Irrigation, Mixed Cropping, Intercropping and Crop Rotation

Question 1 What is irrigation?

Question 2 Why irrigation of crops is necessary?

Question 3 What are the various irrigation systems adopted in India?

Question 4 What is mixed cropping?

Question 5 State few advantages of mixed cropping?

Question 6 Define intercropping with example?

Question 7 Write few differences between mixed and intercropping?

Question 8 Define the term crop rotation?

Question 9 Why should we adopt crop rotation?

Question 10 Why are legumes desirable in crop rotation?

Irrigation

The process of supplying water to crop plants of the crop fields by means of canals, reservoirs, wells, etc, is known as irrigation.

1) Crop plants are irrigated with freshwater to supply two essential elements to them, hydrogen and oxygen. Both of these elements are present in water molecules and are necessary for growth and development of crop plants.

2) Irrigation of crop fields is necessary to provide sufficient moisture for the germination of seeds. This is because seeds do not germinate in dry soils.

3) Irrigation of crop plants is essential for the growth and elongation of the roots of the crop plants. This is because roots of crop plants fail to develop and elongate in dry soil.

4) Irrigation of crops is necessary to increase the number of aerial branches (called tillers) in crop plants so as to get good crop yield. This is because, the number of tillers (aerial branches in cereals), get reduced in a dry soil which leads to loss in the crop yield.

5) Irrigation is essential for the absorption of nutrient elements by the crop plants from the soil. The irrigation water tends to dissolve the nutrients present in the soil of a crop field to form a solution. This solution of nutrients is then absorbed by the roots of crops for the development of the plants.

The irrigation or water requirements of crop plants depends on the following two factors:

1) Irrigation depending on the nature of the crop plants (i.e., crop-based irrigation)

2) Irrigation depending on the nature of soil of the crop fields (i.e., soil-based irrigation)

Crop-based Irrigation

Water requirements of different crops are different during the various stages of their growth and maturation (ripening). Some crop plants require more water, while others need less water.

For example: paddy crop (rice crop) is transplanted in standing water (wet lands) and requires continuous water supply, whereas, other crops such as wheat, gram and cotton requires less water.

For cereals such as wheat, irrigation is required before ploughing the field (i.e., before tilling), at the time of flowering and at the time of development of the grain.

Soil based Irrigation

Irrigation also depends on the nature of the soil in which crop is grown.

a) The crops grown in a sandy soil need irrigation more frequently, whereas the frequency of irrigation is comparatively less for crops grown in a clayey soil.Sandy soil is highly porous having high permeability. When the crop plants standing in a sandy soil are irrigated, then water quickly percolates down the soil and the crop plants are not able to absorb adequate amounts of water. So, due to the poor water retaining capacity of the sandy soil the crops cultivated in sandy soil need more frequent irrigation.

Clayey soil is much less permeable, so it can retain water for a much longer time. So, when the crops grown in a clayey soil is irrigated, the water persists in the soil for a longer time and as a consequence plants grown in clayey soil can absorb this water in adequate amount, Thus, due to good water retaining capacity of the clayey soil, the crops cultivated in clayey soil need irrigation less frequently.

Irrigation Systems

Some most commonly used irrigation systems are the following:

Canal system: In canal system the human-made canals receive water from one two reservoirs or from rivers. Thus, main canal is distributed into branch canals and branch canals further have distributaries or field channels. These unlined field channels may serve individual fields or a group of fields.Under the canal irrigated areas , the rotation system is followed.This provides adequate irrigation to all the fields when the water supply is short. Each field or group of fields are given water by rotation.

Tanks: Tanks are small storage reservoirs, which catch and store the runoff of smaller catchment areas. Small dams are built below the higher elevations of the catchment areas. In the tanks, outflows are controlled according to the availability of water. 

Wells: Wells are constructed wherever exploitable ground water is present.

Wells are of two types

(i) Dug wells: In the dug wells, the water is collected from water bearing strata.These dug wells have their bottom below the ground water table. The water from the shallow strata slowly accumulates in the pit. From these wells, water is lifted by mechanical means.

(ii) Tube wells: A tube well can tap water from the deeper strata. From these wells, water is lifted by diesel or electricity run pumps. Deep bore tube well can supply water continuously for many years

Mixed Cropping

Mixed cropping is the practice of growing of two or more crop simultaneously on the same piece of land.

Objective of mixed cropping: The basic objective in mixed cropping is to minimise the risk and insure against the crop failure due to abnormal weather conditions.

Crop-combination used in mixed cropping: In India, the following combination of the crops are used by farmers in mixed cropping

(1) Maize + Urad bean

(2) Cotton + Moong bean

(3) Groundnut+Sunflower

(4) Sorghum + Pigeon pea

(5) Wheat + Chick pea

(6) Barley + Chick pea

(7) Wheat + Mustard.

Criteria for the selection of the crops for mixed cropping

While selection of the crop is made for the mixed cropping, the following criteria are maintained :

(1) The different crops to be grown together are so selected that the products and waste materials from one crop stimulates the growth of the other crop.

For example : if a cereal crop such as wheat is grown along with a leguminous crop such as pulse (e.g., gram) , then the uptake of nitrogen from the soil by the cereal is compensated by the addition of nitrogen in the soil by the nitrogen-fixing legume.

This has two advantages :

(a) the fertility of the soil is increased and ultimately yield of the crop too is improved

(b) Care is taken to select crops that do not compete with each other for light, nutrients

and water. 

1) One crop is of long duration and other crop is of short duration. Thus, if one crop fails due to shortage of moisture or nutrients, the other crop can cover the risk of complete failure.

2) One crop is tall growing and other is short growing. Thus, component crops used in mixed cropping have different canopy. The crop canopy means the structure of leaves, stems and flowers found above ground.

3) If one crop is deep rooted, the other has shallow roots.

4) One crop needs comparatively lesser water and nutrients than the other.

Advantages of Mixed Cropping

1) The risk of total crop failure is reduced

2) Farmers tend to harvest a variety of produce such as cereal, pulses or vegetables or fodder to meet the various requirements of family or of an agricultural farm.

3) Due to complementary effect of component crops, yield of both crops is increased. e.g. wheat and gram.

4) Fertility of the soil is improved by growing two crops simultaneously.

5) Chances of pest infestation are greatly reduced.

Intercropping

Intercropping is a practice of growing two or more crops simultaneously in a same field in definite row patterns with the objective of increasing productivity per unit area.

Advantages of Intercropping

1) It makes better use of the natural resources of sunlight, land and water.

2) Soil erosion is effectively arrested.

3) Since the seeds of the two crops are not mixed before sowing, fertilizers can be placed as per the need of the crops.

4) Since the seed maturity period of these crops vary, the different crops can be harvested and threshed separately.

5) The produce of each crop can be marketed and consumed separately. 

Mixed Cropping	Intercropping
It has target to minimise risk of crop failure.	It has target to increase productivity per area.
Seeds of two crops are mixed before sowing	Seeds of two crops are not mixed.
It involves no set pattern of rows of crops.	It involves set patterns of rows of crops.
In this method there is a difficulty of fertilizer application to individual crops.	In intercropping fertilizer can be placed as per need of the crops.
Spraying for pest control to individual crop is difficult.	Pesticides can be easily applied to individual crop.
Harvesting and threshing of crops separately not possible.	Both crops can be easily harvested and threshed separately.
Marketing and consumption of only mixed produce is possible.	Product of each crop can be marketed and consumed separately.

Crop Rotation 

Crop rotation can be defined as the practice of growing of different crops on a piece of land in a preplanned succession.

Depending upon the duration crop rotation may be of following three types:

Type of crop rotation

One year rotation

Maize Mustard

Rice Wheat

Two years rotation

Maize – Mustard-Sugarcane – Fenugreek (Methi)

Maize Potato – Sugarcane – Peas

Three years rotation

Rice – Wheat – Moong – Mustard – Sugarcane – Berseem

Cotton – Oat-Sugarcane – Peas – Maize – Wheat

Selection of Crops for Rotation

legumes are included in the crop rotation programme. They are used to increase soil fertility. Those crops which require high fertility level (e.g. wheat) may be grown after growing legumes (e.g., pea). Thus, high input crops such as sugarcane, potato, maize, wheat and rice may be grown before low input required crops.

This practice will promote build up of diseases and insect pests and decrease the similar nutrients from the soil. Thus, while making selection of crops for crop rotation, the following points should be considered :

(i) Availability of moisture through rain or irrigation;

(ii) Status of nutrients in the soil;

(iii) Availability of inputs such as fertilizers, pesticides, human power and machine power.

(iv) Duration of crop-short or long:

(v) Marketing and processing facilities.

Advantages of Crop Rotation

1) It controls pests and weeds. Most pathogens survive on crop residue, but only for a limited time, and most pathogens do not infect multiple crops.

2) Crop rotation reduces the need of fertilizers.

3) Several Crops may be grown in succession with only one soil preparation.

4) By alternation between deep and shallow rooted crops, the soil may be utilised more completely.