ICAR AIEEA PG Agronomy 14 July 2023 (Shift 1) Paper

Heavy metal uptake in leafy vegetables:

• Leafy vegetables exhibit significantly higher biological accumulation factors for heavy metals than root or fruit crops.
• Among common cultivated crops, Spinach (Spinacia oleracea) has exceptionally high transpiration rates and root uptake capacity, accumulating hazardous concentrations of toxic heavy metals like Cadmium ($\text{Cd}$) and Lead ($\text{Pb}$) in its succulent edible leaves when grown on sewage or wastewater-irrigated soils.

Fertilizer composition of Rhenania phosphate:

• Rhenania phosphate (thermophosphate / sintered phosphate) is produced by calcining rock phosphate with soda ash ($\text{Na}_2\text{CO}_3$) and silica at $1100-1200^\circ\text{C}$.
• It contains $28-30\%\text{ P}_2\text{O}_5$ in a citrate-soluble form (($ ext{CaNaPO}_4$)), which makes it an outstanding non-acidifying phosphatic fertilizer for acidic soils.

Regional soil nomenclature in Southern India:

• In Andhra Pradesh (and Telangana), red sandy clay loam soils derived from granitic and gneissic rocks are locally designated as 'Chalka' soils.
• Chalka soils are moderately shallow, light-textured, reddish-brown soils widely cultivated for rainfed crops like castor, groundnut, sorghum, and pigeonpea.

USDA particle size classification scheme:

• Very coarse sand: $2.0-1.0\text{ mm}$
• Coarse sand: $1.0-0.5\text{ mm}$
• Medium sand: $0.5-0.25\text{ mm}$
• Fine sand: $0.25-0.10\text{ mm}$ (upper diameter limit is $0.25\text{ mm}$)
• Very fine sand: $0.10-0.05\text{ mm}$
  (F) Silt: $0.05-0.002\text{ mm}$; Clay: $\lt 0.002\text{ mm}$. Hence, $0.25\text{ mm}$ corresponds to the fine sand fraction class threshold.