• German chemist Justus von Liebig, widely recognized as the 'Father of Agricultural Chemistry', published his seminal work Organic Chemistry in Its Applications to Agriculture and Physiology in 1840.
• In this treatise, alongside the Law of the Minimum, Liebig enunciated the Law of Restitution (Law of Compensation), postulating that mineral nutrients removed by harvested crops must be fully restored to the soil in the form of mineral fertilizers to preserve perpetual soil fertility.
• Jean-Baptiste Boussingault established field plot experiments and nitrogen balance studies, while E. W. Hilgard was a pioneer in soil genesis and arid soil chemistry.
• Thus, the Law of Restitution was propounded by Justus von Liebig in 1840 (Option 1).

Macronutrients vs Micronutrients in plant nutrition:

• Plant essential elements are divided into macronutrients ($\gt 1000\text{ mg/kg}$ dry matter: C, H, O, N, P, K, Ca, Mg, S) and micronutrients ($\lt 100\text{ mg/kg}$ dry matter: Fe, Mn, Zn, Cu, B, Mo, Cl, Ni).
• Iron (Fe) is a micronutrient (trace element), NOT a macronutrient, even though its listed physiological role in redox enzymes and cytochromes is functionally accurate. Hence, pairing Iron as a macronutrient is incorrect.

Physiological and geochemical facts regarding Silicon:

• Statement (A) is correct: Silicon is a recognized beneficial element accumulating in graminaceous crops like rice and sugarcane (silicon accumulator plants).
• Statement (B) is correct: Deposition of amorphous silica ($SiO_2\cdot nH_2O$) in epidermal cell walls creates a double silica-cellulose layer conferring mechanical rigidity and lodging resistance.
• Statement (C) is correct: Silicon alleviates metal toxicities and prevents zinc-deficiency-induced phosphorus toxicity by improving internal nutrient balance.
• Statement (D) is incorrect: Combined oxides of Si, Al, and Fe constitute approximately $90\%$ (not $60\%$) of the mineral fraction of Earth's crust and soil. Hence, (A), (B) and (C) only are correct.