Module 3 Support pack for Soil organic matter Gr11

Study & Master Support Pack | Grade 11 CAPS Module 3 Units 1 & 2 Agricultural Sciences Soil organic matter This support pack for the Soil organic matter module in the Agricultural Sciences Grade 10 CAPS curriculum provides valuable revision activities. All activities have the answers provided. Learners can work through these individually at home or these could form the basis of a catch-up class or online lesson. You have permission to print or photocopy this document or distribute it electronically via email or WhatsApp. For more information on our Study & Master CAPS-approved  textbooks and valuable resource materials, visit www.cambridge.org Brighter Thinking | Better Learning

Module 3 – Soil organic matter Unit 1 Living organic matter Short questions 1. 1.1 The product that is formed after organic material has been well decayed is: A carbon dioxide B cellulose C hemi-cellulose D humus 1.2 Organic matter reduces the swelling of clay when wet, improving the: A colour B texture C pH D structure 1.3 The primary cause of soil degradation is: A erosion B evaporation C decaying D compaction 1.4 Soil containing organic matter: A develops a single grain structure B develops a blocky structure C reduces the swelling of clay D increases the leaching of plant nutrients (4 × 2 = 8) 2. The primary cause of soil degradation is erosion. Name THREE other causes. (3) Longer questions 3. Define the following terms: 3.1 organic material (2) 3.2 humus(2) 4. Discuss FIVE soil conditions that speed up the decay of humus. (10) 5. Discuss FOUR effects of organic matter on soils. (8) Unit 2 Non-living organic matter Short questions 1. 1.1 Immobilisation occurs when: A reduction of nitrates to nitrites occurs B minerals and compounds are made soluble by activities of living organisms C nitrogen supply is limited as the microbes compete with the plants for fertiliser nitrogen D ammonium compounds are oxidised to nitrates 1.2 An example of roughage in the decay of carbon hydrates is: A sugar B lignin C starch D cellulose 1.3 An interaction that is beneficial to the growth, survival and reproduction of two interacting species is: A immobilisation B denitrification C solubilisation D mutualism 1.4 An example of a nitrogen-free extract is: A cellulose B hemi-cellulose C lignin D fats 1.5 Nitrosomonas changes: A nitrites to ammonia B ammonia to nitrites C nitrites to nitrates D nitrates to nitrites (5 × 2 = 10) S T U DY & M A S T E R S U P P O R T PA C K S 1

2. Match each process in column A to the correct description in column B. Column A Column B 2.1 Ammonification A Minerals are made soluble by living organisms 2.2 Denitrification B Nitrogen supply is limited 2.3 Nitrification C Reduction of nitrates to nitrites 2.4 Solubilisation D Conversion of ammonia to nitrates 2.5 Immobilisation E Conversion of organic nitrogen compounds in the soil to ammonia (5 × 2 = 10) Longer questions 3. Name the TWO types of carbon hydrates. (2) 4. List FIVE requirements of soil micro- and macro-organisms. (5) 5. Name the TWO steps in the nitrification process. (2) 6. Name the microbes involved in nitrification and describe how they play a role in the process. (4) 7. Define the following terms: 7.1 mineralisation 7.2 hemi-cellulose 7.3 lignin 7.4 ammonification 7.5 ntrification (5 × 2 = 10) Memorandum Unit 1 Short questions 1.1 D 1.2 D 1.3 A 1.4 C (8) 2. Causes of soil degradation: • compaction • salinisation • depletion(3) Longer questions 3.1  Organic matter consists of the remains of dead plants and animals in the soil that have not yet been decomposed by the soil microbes. (2) 3.2 Humus consists of material that has already been decomposed so that it can no longer be recognised as plant or animal remains. It is dark in colour and well mixed with the soil particles. (2) 4. Conditions that speed up humus decay: • Regular cultivation/aeration: The more soil is cultivated, the better the aeration is. Good aeration stimulates soil microbes. The more soil microbes there are in the soil, the quicker the organic material will decay. • Irrigation: When the water content of the soil is between wilting point and veld water capacity, the soil conditions are optimal for the bacteria that are responsible for decaying of humus. • Warm oil temperature: If the soil temperature is between 25 and 27°C, it is ideal for soil bacteria to decompose organic matter. • Soil colour: The darker the soil, the more optimal the temperature conditions will be for the bacteria that decay organic material. • Soil type: Sandy soil is well aerated and warmer than clay soils, therefore provides better conditions for the bacteria that decay organic material. (10) 2 S T U DY & M A S T E R S U P P O R T PA C K S

5. Effects of organic matter on soils (any four): • It gives soil a dark colour. • The soil develops a crumb structure. • It improves water absorption. • The reduced swelling of clay improves the soil structure. • Leaching of soil nutrients that plants need is reduced. • Soil nutrients are released into the soil to become usable plant nutrients. • The protein content in organic material provides sufficient nitrogen compounds such as nitrates, which can be absorbed by plant roots. (8) Unit 2 Short questions 1.1 C 1.2 B 1.3 D 1.4 A 1.5 B (10) 2.1 E 2.2 C 2.3 D 2.4 A 2.5 B  (10) Longer questions 3. Carbon hydrates types: • nitrogen-free extract • roughages(2) 4. Requirements of soil micro- and macro-organisms (any five): • fresh organic matter • mineral nutrients such as N, P, K • oxygen for respiration • soil moisture • ideal soil temperature of 20–30o C • pH of 6.5–7.5 (5) 5. Steps in the nitrification process: 1) Ammonium compounds are oxidised to nitrites. 2) Nitrites are oxidised to nitrates. (2) 6. Nitrosomonas and Nitrosecoccus change ammonia to nitrites. Nitrobacter change the nitrites to nitrates. (4) 7. Definitions: 7.1 mineralisation: the process of decomposition by which organic compounds are rapidly broken down to elements such as ammonia, sulphur, phosphate ions, carbon dioxide and water (2) 7.2 hemi-cellulose: a polysaccharide found in plant cell walls (2) 7.3 lignin: a polymer found in plant cell walls that makes the walls woody and strong  (2) 7.4 ammonification: involves the conversion of the organic compounds in the soil to ammonium compounds through the action of soil micro-organisms such as fungi and bacteria (2) 7.5 nitrification: involves the conversion of ammonium compounds to nitrate and nitrites (2) S T U DY & M A S T E R S U P P O R T PA C K S 3