الفهرس 
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Abstract
5. SUMMARY AND CONCLUSION
Biogate-fert technique ensure to maximizing water and fertilizer unit productivity for potato crop, Two field experiments were carried out during growing seasons 2019-2020 and 2020-2021, at research farm of National Research Centre in Nubaria region, Egypt to study management of biogate-fert technique on potato crop under drip irrigation system in sandy soil conditions. Study factors were fertigation techniques (fertigation, biogate-fert and fertilization).
Objectives of this study were:
1- Calibration and validation of the SALTMED simulation model by using different techniques (biogate-fert, fertigation, fertilization and its distribution) and to evaluate these fertilizer treatments on potato yield.
2- Following the distribution of bacteria, during different growth stage of cultivation.
3- Evaluate the correlation between soil microorganisms and soil environmental factors such as (salinity, PH, soil fertility and the concentration of element nutrient).
4- Estimate the crop water production function for potato crop.
5- Estimate the total yield and its components such as (stem length, stem weight, number of stem number of tubers, weight of tubers, and volume of tubers.
6- Irrigation water use efficiency.
7- Fertilizer use efficiency.
Treatments:
1. Biogate-fert technique with drip irrigation.
2. Fertigation technique with drip irrigation.
3. Fertilization technique with drip irrigation.
1. Mineral fertilizer:
The recommended doses of mineral fertilizer and chemical fertilizer were considered according to the recommendation of the Horticulture Research Institute, ARC, Ministry of Agriculture and Land Reclamation, were added as fertigation i.e. nitrogen fertilizer was added at a rate of 120 kg/Fed as ammonium sulfate (20.6 % N), 150 kg calcium super phosphate/fed (15.5% P2O5) and 50 kg potassium sulfate (48 % K2O) were added. Mineral fertilizers were applied by injection through the irrigation water.
2. Bio-fertilizer:
The bio-fertilizer was supported by Microbiology department, Agricultural and Biological Research division, National Research Centre. It was containing a mixture of N2-fixing bacteria (Azotobacter chroococcum) and (Bacillus megaterium) or phosphate mobilizing and (Bacillus circulance) or Potassium dissolving. The Azotobacter bacterial strain was used, where the bacterial isolate was seeded on a liquid Azotobacter Agar environment for 1:2 days at a temperature of 28°:30° C to get a cell suspension of 4x108 cell/g soil. The Baccilus megaterium phosphate-degrading bacterial strain was used, where the bacterial isolate was seeded on a liquid Nutrient Ashby environment for 5 days at a temperature of 28°:30° C to get a cell suspension of 6x106 cell/g soil. The bacterial strain Baccilus circulans analyzed phosphate was used, where the bacterial isolate was seeded on a liquid Nutrient Ashby environment for 5 days at a temperature of 28°:30° C to get a cell suspension of 4x106 cell/g soil.
• The first concentration: after 10 days after planting.
• The second concentration: after 15 days of the first treatment.
• The third concentration: after 20 days of the second treatment.
• Dilution is done by 2 liters/ 20 liters of water, and then the irrigation process is done.
The data released from the recent study could be summarized as following:-
• There was a good agreement between simulated and measured nitrogen (ppm), soil moisture and dry matter. There were no large variations in values between simulated and measured values. SALTMED simulation model proved its high sensitivity to simulate sudden nitrogen (ppm), soil moisture and dry matter due to irrigation events.
• The CFU of bacteria increased with the duration of drip irrigation especially bio-fertilizers treatment compared with mineral fertilizers
• the average CFU of bacteria in 0–40-cm soil layers increased by 112 times After two years of drip irrigation, the CFU of bacteria had increased further, and reached more than 78 × 106 CFU g–1 dry soil in the 0–10-cm soil layers, and this indicated that cultivation had improved the soil environment and it was more favorable for bacterial growth.
• In the vertical direction, the CFU of bacteria in the surface soil layers were higher than the sub soil on uncultivated land. This is because the vertical distribution of soil microbes is restricted by the soil physical and chemical characteristics and soil nutrient status. With increased depth, the soil temperature, organic matter and N all decrease, which is not suitable for growth of most microbes.
• In the horizontal direction, for irrigated land the bacteria activity was always higher near the emitter than further away. After the end of cultivation, the bacteria activity near the emitter was 2.24 times that on the land before irrigation. The activities under the emitter, and 10 cm away were higher than at 15, 20 and 30 cm away, in the irrigated land.
• After the period of irrigation with T1, the growing conditions of Potatoes changed as the soil environment greatly improved. The soil salinity decreased significantly in Bio-fertilizer treatment more than chemical and bio-fertilizer+ chemical treatments. The soil salinity and pH in the root layers decreased significantly, the average Ece in 0–40-cm soil layers was 0.33 ds m–1 and average pH was 6.8 Soil fertility was enhanced greatly.
• The soil environment was improved greatly, and there were significant positive correlations between bacteria, phosphate, urea activities; and significant negative correlations with Ece and PH.
• The highest values of potato wp potato were 13.7 kg/m3 and there were high significant differences between values of WP under (Mineral and Bio-fertilizers) and other treatments. These findings may be due to the drip biogate-fert application gave the chance for nutrients to move into the wetted volume in a manner consistent with the flux of the water in the soil, while applying the fertilizers using conventional method causes non-uniformity distribution of fertilizer through the soil profile and consequently, decreasing fertilizer utilization efficiency and crops productivity.
Concluding Remarks
The development of biogation as an alternative technique for improving yield productivity under sandy soil conditions had been evaluated and resulted in a considerable increase in potato yield over the traditional application (fertigation). However, Biogation appeared to be an economically, technically and environmentally feasible alternative technique for enhancement of potato yield productivity and reduce the amounts of added mineral fertilizers by about 25 percent of the crop nutrient requirements.
Recommendation
this study were based on only two years of data and the results may have some limitations, and so further research is needed in the following years. More studies are needed to determine the actual requirements and other related management criteria for biogation technique under different physical field resources, i.e. soil salinity, low water quality and stress conditions.