Explanation:

Agronomy is the science and technology of producing and using plants for food, fuel, fiber, and land reclamation.
Agronomy has come to encompass work in the areas of plant genetics, plant physiology, meteorology, and soil science.
Crops production can go down due to biotic (diseases, insects and nematodes) and abiotic
(drought, salinity, water logging, heat, cold and frost) stresses under different situations. Varieties resistant to these stresses can improve crop production.
Agronomic characteristics are tallness, dwarfness etc of plants. Tallness and profuse branching are desirable characters for fodder crops. Dwarfness is desired in cereals.
Varieties or strains of crops can be selected by breeding for various useful characteristics such as disease resistance, response to fertilisers, product quality and high yields.
One way of incorporating desirable characters into crop varieties is by hybridisation. Hybridisation refers to crossing between genetically dissimilar plants.
This crossing may be intervarietal (between different varieties), interspecific (between two different species of the same genus) or intergeneric (between different genera).
Another way of improving the crop is by introducing a gene that would provide the desired characteristic. This results in genetically modified crops.