الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The pres~nt investigation was carried out to study the effects
of a wide range of main agronOJldcvariables ( N.P •. K. fertilizers,
water regimes and planting dates },and the_interactions of these
variabl.s with environmental factors on the yield response of two
major Egyptian cereal crops, wheat and corn (maize). Also, to develop
a general prediction equation for each crop , evaluate the contribution
of the controlled and uncontrolled variables affecting yield res~onse
and determine the most important variables •
Quantitative evaluations of applied factors -(controlled variables)
and environmental variables (;une~n~rolledvariables) were all necessary
to develop a satisfactory r~lationshipbetween crop grain’yield and the
responsible variables .Thus~ expetiJaental sites were selected in away
to provide a sufficiently wider8Q.ge in each uncontrolled variable to
permit inferences concerning the entire cultivation-areas in which the
crop was produced •
’Data from a series of fertilizer, irrigation and ·planting date
experiments incl,uding uncontrolled environmental variables were combined
to give a general predictiOll equatioD for each crop. Wheat y1.eld.data
used in th1.s study was obtaiJled f~ 37fiel.d expert-u distributed
over the coUntry duz:ina theper:iOi f-roil-1971-1980 -• resulting in a total
of 332 yield _value ot..e”-tiou ...Qml ,data.COIlta1ned 364 yield value
observations obtained froa 32 field experiments located in North and
South Delta ,.and Middle Egypt during the same period aentioned above.
Simple correlation and aultiple regression techniques were used
to fullfil the.objectives of this study. The general model for the
prediction equation obtainedfromaultiple regression analysis is the
quadratic fo~ as follows
where :
y denotes the predicted yield in Ard./Fad.
is the regression intercept •
,b.~~~are the partial regression coefficients •
are the independent (predictor) variables •
i , j • 1,2, •••••• n andi’ j ~or interaction terms •
The t.portaDt reaults obtained fro. thiastudy could be summarized
as follows :
(1) Simple correlation values between crop grain yield and the initial
group of independent variabiea indicated that applied nitrogen ,
irrigation .,.plant~~ate • precedina crop and aoil ~xture are
.the.II08t iJIp~rtant variables in·wheat yield. produetion •.Meanwhile t
for corn yield production • the IIOst iJlportaDt variables are the
applied nitroaeD , irri&atioa and solI texture.
(2) The effective UDcODtrol.lad ”.nablea influenced Jdtrog8D response
.’
’.are than aay other ••• i1.ecl faetctr • TId. ia t~ for theRo crops.
(3) No response was found’to P and K fertilizers for wheat grain yield,
while corn grain yield had a marked response for these two fertilizers
(4) For corn, response to ei·ther P or K was influenced only by nitrogen
application •
(5) The response to nitrogen for wheat grain yield was governed by
its interaction with irrigation , planting date, soil pH and soil
texture. whereas, for com grain yield, the.variables tha~ had
the greatest influence on the r~sponse to nitrogen were,·irrigation
, soil pH and 80il texture •
(6) In aci4ition to influencing response to nitrogen, soil texture
iafluenced response to irrigation for both of the studied crops.
I
(7) Yield response curves for nitrogen application indicated that the
highest grain yield per faddan for wheat wasobtdned when 100 Kg
H/fad. cOJlbined.wit1ilsix irrigations or when the 80il texture was
claS8 ·five ( clay 80il ) • For corn,. the highest grain yield was
obtained frca the application of 120 Kg N/fad. cc.bined with the
higher value. for any. of the ._ two variables •
(8) With each increaae·1a nitropu level .upto 100 r.aJPa4. for wheat
an’ up to 120 Ia!Fad. for CODa ,·there- V_ ml 1aereaae in” the
predicted arata” yi.e.U .’lha-lacreaae vas· f.a ._”creaa~lrate for
__
(9) For the ,two crops. it was found that lesser number of irrigations
are needed to reach maximum yield in soils that contain a higher
portion of clay. and vice versa •
(10) The prediction equations for both wheat and corn proved to have
very good predictivevalue. as indicated by their relatively
. ’.. . .. 2
high values for the. coeff,icient ,0£ ’lDult~pledetermination ( R ).
In addit:L9U. these equations’ seeJDtobe agr1culturallymeaningful
as th~y have sensible regression coefficients and explain
as much yield variations as possible • This indicates clearly
their overall closeness of fit to actual results •
(11) This investigation identified some of the important factors that
should be considered in,planning fertilizer and irrigation programmes
for wheat and corn yield ,studies ,.,~anwhile, the obtain~dresults
could be transformed into a useful practical recommendation for
the research’.worker and the farmer •