The present investigation was performed to evaluate the response of potato
plants to nitrogen fertilizer sources during summer and fall seasons of 1999 and 2000.
using Spunta cultivar. Nitrogen fertilizer was applied at rates of 120. 150 and 180 kg. /
fed. using two sources. the first 0 ne is chicken manure and the second is mineral
fertilizer in the form of ammonium nitrate injected through the irrigation system
(fertigation). The highest rate 0 f nitrogen (180 kg. N / fed.) as 90 kg. N t fed. soil
dressing followed by 90 kg. N I fed. fertigation significantly decreased plant height
than those of the 180 kg. Nt fed. which were applied as fertigation by 17.29 and 30.00
% for summer 1999 and 2000 and 15.49 and 4.74 % for fall 1999 and 2000
respectively. The increase of nitrogen rates which were applied as fertigation from
120 to 180 kg. N I fed. gave more number of leaves per plant by 57.86,39.20 % for
summer and fall 2000 respectively. 150 kg. N I fed. in the form of ammonium nitrate
as fertigation gave higher number of stems than the other treatments .The fresh and
dry weight of leaves, dry matter percentage, and protein content of tubers gradually
increased as nitrogen fertigation was increased from 120 to 180 kg. Nt fed. Low rate
of N application had a negative effect on the number and weight of tubers . The
increase of N application rate from 120 ( 60 kg. N I fed. as chicken manure followed
by 60 kg. Nt fed. as ammonium nitrate) to 180 kg. t fed. ( 0 + 180 kg. N I fed. as
ammonium nitrate) enhanced tuber starch content by 7.94 and 4.62 % of summer
1999 and 2000 and 7.90 and 12.66 % of fall 1999 and 2000 , respectively. The rate of 150 kg. N I fed. applied as fertigation produced 32.95,23.93,48.95 and
10.68 % more tuber fresh weight as compared to those of 180 kg. N I fed. applied as (
90 kg. N I fed. soil dressing followed by 90 kg .N I fed. fertigation ) in both summer of
1999, 2000 and fall of 1999 and 2000 respectively. The increase of nitrogen rate
which was applied as fertigation from 150 to 180 kg. NI fed. increased nitrogen
concentration in tubers by 31.03 and 11.84 % of summer 1999 and 2000 and 44.38
and 15.67 % of fall 1999 and 2000, respectively. From these results, it could be concluded that it is recommended to apply the
nitrogen fertilizer rate of 180 kg. N I fed. as ammonium nitrate injected through drip
irrigation system which increased total yield by 61.05 , 36.60 and 45.38 % in fall 2000
and both summer 1999 and 2000 seasons as compared to those of 180 kg. N I fed. as
90 kg. Nt fed. chicken manure followed by 90 kg. N I fed. ammonium nitrate.