Sustainable Agriculture and Environmental Management
Sustainable Agriculture and Environmental Management tests whether you can maintain productivity while protecting soil, water and biodiversity - and defend the trade-offs with numbers rather than slogans.
Core rules
- Conservation agriculture has three pillars: minimum mechanical soil disturbance, permanent soil cover (residues or cover crops) and diversified rotation.
- Integrated pest management uses monitoring, economic thresholds, resistant varieties and biological control, with selective chemicals last.
- Compost C:N of about 25–30:1 is the working target; high C:N residues immobilise nitrogen, low C:N materials lose N as ammonia.
- Legumes fix N through rhizobia, and that fixed N becomes a credit to the following cereal.
- Erosion control: contour bunds, terracing, strip cropping, windbreaks. Hold soil loss below the tolerable rate (commonly about 10 t/ha/yr) rather than at zero.
Worked example
A bare-fallow slope loses 40 t/ha/yr with a cover-management factor of 1.0. A continuous cover crop reduces that factor to 0.2, so predicted loss = 40 × 0.2 = 8 t/ha/yr, below the 10 t/ha/yr tolerable rate. If the cover crop is grazed bare in the dry season the factor climbs again and the protection is lost - the calculation must describe the whole rotation, not one season.
Traps that cost marks
Equating organic with sustainable; assuming zero tillage is always superior regardless of weed pressure; ignoring N immobilisation after incorporating straw; forgetting that residue removal for fuel or fodder undermines conservation agriculture; treating a single-season yield gain as evidence of sustainability.