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Proper Irrigation is Critical to Corn Success

Proper Irrigation is Critical to Corn Success published on 1 Comment on Proper Irrigation is Critical to Corn Success
Many corn fields in Louisiana need irrigation as plant growth rapidly escalates.

by John S. Kruse, Ph.D.

Louisiana corn producers were blessed for the most part with good soil moisture during the optimal planting window. While the drought of the previous two years is still fresh in everyone’s mind, the late winter and early spring rainfall that moistened the soil profile and refilled many bayous and irrigation reservoirs is most appreciated. However, as temperatures rise and the winds blow steadily, many producers are finding their soil moisture is moving from abundant to scarce rapidly. Early planted corn in particular, is rapidly reaching a critical phase of development and should not be left without adequate water. It may be hard to fathom, but corn planted in late February is approaching tassel. This phase of development is critical to the crop’s success and adequate water is vital. Note in Table 1 that as corn matures beyond 12 leaves, water consumption increases to over 2 inches of water per week. Two inches of rain/irrigation water is equivalent to 54,305 gallons of water per acre. Be sure to know the output capacity of your irrigation wells and how many acres it must cover, then schedule accordingly.

When to get started:

If your fields still have adequate moisture due to timely rainfall, you do not have to water based on crop stage alone. In fact, watering young corn in particular, that already has adequate soil moisture, may promote an unnecessarily shallow root system. Growers and consultants may wish to consider implementing a watering budget to help guide irrigation decisions. The University of Arkansas has a program called the Irrigation Scheduler that is based on soil texture and average pan evaporation rates, and may prove useful . You can find it at:

(http://www.aragriculture.org/computer_programs/irrigation_scheduling/default.asp

Dr. Dewey Lee, Feedgrain Specialist for the University of Georgia, published a corn water use table that is applicable to Louisiana (Table 1), and growers and consultants can use it to predict water use for their crop. The only requirement is to know either the planting date (so you can use the “Days After Planting” Column) or the current growth stage of your corn crop (so you can use the “Growth Stage” Column). This table will provide a good basis of understanding on how much water corn consumes as it develops. Key items to note when thinking about irrigation are how quickly water use increases as the crop matures, how critical adequate water is during tasseling, and how much an adequate water supply is still important right up to “black layer” or physiological maturity.

Table 1. Estimated Water Use of Corn in Georgia (115-119 day maturity) CREDIT: Dr. Dewey Lee, University of Georgia

Growth Stage 

Days After

Planting

Inches Per Day

Inches Per Week Equivalent

Emergence and primary root developing

0-7

8-12

.03

.05

.21

.35

Two leaves expanded and nodal roots forming.

13-17

18-22

.07

.09

.49

.63

Four to six leaves expanding. Growing point near surface.Other leaves and roots developing.

23-27

28-32

33-36

.12

.14

.17

.84

.98

1.19

Six to eight leaves.Tassel developing. Growing point above ground.

37-41

42-45

.19

.21

1.33

1.48

Ten to twelve leaves expanded. Bottom 2-3 leaves lost. Stalks growing rapidly. Ear shoots developing. Potential kernel row number determined.

46-50

51-54

.23

.25

1.61

1.75

Twelve to sixteen leaves. Kernels per row and size of ear determined. Tassel not visible but about full size. Top two ear shoots developing rapidly.

55-59

60-64

.27

.29

1.89

2.03

Tassel emerging, ear shoots elongating.

65-69

.31

2.17

Pollination and silks emerging.

70-74

75-79

.32

.33

2.24

2.31

Blister stage.

80-84

.33

2.31

Milk stage, rapid starch accumulation.

85-89

.34

2.38

Early dough stage, kernels rapidly increasing in weight.

90-94

.34

2.38

Dough stage.

95-99

.33

2.31

Early dent.

100-104

.30

2.10

Dent.

105-109

.27

1.89

Beginning black layer.

110-114

.24

1.68

Black layer (physiological maturity).

115-119

.21

1.48

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