الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Field experiments were was conducted during the two successive seasons of 1996/1997 and 1997/1998 to investigate the effects of soil moisture (manifested as irrigation intervals) and nitrogen fertilizer on vegetative growth , yield nutrient uptake , concentration of chlorophyll and carateniods and water consumptive use of lettuce and table beetsin El-Kanater Horticultural Research Station, Kaliobiya, Governorate . Lettuce and table beet plants were grown under different combinations of 3 soil moisture regimes : wet, medium and dry expressed as 3 irrigation treatments having intervals of 8, 16 or 21 days, respectively ; and 4 fertilization treatments (urea ”U” 46 %N , ammonium sulphate AS 20%N , ammonium nitrate 33 % all at 40 kg N ; and no N.). Results may be summarized as follows (means of the 2 seasons)
1- lettuce plant height increased with increased moisture (mean heights were 52.5 , 50.2 and 48.3 cm for the wet , medium and dry regimes respectively) . The adverse effect of the dry regime was particularly evident under N fertilization . Beet plant height was greatest with medium moisture and lowest with dry moisture giving 45.0 , 42.9 and 36.3 cm for medium wet , and dry regimes respectively , particularly when fertilized with AS.2-Lattuce height showed a pattern of AS >AN>L1 >no N ; with values of 52.5 , 50.6 ; 50.0 and 43.6 for each respectively. For beets AS gave the highest followed by U , which was not significantly superrior to AN ; and all fertilized plants showed more height than the unifertilized. Values were 45.7 , 43.9 , 42.5 and 33.0 cm respectively . The superiority of fertilized over non —fertilized was most pronounced under the medium and wet regimes ; indicating that severe moisture stress is a limiting factor which may not show the full benefit of fertilizers.
3-Fresh yield as affected by moisture showed a pattern of medium >wet >dry with values of 10.8 ,10.5 and 7.4 megagram ”Mg” lettuce /fed (Mg=106 g. i.e. metric ton) respectively ; and 6.9 , 6.2 and 5.0 Mg beets /fed respectively. Su periorly of the medium regime in giving higher yields of lettuce or beets was particularly marked under AS fertilization. Under the dry regime AN was similar or superior to U , but under the medium or wet regimes it was
inferior to U
4-Fresh yield as affected by N treatments shows the following : AS >AN>U>no N for lettuce giving 10.9 ,9.5 10.0 and 4.4 Mg lettuce /fed respectively. The pattern for beets was AS>U>AN> no N with values of 7.4 , 6.9 , 6.4 and 3.8 Mg /Fed. Superiority of fertilized over the nonfertilized was most pronounced under medium or wet regime-. AN was similar orsuperior to U under the thy regime ; but under the wet or the medium regime it was U that gave greater yields over AN . Under all conditions AS gave highest yields.
5-Uptake of N , and P nutrients followed a pattern rather similar to that of the yield . N uptake values were 1544, 1315 and 861 mg/lattuce plant with medium , wet , and thy moisture regimes respectively and 331 , 229, and 209 mg/ N / beet plant, respectively . Values as affeted by fertilizer treatments were 1635, 1485 , 1374 and 464 mg N / lettuce plant for AS , U, AN and no N respectively ; and 309 , 274 , 264 and 174 mg N / beet plant respectively . P uptake values for medium , wet , and dry regimes were 248 , 243 and 179 mg P / lettuce respectively ; 95 , 89 , and 76 mg P / beet plant respectively. For AS , U, AN and no-N treatments values were 275 , 257 , 236 , 124 mg P / lettuce plant respectively ; 87,77, 77 and 47 mg P/ beet plant respectively . Uptake of K by lettuce was highest with the medium regime giving 1763 , 1662 and 1553 mg K / lettuce plant for the medium wet, and thy regimes respectively ; and giving 310 , 216 , and 209 mgK / beet plant respectively . Values of K uptake by lettuce values for AS , U, AN and no-N treatments were 1969 ,2180 , 1856 and 631 mg K / lettuce plant respectively. Values for beet were 300 , 259 , 264 and 155 mg K / beet plant for the same treatments respectively .6- Consumptive water use (CWU) —which represents actual evapotranspiration was lowest with the dry regime. For lettuce it was 278, 236 , and 196 mm for the wet , medium , and dry regimes respectively. Values for beets were 326 , 289 and 253 mm, respectively. Values regarding AS , U, AN , and no —N were for lettuce were 253 , 244 , 242 , and 207 mm respectively .Values for beets were ; 320 , 294, 277 and 263 mm respectively. WUE was higher with the medium regime than the dry or the wet regimes . Values (in kg /m3 )for lettuce were 7.99 , 10.67 and 7.58 with wet , medium and dry regimes respectively . For beets they were 4.51 , 5.75 , and 4.75 and 4.73 kg /m3 respectively . N —fertilization increased WUE with AS giving the highest value especially for lettuce. Treatments of AS , U, AN , and no —N gave of 10.22 , 9.65 , 9.50 and 5.64 kg/ m` respectively for lettuce ; 5.49 , 5.67 , 5.33 and 3.45 Kg/ m3 repectively for beets.
7- Using the modified Penmen equation for estimation of ET gave 13 % and 27 % overestimations above actual ET for lettuce and beets respectively. The Pennman-Montieth equation gave 5 and 24 % For each crop respectively) underestimations . The Doorenbose- Pruitt equation gave 11 and 22 % underestimations respectively below actual Fr.