ISSUE 12   July 20, 2006

CROP WATER REQUIREMENTS

Given the very dry conditions in many regions of the state that we are experiencing, there is great concern that water will be the most limiting factor for crop production this season. Crops differ significantly in their water requirements, drought tolerance and water use efficiency. Crop selection can be one way of matching water availability with crop requirement, though predicting the amount of moisture that is likely to be available in a given season is more often guesswork than science. Nevertheless, with low levels stored moisture in the soil and the limited rainfall this spring, the water requirement of the crop should be given some consideration.

Strictly defining the water use by a crop is difficult as water use is affected by the amount and timing that water is available. For example, a crop like corn is water use efficient (produces more dry matter per inch of water), but also has a relatively high water requirement due to its higher yield potential than most crops. Furthermore, crops differ in how water stress might affect them. Corn, for example is very sensitive to drought during the flowering process. Wheat on the other hand, is sensitive during early vegetative development. A crop that is stressed early in its growth cycle may not be able to recover to the extent that it will be able to use the water that is available, even when rainfall is plentiful during the latter stages of development. The following tables may be useful in categorizing crops to their relative water requirements.

In Table 1, yield levels and water use efficiency for common crops grown in ND are shown. In Table 2, data are summarized for the water use averaged over two seasons of crops grown at the USDA-ARS staion in Mandan.

Table 1.

Approximate yield, water use and water use efficiency of some crops commonly grown in the northern Great Plains.

CROP

Average Yield/A

Average Water Use, Inches

Water Use Efficiency Yield/A/Inch H2O

Alfalfa
Grain Corn
Potatoes
Sugarbeets (Sugar)
Soybeans
Spr. Wheat
Sunflower

5 tons
120 bu.
400 cwt
3.2 tons
35 bu.
40 bu.
1500lb.

24
21
20
19
16
15
14

0.2 ton
6 bu.
20 cwt
0.2 ton
2.2 bu.
2.7 bu.
110 lb.

Flax
Pinto Beans
Barley

25 bu.
2200lb.
55 bu.

12
12
11

1.7 bu.
180 bu.
5 bu.

Source: J.W. Bauder and M. J. Ennen, NDSU Soil Science Department.

Table 2.

Crop

Water Use (Inches)

Dry Pea

11.4

Crambe

11.8

Barley

12.0

Spring Wheat

12.5

Flax

12.6

Dry bean

12.6

Canola

12.8

Soybean

13.5

Safflower

14.2

Sunflower

15.0

Duane Berglund
Extension Agronomist
duane.berglund@ndsu.edu


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