R2102 Feb ‘19
a) State the meaning of EACH of the following terms:
i) soil texture; 2 marks
ii) soil structure. 2 marks
b) Describe the characteristics of TWO NAMED organic materials that can be added to the soil.
This question relates to the following parts of the syllabus:
Outcome 1. Understand the physical and chemical properties of soils.
1.3 Define soil texture and describe associated characteristics.
Define the term ‘soil texture’. Particle sizes of stones, sand, silt, clay (using Soil Survey England and Wales classification).
Describe the characteristics of the following soils: sandy loam, silty loam and clay loam: feel (gritty, silky, sticky/hard), nutrients, water retention, temperature.
1.4 Define soil structure and describe the root environment.
Define the term ‘soil structure’.
Outcome 2. Know the importance of organic matter in the root environment.
2.2 Describe the characteristics and uses of different types of organic matter added to the soil.
Describe the characteristics of the following materials: farmyard manure, garden compost, mushroom compost, composted green waste, leaf mould, chipped bark, composted straw, green manure and crop debris.
Describe the appropriate uses for the above materials, to include: mulching, soil improvement, nutrient supply.
These are straightforward questions that relate directly to the syllabus. For part a) the examiner’s comments mention that candidates who got the two terms the wrong way round couldn’t be awarded any marks, or those who described soil profiles. Texture and structure are terms that are often muddled. A good way of remembering which is which is to think of texture as being the feel of the soil. When you rub a soil sample between your fingers you can feel the different sized particles and whether it feels gritty, silky or smooth and sticky. Then structure is how it all holds together.
Good definitions would be:
i) Soil texture is the relative proportions of the different sized particles, i.e. sand, silt and clay in a soil.
ii) Soil structure is the arrangement of these particles into aggregates, including organic matter, air and water.
For part b) it is a good idea to use clear headings or numbers for the two materials you are selecting. Have a think about the amount of detail you know about the materials you select to make sure you pick two that you can describe well. There are plenty of examples to choose from for this.
The examiners’ comments suggest the following as examples of suitable answers:
‘Farm yard manure needs to be well rotted to avoid scorching plants and is low in nutrients but is applied in bulk. Farm yard manure improves the water retention of the soil and opens up the structure.
Leaf mould is low in nutrients and has an open fibrous structure. It has a variable pH but is usually acidic.
Spent mushroom compost consists of rotted farm yard manure, peat and lime. It has a high pH and decomposes quickly’.
(Although three examples are given here, this is just given as a guide to what you could describe – only ever include the number of examples that are asked for).