1. Water Needs for Horticultural Crop Production
Jim Shrefler, Extension Horticulture, OSU

2. Acknowledgement
This presentation was adapted from “Water Quantity and Quality Requirements for Agriculture” presented by Mr. Steve Upson, Horticulture Consultant, Samuel Roberts Noble Foundation, at the Agriculture Water Source Development Seminar held in Ardmore Oklahoma on August, 6, 2013.

3. Water Quantity and Quality Requirements for Agriculture

4. Crop water quantity considerations Crop water quality considerations
Topics:
Crop water quantity considerations
Crop water quality considerations 4

5. A common question received by Agricultural Extension Agents and Consultants: ‘I want to grow (name the crop). Can you help me?’
If it is a horticultural crop, the response will often be: ‘Tell me about your irrigation source’.

6. Why is the water resource so important?

9. The standard water application recommendation for crop production in Oklahoma is one acre inch per week.
1 acre = 43,560 sq ft
1 inch
Volume equivalent = 27,000 gallons

10. Water in a Harvested Crop
How much water is in a watermelon crop
30,000 lbs. of fruit per acre
93% water
= lbs. of water
Water is 8 lbs. per gallon
3487 = gallons of water

11. Why is water so important ?
Required for Photosynthesis
Mode of transport for mineral nutrients and photosynthate
Cools plant via transpiration

12. Factors determining amount of water to apply include:
Evapotranspiration rate
System efficiency
Rainfall

13. Seasonal Single Site Evapotranspiration (ET) Table - Ardmore, OK
Date
Short Crop ET (in)
Tall Crop ET
(in)
Cool Season Grass ET (in)
Warm Season Grass ET (in)
Pan Evaporation (in)
0.31
0.41
0.29
0.19
0.42
0.24
0.22
0.15
0.30
0.25
0.21
0.14
0.27
0.28
0.17
0.12
0.23
0.20
Total
1.61
1.97
1.50
1.00
2.05

14. Question: I’m having a well drilled on my property
Question: I’m having a well drilled on my property. The driller has informed me there isn’t much of an aquifer to draw from. What is the minimum yield a well needs to make to supply an irrigation system?
Assumptions:
Well can be pumped continuously
Answer: 5 gallons per minute (gpm) per acre
15 gallons per acre is a preferred minimum

15. Pecan Water Requirements
Height
Age (years)
Volume (gallons/day)
Less than 5’
1-3
1 – 4 5’
3 – 5
2 – 5
10’
4 – 7
3 – 7
15’
6 – 8
7 – 10
20’
8 – 10
13 – 17
25’
10 – 12
21 – 27
30’
12 – 13
31 – 39
35’ 15
42 – 53
40’ 25
55 – 70
50’ 40
86 – 108
60’
50 +

16. Question: I have a one acre pond I want to use for irrigation
Question: I have a one acre pond I want to use for irrigation. How many acres of pecan trees can I irrigate?
Assumptions:
Annual requirement = 54 acre inches
Water from rainfall is not accounted for
66% utilization rate
Avg. depth = 7 ft
Answer: 0.75 acres

17. Crop water quality issues:
Sand and silt
Organic particulate matter: weed seed, algae, etc.
Mineral precipitates/pH
Salinity

18. Ideal: 0-300 ppm TDS (total salts) Good for most crops: 300-600 ppm
Crop Irrigation water salinity standards:
Ideal: ppm TDS (total salts)
Good for most crops: ppm
Caution: 600-1,000 ppm
Avoid: > 1,000 ppm total salts
Other measurements: Sodium, Chlorine, SAR

19. Ag Water Requirement Resources
Classification of Irrigation Water Quality
Understanding Your Irrigation Water Test Report
Consider Pecan Trees' Water Needs During Drought
Water is the Most Important Nutrient
Livestock Water Guidelines
Agriculture Testing Services: Water Testing

20. Water sources may or may not be suitable for specific farm needs.
Summary:
Water requirements on the farm can vary in terms of quantity and quality needed.
Water sources may or may not be suitable for specific farm needs.
Understand these requirements before investing your time and money in purchasing a property or developing a water resource. 20