Water Requirements for Main Crops Grown Under Three Different Agro Ecological Zones, Zimbabwe

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1 Middle East Journal of Agriculture Research ISSN Volume: 5 Issue : 1 Jan.-Mar. 216 Pages: Water Requirements for Main Crops Grown Under Three Different Agro Ecological Zones, Zimbabwe 1 Gamal Abdel Rahman, 2 A. M. Talaat and 1 C. Zawe 1 Soil and Water Management, Irrigation Department, Zimbabwe. 2 Desert Research Center, Egypt. Received: 7 December 215 / Accepted: 25 December 215 / Publication date: 1 January 216 ABSTRACT The current work was carried out in the Agriculture Experimental Stations of, and Marondera in Zimbabwe, for studying the water requirements of some field crops; wheat, barley, maize, potatoes, sugar beet, cowpea, soybeans and sunflower grown in and regions and some vegetables crops, onion, cabbages, tomatoes, spinach, covo and Chinese cabbage, in Marondera region. The period of "heavy rains" reaches its maximum value in early December to February and the rain season starts from October to April every year in these regions. Effective rainfall attributed the water requirements during the entire growth cycle of maize, potatoes, sugar beet, cowpea, soybeans and sunflower in and regions, that irrigation is unnecessary in some months from December to February. Also the irrigation intervals (days) of crops vary from 5 to 25 during the growth seasons in all experimental stations. Data of water requirements and irrigation scheduling for seasonal crops grown in both stations, were predicted on the basis of climate, soil type and crop coefficients. The results showed that water requirements of summer crops were higher than those of winter crops for all experimental stations, except for maize. Also, the water requirements of winter crops and vegetables were higher than those of summer crops. Irrigation requirements decreased than water requirements by subtracting the contributions of effective rainfall. Using Sub-surface, drip, sprinkler, gated and siphon irrigation systems can respectively save up to 44%, 41%, 33%, 28% and 23% of water if compared to surface irrigation system. In Marondera, The water requirements for onion as compared to the climatic potential, also indicates water requirements during the growth cycle of onion from March to October under many irrigation systems. The analysis shows that in this region, the total seasonall quantities of water ranged between 8876 to m 3 /he/season. The daily needs ranged from to m 3 /hectare/day Key words: Water requirements, field crops, and regions, Zimbabwe. Introduction Water is one of the most precious and heavily scrutinized natural resources worldwide. Particularly in arid and semi-arid regions and improving agricultural water use efficiency is vitally important in parts of the world that have limited water resources. Innovative irrigation solutions must address the water scarcity problems affecting arid countries. Jensen et al. (199) defined irrigation water requirements as the quantity of water exclusive of precipitation that is required for various beneficial uses. The net irrigation requirements per unit area is the water that must be supplied by irrigation to satisfy ET, leaching and miscellaneous water requirements that are not provided by water stored in the soil and precipitation that enters the soil. Precipitation that drains through a soil is not effective unless it reduces the leaching requirement Allen et al. (1998) concluded that FAO Penman Monteith method is recommended as the sole method for determining ETo. The method has been selected because it closely approximates grass ETo as the location evaluated is physically based, and explicitly incorporates both physiological and aerodynamic parameters. The worldwide use of surface and subsurface drip irrigation systems has increased considerably in recent decades. The main advantage of this system is the potential to increase crop yields while reducing water application, fertilizer and cultivation costs. The soil moisture distribution pattern around a water emitter depends on: (i) the total volume of water applied; (ii) the emitter flow rate, source configuration (surface, subsurface, point or line) and initial boundary conditions; (iii) the soil physical properties and their spatial distribution; (iv) plant root activity ; and (v) irrigation management, El-Maloglou et al. (21) also identified that surface and subsurface drip irrigation system can increase water use efficiency but only if the system is designed to meet the soil and plant conditions. irrigation can achieve high water use efficiencies, but only when the system is designed correctly, with appropriate emitter spacing, flow rate and installation depth (Phene, 1995). Corresponding Author: Gamal Abdel Rahman, Soil and Water Management, Irrigation Department, Zimbabwe 14

2 The type of irrigation system is important and the availability of suitable irrigation systems meets the needs of agricultural expansion. Irrigation water is rapidly becoming the primary limiting factor for crop production. Surface and subsurface drip irrigation systems were proven to increase water productivity (Mailhol et al., 211). The soil moisture distribution patterns showed that the vertical movement of soil moisture was higher than the horizontal movement under both Surface and subsurface drip irrigation systems. The overall wetted area, delimited by the wetting front was largest for the manually controlled irrigation scheduling with both Surface and subsurface drip irrigation systems, the smallest for the smart controller irrigation scheduling under both Surface and subsurface drip irrigation systems, (Al-Ghobari and El-Marazky, 212) Materials and Methods Experimental Site: The study was conducted at, and Marondera Research Stations in Zimbabwe. Field crops: Season Crops Planting Date Harvesting Date Winter Wheat 1-May 3-Sep Barley 1-May 3-Sep Maize 14-Oct 3-Mar Potatoes 1-Aug 28-Dec Summer Sugar Beet 1-Feb 3-Jun Cowpea 1-Feb 21-May Soybeans 15-Nov 14-May Sunflower 15-Nov 14-May Winter Onion 15-Mar 12-Oct Cabbages 15-May 13-Oct Tomatoes 15-Sep 12-Feb Summer Spinach 15-Aug 13-Jan Covo 15-Sep 12-Feb Chinese Cabbage 18-Oct 12-Mar Climatologic data: Potential evapotranspiration (ETo) m m / day: Meteorological data for the concerned regions were collected from the meteorological stations located at the experimental sites in, and Marondera to compute ETo rates using Penman Monteith equation as recommended by the FAO Expert Consultation held in May 199 in Rome, Italy, by using CROPWAT, software version 5.7 (Smith,1992). The amounts of applied irrigation water: D iw = (ETO*Kc) /Ea (Doorenbos and Pruitt, 1984) D iw = {((ETo*Kc) Pe)/(1-LR)}/Ea for field crops Where, D iw = Applied irrigation water, (mm) Kc = Crop coefficient LR = leaching requirements Ea = efficiency (%) Pe = Effective rainfall (mm) (((ETcrop*Kr)/Ea) (Pe mm))+lr Effective Rainfall (Pe): Pe =.8 P 25 (if P > 75 mm/month) Pe =.6 P 1 (if P < 75 mm/month) Brouwer et al. (1989). P = Rainfall (mm) Field irrigation schedules: I = ((p. Sa). D) / (ETc Pe) Doorenbos and Pruitt, (1984) Sa = (F.C.% - W.P. %) x d b x 1. Where: I = Interval of irrigation (days). P = Fraction of available soil water permitting unrestricted evapotranspiration. 15

3 Sa = total available soil water, mm/m soil depth. D = Rooting depth, (m) Etc = maximum crop evapotranspiration (mm) = ETo X Kc. Pe = effective rainfall (mm) F.C. = field capacity of soil water, %. W.P. = wilting point of soil water, %. d b = bulk density of soil, g / cm 3. Soil Properties: Determined for and Experimental Stations as following: and Marondera Soil Texture Sandy loam Sandy loam Sandy Clay Loam Sandy Clay Loam ph EC soil (ds/m) EC water (ds/m) F.C (%) W.P (%) Bulk density g/cm AW. (mm) Results and Discussion Climate: Meteorological data were collected from the meteorological station located inside the experimental fields at, and Marondera with altitude of about 1475 meter above sea level, latitude is 17 o 37` S. and longitude is 31 o 8` E. These data are presented in table (1) and Fig. (1). Table 1: Average mean of meteorological data of the studied areas at the Research Stations, Zimbabwe. Elements Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. Maximum Temp C Minimum Temp C Relative Humidity (%) Wind speed (km/hour) Sunshine (hr) ETo (mm/day) Total rain (mm/month) Maximum Temp C Minimum Temp C Relative Humidity (%) Mean wind speed (km/houre) Sunshine (hr) ETo (mm/day) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec s Fig. 1: Average mean of meteorological data of the studied areas at the Research Stations, Zimbabwe. From table (1) the studied areas were characterized by high annual rainfall, about 84.6 mm / year and ranged between 1.8 to 19.8 mm/month. The rainfall occurs over a long period (October to April). The maximum air temperature ranges between 21.1 ºC (June) and 28.9 ºC (November), with an annual mean of 25.8 ºC, while the minimum air temperature ranges between 6.7 ºC (July) and 16.1 ºC (January), with an annual mean of 12.6 ºC. The Relative humidity is generally moderate and reaches 46 % in September and about 78 % in January, with an annual mean of 63.8 %. The sunshine hours ranges between 6.4 hours in December to 9.8 hours in August and September, with an annual mean of 8.3 hour. The wind velocity ranges between

4 km/hour in May and 19.1 km/hour in September, with an annual mean of km/hour. In terms of the FAO Classification (Doorenbos and Pruitt, 1984), wind velocity at the areas under consideration could be described as moderate. This leads to the fact that such areas are subjected to physical erosion, mainly due to rainfall and wind action. The reference evapotranspiration, varies widely form 3.7 mm/day in January to 7.14 mm/day in September, with an annual mean of 5.23 mm/day. The mean annual is moderate (199 mm/year). Effective rainfall: Rainy season starts in October and finished in April (Table, 2) and (Fig., 2). The amounts of rain water varied between 1.8 and 19.8 mm/month with total of 84.6 mm/year. The amounts of effective rainfall water varied between and mm/month with a total of mm/year. The quantities of water provided by effective rainfall vary between.41 and 4.14 mm / day, while Evapotranspiration needs for crops range between 3.7 and 7.14 mm/day from January to December, which corresponds to the period when all crops water requirements are greatest except wheat and barley. Similar results were obtained by Dastane, (1978) and Brouwer et al. (1989) Table 2: Rain and effective rainfall (mm/month) of the studied areas at Research Stations, Zimbabwe. Elements Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. Total rain Eff. rainfall Eff. rainfall Total rain (mm/month) Effective rainfall (mm/month) 2 (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec s Fig. 2: Rain and effective rainfall (mm) of the studied area at Research Station, Zimbabwe. Examination of the two curves (Fig. 3) shows that the rainfall exceeds superior the water requirements during the entire growth cycle of crops from December to February. This means that the water requirements for some crops are fully met by rainwater during this period, and that irrigation is unnecessary. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). Water requirements for wheat: Table (3) and Figure (4) illustrate the water requirements for wheat as compared to the climatic potential in and regions, Zimbabwe; they also indicate water requirements during the growth cycle of wheat from May to September under many irrigation systems. The analysis shows that in this region, the quantities of water ranged between 5499 to 9899 m3/he/season. The daily needs ranged from to m3/hectare/day. The lowest values are obtained in May, but the highest values obtained in July for many irrigation systems in both sites. The corresponding quantities of are almost the same. 17

5 The values range is in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation needs grow until the end of the growth cycle, as shown by the curve. Irrigation intervals ranged from 1 to 21 days during the growth season. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). (mm/day) ETo (mm/day) Rainfall (mm/day) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec s Fig. 3: Aridity factor of the studied area at Research Station, Zimbabwe. Table 3: Water requirements (m 3 /hectare/day) of wheat grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface May Jun Jul Aug Sep m 3 /ha/season Water requirements of barley: Table (4) and Figure (4) show that the water requirements of barley grown in and regions, Zimbabwe; follow the same trend of wheat. The water requirements vary from May to September under many irrigation systems. The quantities of water ranged between 5475and 9856 m3/he/season. The daily needs ranged from to m3/hectare/day. The lowest values are obtained in May, but the highest values are obtained in July for many irrigation systems. The values ranges are in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation needs grow until the end of the growth cycle, as shown by the curve. Irrigation intervals ranged from 1 to 21 days during the growth season. Similar results were obtained by Robina et al. (27), Abdel-Rahman et al. (28)a,b and Abdel-Rahman et al. (21). Water requirements of maize: Table (5) and Figure (4) present the water requirements for maize in and regions, Zimbabwe. Effective rainfall (the amount of rainwater actually used by crops) increases from planting time to the end of April. During this period, the water requirements for maize, which range from to

6 m 3 /hectare/day, are generally met. The quantities of water vary between 4841 to 8715 m 3 /he/season. Irrigation intervals ranged from 11 to 13 days during the growth season. The trend shows that water requirements for maize in this region are met particularly by the amount of rainwater which is available to crops. This tendency continues from October until March. Complementary irrigation is therefore needed to mitigate the water deficit. Irrigation needs grow until the end of the growth cycle, as shown by the curve. The lowest are values obtained in October, but the highest values are obtained in December for many irrigation systems for both sites. The values ranges are in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Similar results were found by Robina et al. (27), Abdel-Rahman et al. (28) a,b and Abdel-Rahman et al. (21). 16 Sub-surface Siphon Surface (m 3 /hectar/season) Wheat Barley Maize Potatoes Sugar Beet Cowpea SoyabeansSunflower Crops Fig. 4: Water requirements (m 3 /hectar/season) of crops grown in and regions, Zimbabwe. Table 4: Water requirements (m 3 /hectare/day) of barley grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface May Jun Jul Aug Sep m 3 /ha/season Table 5: Water requirements (m 3 /hectare/day) of maize grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface Nov Dec Aug Sep Oct m 3 /ha/season Water requirements of potatoes: Table (6) and Figure (4) present the water requirements for potatoes grown in and regions, Zimbabwe. Effective rainfall (the amount of rainwater actually used by crops) increases from October to the end of December. During this period, the water requirements for potatoes, which range from 3.54 to 19

7 m 3 /hectare/day, are generally met. The quantities of water vary from 7988 to m 3 /he/season. Irrigation intervals ranged from 5 to 12 days during the growth season. The lowest values are obtained in December, but the highest values are obtained in October for many irrigation systems. The values ranges are in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems for both sites. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). Water requirements of Sugar Beet: Table (7) and Figure (4) present the water requirements for sugar beet in and regions, Zimbabwe. Effective rainfall increases from February to April. During this period, the water requirements of sugar beet, range from to m 3 /hectare/day. The quantities of water vary from 6675 to 1215 m 3 /he/season. Irrigation intervals ranged from 1 to 25 days during the growth season. The same results were obtained for site. The lowest values obtained in February, but the highest values obtained in April for many irrigation systems. The values are ranged in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Similar results were obtained by Robina et al. (27), Abdel-Rahman et al. (28)a,b and Abdel-Rahman et al. (21). Water requirements of cowpea: Table (8) and Figure (4) present the water requirements for cowpea in and regions, Zimbabwe. Effective rainfall increases from February to April. During this period, the water requirements of cowpea, which range from 18. to m 3 /hectare/day. The quantities of water are varying between 463 to 7314 m 3 /he/season. The other site a little bit difference. The lowest values are obtained in February, but the highest values are those of April for many irrigation systems. The values are in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 1 to 23 days during the growth season. Similar results were reported by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). Table 6: Water requirements (m 3 /hectare/day) of potatoes grown in and regions, Zimbabwe. Subsurfac Siphon Surface e Siphon Surface Nov Dec Aug Sep Oct m 3 /ha/season Table 7: Water requirements (m 3 /hectare/day) of sugar beet grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface Feb Mar Apr May Jun m 3 /ha/season Table 8: Water requirements (m 3 /hectare/day) of cowpea grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface Feb Mar Apr May m 3 /ha/season

8 Water requirements of soybeans: Table (9) and Figure (4) present the water requirements for soybeans in and regions, Zimbabwe. Rainfall occurred from November to May. During this period, the water requirements of soybeans,which range from to m 3 /hectare/day. The quantities of water vary between 6436 to m 3 /ha/season. Water requirements of sunflower: Table (1) and Figure (4) present the water requirements for sunflower in and regions, Zimbabwe. Rainfall occurred from the plant date in November February to the end of growth in May. During this period, the water requirements of sunflower, range from 2.9 to 9.74 m 3 /hectare/day. The quantities of water vary between 7136 and m 3 /he/season. The lowest values are obtained in May, but the highest values are in February for many irrigation systems. The values ranged in are order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 1 to 25 days during the growth season. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27): Table 9: Water requirements (m 3 /hectare/day) of soybeans grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface Nov Dec Jan Feb Mar Apr May m 3 /ha/season Table 1: Water requirements (m 3 /hectare/day) of sunflower grown in and regions, Zimbabwe. surface Sub- Siphon Surface Siphon Surface Nov Dec Jan Feb Mar Apr May m 3 /ha/season Water requirements for onion: Table (11) and Figure (5) illustrates the water requirements for onion as compared to the climatic potential in Marondera region, Zimbabwe; they also indicate water requirements during the growth cycle of onion from March to October under many irrigation systems. The analysis shows that in this region, the total seasonal quantities of water ranged between 8876 and m3/he/season. The daily needs range from to m 3 /hectare/day. The lowest values are obtained in May, but the highest values are in July for many irrigation systems. The values are ranged in order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 1 to 2 days during the growth season. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). Table 11: Water requirements (m 3 /hectare/day) of onion grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface Mar Apr May Jun Jul Aug Sep Oct m 3 /ha/season

9 Seasonal irrigation water requirements (m3/he/season)) Sub-surface Siphon Surface Onion Cabbages Tomatoes Spinach Covo Chinese Vegetables Cabbage Fig. 5: Water requirements (m3/hectar/season) of crops grown in Marondera region, Zimbabwe. Water requirements of cabbages: Table (12) and Figure (5) show the water requirements of cabbages grown in Marondera region, Zimbabwe. The water requirements vary from May to October under many irrigation systems. The total seasonal quantities of water ranged between 6328 to 1139 m 3 /he/season. The daily needs ranged from to m 3 /hectare/day. The lowest values are obtained in May, while the highest values obtained in July for many irrigation systems. The values ranged in of order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 6 to 16 days during the growth season. Similar results were obtained by Robina et al. (27), Abdel-Rahman et al. (28)a,b and Abdel-Rahman et al. (21). Table 12: Water requirements (m3/hectare/day) of cabbages grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface May Jun Jul Aug Sep Oct (m 3 /ha/season Water requirements of tomatoes: Table (13) and Figure (5) present the water requirements for tomatoes in Marondera region, Zimbabwe, which vary from and m 3 /hectare/day, and the total seasonal quantities of water vary between 5728 and 1311 m 3 /he/season. The lowest values are in September, but the highest values are in November for many irrigation systems. The values are ranged in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 11 to 25 days during the growth season. Similar results were obtained by Gouyahali and El-Hassan (21); Some et al. (24) and Robina et al. (27). Table 13: Water requirements (m 3 /hectare/day) of tomatoes grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface Nov Dec Jan Feb Sep Oct (m 3 /he/season

10 Water requirements of spinach : Table (14) and Figure (5) present the water requirements for spinach in Marondera region, Zimbabwe, the water requirements for spinach, range from to 1.97 m 3 /hectare/day, and the total seasonal quantities of water vary between 562 and 184 m 3 /he/season. The lowest values are obtained in August, but the highest values obtained in November for many irrigation systems. The values are ranked in the order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 5 to 12 days during the growth season. Similar results were reported by Robina et al. (27), Abdel-Rahman et al. (28)a,b and Abdel-Rahman et al. (21). Table 14: Water requirements (m 3 /hectare/day) of spinach grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface Nov Dec Jan Aug Sep Oct m 3 /he/ season Water requirements of covo : Table (15) and Figure (5) present the water requirements for covo grown in Marondera region, Zimbabwe, which range from and 1.97 m 3 /hectare/day. The total seasonal quantities of water vary between 531 and 9558 m 3 /he/season. Table 15: Water requirements (m 3 /hectare/day) of covo grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface Nov Dec Jan Feb Sep Oct m 3 /he/season Water requirements of Chinese cabbage: Table (16) and Figure (6) present the water requirements for Chinese cabbage in Marondera region, Zimbabwe, range from to m 3 /hectare/day. The total seasonal quantities of water vary between 4586 to 8254 m 3 /he/season. The lowest values are obtained in October, which the highest values obtained in January for many irrigation systems. The values are ranged in order: sub-surface < drip < sprinkler < gated < siphon < surface irrigation systems. Irrigation intervals ranged from 1 to 18 days during the growth season. Similar results were reported by Robina et al. (27), Abdel-Rahman et al. (28) a,b and Abdel-Rahman et al. (21). Table 16: Water requirements (m 3 /hectare/day) of Chinese cabbage grown in Marondera region, Zimbabwe. Sub-surface Siphon Surface Nov Dec Jan Feb Mar Oct m 3 /ha/season) Irrigation requirements: Irrigation requirements are equal to water requirements, but irrigation requirements are the actual and practical irrigation needs after subtracting the effective rainfall (that is, the amount of rainwater actually used by crops) during all growth stages of crops. Irrigation requirements: Irrigation requirements in and (Fig., 7) are the equal water requirements, but irrigation requirements are the actual irrigation needs after subtracting the effective rainfall (that is, the amount of rainwater actually used by crops) during all growth stages of crops. 23

11 16 Sub-surface Siphon Surface (m3/hectar/season) Onion Cabbages Tomatoes Spinarch Covo Chinese Cabbage Vegetables Fig. 6: Irrigation requirements (m 3 /hectar/season) of crops grown in Marondera region, Zimbabwe. 14 Sub-surface Siphon Surface 12 1 (m3/hectar/season) Wheat Barley Maize Potatoes Sugar Beet Cowpea Soyabeans Sunflower Crops Fig. 7: Irrigation requirements (m3/hectar/season) of crops grown in and region, Zimbabwe. 24

12 Irrigation scheduling: Data in table (17) and Fig. (8) show that the irrigation intervals (days) of crops grown in and regions ranged from 1 to 21 for wheat, 1 to 21 for barley, 11 to 13 for maize, 5 to 12 for potatoes, 1 to 25 for sugar beet, 1 to 23 for cowpea, 1 to 25 for soybean and 1 to 24 days for sunflower during the growth seasons. Comparison between water requirements and irrigation requirements: An examination of the two figures shows that the effective rainfall attributed the water requirements during the entire growth cycle of tomatoes, spinach, covo and Chinese cabbage. This means that the water requirements for these crops are somewhat met by rainwater during October to April, and that irrigation is unnecessary in some months. Similar results were obtained by Robina et al. (27), Abdel-Rahman et al. (28)a,b and Abdel-Rahman et al. (21). Table 17: Irrigation water intervals (days) for studied crops under different irrigation systems in and regions, Zimbabwe. Wheat Barley Maize Potatoes Sugar Beet Cowpea Soybeans Sunflower D H D H D H D H D H D H D H D H Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 5 8 Oct Nov. Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Days 1 5 Wheat Barley Maize Potatoes Sugar Beet Cowpea Soyabeans Sunflower Crops Fig. 8: Irrigation intervals (days) of crops grown under some irrigation systems in and region, Zimbabwe. 25

13 Sub-surface Siphon Surface m3/hectar/season Water requirements Irrigation requirements Water requirements Irrigation requirements Water requirements Irrigation requirements Water requirements Irrigation requirements Water requirements Irrigation requirements Water requirements Irrigation requirements Onion Cabbages Tomatoes Spinach Covo Chinese Cabbage Fig. 9: Water requirements and Irrigation requirements (m3/hectar/season) of crops grown in Marondera region, Zimbabwe. Irrigation scheduling: Data in table (18) and Fig. (1) show that the irrigation intervals (days) of crops in Marondera region ranged from 1 to 2 for onion, 6 to 16 for cabbages, 11 to 25 for tomatoes, 5 to 12 for spinach, 8 to 25 for covo and 1 to 18 days for Chinese cabbage during the growth seasons Similar trends were reported by Dastane (1978), Doorenbos and Pruitt (1984), Brouwer et al. (1989) and Allen, et al. (1998). Table 18: Irrigation water intervals (days) for studied crops under different irrigation systems in and regions, Zimbabwe. Onion Onion Cabbages Tomatoes Spanich Covo Chinese cabbage Nov Dec Jan Feb Mar Apr 1 May Jun Jul 16 9 Aug Sep Oct

14 3 Nov. Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct 25 2 Days Onion Cabbages Tomatoes Spinach Covo Chinese Cabbage Crops Fig. 1: Irrigation intervals (days) of crops grown under some irrigation systems in Marondera region, Zimbabwe. Conclusions and Recommendations: From previous results, we can conclude that the effective rainfall contributions in the water requirements during the entire growth cycle of tomatoes, spinach, covo and Chinese cabbage. This means that the water requirements for these crops are somewhat met by rainwater during October to April, and that irrigation is unnecessary in some months. The effective rainfall attributed the water requirements during the entire growth cycle of tomatoes, spinach, covo and Chinese cabbage. This means that the water requirements for these crops are some met by rainwater during October to April, and that irrigation is unnecessary in some months. The irrigation intervals (days) of crops in the studied regions ranged from1 to 21 for wheat, 1 to 21 for barley, 11 to 13 for maize, 7 to 2 for potatoes, 1 to 26 for sugar beet, 1 to 24 for cowpea, 12 to 31 for soybean and 12 to 3 days for sunflower during,1 to 2 for onion, 6 to 16 for cabbages, 11 to 25 for tomatoes, 5 to 12 for spinach, 8 to 25 for covo and 1 to 18 days for Chinese cabbage during the growth seasons. The trend shows that irrigation requirements for maize in this region are met particularly by the amount of rainwater which is available from January March to crops. Rainy season tendency continues from October until March. Irrigation needs to grow until the end of the growth cycle, as shown by the curve. Table shows that the rainfall exceeds superior the water requirements during the entire growth cycle of maize from January to March. This means that the water requirements for maize are fully met by rainwater during this period, and that irrigation is unnecessary. The lowest values obtained in December, but the highest values obtained in November for many irrigation systems. Irrigation intervals ranged from 15 to 18 days during the growth season. Similar results were obtained From previous results, we conclude that the effective rainfall contributions in the water requirements during the entire growth cycle of tomatoes, spinach, covo and Chinese cabbage. This means that the water requirements for these crops are some met by rainwater during October to April, and that irrigation is unnecessary in some months. 1- Using Sub-surface, drip, sprinkler, gated and siphon irrigation systems can respectively save up to 44%, 41%, 33%, 28% and 23% of water as compared to surface irrigation system. 2- Further studied along these lines, determine the decreasing value in irrigation requirements that give an acceptable decreasing in yield for different crops. References Abdel-Rahman, G., S.H. Seidhom and Some, Leopold. 21. Soil and water relationships of some crops in Sahel-Dori, Burkina Faso. American-Eurasian J. Agric. & Environ. Sci., 7(3): Abdel-Rahman, G., S.H. Seidhom, A.M. Talaat and Some, Leopold, 28a. Water requirements of some crops in Bobo-Dioulasso, Western region of Burkina Faso. J. Applied Sci. Res., 4(12):

15 Abdel-Rahman, G., S.H. Seidhom, A.M. Talaat and Seidhome, Leopold, 28b. Soil water balance of some crops in Bobo-Dioulasso, Western region of Burkina Faso. J. Applied Sci. Res., 4(12): Allen, R.G., L.S. Pereira, D. Raes and M. Smith, Crop evapotranspiration. Guidelines for computing crop water requirements. Irrig. & Drain. Paper, No. 56, FAO, Rome, Italy. Ayers, R.S. and D.W. Westcot, Water quality for agriculture. Irrig. & Drain. Paper No. 29, FAO, Rome, Italy. Brouwer C., K. Prins and M. Heibloem, Irrigation Water Management: Irrigation Scheduling, Training manual No. 4, FAO, Rome, Italy. Dastane, N.G., 1978) Effective rainfall in irrigated agriculture. FAO Irrigation and Drainage Paper, FAO 25, Rome, Italy. Doorenbos, J. and W.O. Pruitt, Crop water requirements. Irrig. & Drain. Paper No. 24, FAO, Rome, Italy. Gouyahali Son, and B. El-Hassan, 21. Problems of crop establishment in West Burkina Faso. I World Congress on Conservation Agriculture, Madrid, 1-5 October. Jensen, M.E., R.D. Burman and R.G. Allen, 199. Evapotranspiration and irrigation water requirements. ASCE, American Society of Civil Engineers. 7, New York, NY. Rhoades, J.D., 1984a. Reusing saline drainage waters for irrigation: A strategy to reduce salt loading of rivers. In: Salinity in Watercourses and Reservoirs, R.H. French (ed). Proc Internat. Symp. on State-ofthe-Art Control of Salinity, July 1983, Salt Lake City, Utah. Ann Arbor Science, pp: Robina, W., M. Florent and M. Giovanni, 27. Actual Crop Water Use in Project Countries. A Synthesis at the Regional Level. The World Bank Development Research Group. Sustainable Rural and Urban Development Team, Policy Research Working, Smith, M., CROPWAT. A computer program for irrigation planning and management. Irrig. & Drain. Paper, No. 46, FAO, Rome, Italy. Some, L., Y. Dembele, M. Ouedraogo, M. Some, K. Bernadette, L. Faustin and Sh. Sangare, 24. Crops and soil water balance study with the CROPWAT model in Bobo-Dioulasso, BURKINA FASO. Institut De L environnement Et De Recherches Agricoles (INERA). 28