IMPROVEMENT IN CROP YIELD

Our scientists have made it possible to increase the production of food grains four times more from 1960 to 2004 with only 25% increase in the cultivable land area. It has been possible by three major activities which are:

• Crop variety improvement
• Crop production management
• Crop protection management

The various practices that are followed at various stages of production are as follows :

• Preparation of soil
• Sowing
• Application of manures and fertilizers
• Irrigation
• Weed control
• Crop protection
• Harvesting, threshing and winnowing
• Storage
• Crop improvement
• Rotation of crops, mixed and multiple cropping.

CROP VARIETY IMPROVEMENT

Ever since man settled down in a place to start a social and cultural life, he began cultivating crops. Nearly all the present day crop plants were developed by pre historic man by altering the wild ancestral species.

The present day plants are improved varieties and have been produced by careful artificial selection and plant breeding practices. Thus,

The science of improvement of plants by improving their genetic potentialities is called plant breeding.

Plant breeding techniques:

There are four main plant breeding techniques. They are :

• Introduction : The seeds of a plant with some special features are brought from some place and grown in a new place. This is called introduction. If the plant species survives, it is selected for further cultivation.
• Selection : It is the oldest method of crop improvement even carried out by the pre historic human beings. Individual plants or group of plants having desirable characters like disease resistance, product quality, high yields, etc are selected eliminating the undesirable ones.
• Hybridization : It is a technique of plant breeding in which the two plants having desired characters are made to cross and develop seeds. The pollen grains of one plant (selected as male) are collected for pollination. The stigma of another plant (selected as female) is dusted with the pollen grains of male plant. After pollination, the fusion of desired male and female gametes results in hybrid embryo having characters of both the plants. The seeds of this plant are collected and grown in the fields.

There are various types of hybridizations. They are:

• Intravarietal hybridization : It is between the two plants of same variety.
• Intervarietal hybridization : It is between two plants belonging to different varieties but same species.
• Interspecific hybridization : It is between the different species of the same genus.
• Intergeneric hybridization : It is between different genera.
• Recombinant DNA technology or Genetic Engineering : The above mentioned methods of crop improvement (such as selection and hybridization) involves the complete genome of plants. The latest recombinant DNA technology involves transfer of one or more genes from one plant to another. The plant in which the foreign gene has been introduced is called transgenic plant or genetically modified organism / plant (GMO).

Aims and objectives of plant breeding:

The various factors for which variety improvement is done are as follows :

• High yield : It is the main concern of the plant breeder which is achieved by developing and selecting more efficient genotype.
• Improved quality : Quality is another objective of plant breeding. For example sweet, juicy and seedless oranges are preferred over a large number of sour, pithy ones. Quality improvement is required in grain size, protein quality in pulses, cooking quality in rice, malting quality of barley, etc.
• Biotic and abiotic resistances : Under natural condition the crop plants are prone to certain biotic (diseases caused by bacteria, fungi, etc, or damage caused by insects) and abiotic (drought, salinity, heat, etc) stresses which cause a great loss of production. Plant breeders, therefore, develop resistant varieties to control these stresses.
• Changes in maturity duration : By reducing the time duration from sowing to harvesting, the production of a crop can be increased many times. The farmers can grow many rounds of crops in a year in the same field by reducing the duration of crop. Uniform maturity of crop makes the process of harvesting easy and reduces losses during harvesting.
• Wider adaptability : An ability to withstand the extremes of moisture, drought, temperature, by cultivated plants is another desirable trait by the breeders. Developing such varieties, which can be grown under different environmental conditions, help farmers to grow one variety under different climatic conditions in different areas.
• Desirable agronomic characteristics : Plant breeders have also extended their hands towards the improvement of plants for the other needs. For example, cotton with long fibres and more fabric strength has been developed through hybridization.

Crop Production Management:

In order to improve and manage our crop production system, we have to focus on cheaper and farmer friendly approaches. as there is direct co-relationship between the higher yields and input applications.

Successful crop Productions upon:

• Understanding how drops develop and grow.
• How various factors affect the growth and development of crops and
• How each factor can be modified and managed.

Approaches for crop production :

• Nutrient management
• irrigation
• Mixed cropping
• Inter cropping
• crop rotation

(i) Nutrient management : Plant nutrients are the mineral elements needed by the plants for their growth, development and maintenance. plants absorb a large number of elements from soil, besides water and air, only 16 elements are essential nutrients for plants, out of 40 elements in plant ash. they are :

• Carbon
• iron
• hydrogen
• Manganese
• Oxygen
• Phosphorus
• Nitrogen
• Zinc
• Phosphors
• Copper
• Potassium
• Molybdenum
• Magnesium
• Chlorine
• Sulphur
• Calcium

Sources of plant nutrient : the plants obtain their nutrients mainly from the soil. out of the total 16 nutrients, as many as 13 are absorbed from the soil.

Characteristics of an essential plant nutrient :

• In the absence of such element, the plant is not complete its life cycle.
• Such element much have a direct influence on the plant nutrition and metabolism.
• The requirement of such element can be corrected or prevented only by supplying that Nutrient.

Classification of plant nutrients: Some mineral elements are required by the plants in large amounts whereas others are needed in very small amounts. So, on the basis of the quantities required, the various mineral elements have been grouped under two headings :

Macronutrients : The mineral elements which are required by the plants in large quantities (more than 1ppm) are called macronutrients.

e.g., carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.

Micronutrients : The mineral elements which are required by the plants in small quantities (less than 1 ppm) are called micronutrients.

e.g., iron, manganese, copper, zinc, boron, molybdenum and chlorine.

The most important nutrients or mineral elements required for plant growth are nitrogen, phosphorus and potassium (NPK).

Out of the sixteen essential nutrients, some are required by plants in relatively large amounts than the others. the nutrients required in relatively large quantities are called macronutrients or major elements, while the ones required in very small quantities or traces are called micronutrients or minor elements. deficiency of the nutrients affects physiological process in plants as well as their reproduction, growth and susceptibility to diseases. to overcome the deficiency of nutrients, the soil can be enriched by adding manures and fertilisers.

• Besides these, carbon, oxygen and hydrogen are called framework elements.