This publication from Kansas State University Agricultural Experiment Station
and Cooperative Extension Service has been archived.
Current information: http://www.ksre.ksu.edu.
APRIL 1975
Irrigating Corn in Extreme
West-Central Kansas
Merlin A. Dillon·, Crops Research Agronom ist
Roy E. Gwin, Supt., Tribune Experim ent Station
Declin es in ground water levels in this area
have sharpe ned interes t in irrigati on efficien cy.
During the last three years we evalua ted irrigation amoun ts and timing influen ce on corn yields
aUL"XQa Res_ults LaGLFaWHGt hat aDUHIXOt iming
Cit arngat1 on wtll maantaan co rn ytelds and use
less water.
Our 3-year test was with furrow irrigati on
on Ulysse s silt lo·a m. All plots receive d a preplant irrigati on. Each in-seas on irrigati on was
approx imately 7.5 inches. Applic ation efficien cy
may range from 50 to 75% for furrow irrigati on.
Phosph orus was applied uniform ly each year.
We compa red irrigati on schedu les. usi ng preplant only ·a nd at three soil-mo isture tension s
with two nitroge n fertiliz er levels, two plant
popula tion lev:els, and three comme rcial corn
hybrid s.
Whe n to irrigate was determ ined by monito ring soi_l mo.isture t ension . Tension is the re lative
.difficu lty of extract ing moistu re from the soil.
Wateri ng when the soil water tensio n was 0.8
AGRICULTURAL EXPERIMENT STATION
Kansas State Universi ty, Manhatt an
a
YGu.·
<:: "":"''i fh
n;;...<'"\_.- t,... ..
This publication from Kansas State University Agricultural Experiment Station
and Cooperative Extension Service has been archived.
Current information: http://www.ksre.ksu.edu.
bar a! 2 feet deep UHTXLUaG" :'ateri ng an DYHUaBa
2.7 t1mes a se·ason: tw1ce m 1973 and f\..... _.'e
times in 1972 and 1974 (Table 1). Water ing
when soil water tensio n was 0.8 bar produ ced
the highe st yield, 134 bushe [s an acre (Figure l ).
When pre-p lant irrigation filled the soil profil e
to six feet, then either two or three in-sea son
irriga tions (depe nding on the year) produ ced
maxim um yields . Irriga ting up to eight times
a yea r produ ced no highe r yields durin g three
years, 1972- 1974. lrrig'atin'g prepl ant only, produced 85% as much grain as the top yield with
43% as much applie d water .
The 0.8 bar treatm ent required that the first
in-sea son irriga tion be applie d July 7; later irrigation s w ere 22 days apart (3-yea r avera ge).
Irriga ting when soil moist ure tensio n was lower
required earlie r ·and more frequ e nt irrigations.
The 0.6 bar tensio n required irriga tion by June
30 with later irriga tions ave raging 16 days
apart; the 0.4 bar tension, by June 19 a nd 10
days apart. The interv als b etwee n irriga tions
varied with p lant-u se and rainfa ll. An entire
fi e ld canno t be water ed so precis e ly as our
plots were; howe ver, our results should be used
as a mana geme nt guide to timing or sched uling
irrigation.
Regar dless of other treatm ents, 160 lbs/ A
nitrog en was requi red a nd resulted in 139
bushe ls an acre versu s 113-b ushel avera ge with
80 lbs/ A of nitrog en (Figure 1). So, it wou ld
be a mista ke to sharp ly reduce nitrog en applie d,
antici pating a water shorta ge. Nitrog en rates
might be reduced slight ly but our 50% nitrog en
reduc tion cut yields too much .
The effect of plant popul ation d epend ed on
other treatm ents (Figure 2). The highe r popul ation was fa vored where nitrog en w as adequ ate .
Howe ver, when nitrog en was short (80 lbs/ A),
the high popul ation reduc ed y ield. That was
more apparent when both water and nitrog en
were in short suppl y. Most surpri sing was that
plant popul ation did not affect yields for the
pre-p lant only treatm ent. We expec ted the
lower popul ation to be favore d under pre-p lant
irrig·ation only.
The three comm ercial hybrids avera ged about
the same over the three years . They respo nded
differ ently but their respo nses va ried from year
to year giving no clear- cut conclu sions. It is im-
Table 1. Effects of plant popul ations , QLWUR
arates,
Tribu ne, Kansas-, 3-yea r avera ges, 1972- 74.
Popula tion
Plants/ A
Nitroge n
Pre-pla nt
lbs/A
ilr aLUULJDWLRQ1
sched ules on yields of irriga ted corn,
Yield, ·bu/ A @ 15.5% moistu re
0.8 bar
0.6 bar
0.4 bar
Averag e
bu/ A
16,00 0
80
110
24,00 0
124
80
110
119
119
115
16,00 0
100
160
112
116
143
112
24,00 0
121
160
142
126
142
149
137
144
114
149
134
142
127
131
126
Avera ge
I . Irrigati on w as sched uled by soi l moistu re
tension . Irrigate d as follows :
Pre-pla nt irrigate d on ly
0.8 bar irrigate d 3 times in I 9'72 and
1974, 2 times in 1973
0.6 bar irrigate d 4 times in 1972 and 1974,
3 times in 1973
0.4 bar irrigate d 8 times in 1972 and 1974,
7 times in 1973.
Approx imately 7.5 inche s per app lica tion app lie
d in furrow s l/4 mile long, 12-hou r set; wate red
pre-pla nt to saturate
the soil profile to six fee t.
W ;- rr'
"'Son
This publication from Kansas State University Agricultural Experiment Station
and Cooperative Extension Service has been archived.
Current information: http://www.ksre.ksu.edu.
150
140
160 lbs N/A
130
120
110
80 lbs N/A
100
90
l
0.6
0.8
BAR
BAR
Irrigation
Pre-plant
0.4
BAR
Figure 1. Effects of nitrogen rate and irrigation frequency
on corn yields, Tribune,. Kansas, 3-year avg., 1972-74.
150
140
130
Pre-plant only
0.8 BAR
110
100
>-
90
80
70
=.oo
This publication from Kansas State University Agricultural Experiment Station
and Cooperative Extension Service has been archived.
Current information: http://www.ksre.ksu.edu.
portant to recognize that hybrids react individually to various environme ntal conditions .
Results of our tests are summariz ed in more
detail in Table 1. Highest yields were from 2
or 3 in-season irrigations with 24,000 plants ar
acre and 160 pounds per acre of applied nitrogen. Limited in-season irrigation is most practical when a moderate to large amount of available water is stored before planting.
Soil moisture tension can be monitored by
tensiomet ers or electrica I resistance blocks.
Tensiomet ers, limited to tensions below 0.85
bar, cost about $20 each. Tensiomet ers used
in this test were obtained from Soil Moisture
Equipmen t Corporatio n, Santa Barbara, California.
Informatio n in this report is for farmers, producers, colleagues , industry cooperato rs, and
other interested persons. It is intended to help
in irrigation managem ent. It is not a recommen dation but represents three years' research at
one location.
Contribut ion 27, Trib'une Branch Experimen t
Station, Kansas Agricultur al Experimen t Station,
Manhattan , Kansas 66506.
Publicatio ns and public meetings by the Kansas Agricultur al Experimen t Stati·on are available
and open to the public regardless of race, color,
national origin, VaY a QOaLI?