Agricultural Sciences Grade 11 P1 2018 Memo (Eng)

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 11 NOVEMBER 2018 AGRICULTURAL SCIENCES P1 MARKING GUIDELINE MARKS: 150 This marking guideline consists of 9 pages.

Downloaded from hlayiso.com 2 AGRICULTURAL SCIENCES P1 (EC/NOVEMBER 2018) SECTION A QUESTION 1 1.1 1.1.1 B √√ 1.1.2 D √√ 1.1.3 A √√ 1.1.4 D √√ 1.1.5 C √√ 1.1.6 C √√ 1.1.7 B √√ 1.1.8 A √√ 1.1.9 C √√ 1.1.10 B √√ (10 x 2) (20) 1.2 1.2.1 B only √√ 1.2.2 A only √√ 1.2.3 None √√ 1.2.4 Both A and B √√ 1.2.5 A only √√ (5 x 2) (10) 1.3 1.3.1 Molecule √√ 1.3.2 Hydrogenation √√ 1.3.3 Porosity √√ 1.3.4 Soil profile √√ 1.3.5 Mottled √√ (5 x 2) (10) 1.4 1.4.1 Mixture √ 1.4.2 Capillary √ 1.4.3 Soil form √ 1.4.4 Colloid √ 1.4.5 Mineralisation √ (5 x 1) (5) TOTAL SECTION A: 45 Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/NOVEMBER 2018) AGRICULTURAL SCIENCES P1 3 SECTION B QUESTION 2: BASIC AGRICULTURAL CHEMISTRY 2.1 Periodic table 2.1.1 Completion of the table (a) 3√ (b) 63,5 √ (c) 12 √ (d) 24 √ (e) 2√ (f) 20 √ (6) 2.1.2 Common characteristic of elements in (a) Period They have the same number of atomic orbitals/ electron shell √ (1) (b) Group Have the same number of electrons in their outer orbital √ (1) 2.1.3 Difference between halogens and noble gases regarding chemical reactivity Halogens/group 17 They are very chemically reactive √ Noble gases/group 18 They are chemically inactive gases √ (2) 2.1.4 Reason for a difference in halogen and noble gases Halogens They require one electron to fill their outer shell √ Noble gases They have a full outer shell √ (2) 2.2 Structural formula of compounds 2.2.1 Indication of the functional group (a) A: Hydroxyl/OH √ (1) (b) C: Carboxyl/ COOH √ (1) 2.2.2 Chemical formula of methanoic H √. COOH √ (2) 2.2.3 THREE protective roles of ethane in plants  It is found in cuticle and therefore protects plants against water loss √  Protects against bacteria, fungi and harmful insects √  Prevents the leaching of minerals during irrigation or rainy days √ (3) Copyright reserved Please turn over

Downloaded from hlayiso.com 4 AGRICULTURAL SCIENCES P1 (EC/NOVEMBER 2018) 2.2.4 Lewis structure of ammonia Criteria to mark Lewis structure  Correct elements (H) √  Correct element (N) √  Correct number of valence electrons √  Correct bonding √ (4) 2.2.5 Comparing compound A and B based on structural formula Compound A/ethanol one hydrogen atom is replaced by a hydroxyl/ OH √ Compound B/ethane two carbons and six hydrogen atoms combine √ (2) 2.3 Pyramid of organic compounds 2.3.1 Naming of the organic compound A: Carbohydrate √ C: Protein √ (2) 2.3.2 Indication of the building block of the compound C Amino acid √ D Fatty acid and glycerol √ (2) 2.3.3 Distinction between simple and complex protein  Simple proteins are proteins which yield only amino- acids when broken down √  Complex proteins are simple proteins combined with a non-protein material √ (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/NOVEMBER 2018) AGRICULTURAL SCIENCES P1 5 2.3.4 TWO reasons why compound B is important.  Source of energy √  Forms structural material in plants √  Provides fibre for the functioning of digestive system √ (Any 2) (2) 2.3.5 Indication of compound in D as saturated or unsaturated Unsaturated √ (1) 2.3.6 Reason It has a double bond between carbon atoms √ (1) [35] QUESTION 3: SOIL SCIENCE 3.1 3.1.1 Identification of the structure labeled A Prism-like structure (1) 3.1.2 THREE malpractices leading to the destruction of structure  Excessive cultivation/tillage accelerates the decomposition of organic matter √  Cultivation of wet soil increases compaction √  Removal of plant residue prevent building up of organic matter √  Overgrazing reduces soil organic matter √  Use of heavy material lead to soil compaction √  Practising flood irrigation √ (Any 3) (3) 3.1.3 TWO ways to prevent compaction in structure C  Application of organic content on soil √  Reducing tillage/minimum tillage √  Mulching/soil cover √  Avoid tillage when the soil is wet √ (Any 2) (2) 3.1.4 Comparing with a reason the structure B and D regarding suitability for cultivation Structure B Suitable for cultivation √ because the peds are softer and more porous √ (2) Structure D Not suitable for cultivation√ because it has a limited permeability √ (2) 3.2 Indication of the method to determine soil texture 3.2.1 Texture diagram √ (1) 3.2.2 Laser diffraction √ (1) 3.2.3 Settling columns √ (1) Copyright reserved Please turn over

Downloaded from hlayiso.com 6 AGRICULTURAL SCIENCES P1 (EC/NOVEMBER 2018) 3.3 Influence of clay and sand on soil characteristics 3.3.1 Chemical reactivity Clay has a larger surface area for chemical reactions because particles are small √ Sand has a small surface area for chemical reaction due to bigger particles √ (2) 3.3.2 Fertility Clay is more fertile because it has a higher cation adsorption capacity √ Sand soil is less fertile due to low organic matter and low cation adsorption capacity √ (2) 3.3.3 Erodability Clay particles are bound together and not easily eroded √ Sandy soil is light and loose therefore easily eroded √ (2) 3.4 Soil temperature 3.4.1 Explanation of the trend in soil temperature Gradual increase of temperature from 10 hours until it reaches the peak at 28 hours √ and declines afterwards √ and stabilises from 45–60 hours √ (2) 3.4.2 Table: The table showing soil temperature ranges over 60 hours HOURS SOIL TEMPERATURE 0C 10 23 20 41 30 46 40 44 50 35 60 35 Criteria/rubric/marking guidelines:  Correct heading √  Table √  Hours and soil temperature √  Correct unit (0C) √  Accuracy of values for hours column√  Accuracy of values for the temperature column√ (6) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/NOVEMBER 2018) AGRICULTURAL SCIENCES P1 7 3.4.3 TWO ways to manipulate temperature other than mulch  Managing soil moisture content/Irrigation and draining soil √  Clear plastic cover √  Shading √  Controlled environment/greenhouse √  Tillage practices like deep or shallow ploughing to allow more air circulation (Any 2) (2) 3.5 Soil air 3.5.1 Deduction of TWO factors influencing storage and movement of soil air from the scenario  Soil condition √  Soil depth √  Pore size distribution/porosity √ (Any 2) (2) 3.5.2 Comparison between oxygen and carbon dioxide in soil with those in the atmosphere Soil air contains a much greater proportion of CO2 than atmospheric air √ Level of oxygen in soil air is less than the oxygen level in the atmosphere √ (2) 3.5.3 Relationship between porosity and bulk density The higher the bulk density √ the lesser the pore space √ OR The lower the bulk density √ the more the pore space √ (2) [35] Copyright reserved Please turn over

Downloaded from hlayiso.com 8 AGRICULTURAL SCIENCES P1 (EC/NOVEMBER 2018) QUESTION 4: SOIL SCIENCE 4.1 Soil horizontal layers 4.1.1 Identification of the letter representing the horizon (a) D√ (b) E√ (c) C√ (d) B√ (4) 4.1.2 Soil profiles (a) Wet soil A G OR O C G √√ (2) (b) Eroded soil B √√ C (2) 4.2 Soil classification 4.2.1 THREE reasons for soil classification  Determining the crop production potential of soil √  Improved soil science communication √  Optimal utilization of country’s natural resources √  Valuation of soil √  Scientific planning of a farm √  Development of new regions √ (Any 3) (3) 4.2.2 Categories of a binomial soil classification system  Soil form √  Soil family/soil series √ (2) 4.2.3 TWO visible characteristics showing Vertic A horizon  Strongly developed structure/blocky √  Sticky when wet √  Large cracks √  High plasticity index √  Dark-coloured or red √ (Any 2) (2) 4.3 Cation adsorption 4.3.1 Type of acidity in colloid A Reserve acidity √ (1) 4.3.2 Reason for the reserve acidity Hydrogen cation √ are adsorbed on the surface of colloid √ (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/NOVEMBER 2018) AGRICULTURAL SCIENCES P1 9 4.3.3 TWO factors causing acidity  Carbon dioxide dissolving in water √  Application of nitrogen fertilisers containing ammonium √  Fertilisers containing sulphur which add a hydrogen √  Acid rain √  High rainfall leaching basic cations √ (Any 2) (2) 4.3.4 Justification of the brackishness Sodium cation √ are adsorbed on the colloid √ (2) 4.3.5 Chemical substance to reclaim brackishness Gypsum √ (1) 4.4 Nutrient cycle 4.4.1 Identification of the nutrient cycle Carbon cycle √ (1) 4.4.2 Processes in A and C A – Photosynthesis √ (2) C – Feeding √ 4.4.3 Indication of the processes in D Combustion √ (1) 4.4.4 Role of soil organisms in the cycle They break down plant and animal remains √ to release carbon dioxide into the atmosphere to continue with the cycle √ (2) 4.5 Scenario on organic matter content 4.5.1 Identification of farmer with (a) High organic matter content – Farmer B √ (b) Low organic matter content – Farmer A √ (2) 4.5.2 Explanation of how soil tillage can impact on the level of organic matter content Tillage stimulates soil microbes √ which feed on the organic matter and therefore lowers organic matter content on soil √ (2) 4.5.3 TWO physical effects of high organic matter content on soil  Compaction is prevented √  Soil is well drained/aerated √  Soil is less susceptible to erosion √  Improved water absorption √  Increased water – holding capacity √  Soil becomes warmer as it absorbs more heat √  Soil is less inclined to swell when wet √  Soil cultivates easily √ (Any 2) (2) [35] TOTAL SECTION B: 105 GRAND TOTAL: 150 Copyright reserved Please turn over