الفهرس 
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Abstract
The current study was carried out in a field scale during two successive growth seasons (2009/2010 and 2010/2011) on tomato plants which were irrigated with saline well water using drip irrigation system subjected to water stress and were grown under application of potassium fertilization in newly reclaimed lands at the Agricultural Experiments and Research Center which belongs to Faculty of Agriculture, Minia University. The Agricultural Experiments and Research Center is located in the West district of Samalout, El-Minia Governorate, Egypt. As attempt to elevate fertility of the soil, a large amount of clay was transferred to the site in May 2009, so the soil surface (0 – 30 cm) texture became loam. The current study aims to investigate effects of irrigation well water salinity and water stress on some soil chemical properties, growth, yield, and fruit quality parameters of tomato, and chemical composition of tomato plants under application of potassium fertilization using drip irrigation system.
The experimental field was drip irrigated from a well water. The experimental design was factorial in a completely randomized block with three replicates. The experimental design consisted of one salinity and water stress alleviated amendments (potassium fertilization).
The experimental design included two levels of irrigation well water salinity [slightly saline irrigation water (well water No. 1 of 2.24 dS m-1) and medium saline irrigation water No. 2 of 3.86 dS m-1)], three treatments of irrigation intervals (irrigation of tomato plants every 3, 4, and 5 days), and three levels of potassium fertilization (96, 120, 144 kg K2O/feddan); which were applied singly or in combination, making a total number of eighteen treatments of all, with 3 replicates.
The obtained results of the current study can be summarized under the following main eight subjects:
5.1. Evaluation of irrigation water quality
1- Concerning salinity problem related with irrigation water quality according to the guideline for interpretations of water quality for irrigation as described by Ayers and Westcot (1994); E.C. value of well water No. 1 is in the range of 0.7 - 3.0 dS m-1 which lies under the degree of restriction on use of ’’Slight to Moderate’’, which implies that this well water may cause a slight to moderate salinity problem in soil. However, E.C. value of well water No. 2 is > 3.0 dS m-1 which lies under the degree of restriction on use of ’’severe’’ in both growth seasons, which indicates that this well water may cause a severe salinity problem in soil.
2- Regarding infiltration problem related to irrigation water quality and according to the guideline for interpretations of water quality for irrigation as described by Ayers and Westcot (1994); sodium adsorption ratio (SAR) of both well waters No. 1 and No. 2 were in the range of 0.0 - 3.0 SAR and E.C. was more than 0.7 dS m-1 which lies under the degree of restriction on use ” None’’, suggesting that using these wells water in irrigation may not cause an infiltration problem in the investigated soil.
3- Considering specific ion toxicity related to irrigation water quality and according to the guideline for interpretations of water quality for irrigation as described by Ayers and Westcot (1994); the SAR value of well water No. 1 and the well water No. 2 is < 3.0 SAR (surface irrigation) which lies under the degree of restriction on use of ”None”, which implies that using well water No. 1 and well water No. 2 in irrigation of tomato plants may not cause a sodium toxicity problem in tomato plants.
The chloride concentration in well water No. 1 is in the range of 4.0 - 10.0 meq/l (surface irrigation) which lies under the degree of restriction on use of ”Slight to Moderate”, implying that using well water No. 1 in irrigation of tomato plants may cause an increasing chloride toxicity problem. The chloride concentration in well water No. 2 is > 10.0 meq/l (surface irrigation) which lies under the degree of restriction on use of ”Severe”, suggesting that using the well water No. 2 in irrigation of tomato plants may cause a severe chloride toxicity problem.
4- Concerning the miscellaneous problems related to irrigation water quality, and according to the guideline for interpretations of water quality for irrigation as described by Ayers and Westcot (1994); bicarbonate concentration in well water No. 1 and well water No. 2 is in the range of 1.5 - 8.5 meq/l (overhead sprinkling only) which lies under the degree of restriction on use of ’’Slight to Moderate’’, indicating that using well water No. 1 and well water No. 2 in irrigation of tomato plants may cause an increasing problem of white scale formation on leaves or fruit when sprinklers are used.
The pH value of well water No. 1 and well water No. 2 is in the normal range of 6.5 - 8.4, implies that using the well water No. 1 and well water No. 2 in irrigation of tomato plants may not cause a nutritional imbalance or may not contain a toxic ion.
5- Regarding the chemical criteria of irrigation water quality, and according to the guideline for interpretations of water quality for irrigation as described by Ayers and Westcot (1994); the Ca/Mg ratio in well water No. 1 and the well water No. 2 is > 1.0, suggests that using well water No. 1 and the well water No. 2 in irrigation of the tomato plants may not cause a calcium deficiency problem or a soil infiltration problem.
5.2. Effects of salinity and water stress on some soil chemical properties under application of potassium fertilization
4.2.1. Salinity buildup in soil during tomato growth season
1- The electrical conductivity value in soil at end of both two tomato growth seasons was significantly increased (p = 0.05) by increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1.
2- Increasing irrigation intervals from 3 up to 5 days significantly increased (p = 0.05) electrical conductivity value in soil at end of both two tomato growth season
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan significantly increased (p = 0.05) electrical conductivity value in soil at end of two tomato growth seasons.
5.2.2. Changes in soil pH during tomato growth season
1- The pH value in soil at end of two tomato growth seasons was slightly increased as a result of increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1. The slight increase in pH of soil at end of both two tomato growth seasons was significant (p = 0.05).
2- The pH value of soil at end of both two tomato growth seasons was slightly increased as irrigation intervals increased from 3 up to 5 days. This slight increase in the pH value of soil at end of both two tomato growth seasons was not significant (p = 0.05).
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan did not give any significant effect (p = 0.05) on pH value of soil at end of both two tomato growth seasons.
5.2.3. Changes in some soluble cations in soil during tomato growth season
1- Soluble cations (Ca, Mg, Na, and K) concentration values in soil at end of both two tomato growth seasons was significantly increased (p = 0.05) compared with the initial content in the soil before tomato planting.
2- Increasing the irrigation intervals from 3 up to 5 days decreased the soluble cations (Ca, Mg, Na, and K) concentration values in soil at end of the two tomato growth seasons.
3- The soluble cations (Ca, Mg, and Na) concentration values in the soil at end of the two tomato growth seasons was decreased when potassium fertilization level was increased from 96 up to 144 kg K2O/feddan. On the other hand, increasing potassium fertilization level from 96 up to 144 kg K2O/feddan significantly increased (p = 0.05) soluble K in the soil at end of the two tomato growth seasons.
5.2.4. Changes in some soluble anions in soil during both tomato growth season
1- It is clear that the soluble anions (Cl and SO4) concentration values in both growth seasons as well as HCO3 concentration value (in the first season only) was significantly increased (p = 0.05) with increasing irrigation water salinity.
2- Increasing the irrigation interval from 3 up to 5 days decreased the soluble anions (Cl, HCO3, and SO4) concentration values in the soil at the end of the two tomato growth seasons. The decrease in the soluble anions (Cl and HCO3) concentration values in the soil was significant (p = 0.05) at end of the two tomato growth seasons, whereas, the decrease in the soluble SO4 concentration value was not significant (p = 0.05).
3- The soluble anions (Cl, HCO3, and SO4) concentration values in the soil at the end of the two tomato growth seasons was increased by increasing potassium fertilization level from 96 up to 144 kg K2O/feddan. The increase in the soluble anions (Cl and SO4) concentration values in the soil at the end of the two tomato growth seasons as well as HCO3 concentration value (in the second season only) was significant (p = 0.05)..
5.3. Effects of salinity and water stress on tomato growth under application of potassium fertilization
1- Increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 slightly decreased the tomato plant height and tomato shoots fresh weight. This slight decrease was significant (p = 0.05) in both growth seasons. While, it slightly increased tomato shoots dry weight in both growth seasons. The slight increase in tomato shoots dry weight was not significant (p = 0.05) in both growth seasons.
2- Increasing irrigation intervals from 3 to 5 days increased tomato plant height and dry weight of tomato shoots, however, it decreased fresh weight of tomato shoots in both growth seasons.
3- Tomato vegetative parameters (plant height, fresh weight of tomato shoots, and dry weight of tomato shoots) were increased by increasing potassium fertilization level from 96 to 144 kg K2O/feddan in both growth seasons.
5.4. Effects of salinity and water stress on tomato yield and yield components under application of potassium fertilization
1- It can be seen that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly increased (p = 0.05) average fruit weight and fresh fruit yield, however, it slightly increased the number of tomato fruits per plant. The slight increase in number of tomato fruits per plant was not significant (p = 0.05) in the first growth season, whereas, it was significant (p = 0.05) in the second growth season.
2- It is obvious that increasing irrigation intervals from 3 to 5 days yield parameters of tomato (number of fruits per plant, average fruit weight, and fresh fruit yield).
3- It is clear that increasing potassium fertilization level from 96 to 120 kg K2O/feddan increased number of tomato fruits per plant, average fruit weight, and fresh fruit yield, however, increasing potassium fertilization level from 96 to 144 kg K2O/feddan decreased tomato fruit yield.
5.5. Effect of salinity and water stress on tomato quality under application of potassium fertilization
1- It can be seen that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly increased (p = 0.05) total soluble solids and shelf life duration, however, it significantly decreased (p = 0.05) dry weight of tomato fruit.
2- It appears that increasing irrigation interval from 3 up to 5 days significantly increased (p = 0.05) total soluble solids and shelf life duration, however, it insignificantly decreased (p = 0.05) dry weight of tomato fruit.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan increased quality parameters (total soluble solids and shelf life duration, whereas it slightly decreased dry weight of tomato fruits in both growth seasons.
5.6. Effects of salinity and water stress on nutrients concentration in tomato plants under application of potassium fertilization
5.6.1. Nitrogen concentration in tomato plants
1- It can be seen that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly decreased (p = 0.05) nitrogen concentration in both tomato shoots and fruits
2- The nitrogen concentration in tomato shoots and fruits were decreased with increasing irrigation intervals from 3 up to 5 days in both growth seasons. The decrease in nitrogen concentration in tomato fruits was significant (p = 0.05) in both growth seasons.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan significantly decreased (p = 0.05) the nitrogen concentration in tomato shoots and fruits in both growth seasons. However, increasing the potassium fertilization level from 96 to 120 kg K2O/feddan significantly increased (p = 0.05) the nitrogen concentration in tomato fruits in both growth seasons.
5.6.2. Phosphorus concentration in tomato plants
1- Increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 decreased phosphorus concentration in tomato shoots and fruits in both growth seasons.
2- Increasing irrigation intervals from 3 to 5 days slightly decreased phosphorus concentration in tomato shoots and fruits in both growth seasons. The slight decrease in phosphorus concentration in tomato shoots and fruits was insignificant (p = 0.05) in both growth seasons.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan slightly decreased phosphorus concentration in tomato shoots, whereas, it had no effect on phosphorus concentration in tomato fruits in both growth seasons. The slight decrease in phosphorus concentration was insignificant (p = 0.05) in both growth seasons.
5.6.3. Potassium concentration in tomato plants
1- It is evident that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 decreased potassium concentration in tomato shoots and fruits in both growth seasons. The decrease in potassium concentration in tomato shoots and fruits was not significant (p = 0.05) in both growth seasons.
2- Potassium concentration in tomato shoots and fruits was decreased with increasing irrigation intervals from 3 up to 5 days in both growth seasons. The decrease in potassium concentration in tomato shoots was significant (p = 0.05), while, the decrease in potassium concentration in tomato fruits was not significant (p = 0.05) in both growth seasons.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan significantly increased (p = 0.05) potassium concentration in tomato shoots and fruits in both growth seasons.
5.7. Effects of salinity and water stress on nutrients uptake by tomato fruits under application of potassium fertilization and using drip irrigation system
1- It can be seen that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly decreased (p = 0.05) nitrogen, phosphorus and potassium uptake by tomato fruit.
2- It is clear that increasing irrigation intervals from 3 to 5 days significantly decreased (p = 0.05) nitrogen, phosphorus and potassium uptake by tomato fruits in both growth seasons.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan significantly increased (p = 0.05) with nitrogen, phosphorus and potassium uptake by tomato fruits in both growth seasons.
5.8. Effects of salinity and water stress on Na and Cl accumulation in tomato plants under application of potassium fertilization
5.8.1. Sodium concentration and uptake by tomato plants
1- It can be observed that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly increased (p = 0.05) sodium concentration in tomato shoots, while, it significantly decreased (p = 0.05) sodium concentration in tomato fruits and its uptake in both growth seasons.
2- It is clear that increasing irrigation intervals from 3 up to 5 days decreased sodium concentration in tomato shoots and fruits, whereas, it increased sodium uptake by tomato fruits in both growth seasons. Neither the decreased in sodium concentration nor the increased sodium uptake was significant (p = 0.05) in both growth seasons.
3- Increasing potassium fertilization level from 96 up to 144 kg K2O/feddan insignificantly decreased (p = 0.05) sodium concentration in tomato shoots and fruits, and significantly decreased (p = 0.05) sodium uptake by tomato fruit in both growth seasons.
5.8.2. Chloride concentration and uptake by tomato plants
1- It can be observed that chloride concentration in tomato shoots and fruits and its uptake by tomato fruits were significantly decreased (p = 0.05) with increasing the irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 in both growth seasons.
2- It is clear that increasing irrigation intervals from 3 up to 5 days decreased chloride concentration in tomato shoots and fruits and its uptake by tomato fruits in both growth seasons.
3- Chloride concentration in tomato shoots and fruits and its uptake by tomato fruits were significantly decreased (p = 0.05) by increasing potassium fertilization level from 96 up to 144 kg K2O/feddan in both growth seasons.
5.8.3. K+/Na+ ratio in the tomato plants
1- It can be seen that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly decreased (p = 0.05) K+/Na+ ratio in tomato shoots, however, it significantly increased (p = 0.05) K+/Na+ ratio in tomato fruits in both growth seasons.
2- Increasing irrigation intervals from 3 up to 5 days significantly decreased (p = 0.05) the K+/Na+ ratio in tomato shoots in both growth seasons as well as K+/Na+ ratio in tomato fruits in first growth season.
3- The K+/Na+ ratio in tomato shoots and fruits was significantly increased (p = 0.05) as a result of increasing potassium fertilization level from 96 up to 144 kg K2O/feddan in both growth seasons.
5.8.4. Na+/Cl- ratio in tomato plants
1- It is clear that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 significantly increased (p = 0.05) Na+/Cl- ratio in tomato shoots in both growth seasons, however, it decreased Na+/Cl- ratio in tomato fruits in first growth season was by both growth seasons.
2- It is evident that increasing irrigation intervals from 3 up to 5 days significantly increased (p = 0.05) Na+/Cl- ratio in tomato shoots in both growth seasons as well as Na+/Cl- ratio in tomato fruits in first growth season.
3- The Na+/Cl- ratio in tomato shoots and fruits was increased with increasing potassium fertilization level from 96 up to 144 kg K2O/feddan in first growth season, however, it was slightly decreased in second growth season.