Certified Professional Soil Scientist (CPSS) · USA · Soil Science Society of America
Original practice questions written to the published syllabus · not past papersMinimum soil disturbance, permanent soil cover and diversified rotations, and the looser 'regenerative' label built around them: the evidence on yields, soil carbon and water, and how outcome-based regenerative claims are verified.
In the exams: ICAR AICE Agronomy and Soil Science (conservation agriculture); CCA Sustainability specialty; agri-food company sustainability roles
Certified Crop Adviser with Sustainability Specialty and Certified Professional Soil Scientist
Applying soil health principles, residue cover measurement, cover crop selection and nitrogen credits, weed resistance management under no-till, erosion prediction, and evaluating soil carbon and regenerative claims.
How our questions for Certified Professional Soil Scientist spread across the units of Conservation & Regenerative Agriculture. Difficulty: 2 easy, 9 medium, 6 hard.
| Effects on soil health, water infiltration and erosion | 6 | |
| No-till and reduced tillage systems | 3 | |
| Residue retention and mulching | 3 | |
| Cover crops and green manures | 2 | |
| Effects on yields: evidence by climate and soil | 1 | |
| Regenerative agriculture: definitions and outcome frameworks | 1 | |
| Verifying regenerative claims in supply chains | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Under long-term no-till, phosphorus and potassium tend to accumulate near the surface. This is called:
B. Nutrient stratification
Without mixing, broadcast and residue-returned P and K concentrate near the surface (stratification); banding places nutrients deeper.
After eight years of no-till, a farmer tills once to deal with compaction and perennial weeds. What does research generally suggest about such strategic tillage?
C. Its effects on soil properties tend to be modest and short-lived, so it is a pragmatic tool
Studies suggest one-off tillage after long no-till usually has smaller and shorter effects than feared, though it releases some organic matter and disturbs fauna.
Surface residue reduces water erosion mainly because it:
C. Absorbs raindrop energy, prevents sealing and slows runoff
Residue intercepts raindrops, prevents crusting and slows overland flow, increasing infiltration and trapping sediment.
Soil contains 12 g organic carbon per kg, bulk density is 1.4 t/m3 and the sampled depth is 0.3 m. The SOC stock is:
D. 50.4 t C/ha
SOC (t/ha) = 12 x 1.4 x 0.3 x 10 = 50.4. Forgetting the factor 10 gives 5.04; using depth in cm without adjusting gives 504; 16.8 omits depth.
Which is one of the four USDA NRCS soil health principles?
C. Maximise continuous living roots
NRCS principles: minimise disturbance, maximise diversity, keep the soil covered, maximise continuous living roots.
Why can comparing soil carbon stocks to a fixed depth overstate carbon gains under no-till?
B. No-till can raise bulk density, so fixed depths hold more soil mass; use equivalent soil mass
Higher bulk density means more mass per depth; equivalent soil mass compares the same mass of soil.
Powlson and colleagues (2014) and Luo and colleagues (2010) concluded that the climate mitigation potential of no-till:
B. Has often been overstated, as whole-profile carbon gains are frequently small
No-till raises surface SOC but deeper layers may lose carbon; whole-profile gains are often small, though other benefits remain.
Long-term CA usually changes surface soil infiltration compared with conventional tillage in which direction?
B. Higher infiltration, through stable aggregates, macropores and residue cover
Aggregates, earthworm and root channels, and cover usually raise infiltration over time.
Why do many regenerative programmes combine practice adoption with periodic outcome measurement rather than relying on outcomes alone?
B. Soil carbon changes slowly, varies and is costly to measure, so practices give interim evidence
Slow, variable outcomes make purely outcome-based schemes risky for farmers and programmes.
A no-till field shows higher soil carbon than a ploughed field in the top 10 cm, but slightly less at 10-30 cm. What is the most accurate conclusion?
D. Whole-profile stocks must be compared, on an equivalent soil mass basis, before claiming a net gain
Redistribution with depth is common; net gains require whole-profile, equivalent-soil-mass comparison.
Ten here, 17 in the app. The Laisha app has every practice question we have written to Certified Professional Soil Scientist in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
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