Study of Soil and Climate

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Date Version Author Note06/07/2012 0.1 Vigyan Ashram Original document created12/07/2012 0.2 Vigyan Ashram Modified the document

Introduction

Soil is an important matter for cultivation of crops. Soil supplies all the important factors for the growth of the crop plants. The yielding potential is largely dependent on the soil in which the crop grows. The type and properties of soil directly affect the crop growth and yield; hence management and conservation of soil should be done with interest.

Climate is also a factor that affects the crop growth and productivity. As we all know Indian agriculture mostly depends on climatic conditions, a changing weather scenario affects the yield and quality of crop plants and one should find ways to tackle the problem of such weather effects.

ObjectivesAfter reading this lesson you will be able to

Learn the importance of soil and climate in crop production. Learn about the methods of soil improvement and conservation. Abe to decide proper crop to be cultivated from study of soil in the

field. Learn about different climatic zones and crop growing seasons in

our country. Able to identify climatic conditions and decide crop to be grown in

your area. Study your soil samples/soil and decide on selection of crop.

SoilWe can define soil as the topmost layer of surface of earth in which the crops grow.

Soil is an upper layer of the earth crust on which crops completely depend for support and nutrition.

Basically soil is made up of different components. Following figure gives an idea of components of soil.

Fig. 1 - Components of soil

Functions of soil

Soil plays an important role in the growth of any crop and eventually quality and quantity of the yield. So, it is very important to understand the functions of soil first.

1. Providing support – Soil helps the crop by providing firm support to its roots.

2. Supply of water - Roots takes water from soil which is utilized for photosynthetic activities.

3. Supply of Nutrients – Soil is the main supplier of all the thirteen important nutrients required for growth of any crop.

4. Many micro organisms in soil perform many different functions which are very helpful and essential for crop growth. For ex. Nitrogen fixation, phosphate and sulphur solubilisation, decomposition of organic matter etc.

Formation of soil

Now, lets us see how the soil is formed. Soil is formed from the rocks by the process called weathering of rocks and by different pedogenic processes (Pedogenic process is a simple process of soil development). The properties of soil are mostly based on the rock from which it is formed as well as climatic conditions, organisms and time. An overall study of soil profile gives us knowledge about its formation and its quality.

Factors which contribute in the formation of soil are:

Fig. 2 – Soil formation

Types of soil:Soil types are classified according to many factors like colour, depth, PH, productivity, texture of soil and process of formation of soil.

Soil types according to the depth of soil are:1. Shallow Soil- The depth of this soil is less than 22.5 cm. Only

crops with shallow roots are grown in such soil. e.g. Paddy, Nagli (Nachani).

2. Medium deep soil - Depth of this soil is between 22.5 to 45 cm. Crops with medium deep roots are grown in this type of soil. e.g. Sugar cane, Banana, Gram.

3. Deep soil - Depth of this soil is more than 45 cm. Crops with long and deep roots are grown in this type of soil. e.g.-Mango, coconut

Major soil types found in India

Fig. 3 – Map showing major soil types in India

We just learned that factors like climatic conditions, topography of a place affect and decide properties of soil from that place. So properties of soil found in India and in America will be different even when they grow the same crop.

Soil types according to the Topography/ climatic conditions of soil are:

1. Red soil: Red soil is also called Yellow soil. Red soil is mainly formed due to the decomposition of ancient crystalline rocks. These soils are generally light textured with porous and friable structure. There is no lime Kankar and free carbonates. They are neutral to acidic reaction and are deficient in nitrogen humus, phosphoric acid and lime. These soils are rich in potash. In India, red soils cover almost the whole of Tamil Nadu, Kanataka, parts of Andhra Pradesh, Orissa, eastern parts of Madhya Pradesh and south-eastern part of Maharashtra. This type of soil is suitable for rice, millets, tobacco and vegetables (also groundnuts and potatoes at higher elevations)

Fig. 4 – Red soil

2. Laterites and Lateritic soil:This type of soil is red to reddish yellow in colour. It is porous and claylike. Lateritic soils are found in typical monsoon conditions i.e. under conditions of high temperature with heavy rainfall with alternate dry and wet periods. These soils are low in Nitrogen (N), Potassium (K), Lime and Magnesia and contain more Iron. Lateritic soils may contain clay minerals; but they tend to be silica-poor since silica is leached out by waters passing through the soil. These soils are found in parts of Western Ghats, Eastern Ghats, Karnataka, Kerala, Orissa, West Bengal, Assam, Tamil Nadu, etc. It is suitable for tea, coffee, rubber, cinchona, coconut and suitable for rice and millet cultivation if manure are added.

Fig. 5(a) – Lateritic soil Fig. 5(b) – Lateritic soil

3. Black soil:Black soil is also called Regur. Its ‘black’ colour comes from the compounds of iron and aluminium. These are mostly clay soils and form deep cracks during dry season. Black soils have been formed due to the solidification of lava during volcanic activity, thousands of years ago. These soils are deficient in nitrogen, phosphoric acid and organic matter. Black soils are found in Deccan Plateau –Maharashtra, Gujarat, Madhya Pradesh, Karnataka, Andhra Pradesh and Tamil Nadu. These soils are ideal for cotton crop. Apart from cotton cultivation, these fertile soils are suitable for growing cereals, oilseeds, citrus fruits and vegetables, tobacco and sugarcane.

Fig. 6 – Black soil

4. Alluvial soils:These soils occur along rivers and represent the soil materials that have been deposited by the rivers when are in flood. Their chemical composition makes them one of the most fertile soils in the world. But usually they are deficient in nitrogen, humus and phosphorus. Alluvial soils are mostly found in north-east belt of India i.e. from Punjab to Assam. They also occur in the valleys of Narmada and Tapi rivers in Madhya Pradesh and Gujrat, Mahanadi in Madhya Pradesh, Godawari river in Andhra Pradesh and Kaveri river in Tamil Nadu.

5. Desert soils:These soils are mostly sandy soils that occur in the low rainfall track. They are well supplied with soluble salts but are low in nitrogen, organic matter and have a high pH value. These soils are quite productive. These are often subjected to wind erosion.

Fig. 7 – Desert soil

6. Forest and hill soils:These soils are mainly found on the hill slopes covered by forests. They normally occur at high elevations as well as at low elevations, where the rainfall is sufficient to support trees. These soils are very shallow, steep, stony and infertile for the production of field crops. However they serve a very useful purpose by supplying forest product such as timber and fuel. Forest and hill soils are good for plantation of tea, coffee, spices and tropical fruits.

7. Saline and Alkaline soils:These soils occur in areas having a little more rainfall than the areas of desert soils. They show white incrustation of salts of Calcium and Magnesium and Sodium on the surface. These are poor in drainage and are infertile. The accumulation of salts makes the soil infertile and renders it unfit for agriculture.

8. Peaty and Marshy soils:These types of soils are found in Kerala, coastal track of Orissa, Sunderban area of West Bengal. When the vegetation growing in such wet places dies, it decomposes very slowly dues to excessive

wetness of soils and after several hundreds of year a layer of partly decayed organic matter accumulates on the surface, giving rise to such peaty and marshy soils. These are black in colour, heavy and highly acidic soils. When properly drained and fertilized, these soils produce good crops of rice.

Characteristics of an ideal soil: Till now, we learned about different types of soils found in different parts of our country. They all have some special characteristics. But there are some generic characteristics which all types of soils should have. We will study those in this section. Here are the characteristics of an ideal soil:

The soil should be well aerated. pH of the soil should be between 6 to 8. It should have good water holding capacity. It should also have well drainage capability for excess water. Soil should have good amount of organic matter and available

nutrients. It should be free from soil borne diseases and pests. Soil should be deep, friable and well textured.

Soil improvementAbove characteristics are of an ideal soil. But it is difficult to find such soil always. If your soil is lacking in one or many characteristics mentioned above, what should be done? We should try to fix the problem. This is also called soil improvement. Since the quality of soil directly affects the crop quality and yield, it is better to improve the soil quality itself. First, we will see generic soil problems:

Yield of crop will affect if -

Soils are having acidic or basic reaction (i.e pH of soil is below 6 or above 8)

Soils have poor drainage Soils have low water holding capacity Soil is salt affected Soils have pathogen

These types of soils are known as problem soils. Such soils have bad effects on crop growth and plants show deficiencies of different nutrients. There are several ways to improve the quality of your soil.

Soil improvement methods:1. Bunding and leveling: The soil should be leveled properly and

provided with strong bunds along with field boundary so that water holding capacity will improve and upper layer of soil will not wash away.

2. Provision of irrigation water: Sufficient salt free water should be made available so that extra salts (water soluble salts) in soil will wash down. This method is also called as leaching.

3. Drainage: Provision of adequate drainage is essential, especially in case of basic (pH above 8) soils. Proper surface and subsurface drainage are important factors in soil improvement.

4. Application of amendments: Gypsum is the standard amendment for alkaline soils. For acid soils calcium carbonate is applied as amendment.

Apart from above methods, proper crop rotation and addition of organic manures are also effective ways in soil improvement.

ClimateDifferent parameters of climate have direct and indirect effect on growth and yield of crop plants. As our country is having varied climatic conditions from Himalaya to Kanyakumari, climate plays an important role in agricultural production.

Climate – Long term average condition of climatic factors of a particular place is known as climate. E.g. Hot and dry or Hot and humid.

Weather - The condition of climatic factors of a particular place at a particular time is called as weather.

Weather can be different at different places in the same climatic region. But it lasts for a short time. So, we will not discuss much about weather and discuss only about climate in this chapter.

Parameters of climate:

Here are some important climatic factors or parameters and their role in plant growth:

Temperature – It is one of the important factors limiting the growth of crops. Each crop has its own range of temperature i.e. its minimum, maximum and optimum temperature for growth. Crops either die or cease their growth when the temperature is very high or very low. On the basis of temperature, our country is divided in six temperature zones:

Fig. 8 – Different temperature zones in India

Highland (Alpine): Very cold with permanent snow fall

Humid Subtropical: Cold winters with humid wind from Bay of Bengal with moderate to high rainfall

Tropical wet and dry:Wet and dry climate with moderate rainfall

Arid:Dry, hot with low rainfall

Semi arid:Hot and dry climate with low to moderate rainfall

Tropical wet:High rainfall with humid climate

Crops are classified broadly as warm or cool weather crops.

S. No. Name of cropsPreferable temperature range

1Cotton, Sorghum, Rice, Sugarcane, Ground nut

20° – 30° C

2Wheat, Oat, Potato, Sugar beet, Peas

15° – 20° C

As above, all the crops in our country can be divided into different climatic zones and that’s why they are grown in that particular area. For example: wheat is more prominent in Punjab / Hariyan state while cotton is more prominent in Maharashtra / Madhya Pradesh state.

Humidity - Humidity means amount water vapors in the air. High humidity favors growth by reducing transpiration but it increases possibility of pests and diseases and hence affects quality of fruits. Humidity is expressed in terms of Relative Humidity. It is expressed in percentage. It is defined as the ratio of amount of water vapor present in the air at a particular place to the amount of water vapor in the saturated air. Just like temperature, many crops are sensitive to amount humidity in the air. Crops like black paper, clove, cardamom grow well in high humidity while crops like wheat, jawar, bajara flavors low humid conditions.

Rainfall - The major source for soil moisture is rainfall. The total amount and distribution of rainfall is important for crop growth. Heavy rain in short period is dangerous as it leads to water logging, cause soil erosion, affect fruit setting and pollination. Indian agriculture is largely depending on rainfall. As distribution of rainfall is not even (some area it is scanty and in other areas it

may be heavy) amount of rainfall in particular season plays very important role in Indian agricultural economy. Amount of water required for any particular crop is again different from crop to crop. For eg. rice requires high rainfall while bajara requires very less rainfall to grow.

Light: Light is an important factor for photosynthesis. Rate of photosynthesis is proportional to light intensity up to a certain limit. But excess light beyond the limit reduces chlorophyll content from the leaves. The duration of light in a day has a significant effect on flowering of certain plants. This duration is called as photoperiod. According to the photoperiod, plants are called short day, long day or day neutral plants. For eg. Short day plants like Chrysanthemums, Christmas cactus requires at least 12 hours of dark period for flowering. Long day plants like Aster, lettuce, spinach requires at least 12 hours of light each day.

Wind: Moderate wind velocity is useful for pollination, but high wind velocity causes damage to crops. High wind velocity also causes soil erosion and transpiration losses.

Frost: Highly condensed or frozen form of water vapor is called as frost. Many tropical and subtropical plants are susceptible to frost.

Dew: Dew affects crops when humid air gets condense and accumulates on plant leaves. It happens especially in the winter season when morning temperature goes down rapidly. Even though dew does not directly affect plant growth, dieses and pest attacks are more when dew remains more. Eg. In grape cultivation, disease named as ‘Powdery Mildews’ attack the crop as dew remains on leaves for prolong period.

Instruments used to measure weather parameters:

Following meteorological instruments are used to measure different weather parameters:

Sr. No. Weather Parameter Instrument used

1 Rainfall Rain gauge (mm)

2 Temperature Thermometer (0C)

3 Sunshine Sunshine recorder (hr/day)

4 Wind velocity Anemometer (km/s)

5 Wind direction Wind wane

6 Humidity Hygrometer (%RH)

Fig. 9 - Rain Gauge

Fig. 10 – Sunshine recorder

Fig. 11 – Anemometer

Fig. 12 – Wind wane

Summary

Here is the summary of what you have learned in this chapter:

Soil supplies all the important factors for the growth of crop plants.

The type and properties of soil directly affect the crop growth and yield, hence management and conservation of soil is very important.

Ideal soil for crop production should be well aerated, have good water holding capacity, and optimum pH.

The soil quality of a problem soil can be improved by proper bunding and leveling of soil, providing irrigation water, application of amendments and suitable cropping pattern.

Indian agriculture is largely dependent on climatic conditions. The parameters of climate viz. Temperature, Humidity, Rainfall,

Light, Wind and frost have direct and indirect effect on growth and yield of crop plants.

Activity

1. Go to nearby farms / village and Discuss with farmers/farmers group about their opinion on the crop and soil relation , Soil properties and functions, soil problems in their area with the farmer. Note down your observations. Compare your observations with an expert.

2. Collect soil sample from your nearest agriculture field and record its reading like soil color, soil structure as sandy / loamy , crop to be grown , soil field capacity*, soil pH ( by pH paper from your school laboratory) etc.

3. Collect soil sample from your IBT school land ( for IBT schools) and do complete soil testing (with portable soil testing kit) for you project crop.

References:

http://www.britannica.comindiawaterportal.orghttp://www.mapsofindia.comhttp://geographyias.blogspot.inphysicalgeography.neten.wikipedia.orgrhinohide.wordpress.comgeographyhigh.connectfree.co.ukweather.thefuntimesguide.comgeometrytech3.wikispaces.comstuffintheair.comarthursclipart.orghttp://www.indianetzone.comhttp://www.physicalgeography.net/fundamentals/10u.html