الفهرس 
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Abstract
In this study, two field experiments were carried out during the growing seasons of 2011/2012 and 2012/2013, at the experimental farm of the south-west portion on a saline soil at Tina plain region, south Sinai governorate, Egypt. The experiments were carried out in order to investigate the effects of humic acid and salinity and their interactions on vegetative growth, yield and quality of tomato (Lycopersicon esculentum Mill). Seeds of tomato cultivar ”Castle-rock”.
The two fields Soil salinity were moderate and high ranging between 2 to 3 mmohs/cm/25Co and the other field soil salinity ranged between 5 to 8 mmohs/cm/25Co.Potassium humate (86% Humic acid and 6% potassium oxide) was added with different four dozes i.e., (0 kg/fed - control, with distilled water), 0.5, 1 and 2 kg/fed., at two times, the first (50% of the amount) was added after 15 days from transplanting and the second one (50% of the amount) was carried out after one month from the first addition
Asplit plot design with three replicates was used where the soil salinity was the main plots and potassium humate treatments were located in the subplots.The results of this experiment can be summarized as follows:
1. Humic acid effect on Soil properties :
1.1. Crop water use efficiency
According to the experiment results the addition of humic acid concentration 1kg /fed reduced the effect of soil salinity on the yield therefore this concentration gave the highest yield. However, humic acid with low soil salinity resulted in higher value of Crop water use efficiency in addition to a high amount of seasonal yield compared with high soil salinity, on the other head, improving the crop water use efficiency of tested field.
1.2. Soil salinity as affected by humic acid concentrations.
For Moderate Soil Salinity Level the data and the figures revealed that the values of soil salinity EC (dSm/m/25Co) were significantly affected by increasing the rates of humic. This means that, the salts concentration with Moderate Soil Salinity Level decreased with the increase of concentration of humic acid rate.
The average electrical conductivity (EC) in (dSm/m/25Co) which was measured with the time (beginning, mid, maturity and end of the growing season) using different humic acid rates for two soil salinity levels (For Moderate and high Soil Salinity Levels) was observed that, soil salinity value decreased with the time for all humic concentrations.
Application of humic acid rate led to a reduction of soil salinity because humic acid could improve the soil physical properties (increasing soil porosity). The decomposition of humic acid releases acids forming compounds and active microorganisms, which react with the soluble salts already present in soil either to convert them into soluble salts or at least increase their solubility.
1.3. Sodium adsorption ratio (SAR) of soil.
The SAR decreased with increasing the levels of humic acid the lowest value of SAR was 2.00 for soil treated with humic acid by the rate of 2 kg fed-1 when soil salinity level was 2-3 dSm/m/25Co.
They attributed the reduction in SAR with increasing the rates of Humic acid either due to an increase in divalent cations (Ca+Mg) or decrease in mono-valent cation (Na). Values of Na could decrease during leaching while Ca+Mg increase due to reactions of organic acids with CaCO.
1.4. N-NO3 of soil.
The application of humic acid rates significantly increased the available N-NO3 in soil in both seasons.
1.5. PO4 of soil.
The corresponding relative increase of mean values PO4 availability in soil is affected by humic acid.
1.6. Yield as affected by humic acid (under different soil salinity levels).
There are significant increases in yield of tomato detected due to the decrease of soil salinity.
The favorable tomato yield were obtained in our experiments at 2-3 dSm/m/25Co and 1.0 kg/fed humic acid. This may be due to the salt-stress effects and Humic acid as the humic acid improved the chemical properties of the soil by increasing the soil microorganisms which enhance nutrient status of the tomato plants.
2. Humic acid effect on Tomato plants:
2.1. Vegetative characteristics:
The vegetative growth of tomato responded positively to salinity. Soil of salinity between 2:3 m mhos increased plant height, branch and leaf number, leaf area, haulm fresh, dry weight, chlorophyll content and root weight per plants in the two seasons as compared with soil of salinity between 5:8 mmohs/cm/25Co The addition of 1kg/fed or 2kg/fed humic acid increased plant height, branch and leaf number, leaf area, haulm fresh, dry weight, chlorophyll content and root weight per plants in the two seasons as compared with other addition of humic acid treatments.
The interaction between salinity and humic acid showed that tomato plants growing under soil of salinity between 2:3 mmohs/cm/25Co with addition of 1kg/fed or 2kg/fed humic acid produced the highest plant height, branch and leaf number, leaf area, haulm fresh, dry weight, chlorophyll content and root weight per plants
2.2. Chemical constituents of plant foliage:
The plant chemical constituents responded positively to salinity. Soil of salinity between 2:3 mmhos decreased plant chemical constituents in the two seasons as compared with soil of salinity between 5:8 mmhos.
The addition of 1kg/fad or 2kg/fad of humic acid increased plant chemical constituents in the two seasons as compared with other addition of humic acid treatments
Tomato plants growing under soil of salinity between 5:8 mmhos with addition of 1kg/fad or 2kg/fad of humic acid produced the highest plant proline content in the two seasons as compared with other interaction treatments.
2.3. Flowering characteristics:
1. The number of flowering and number of produced flowers per plant responded positively to salinity. Soil of salinity between 2:3 mmohs/cm/25Co increased Number of flowering (Date of first flower) and number of flowers per plants in the two seasons as compared with soil of salinity between 5:8 mmohs/cm/25Co.
2.The addition of 1kg/fed or 2kg/fed of humic acid increased number of flowers per plants in the two seasons as compared with other addition of humic acid treatments.
3.Tomato plants growing under soil of salinity between 2:3 mmohs/cm/25Co with addition of 1kg/fed or 2kg/fed of humic acid produced the highest number of flowers per plant in the two seasons as compared with other interaction treatments.
2.4. Yield and it’s components:
The yield and it’s components of tomato responded positively to salinity. Soil of salinity between 2:3 mmohs/cm/25Co increased number of fruits per plants, fruit yield, total yield and marketable yield in the two seasons as compared with soil of salinity between 5:8 mmohs/cm/25Co. While, Soil of salinity between 2:3 mmohs/cm/25Co decreased un-marketable yield as compared with soil of salinity between 5:8 mmohs/cm/25Co .
the addition of 1kg/fed or 2kg/fed humic acid increased number of fruits per plants, fruit yield, total yield, marketable yield in the two seasons as compared with other addition of humic acid treatments. On other hand, the addition of 2kg/fed of humic acid decreased un-marketable yield as compared with other addition of humic acid treatments.
The interaction between salinity and humic acid showed that tomato plants growing under soil of salinity between 2:3 mmohs/cm/25Co with addition of 1kg/fed or 2kg/fed of humic acid produced the highest number of fruits per plants fruit yield, total yield, and marketable yield. While, un-marketable yield deceased under soil of salinity between 2:3 mmohs/cm/25Co with addition of 2kg/fad of humic acid in the two seasons as compared with other interaction treatments.
2.5. Fruits quality:
The fruit size and color chart responded positively to salinity. Soil of salinity between 2:3 mmohs/cm/25Co increased fruit size and decreased color chart in the two seasons as compared with soil of salinity between 5:8 mmohs/cm/25Co.
The addition of 1kg/fed or 2kg/fed of humic acid increased fruit size and decreased color chart in the two seasons as compared with other addition of humic acid treatments.
Tomato plants growing under soil of salinity between 2:3 mmohs/cm/25Co with addition of 1kg/fad or 2kg/fad of humic acid produced the highest fruit size and lowest color chart in the two seasons as compared with other interaction treatments.
The total soluble solids content and vitamin C responded positively to salinity. Soil of salinity between 2:3 mmohs/cm/25Cos decreased total soluble solids content and vitamin C in the two seasons as compared with soil of salinity between 5:8 mmohs/cm/25Co.
The addition of 1kg/fed or 2kg/fed of humic acid increased total soluble solids content and vitamin C in the two seasons as compared with other addition of humic acid treatments.
Tomato plants growing under soil of salinity between 2:3 mmohs/cm/25Co with addition of 2kg/fad of humic acid produced the highest total soluble solids content and vitamin C in the two seasons as compared with other interaction treatments.