[en] A number of experiments were conducted to investigate the influence of different N rates applied through drip irrigation on the growth and N uptake by tomato, pepper, cucumber, melon and eggplant under greenhouse conditions. It was found that, for tomato, the % NUE was significantly increased by applying the N fertilizer through fertigation (53.9%) as compared to the soil application (34.0%) at 100 mg N/L. In general, any further increase of N fertilizer did not have an improving effect on the tomato yield. With pepper, the % NUE was significantly increased by applying the N fertilizer in the irrigation water (49.2%) as compared to the soil application (33.9%) at the same N level (140 mg N/L), being the optimum N rate under our greenhouse conditions. At a fertilization level of 100 mg N/L with fertigation, the % NUE was significantly increased as compared to the soil application. With respectively cucumber, melon and eggplant; the % NUE with fertigation was 63.4, 21.4 and 50.8%, while with soil application it was 34,0 11.0 and 18.8%. (author)

[en] Urea fertilizer and water use efficiency by tomato (Early Urbana VF) were studied in a sandy loam soil, comparing trickle fertigation and conventional furrow irrigation -- band fertilization systems. During the period of 1995-1998, a conventional treatment, NS, with band application of 50, 150 and 100 kg N as urea, P as diammonium phosphate and K as potassium sulfate respectively was carried out. The average concentration of N in the total irrigation water was 0, 38, 76 and 114 mg/L for the N0, N1, N2 and N3 fertigation treatments, respectively. All fertigation treatments also received equally 24 and 16 mg/L P and K, respectively. An increase of K for the conventional treatment to 1200 kg/ha in 1998 coincided with the increase of the same element to 190 mg/L for the trickle irrigated treatments. To evaluate the urea-N use efficiency, the plants of isotope subplots received 2% ¹⁵N a.e. urea. The soil moisture in all treatments was measured by the neutron moisture gauge. During the first 3 years of experimentation there was no significant difference between the yields of the treatments. For the years 1995 through 1997 the average tomato yield was low in comparison to the yield shown in most reports. The yield variance among treatments and years was negligible. The highest fruit yield, 27.3 t/ha for the N1 treatment was observed in 1997. In this experiment, the low yield and urea-N use efficiency can be primarily attributed to unbalanced applied fertilizers in the trickle irrigation system. The highest urea-N use efficiency was 12.3% for the fertigation N1 treatment in 1997. In the 1998, a repetition of the experiment with increasing K rates for all treatments at the same experimental site, led to a considerable increase in yield and urea-N use efficiency as compared to previous years. The tomato fresh fruit yield attained for N0, N1, N2, N3 and NS respectively 84, 76, 69, 36 and 26 t/ha. Based on the 14N/15N ratio analysis of the dry matter the urea-N use efficiency was 42, 25, 11 and 6 for the N1, N2, N3, and NS treatments, respectively. All N treatments under trickle irrigation and conventional furrow irrigation received on average a total amount of 6,536 and 12,286 m3/ha irrigation water (1996-1998). The total water use efficiency for the NS treatment was the lowest (24 kg/ha.cm) of all treatments and was the highest for the fertigation treatment N1 (51 kg/ha.cm) (1996-1997). The yield increase of the fertigation treatments enhanced the water use efficiency for 1998 as compared to 1996 and 1997. The overall water use efficiency was the lowest for the NS treatment (33.3 kg/ha.cm) and the highest for urea-N0 treatment (155.4 kg/ha.cm) and urea-N1 treatment (154.1 kg/ha.cm) for 1998. This investigation indicates that application of conventional quantities of fertilizers via trickle irrigation is not suitable. In the second phase (1999-2000) of this project, with the application of proper amounts and proportions of fertilizers plus microelements, it is expected to obtain better results. (author)

[en] The objective of this study was to increase water and fertilizer use efficiency for conventional fertilization and fertigation. The following treatments were included and studied in an RCB design with four replications of each treatment: Zero N, 30, 60 and 90 ppm N in the irrigation water. Additional soil application equivalent to one fertigation treatment was also included. The fertilizers were injected into the irrigation water by means of an injection pump. Garlic was planted in plot with dimensions of 3mx4.5m. Irrigation was applied to replenish 80% of the Class A pan evaporation on a weekly bases. Access tubes for neutron probe reading were mounted in each plot in three replications. The readings were taken before and after each irrigation or rainfall at 15, 30, 45, 60 and 90 cm soil depth. The labelled N fertilizers (¹⁵N) were applied to microplots which contained five plants within each plot. At harvest, plant samples were taken from the microplots for the ¹⁵N measurements. Plant samples were collected and prepared according to the instructions for sampling for ¹⁵N analysis. The yield and its components were obtained from the macroplot. The yield continued to increase with increasing N fertigation rates. The fresh weight per head and per segment showed a similar trend as the yield did. However, the number of segments per head was not affected significantly by the investigated treatments in this study. This may indicate that the zero N treatments produced heads with small segments compared to that produced with N application. The dry weight of shoot, segment and segment membrane responded positively to the rates of N fertigation, reaching the maximum value at the rates of 80 and 120 kg N, irrespective of N fertigation or soil application. The soil application gave a production as high as the best fertigated N rate but lower than the zero N treatment. The percentage of N content in fruits and leaves was the highest with the fertigation treatments where the lowest value was obtained with the zero N rate. The N content was lower with the soil application treatments. A similar trend was obtained for the total N uptake. The soil application treatment gave a Ndff value, which was lower than the fertigated treatments for the whole plant. Fertilizer utilization by fruits was lowest for the soil application treatments compared to the fertigation treatments. No significant differences were obtained among the fertigation treatments themselves. Weekly water consumption ranged from about 10 mm at the beginning of the growing season to about 37 mm at mid season. The crop coefficient Kc was about 0.5 at the earlier growth stages; then it increased to 0.95 at growth stages of the maximum growth. Water use efficiency was the highest for the N2 fertigation treatments. The fertigation treatment (N2) had a higher water use efficiency than the soil application of the similar rate. The maximum water depletion was observed in the top 30 cm. (author)

[en] The experiment aimed at studying the impact of type of fertilizer application and irrigation techniques on the yield parameters of spring potatoes by using ¹⁵N. In 1997 and 1998, a potato crop (Spunta) was planted in a clayey soil in Tell Amara, Central Beqaa, in a randomized block design. It consisted of five treatments and four replicates. The goal of the research was to study the effect of three rates of N fertigation (N1=240, N2=360, N3=480 kg N/ha for 1997 and N1=120, N2=240, N3=360 kg N/ha for 1998) on potato performance and production, comparing full fertigation with conventional fertilizer application and irrigated with drip and macro sprinkler. Water demands and irrigation were scheduled according to the mean annual potential evapotranspiration in 1997 and Class A pan in 1998, and monitored by the neutron probe and tensiometers. The results show that, at harvest, both crops followed the same yield pattern. The highest tuber yield was obtained from N1 and the lowest from N3. These values were 58 ton/ha for 1997 and 32.5 ton/ha for the 1998 trial. The 1998 spring crop was more efficient in terms of N utilization. The reduction of N input in N1 resulted in 90% N-fertilizer recovery. In the treatment with soil N application, drip irrigation saved up to 50% of water and improved the efficiency of removed N. Starting from the 89th day after planting, sprinklers caused a significant difference in NO3- concentration leached beyond 60 cm depth. Thus, fertigation was superior with regard to fertilizer and water saving and it decreased the risk of N building up in the soil and shallow groundwater resulting in pollution. (author)

[en] Field studies were conducted during two seasons at the Deir Alla Research Center to compare the conventional fertilization method with fertigation on water and nitrogen use efficiency with a tomato crop (cv. Gardenia). Four N application rates (0, 50, 100 and 150 mg N/L) were applied with the irrigation water and one soil application (NS) treatment, equivalent to one of the fertigation treatments, was included. Labelled ammonium sulfate was applied to microplots within the macroplots to evaluate the N recovery and utilization efficiency. Results obtained from two seasons indicate that increasing the N rate significantly increased the total and marketable yield by both methods of application, suggesting that the crop was underfertilized. The soil application treatment gave a higher yield than the control (N0) and a lower one than the fertigated treatments. In comparison to the N0, the total number of fruits in both seasons was significantly increased at all N levels. The soil application (Ns) treatment gave the lowest number of fruits compared to the fertigation treatments in the first season and a higher number than the fertigated treatments in the second season. The parameters of fruit quality (pH of juice, titratable acidity (TA%) and total soluble solids (TSS%)) were in the acceptable range. They were not significantly affected by the rates and methods of the N application in both seasons. The rates and methods of N application did not affect the accumulation of dry matter (DM) of the fruits and shoots during the first season. But in the second season, the accumulation was higher than in the first season and it was significantly affected by the concentration and method of N application. With the soil application treatment (Ns) a higher DM content was accumulated than in the control (N0), but lower than the fertigated treatments. The total N uptake by the fruits and shoots during both seasons with the fertigated treatments was higher than with the soil application treatment (Ns) and the control (N0). The total N derived from fertilizer (Ndff) in both seasons, obtained by the shoots and fruits decreased as the N concentration increased. Therefore, the lower fertigated treatment gave a significantly higher Ndff content in comparison to the other fertigation treatments and the traditional method (Ns). The soil application treatment gave the lowest Ndff value. The same trend was observed for the shoots and fruits. The result of N utilization indicates that the fertilizer utilization by the fruits and shoots in both seasons tended to be the highest for the lowest N rate fertigation treatment and the lowest for the soil application treatment. (author)

[en] Crop modelling is considered an essential tool of planning. The automation of irrigation scheduling using crop models would contribute to an optimisation of water and fertiliser use of protected crops. To achieve this purpose, two experiments were carried. The first one aimed at determining water requirements and irrigation scheduling using climatic data. The second experiment was to establish the influence of irrigation interval and fertigation regime on water use efficiency. The results gave a simple model for the determination of the water requirements of protected cucumber by the use of climatic data: ETc=K* Ep. K and Ep are calculated using climatic data outside the greenhouse. As for water use efficiency, the second experiment highlighted the fact that a high frequency and continuous feeding are highly recommended for maximising yield. (author)

[en] A greenhouse experiment was carried out at the Al-Muzahmiya Research Station, King Abdulaziz City for Science and Technology, Riyadh, to evaluate the effect of fertigation on cucumber yield. Five labelled N (¹⁵N) treatments namely a control, soil application (120 mg N L^-1), N-1 (60 mg N L^-1 ), N-2 (120 mg N L^-1 ) and N-3 (180 mg N L^-1 ) were tried for their effect on greenhouse cucumber yield. A cucumber cultivar (Figaro F-1) was sown as test crop. The experiment was carried out during the period from April to July, 1997. The mean fresh fruit cucumber yield ranged between 7.73 to 33.74 t ha^-1. Highest yield was obtained with the labelled N application of 180 mg L^-1 . The mean ranges for the different elements in the plant leaves were 1.33- 2.70% (N), 0.364-0.515% (P) and 1.57-3.82% (K). Whereas, in the plant shoot these ranges were 1.26-2.42% (N), 0.28-0.49% (P) and 4.74-9.45% (K). The mean content of the different elements in the cucumber fruit was 2.15-3.70% (N), 0.47-0.73% (P) and 4.40-5.23% (K). The soil salinity varied between 2.23-4.66 dS m^-1 in the top soil (0-20 cm depth) and 0.95-2.62 dS m^-1 in the sub-surface (20-40 cm depth) soil. The application did not affect significantly the soil salinity and was found well below the hazardous limit for most crops. The evolution of the other elements was different.. For example, elements such as Ca, P and K showed an increase while Na showed a decrease, whereas the Mg content did not respond with increasing N application. The soil moisture ranged between 8.06-9.15% (0-20 cm depth) and 5.51-9.36% (20-40 cm depth) and did not show any effect of N application. The nitrogen use efficiency (NUE) varied between 72.70 to 129.53 kg kg^-1 N in the different N treatments. The mean 15 N a.e. ranged from 0.010 to 0.844% (leaves), 0.058 to 0.855% (shoots), 0.044 to 0.747 (roots) and 0.07 to 0.823 % (fruits). In conclusion, the mean highest yield of cucumber as fresh fruit was 33.74 t ha^-1 , obtained with 180 mg N L^-1 relative to all other treatments. Nitrogen applied through fertigation was more effective towards yield improvement than soil application. The NUE was highest with 60 mg N L^-1 as compared to all other higher dose of N application. The research findings showed that there is a lot of potential for adoption of fertigation practices in order to increase the production of greenhouse crops, improving the economics of these crops. (author)

[en] Cucumber and tomato are the most important protected vegetables in coastal Lebanon. Recent research established that in these intensive systems, irrigation and fertilization are still empirically applied. Techniques such as fertigation are used but associated to traditional practices of soil application of fertilizers and animal manure addition. In 1997, a pot experiment was conducted in order to find the optimal irrigation frequency and modality of fertigation. For this, four frequencies of irrigation were combined with two modalities: discontinuous irrigation as practiced by the growers and continuous irrigation, as recommended by the scientists. In these closed-system conditions, the frequency of irrigation influenced the dry matter production. In addition, the percentages of nitrogen derived from fertilizers were very high, from 89 to 95%. The discontinuous modality allowed for greater nitrate leaching. The evaluation of the main findings for plants grown in the soil, was conducted in 1998, in a greenhouse, 35 km north of Beirut. The treatments were reduced to two frequencies of irrigation combined with the two modalities of fertigation. The objectives were to assess, with the use of ¹⁵N labelled fertilizers, the most efficient treatment as far as plant performance and losses from the plant-soil system are concerned. (author)

[en] Nitrogen fertilization and irrigation methods are the key factors of yield increase. With proper management of these two factors a good production and protection of the environment could be attained at the same time. Field experiments were carried out at Hama (Tezeen's Agricultural Research Station) for four consecutive years 1995=1998. The objectives of this study were: Assessment of nitrogen fertilizer use efficiency (NFUE) under conventional and fertigation practices; Nitrogen requirements of cotton crop grown under fertigation practices: Comparative study of water use efficiency (WUE), and seed cotton yield of cotton crop grown under conventional and drip irrigation. Treatments consisted of five nitrogen rates for the fertigated cotton crop (0, 60, 120, 180 and 240 kg N ha^-1). While of the surface irrigated cotton treatment only one recommended rate by MAAR was applied (180 kg N ha ^-1). Irrigation methods and N treatments were arranged in RBD. The soil water content and available soil nitrogen were monitored according to the standard procedures. The results revealed that fertigation of cotton under the given circumstances improved water use efficiency, nitrogen use efficiency, seed cotton yield, dry matter production, earliness and in some cases lint properties. Under fertigation practices 35-55% of the irrigation water was saved in comparison with surface irrigated cotton grown under the same condition. The seed cotton yield was increased by more than 50% relatively to the surface irrigated cotton. Furthermore, water use efficiency of the fertigated cotton was increased by almost 90 %. (author)

[en] Mediterranean countries have a severe shortage of water resources for agricultural, municipal and industrial purposes. This situation is aggravated daily due to the rapidly increasing population in the area. Agriculture is the biggest consumer of water with about 80% of the renewable resource used for irrigation. Traditional irrigation methods are highly inefficient: only about one-third of the applied water is actually transpired by the crops. Clearly, there is great scope for improved irrigation management. Intensification of agricultural production to meet growing market demand requires the simultaneous application of irrigation water and fertilizers. Application of fertilizer in drip irrigation (fertigation) is an effective way to promote efficient use of these scarce and expensive resources. There is widespread interest in Mediterranean countries in fertigation. Nevertheless, information on the form and concentration of the nutrients required for different crops is presently inadequate. Moreover, the low fertilizer recoveries due to extensive fertilization practiced during the last few decades have created serious agricultural and environmental problems. High nitrate concentrations in groundwater and deterioration of some important quality parameters of agricultural products are the main concerns. Recognizing the potential role of nuclear techniques in identifying improved water and fertilizer management practices, the IAEA implemented two regional technical co-operation projects during the period 1995-2000 with eight participating countries from the West Asia region: The Islamic Republic of Iran, Jordan, Lebanon, Saudi Arabia, the Syria Arab Republic, Turkey, United Arab Emirates and Yemen. The main objective was to establish water balance and fertigation practices using nuclear techniques, with a view to improving crop production in arid and semi-arid zones. The projects aimed to compare the following parameters under conventional fertilizer and water management practices with fertigation: Crop yields, N fertilizer recovery, Water use efficiency and crop water requirements, and Nitrate leaching. Water use and N-fertilizer efficiency under drip irrigation compared with conventional agricultural practices were estimated using neutron probe and ¹⁵N recovery techniques, respectively