What is Agronomy? - Definition, Principles, Components & Importance

Definition of Agronomy

Agronomy is the science and technology of using plants for food with the earliest evidence pointing to the Middle East as the first site of planned harvesting of plants.

The term 'Agronomy' was coined to explain the concept of crop production systems. There is a strong link between crop and the major medium of its (soil). Production connotes management. Agronomy is therefore the science of soil management for crop production i.e. adapting crops to soil environment for optimum and sustainable crop production. The Greek words agros (αγρός) which means field, and nomos (νόμος) (i.e. to manage) aptly explain the term.

History of Agronomy

Agronomy and agriculture have been around for many years. Agriculture is the heart of a society, without which a society would not grow. From the Stone Age (about 10,000 B.C.), the early man initiated a sedentary lifestyle in which he moved from being a hunter and gatherer of fruit; to domestication of livestock. He also instituted principles of selection from many varieties of over 250,000 species of higher plants. He used about 3,000 and today, over 50 species are widely cultivated. This principle is referred to as plant domestication and it has gone through research for improvement over the centuries.

The concept of crop production had been evolving until scientific approach was introduced at Rothamstead Experimental Station in United Kingdom in 1834 and by 1900, universal acceptability was accorded this science. The fundamental science of which Agronomy is a derivative includes Botany, Chemistry and Physics. The introduction of Biotechnology, Hydroponics, Aquaponics and Aeroponics is a new dimension in crop production systems.

Today, geography and environmental sciences (agroclimatology) boost agronomy and have become an integral part of the concept of sustainable crop production.

Components of Agronomy

The two basic components of agronomy are:

  • Crop science
  • Soil resources management

These two components are further divided into the following applied sciences and each makes significant contributions to sustainable optimal yield and high crop quality.

Soil Resources Management Components

  • Fertility/Soil testing;
  • Soil Biology (macro and micro);
  • Soil Physics;
  • Soil Chemistry;
  • Soil Survey/Pedology;
  • Soil Mineralogy;
  • Soil Conservation and Mechanisation; and
  • Agroclimatology.

Crop Science Components

  • Crop production;
  • Crop physiology;
  • Plant nutrition;
  • Weed science;
  • Forage/Pasture agronomy;
  • Plant breeding;
  • Seed production technology;
  • Tissue culture;
  • Horticulture; and
  • Farming systems.

Divisions of Horticulture

  1. Olericulture - Science of growing vegetables 
  2. Pomology - Science of cultivation of fruits
  3. Floriculture - Science of growing flowers (ornamentals)
  4. Landscaping - modification of the visible features of an area of land.

Characteristics of Horticultural Crops

  1. High moisture content (80-90%);
  2. High respiration rates from parent plant;
  3. Large unit size;
  4. Soft texture, easily bruised;
  5. Perishable, short natural shelf life;
  6. Losses of about 30-70%; and
  7. Continuous respiration after detachment from parent plant.
Lists of Common Vegetables and Fruits

Examples of some Common Flowers

  • Begonia boweri
  • Calatlea albertii
  • Differbachia seguire
  • Cordylie indivisa
  • Kalanchoe tomentosa
  • Ficus lyrata or bejamina
  • Codiacum variegalum (crotons)
  • Hedera
  • Euphorbia pulcherima
  • Camelia japonica
  • Agave sp.
  • Ananas sp.
  • Fitonia sp.
  • Dracaena marginata
  • Euphorbia fulgars
  • Anthurium scherzerianum
  • Iris sp.
  • Tulip sp.
  • Rosa sp.
  • Freesia sp.
  • Orchids
  • Dianthus sp.

Principles of Crop Production and Farming

The focus of crop production is realising optimal yield of any cultivar. Thus, the following are the steps involved in raising crops:

  • Site selection;
  • Bush (land clearing);
  • Stumping;
  • Land preparation (ploughing and harrowing);
  • Seed bed preparation (ridging, heap or mound preparation);
  • Crop establishment (planting, sowing or transplanting);
  • Weeding;
  • Other special operations such as staking, training of vines, pruning and trimming;
  • Fertiliser application (chemical, organic, organomineral or bio fertilisers);
  • Pest and disease management (prevention and control);
  • Harvesting;
  • Value addition by processing/packaging, Consumption, Storage or Sales.

Methods of Sowing

  • Drilling: This involves making a straight hollow line and placing the seeds, followed by covering it with soil.
  • Dibbling: making/digging holes at regular intervals (spacing) and placing seeds.
  • Broadcasting: haphazard scattering/spreading of light seeds all over the prepared field. The light seeds are sometimes mixed with fine sand e.g. seeds of Amaranthus and Celosia spp. before drilling or broadcasting.

Farming Systems in Crop Production

Various combination patterns of crops on the field are captured by the term 'farming system'.

The traditional farming system started from shifting cultivation and it advanced to bush fallow system. When land became constrained due to population pressure, industrialisation and urbanisation, shifting cultivation gave way to continuous cropping with different crop combinations. The following are common examples of ways crops could be combined:

  • Sole Cropping: Planting a single type of crop per time on a field.
  • Mixed or Multiple Cropping: Planting more than one crop at a time on the field in either of the following patterns.

Intercropping - Planting a crop within the production cycle of another crop, e.g. maize and yam.

Relay cropping - Planting of a crop towards the end of another crop e.g. maize and cowpea. 

Crop rotation: Planting of at least four crops, one per time on a piece of land following some principles such as crop classification and feeding zone of the roots of the crops.

Influence of Climate and Environment on Crop Production

Nigeria is a land of contrast, ranging from the coastal plain across the primary forest (mangrove and rainforest) to derived savanna- Guinea, Sudan and Sahel savannas. Climate, length of rainy season and vegetation types dictate what crops to cultivate and the yield expectancy in each locality. Basically, there are two cropping seasons in the south: Rainy and Dry seasons.

There are advantages and disadvantages in these two seasons, favouring or otherwise affecting yield and crop quality. With the incursion of the Sahara desert (desertification), most ecological zones are now reduced to only one season. This modification of seasons is man-made and is responsible for environmental degradation, drops in crop production potential of the soil and hunger. 

For economic viability of crop production, input factors need to be optimally and efficiently managed. Transition from peasant (hoe/cutlasses) agriculture to mechanised farming has been slow due to low mana- gerial competence; land fragmentation; poor or unavailability of basic facilities, rudimentary mechanical knowledge; and adoption rather than adaptation of new technology to our environment.

Major Groups of Crop Plants

  • Arable or Field Crops: These may be annuals, ephemerals or biennials e.g. maize and cowpea.
  • Permanent or Tree Crops: They are the perennials such as oil palm, cacao, rubber, kolanut, coconut etc.
  • Forage Crops: These are usually grasses and legumes grown in pastures for the purpose of providing herbage for farm animals. Examples include Elephant grass (Pennisetum purpureum), Guinea grass (Panicum maximum), and Star grass (Cynodon spp.).

Classification of Crops

Based on their agronomic uses, the various classes are:

  • Cereals e.g, maize, rice, sorghum, wheat, barley, millet;
  • Legumes e.g. cowpea, soyabeans, pigeon pea; (iii) Forage and fodder crops e.g. guinea grass;
  • Root and tuber crops e.g. cassava, yam; cocoyam, sweet potato;
  • Fibre crops e.g. cotton, jute;
  • Fruits and nuts e.g. banana, citrus, mango, guava, cashew;
  • Sugar crops e.g. sugarcane;
  • Spices e.g. ginger, pepper and cinnamon;
  • Drugs and beverages e.g. tea, coffee, cocoa and kola;
  • Essential Oils e.g. lemon grass oil and citrus oil;
  • Oils and fats e.g. groundnut, oil palm, soyabean, sunflower; and
  • Vegetable crops e,g. "Tete' (Amaranthus caudatus), 'Ewedu' (Corchorus olitorius), 'Soko' (Celosia spp.), and fruity vegetables such as Okra and Tomatoes.

Based on their special purpose or uses, crops can be classified as:

  • Cover crops;
  • Cash crops;
  • Fertility crops;
  • Silage crops;
  • Companion crops; and
  • Trap crops

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