O.C)+(weight of compost×O.C.)]}/Total weight

%O.C of soilAmount of compost needed to add for 100 gm of soil
Table no.2 Amount of compost added to the soil
Fig 5. Mixing of compost with soil



After mixing of compost with soil beds were filled with mixed soil. And then sowing of spinach seeds were done with the help of khurpi at the spacing 15×15cm.The seed rate was 3 seeds per hole. At final, water was given to each bed.

Fig 6. Sowing of spinach


Tying of Shadenet:

For tying of shadenet, the shadenet was collected from polyhouse of Vigyan Ashram. Also the rods were collected from scrap yard. The rods were cut to the desired length with the help of hand grinder.

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Fig 7. Tying of shadenet and cutting of rod


Mulching of agricultural waste:

Material used for mulching : Soyabean Straw

After collection of Soyabean straw, mulching of it on spinach beds of thickness upto 1 cm were done. Out of 9 beds, 3 beds were mulched.

Fig.8 Collection of soyabean straw and mulching of it on beds

26/02/2022 – 14/04/2022

Irrigation application to the Spinach beds:

DateWater application (litres)(Mulching)Water application (litres)(without mulching)
Total water83.598.5
Table. Irrigation application

From above table, it is seen that quantity of water required for the beds of with mulching is less than beds of without mulching.

Fig. Application of water to the beds

At the beginning, due to more application of water to the red soil, it caused water logging. Therefore, the seeds were rottened and hence they were not germinated.


LOD (Loss on drying) of red soil was calculated to estimate irrigation application to the spinach. Following are the calculations of LOD.

TimeWithout mulchingWith mulching
10:00 AM30.1131.31
12:00 PM27.6629.86
2:00 PM19.7327.22
4:00 PM17.7024.89
Table: Calculations of LOD in %

06/04/2022 – 08/04/2022

Determination of organic carbon of red soil.

After more than a month, organic carbon of red soil was calculated by walkley black method. Following are the reading of it.

Fig. Organic carbon determination
Sr no.Blank titration readingTitration with sample readingO.C%
Table: Calculations of organic carbon


Harvesting of spinach:

Fig . Spinach harvesting

Morphological characteristics of spinach:

Beds of with mulching:

Fig .Beds of spinach with mulching
O.C %Average number of leavesAverage leaf sizeAverage plant height
0.617.4 17.115.9
Table . Morphological parameters of spinach beds with mulching

From above table it is seen that, maximum average number of leaves are found in bed in which organic carbon is 1.8% followed by bed in which O.C is 1.2%. Also Maximum average leaf size is foundation in bed kahich organised varnan 1.2% and average plant height is found in that bed which have organic carbon 1.8% and it is followed by bed of O.C 0.6%.

Beds without mulching:

Fig .Beds of spinach without mulching
O.C %Average number of leavesAverage leaf sizeAverage plant height
1.216.8 7.510.6
Table no. Morphological parameters of beds without mulching

From above table it is seen that, maximum average number of leaves are found in bed in which organic carbon is 1.8% followed by bed in which O.C is 0.6%. Maximum average leaf size is found in bed which have O.C 1.8% and maximum average plant height is found in that bed which have organic carbon 1.8% and it is followed by bed of O.C 1.2%.


Determination of water holding capacity of soil:

To check the effect of organic carbon on water holding capcity of red soil, it is again determined.The initial water holding capcity of red soil was 60%. After harvesting of spinach, the water holding capacity of soil is determined and it was found that it is increased with increased in level of organic carbon. Following are the results of water holding capacity of red soil.

Level of organic carbonWater holding capacity of soil after harvesting
Table: Water holding capacity of soil.


  1. Increase in the growth parameters of spinach crop was noticed in all beds with increase in level of organic carbon.
  2. The maximum number of leaves, plant height and leaf lenghts were found in bed which have organic carbon 1.8%.
  3. It was found that the increased in the level of organic carbon increased in water holding capacity of soil. It is increased by 11% and 24% with increase in organic carbon content by 1% and 2% respectively.
  4. Better crop yield and minimum quantity of water requirement is found in beds of mulching compared to beds of without mulching. About 16% less water required for the beds of with mulching.
  5. The result of the study have demonstrated that crop production in soil and water holding capacity of soil could be improved by adding compost to the soil.