Sumit Sharma and Jason G. Warren,

Department of Plant and Soil Sciences

Oklahoma State University

Department of Plant

and Soil Sciences

Subsurface Drip Irrigation:

Impact of Management and

Crop Selection on Soil Water

Dynamics

Background

Oklahoma Panhandle

Agriculture depends on

the Ogallala Aquifer

Well monitoring started

in 1937 (USGS, 1976)

Saturated thickness

declined 25-50%

(USGS, 2013)

Resulting in

declining well

capacities

Introduction

86% of water extracted is used for irrigation

Corn: Major consumer of irrigation water

Main source of grain for local feedyards

Declining Water Capacities will impact:

Crop production

Economy

Options:

Combine Wells: long term impacts

Reduce irrigation Acreage: reduce production

Alternatives

Management of irrigation: Subsurface drip irrigation

Alternative crop: Grain Sorghum

Accepted by feedyards

Price is comparable to corn

Published evidence of lower water demand

and high water use efficiency (compared to

corn)

However, no irrigation management strategies data

based on well capacities is available

Objective

Objective of this study was to evaluate the impact of

different irrigation distribution strategies on soil water

extraction by corn and grain sorghum and its influence

on yields.

Hypothesis: Our hypothesis is that less frequent but

larger irrigation events would increase the depth of soil

water extraction.

Method

Study was conducted at Oklahoma Panhandle

Research and Extension Center, Goodwell, OK.

Subsurface drip system installed at the station was

used in this study.

Drip tape was buried 12 in. deep and 60 in. wide.

Each drip tape waters two crop rows planted at 30

in.

Date Management

Corn Sorghum

Planting April 20 2017 June 6 2017

Population 32500/acre 65000/acre

Fertilizer (UAN) 279 lb N 180 lb N

Harvest October 12 2017 To be harvested

Method

Irrigation

Treatment

Corn Irrigation

Treatment

Sorghum

1 0.35 in/day* 6 0.35 in/day*

2 1.05 in/3 day* 7 Extra from trt1

3 1.05 in/4 day 8 0.35 in/4 day

4 0.79 in/4 days 9 1.05 in/3 day*

5 0.27 in/day 10 0.27 in/4 day

*full water

Highlighted treatments represent simulations of split pivots where water is shared.

Trt 1 and 2 are full water on corn, independent of milo

Trt 6 and 9 are full water on milo they are not dependent on corn irrigation,

assuming milo irrigated independently of corn

Method

30 in.

15 in.24 in.

6 in.

Tape

Watermark

Soil Moisture

Sensor- 6450

Soil Moisture (Corn)

-300

-250

-200

-150

-100

-50

0

5/20 6/9 6/29 7/19 8/8 8/28 9/17 10/7

So

il W

ate

r P

ote

ntia

l (c

ba

rs)

Date (mm/dd)

Treatment 4 (0.79 in/4th day)

6" Row

24"

6" Tape

On Tape

-300

-250

-200

-150

-100

-50

0

5/20 6/9 6/29 7/19 8/8 8/28 9/17 10/7

So

il W

ate

r P

ote

ntia

l (c

ba

rs)

Time (mm/dd)

Treatment 5 (0.27 in/day)

6" Raw

24"

6" Tape

On Tape

Results (Corn)

0

50

100

150

200

250

1 2 3 4 5

Yeid

l (b

u/a

cre

)

Irrigation Treatment

Average Corn Yield

Treatment Total

1 = 0.35 in/day 19.1

2 = 1.05 in/3 day 17.7

3 = 1.05 in/4 day 14.8

4 = 0.79 in/4 day 11.3

5 = 0.27 in/day 15.2

a

b

aa a

Similar lowercase alphabets

above bars represent no

significant difference at p<0.05

and vice-versa.

Soil Moisture (Sorghum)

-300

-250

-200

-150

-100

-50

0

6/26 7/16 8/5 8/25 9/14 10/4

So

il W

ate

r P

ote

ntia

l (c

ba

rs)

Time (mm/dd)

Treatment 6 (0.35/day full water)

6" Row

24"

6" Tape

On Tape

-300

-250

-200

-150

-100

-50

0

6/26 7/16 8/5 8/25 9/14 10/4

So

il W

ate

r P

ote

ntia

l (c

ba

rs)

Time (mm/dd)

Treatment 9 (1.05/3 day full water)

6" Row

24"

6" Tape

Summary

An experiment was conducted to understand the soil

water extraction behavior of corn and grain sorghum

under different irrigation distribution regimes in

Oklahoma Panhandle region.

Our results (preliminary) indicate that depth of water

extraction was inversely proportional to irrigation

applied.

Moisture sensors did detect temporal differences in

soil moisture

Corn yields were proportional to total irrigation

applied.

Questions