Briefly describe the importance of evaporation in agriculture and sketch the process of evaporation in the farmland. (3 marks) (b) A farmer tries a new crop with 4 months – growth length to plant at humid farmland, which is located at latitude 10° North. By using appropriate method, determine the seasonal consumptive use, U for ONE selected crop. The mean monthly temperature for May June July and August are 63.6°F, 65.7°F, 71.3°F and 73.4°F, respectively. Refer TABLE Q3(b)(i) to select a crop and consumptive use, and TABLE Q3(b)(ii) for daytime hours coefficient. TABLE Q3(b)(i) Seasonal consumptive use crop coefficients for irrigated crops Length of normal growing Consumptive Crop season or period use coefficient Maximum monthly Alfalfa Between frosts 0.80-0.90 0.95-1.25 Bananas Full year 0.80-1.00 Beans 3 months 0.60-0.70 0.75-0.85 Cocos Full year 0.70-0.80 Coffee Full year 0.70-0.80 Com (maize) 4 months 0.75 0.85 0.80-1.20 Cotton 7 months 0.60-0.70 0.75-1.10 Dates Full year 0.65 0.80 Flax 7-8 months 0.70-0.80 Grains, small 3 months 0.75-0.85 0.85-1.00 Grain, sorghums 4-5 months 0.70-0.80 0.85-1.10 Oilseeds 3-5 months 0.65-0.75 Orchard crops Avocado Full year 0.50-0.55 Grapefruit Full year 0.55-0.65 Orange and lemon Full year 0.45-0.55 0.65-0.75″ Walnuts Between frosts 0.60 0.70 Deciduous Between frosts 0.60-0.70 0.70-0.95 Pasture crops: Grass Between frosts 0.75-0.85 0.85-1.15 Ladino white clover Between frosts 0.80 0.85 Potatoes 3-5 months 0.65-0.75 0.85-1.00 Rice 3-5 months 1.00-110 1.10-1.30 Soybeans 140 days 0.65-0.70 Sugar beets 6 months 0.65-0.75 0.85-1.00 Sugarcane Full year 0.80-0.90 Tobacco 4 months 0.70-0.80 Tomatoes 4 months 0.65 0.70 Truck crops, small 2-4 months 0.60-0.70 Vineyard 5-7 months 0.50-0.60 – Latitude North South 60° 50″ 40″ 30° 20″ 104 09 Jan Jul 0.15 0.19 0.22 0.24 0.25 0.26 0.27 Feb Aug 0.20 0.23 0.24 0.25 0.26 0.27 0.27 TABLE Q3(b)(ii) Daytime hours coefficient Month Mar Apr May Jun Jul Aug Sep Oct Sep Oct Nov Dec Jan Feb Mar Apr 0.26 0.32 0.38 0.41 0.40 0.34 0.28 0.22 0.27 0.31 0.34 0.36 0.35 0.32 0.28 0.24 0.27 0.30 0.32 0.34 0.33 0.31 0.28 0.25 0.27 0.29 0.31 0.32 0.31 0.30 0.28 0.26 0.27 0.28 0.29 0.30 0.30 0.29 0.28 0.26 0.27 0.28 0.28 0.29 0.29 0.28 0.28 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 Nov May 0.17 0.20 0.22 0.24 0.25 0.26 0.27 Dec Jun 0.13 0.18 0.21 0.23 0.25 0.26 0.27 Note: Values for Pare determined by dividing the mean daily daytime hours for a specified month by the total daytime hours in a year and then multiplying the ratio by 100.
