Soils and fertilisation: pick the incorrect (wrong) statement from the following agronomic assertions.

Introduction / Context:
Understanding how soil type and nutrient regimes affect plant growth and food safety is essential in agronomy. This item asks you to identify an incorrect statement among several that concern soil physical properties and nutrient impacts on crop quality and human health.

Given Data / Assumptions:

• Loam versus clayey soil effects on root penetration and growth.
• Health risks of excessive nitrogen leading to nitrate leaching into water supplies.
• Role of potassium in quality parameters versus specific pigments such as carotene.
• Fluoride uptake issues are complex and more related to water sources than simple soil alkalinity.

Concept / Approach:
Potassium improves stress tolerance, sugar/starch accumulation, and firmness, but a blanket claim that “excess potassic fertiliser increases carotene” is not generally supported as a direct causal relationship; variety, maturity, and other nutrients dominate carotene levels. Therefore, the potash/carotene statement is the most clearly incorrect among the options provided.

Step-by-Step Solution:

Verification / Alternative check:
Extension literature ties K to fruit quality and storage but does not endorse a direct proportional carotene enhancement from excess K; carotenoid biosynthesis depends on genetics and multiple environmental factors.

Why Other Options Are Wrong:

• Option (a) is broadly correct regarding soil texture.
• Option (b) correctly points to nitrate-related health risks; “diarrhoea” is less canonical, but cyanosis risk is real.
• Option (d) is debatable but not as clearly wrong as (c) in standard curricula.
• Option (e) is good agronomic practice.

Common Pitfalls:
Confusing quality improvements attributed to potassium (sugar, firmness) with specific pigment increases; causality is multifactorial.

Final Answer:
Applying a large excess of potassic fertiliser increases valuable carotene in fruits and vegetables.