Principles of Agronomy

Tillage is classified as: (1) Primary tillage — deep ploughing to invert and break the soil (mould-board plough, disc plough); (2) Secondary tillage — shallow operations to prepare the seedbed (harrowing, clod crushing, levelling); (3) Zero/No-tillage — crop is sown without any prior land preparation, directly into the previous crop's stubble. Zero tillage conserves soil moisture, reduces cost, and is widely used in wheat after paddy in Punjab and Haryana.

Mixed cropping: two or more crops sown simultaneously without a defined row pattern — no separate harvest. Intercropping: two or more crops grown simultaneously in defined rows, each harvested separately; expressed as Land Equivalent Ratio (LER). Relay cropping: second crop is sown into a standing first crop before it is harvested — temporal overlap but not spatial competition throughout. Sequential cropping: second crop sown after complete harvest of first.

The Planning Commission of India identified 15 agro-climatic zones based on soil type, climate, and physiography. ICAR further subdivided these into 127 sub-zones for crop planning. The 15 zones range from Zone I (Western Himalayan Region) to Zone XV (Islands of Andaman, Nicobar and Lakshadweep).

Organic farming in India is certified under the National Programme for Organic Production (NPOP) administered by APEDA under the Ministry of Commerce. NPOP standards are equivalent to EU organic standards, enabling export certification. The Participatory Guarantee System (PGS-India) is used for domestic market certification of small and marginal farmers.

LER = (yield of intercrop A / sole crop A yield) + (yield of intercrop B / sole crop B yield). An LER > 1.0 means intercropping is more productive per unit land than sole cropping. For example, LER = 1.3 means intercropping gives 30% more output from the same land. LER > 1 justifies intercropping on smallholder farms where land is limiting.

Principles of Agronomy is tested in IBPS AFO (Professional Knowledge), NABARD Grade A/B (Agriculture paper), ICAR JRF (Agronomy discipline), Pre-PG entrance (IARI, BHU, TNAU), and all state PSC Agriculture Officer exams. Cropping system definitions, LER, and agro-climatic zones are among the most repeated topics.