Key operational features and timeline of PMFBY:

• PMFBY was formally launched by the Government of India in February 2016 and implemented starting from the Kharif 2016 season (not Kharif 2015), making statement 3 incorrect.
• It operates on an 'Area Approach' basis where defined areas (villages/panchayats) are designated as Insurance Units for major crops.
• It is globally the largest crop insurance scheme in terms of farmer applications enrolled per year.
• In Kharif 2020, participation was made completely voluntary for all farmers, including loanee farmers.

Comparative fertilizer consumption (NPK kg/ha) across Indian states in 2020-21:

• Maharashtra recorded approximately $120-135\text{ kg/ha}$, which is lower than the other three listed high-consumption states.
• Telangana and Bihar recorded high fertilizer consumption exceeding $240\text{ kg/ha}$ and $220\text{ kg/ha}$ respectively due to intensive irrigated paddy and cropping systems.
• West Bengal consumed around $175-185\text{ kg/ha}$.
• Among the four given options, Maharashtra has the lowest consumption per hectare.

Classification of ecological factors influencing crop growth:

• Edaphic factors relate directly to soil physical, chemical, and biological conditions. Hence, soil organisms (along with soil moisture, soil air, temperature, and nutrients) are edaphic factors.
• Precipitation, atmospheric humidity, and solar radiation are climatic factors.
• Altitude and slope represent physiographic (topographic) factors.

Historical milestone in plant nutrition:

• Arnon and Stout ($1939$) propounded the three fundamental criteria of nutrient essentiality in higher plants.
• The three criteria state: (1) A plant cannot complete its life cycle in the absence of the element, (2) The function cannot be replaced by any other element, and (3) The element must be directly involved in plant nutrition and metabolism.
• Arnon later refined these criteria in $1954$.

Plant toxicology and cyanogenic glycosides:

• Hydrocyanic acid (HCN or prussic acid) toxicity is a well-known risk in Sorghum (jowar), particularly during early seedling growth or when the crop experiences moisture stress.
• Sorghum produces the cyanogenic glucoside dhurrin in young leaves, which hydrolyzes into free HCN in ruminant stomachs, potentially causing fatal poisoning if concentration exceeds $200\text{ ppm}$.
• Lathyrus is associated with neurotoxin ODAP (lathyrism).