Water consumption for 100 ha crop

i have seen quite large agricultural activities in the Saudi desert, probably fed by underground water reserves. 

Do you have a suggestions for the average water consumption kg/ha per month for such for the following crops:

a) wheat

b) alfalfa 

And would that be comparable (the water consumption) for areas in the Sahel zone, where crop could be farmed  if water would be available as needed?

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• Irrigation
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• Irrigation Engineer

5 Answers

1. From previous experience in Saudi Arabia's Central region Alfalfa crops irrigated with central pivot systems required in average of 800-1000 gallons per minute flow rates around the clock per 40 Ha. crop circles

    

2. Download Cropwat and Climwat (FAO)  and you can calculated easily the crop water use for most places in the world for most crops. 

3. Generally water has a big value in hyper arid areas such as Saudi Arabia, so it is useless to cultivate Alfa Alfa and Wheat in a big areas, for wheat we tries in Egypt to cultivate it under drip irrigation system in narrow rows, and the water consumption was decreased by 50% compared with sprinkler irrigation system with good management, and the water use productivity was 1.2 kg/m3.

   For Alfa Alfa, it could be cultivated nearest to the shores areas, also you could use some alternatives for animal feeding such as ponikam which is salinity tolerant crop so you can use other resources of water not only fresh underground water, or cultivate barely which is also salininty tolerant and cultivate it again for 9 weeks to feed animals in hydroponics chambers.

    

   Dr. Hani Mehanna

   1 Comment

   1. Thank you, much appreciated.

4. Water use is high in alfalfa because it has a long growing season, a deep root system, and a dense canopy of vegetation. The amount of water needed for alfalfa production is a function of temperature, wind, humidity, and the amount and intensity of light. The irrigation requirement for alfalfa is determined by rainfall and the water holding capacity of the soils growing the crop. Commonly cited ranges in water requirements for alfalfa are 20 to 46 inches of water per season, depending on climate, elevation, growing season, number of cuttings, latitude, and fall dormancy rating of the alfalfa variety. Not much water is exported with alfalfa hay. Potential irrigated alfalfa hay yield at elevations near 4000 feet is about 7.5 tons/acre. Hay harvested at 12% moisture removes 240 lbs water/ton hay, or 1,800 lbs/acre for a normal crop of alfalfa hay per year. Evapotranspiration (ET) is the primary use of water by alfalfa and averages about 36 inches/year (900 mm) at Kimberly. The ET at peak periods of 0.4 inches/day (10 mm/day) can reach 4080 tons of water per acre and 45 tons per acre per day. As shown in Figure 1, adequate center pivot irrigation system capacity is critical for maintaining acceptable soil moisture levels (and yield potential) later in the season. Systems designed and operated to apply less  than 7 gallons per minute are not able to match ET and must rely on soil water bank to supply the deficit.

   1 Comment

   1. Dear Gunny,

      Thank you very much.

      To summarize, and a rough approach.

      For Wheat:

      0.5m water for 100 Bushel per growing season = 5’000m3 water per season per ha.

       

      Alfalfa hey:

      ..36 inches per season ...= 

      10’000t of water per season per ha?

      If I could two seasons in the same year, the amount doubles?

       

      Is that correct?

      Thank you,

      Boris

       

5. The right amount of water with proper timing to grow 100 bushel wheat. The basic rule of thumb for wheat grain production is that it takes 5 inches of moisture to insure a crop, with a yield increase of 7 bushels of grain for each additional inch of moisture. For 100 bushel wheat, the water requirement is approximately 20 inches per acre (1 3/4 acre feet), which rainfall, stored soil moisture, and irrigation must supply over the course of the growing season. Three feet of moist silt loam soil will hold about 3-4 inches at 50% depletion, so one must schedule irrigations to this limit

   Obviously, you can't irrigate constantly, so here is what you need:

   • Moist soil depth of 3 feet at planting (silt loam)
   • Cool, uniform temperatures through tillering
   • Four inches of moisture after tillering
   • Four inches of moisture at boot stage
   • Four inches of moisture at heading
   • Five inches of moisture at soft dough

   If your soil is not a gravel-free silt loam, but a sandier or shallower soil, you'll need to irrigate more frequently and apply a little less water each time to get the required 1 3/4 acre feet of water. 

   1 Comment

   1. For alfalfa the total water need over its growing period (averaging 220 days and ranging from 100-365 days  the water needs mm range from 800-1600 mm. Taking an average of  1200 mm the crop needs per hectare work 12,000 m3 per ha. Wheat average is about 550 mm-over a growing period ranging from 120 to 150 days or 550 m3 per ha-You can then follow the farming practices advised by Gunny Hundetmark above.