In agriculture, agronomy is a branch that mainly deals with which of the following aspects?

Introduction / Context:
Agriculture is a broad field that includes many specialised branches such as horticulture, animal husbandry, soil science, and agronomy. Aspiring candidates for competitive exams in India are expected to know basic definitions from agricultural science. This question focuses on the meaning of agronomy and asks you to identify which components of farming it primarily covers.

Given Data / Assumptions:

- The term given is "agronomy", a well known branch within agricultural science.

- Options mention the study of crops, the study of soil, both together, or unrelated topics like machinery only.

- It is assumed that we refer to standard academic definitions used in Indian agriculture courses.

- No numerical calculation is involved; the question is purely conceptual and definitional.

Concept / Approach:
Agronomy is commonly defined as the branch of agriculture that deals with the principles and practices of field crop production and soil management. This means that agronomists focus on how to grow crops efficiently and sustainably by understanding both plant requirements and soil conditions. Therefore, both the study of crops and the study of soil fall under agronomy. The correct approach is to recall this integrated definition and choose the option that combines these two aspects rather than picking only a single component.

Step-by-Step Solution:
Step 1: Recall that agronomy is concerned with field crops like cereals, pulses, oilseeds, and fibre crops, along with their production technologies. Step 2: Remember that agronomy also includes soil management, which covers tillage, irrigation, fertiliser use, soil conservation, and maintaining soil health. Step 3: Recognise that because agronomy studies how crops and soil interact, it necessarily involves both plant and soil aspects. Step 4: Evaluate option A (study of crops) and option B (study of soil) and see that each captures only part of the full meaning. Step 5: Notice that option C explicitly states "Both study of crops and study of soil", which matches the standard definition. Step 6: Conclude that option C is correct and that options D and E can be rejected.

Verification / Alternative Check:
If you look at the names of common agronomy textbooks, you will find that they usually cover both crop husbandry and soil management topics together. For example, topics such as crop rotation, mixed cropping, fertiliser scheduling, and water management all require understanding both plant needs and soil conditions. This supports the idea that agronomy is not limited to crops or soil alone but focuses on their combined management for maximum yield and sustainability.

Why Other Options Are Wrong:
Option A, study of crops, is incomplete because it ignores soil management, which is central to agronomy. Option B, study of soil, corresponds more closely to pure soil science, which is a related but separate discipline. Option D, none of the above, is incorrect because there is a correct choice given in option C. Option E, study of agricultural machinery only, refers more to agricultural engineering than agronomy.

Common Pitfalls:
Many students confuse agronomy with horticulture or soil science. Horticulture deals mainly with fruits, vegetables, flowers, and ornamental plants, often on a smaller and more intensive scale. Soil science focuses specifically on the physical, chemical, and biological properties of soil. Agronomy, by contrast, combines knowledge of soil and field crops to design systems of crop production. Keeping these distinctions clear will help you avoid picking a partial definition in similar questions.

Final Answer:
Agronomy is the branch of agriculture that deals with Both study of crops and study of soil, emphasising field crop production together with proper soil management.