Agronomy MCQ Flashcards

What is the main purpose of applying a pre-emergent herbicide?

Answer: Prevent weed seed germination after planting but before emergence

Pre-emergent herbicides form a chemical barrier in the soil that inhibits weed seed germination and early seedling growth before weeds emerge.

In corn production, what is the 'critical period for weed control'?

Answer: V1 to V8 growth stages when weeds compete most for resources

Weeds emerging with corn during the V1–V8 period cause the greatest yield loss because they compete directly for light, water, and nutrients during early crop establishment.

Which type of fertilizer application places nutrients directly in the root zone near the seed at planting?

Answer: Starter fertilizer (in-furrow or 2×2)

Starter fertilizer placed in-furrow or 2 inches beside and 2 inches below the seed supplies readily available nutrients to seedling roots in cool, wet conditions.

What does the term 'lodging' refer to in cereal crops?

Answer: Premature stem breakage or root failure causing plants to fall over

Lodging occurs when cereal crop stems break (stem lodging) or roots give way (root lodging), reducing harvestability and grain yield.

Which method is used to determine the lime requirement of an acidic soil?

Answer: Buffer pH test (e.g., Shoemaker-McLean-Pratt)

A buffer pH test measures soil's resistance to pH change and is used to calculate how much agricultural lime is needed to raise pH to a target level.

Which pest is the primary vector for Barley Yellow Dwarf Virus (BYDV) in small grains?

Answer: Aphids

Aphids, particularly the bird cherry-oat aphid and English grain aphid, transmit BYDV to wheat, barley, and oats during feeding.

The concept of 'evapotranspiration' (ET) in agronomy combines which two processes?

Answer: Soil evaporation and plant transpiration

Evapotranspiration is the combined water loss from soil surface evaporation and plant leaf transpiration, used to schedule irrigation.