الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Nitrogen application to soils has greatly increased
in the past 10 years. Millions of tons of N fertilizers have
been added to soils at each year, often disregarding the
possible decrease in the efficiency use when losses of N
occurred. Ammonium N is oxidized to NO-3- N in mo~t soils
during all seasons except when environmental conditions are
prohibitive. If N could be kept in the NH+. form until plant
utili~ation. less N loSS would occur. The n$t result would
be greater Nuse efficiency.
The ideal fertiliz~r m~y be considered as orie that
(1) needs only a single application to ’supply the amounts of
nutrients required for optimum plant growth during the
entire growing season, (2) has:high maximum percentage recovery
in order to achieve higher return to production input.
and (3) has minimum detrimental effects on soil. water and
atmospheric environments. In recent years considerable
interest has been evident in controlled- release N fertilizers
to regulate the supply of nitrogen of the plant through
-out the growing Beason, thus minimizing N losses and
maximizing the efficiency of the applied N in terms of
uptake and yield.
The purpo8~ of this study was to evaluate the efficiency
of some N- slow- release fertilizers applied alone or
in combination· with phosphatic fertilizers. The research
work embodied in this investigation included four experiments:
1- First green-house experiment:
The first green~ house experiment was carried out in
the summer season of 1992 at the Giza Farm, Soils and Water
Research Institute, to evaluate both direct and residual
effect of N source, i.e. ammonium nitrate, ammonium sulphate,
urea, seu, UF and Kpp- UF combined with calcium superphosphate
for corn grown on an alluvial caly loam soil.
The obtained results could’be.8WD11larized as follows
1- Regardless P appli~ation, most of the N sources,
except urea and seu showed almost similar irowth response
pattern where’ dry matter, ’cyieJd ins isniff cant;lyincreased : , -,’,.1
with N application a8comp;a~e:(Ito original treat.m’entsafAS
and AN, which were equally eftictive.
2- The slow- release fertilizer KPP- UF (alone) and
seD combined with 15 kg P205/ fed. were the most effictive ..
treatments in respect to corn growth followed by UFo
3- Corn plants increased gradually .Ln their content
of N, P and K by increasing the rate of applied Buperphosphate.
On the other hand KPP- UF showed the highest
stimulative effect on P and Kcontent of corn plants.
4- KPP- UP and seu produced the highest values of N
uptake by corn plants when they were added in combination
with superphosphate.
2- Nitrogen and potassium losses from clay 100m soil treated
with sol~ble and slow- release fertilizers under corn
and fallow:
]- Values of total leached soluble N (NH4+ + No”::’3)
during 9 weeks were maximized under fallow conditions. In
respect to NH3 loss, the highest figures were observed under
fallow condition. while. the rate of loss was decrease with
N fertilization according to the order
AS > AN > Urea > seu ’) KPP- UF .
2- Leaching 10s8 of Nij+4- N is negligible either
under fallow conditions or with corn cropping during the
experimental periods. Only with AN and seu, the N loss was
not appreciable under fallow till the 6th week. but AN was
very low only under cropping at the same period.
3- Appreciable NO-3-N could not be detected •i. n leachates
of soil treated with either seu Or ~pp- UF under fallow
or under corn cropping. AI_ost similar trends were also
obtained with the total amount~ of N leached.
4- It is very much interesting to observe that the
loss of soil K through leaching was minimized. in case of KPP
-UF fertilization.
5- The amounts of Nand K leached at from the treatments
of AN, AS. urea. SCU and’KPP-UF explain the dry matter
yield of corn results. KPP- UF and SCU produced higher dry
weight of corn plants and N. P arid K uptake than the other
N- sources.
11- Field experiment:
A field experiment was established at Bahteem Agricultural
Research Station on a clay loamy soil for three
successive growing season duririg 1989 and 1990. Sunflower
plant (”elianthus annuus L.) cv. Giza 1 was grown on the
experimental site in 1989. A wheat (L..aestivuIQ L.) crop.
cv. Sakha was grown in October season. 1989. followed by
corn plant (Zea mays L.)cv. ,Giza 2.
In the first trial ur~a was applied at 45 kiN/fed.
in two equal doses. i.e. just before sowing and before the
3rd irrigation. The slow release fertilizers KPP- UF and UF
were added at the same rate in one dose. just before sowing.
Superphosphate was applied in two doses. i.e. 15 a..nd 30 kg
P20!/ fed.. however. potassium sulphate was added at 24 kg
K20/ fed. as a basal dress to all experimental plots before
planting. Thus. there were 3 N- treatments having Nfertilizers
+ 15 kg P20S and another 3 N- treatments having
30 kg P20S/ fed~ besideth.e control treatlnebnt in a COllplete
randomized block desigp with four replicates.
The obtained results are su•••a•rlzed as follows;
1,- Fertilization with”,readily soluble or slow-release
N-fertiJizers in sunflowerp!ant enhanced plant, height stem
diameter. head diameter and~husk percent compared with the
untreated one.
2- There was no signi!icant difference in t~e vegetative
characteristics: ~eed,weight per plant, yield of seeds
and weight of 100 seed (seed index) of sunflower plant. Oil
concentration in the seeds was increased as P20S addition
was increased from 15 to 30 kg P20S/ feddan.
3- Slow- release fert£lizers have the disadvantage
that they are not suitable for crops that require considerable
supplementals of nitrogen through a short growth period.
In such case a supporting dose of readily soluble N may over
-come this disadvantage.
4- The application of slow- release tertil’izers combined
with 15 or 30 kg P20~/ fad., resulted in higher dry
weight of wheat plants as compared with the soluble release
ones, or with the control.
5~ The dry weight of wheat plants obtained from the
untreated plots ammounted to about 50 ’I. of that produced
from plots treated with the recommended treatment. With KPPUF
fertilization. the reduction was decreased by 10 ’I. only
comprising about 90 ~ of the yield in case of recommended
dose fertilizer.
6- There is a positive significant influence in nutrients
uptake by wheat plants with slow- release fertilization.
The order of increase in nutrients uptake was as
follows UF 45 kg N/ fed. + 30’kg P20!5 / fed. > KPP- UP 45
kg N/ fed. + 30 kgP:iOe/:,fed. ) KPP- UF 45 kg N/ f~d. + 15
7- A stimulation effect on plant height. ..number of ’
tillers and number of spikes ~er plant was gradually dbserved
comparing ~he slow- rel~ase fertilizer.withthe solubl~
one. The residual effects of KPP- UF treatments was observed
to give the highest values either by the application of 45
kg N + 30 kg P20S / fedd~n or by 45 kg N + 15 kg P20!5/ fed.
as compared to the application of urea.
8- Considering the residual effect due to N f e r t il ization
on grain yield of wheat plants; the obtained response
decreased in the following order : 45 kg N as KPP- UF + 30
kg P203/ fed. ; 45 kg N as UF + 30 kg P20!l / fed. ; 45 kg N as
KPP- UFo 45 kg N as urea + 30 kg P20!l / fed. ; 45 kg N as
urea + 15 kg P20~ / fed. and the controlled plants.
9- With respect to straw yield of wheat planted after
sunflower, the residual effect due to slow- release fertili-
~er seems to be adequate either it was added alone or
combined with 15 or 30 kg P20lS/ feddan.
10- The residual.effectfromKPP- UP and UP either
alone or associated with S5 kg/ fed. ure~- N, aignificantly
enhanced the length of ear~the number 6f ears per plant, the
diameter of ear and the shelling percent of corn as compared
to unfertilized plots, but there were no significant
differences between them and the values obtained under the
recommended treatment.
11- Regardless of the effect of residual treatments
combined with superphosphate, a compensation rate w~s generrally
adequate to corn yield. the preference of the slowrelease
fertilizers i. eminent.
Ammonia loss byvolatilization:
1- In calcareous soil, ~he obtained results revealed
that NH3 loss generally followed this descending. order of :
AS > urea > AN > KPP- Of > UF > SCU, within 4 weeks period.
The rate of volatilization from AS and urea was much greater
than from AN.
2- The risk of NH310ss increases in sandy soil, and
the treatments had the following descending order:
AS > Urea > AN> KPP- UF > UF > seu.
3- The greatest values of NH3 loss were observed in
clay loam soil treated with urea and AS. While NH3 loss from
KPP- UF, seu and UF occurred to 8 less extent.