Accurately estimation of actual crop evapotranspiration (ETa) as a parameter of irrigation scheduling is very critical for efficient use of limited irrigation water resources. The objectives of this study were to (1) build, verify and validate an expert system for managing on-farm irrigation water of some soils under Egyptian conditions, (2) study the effect of coefficient of uniformity (CU) and distribution uniformity for center pivot irrigation system, (3) study the effect of the precise estimation of daily actual crop evapotranspiration (ETa) on maximizing yield and improved water use efficiency. A rule-based program named CPISM-ES (Center Pivot Irrigation System Management- Expert System) was codes and compiled using python3.7.2 language. The program was verified using ready-to-use software programs (cropwat-8 and climwat 2) for estimating the daily reference evapotranspiration and a spreadsheet named the (FAO56Ax8.xls) introduced by FAO-56 for estimating the irrigation water management parameters. It also was validated by carrying out a field experiment at site :-El Salhyia(11.2 m above sea level, 30,35°N,30,26°E), was obtained from several different sources. The irrigation expert system aims to provide the farmers by the irrigation expertise to determine the exact water needed at exact time according to the crop requirements and the environmental factors which effect factors. The experiment included the following factors: a) obtaining climatic data from a weather station b) estimation crop evapotranspiration) coefficient of uniformity (CU) and distribution uniformity for center pivot irrigation system.  1- The estimation of actual crop evapotranspiration (ETa) using crop coefficient. 2- The seasonal cumulative ETa estimated by single-kc approach of El Salhyia (1875 m3 f.1season-1). 3- Yield: the highest of crop potatoes for El Salhyia (16.2 t.fed-1). 4- Water use efficiency: the maximum value of water use efficiency for El Salhyia (0.75 kg m-3).

In spite of the development observed in the area and production of potatoes crop in Yemen for the period of (1990-2010) to the level of self-sufficiency, the exported quantity, however, still very limited, It even decreased sharply in 2010 by 84.5%, compared to it's level exported in 2006. Stagnant productivity of potatoes in Yemen at around 13 ton only per-hectare, in front of (35- 45) ton/h globally, is believed to be the main obstacle standing behind the failure of exportation the Yemeni potatoes to the abroad. According to field study, several results have been obtained, the most important of which: The variables, such as, chemical fertilizer, equipment, manure and seeds are found to be the most effective factors on the output of potatoes. It is proved statistically significant at (0.01) level and responsible for the change occurred in the production of sampled individuals by 77% (R2), however, the result show that the quantity used in the production process of potatoes by mentioned above factors fill short to meat the level of optimal quantity required to maximize the profit.  The size of optimal level of production was estimated at (19.9) ton and the price of potatoes accepted by producers was estimated at 121390 YR/Ton. According to percentage of importance, seeds came first at the total variable cost by 31%, then, irrigation by 17.6%, fertilizers and pesticides 14.6%. Net revenue was estimated at (493640) YR, and the benefit /cost ratio was estimated at 1.40. The most important recommendation reached by this study is directed toward more using inputs in process of production by producers of potatoes, to maximize profit and increase productivity of area cultivated.

This work was carried out in two successive summer plantations of 2004 and 2005 on potatoes cv. Spunta at Abou Awad village , Aga, Dakahlia Governorate, to study the influence of Vesicular Arbuscular Mycorrhizal (VAM) fungi , nitrogen and potassium fertilization at rates of 50, 75 and 100% of recommended rate / fed. with foliar spraying of micronutrients (Fe150 , Zn 75, and Mn 75 ppm) and their interactions on plant growth , yield and its components, as well as chemical composition .Application of the tested rates of nitrogen and the potassium induced significant increase in vegetative characteristics (plant height, foliage fresh and foliage dry weight) total tuber yield (t/fed) , number of tubers/plant and tuber weight/plant, tuber dry matter , starch and nitrate content in tuber, as well as N,P and K concentra-tions in the leaves and micronutrients in the leaves (Fe, Mn and Zn) in both seasons.Similarly, plant height, chlorophyll content, fo-liage fresh and dry weights , total yield (t/fed), number of tubers , tuber weight/ plant, tuber dry weight , starch and nitrate content in tuber, NPK concentration in leaves and tubers , micronutrient content (Fe, Zn and Mn) in leaves gave the highest values with inoculation by VA Mycorrhizal fungi and some micronutrients .The interaction between NK, VAM fungi and micronutrient gave the highest values of vege-tative growth characteristics, number of tu-bers/plant, NPK in leaves and tubers and micronu-trients (Zn and Mn) in leaves when potatoes was fertilized with 100% NK of the recommended rate and inoculate with VAM fungi plus foliar spraying by micronutrients (Fe, Zn and Mn).as well as total yield (t/fed), tuber weight/plant, tuber dry weight, starch content in tuber , Mn and Zn in leaves, while The lowest content of nitrate in tubers was found when plants were applied with 50 (%) NK of recommended rate with inoculation by VA My-corrhizal fungi.Generally, the best results were obtained when potato received 75 % of NK of the recommended rate, inoculated by VA Mycorrhizal fungi and sprayed with micronutrients at dose of Fe 150, Mn 75 and Zn 75 ppm. This treatment resulted in the highest total tuber yield and its components and reduced chemical fertilizer inputs.

European Union countries are considered most important markets for imported Egyptian potatoes, and despite of that, the quantity of Egyptian exports from this crop is not appropriate with the export potential of Egypt. The study aims to identify the current status of Egyptian potatoes exports to the European Union, a study of the competitive situation of Egyptian potatoes in the most important markets within the European Union and finally, estimate the demand function of Egyptian potatoes in the most important EU markets. The study concluded that Italy and Greece are the most important EU markets importing Egyptian potatoes. This amount was about 64.3%, 66.8% of the average total quantity and value of Egyptian exports of potatoes to the European Union during the period (2000-2014) respectively, and their imports increased annually at different rates during the period (1995–2014). The market share of Egyptian potatoes within the EU market is very small with the exception of the Greece market and the Italian market.   Based on such results, the study recommends the following   Focus on increasing exports of Egyptian potatoes to countries with a high volume of imports of potatoes such as the Netherlands, Belgium, Spain and France. To review the prices of potatoes exports to Italy and the most suitable periods of increasing its quantity to this market, taking care that this does not put the Egyptian potatoes in a price competition with French and German potatoes. Continuation and further work on improving the quality of potatoes, in addition to the expansion in the cultivation of potatoes in the brown rot-free, so as to benefit from competitive advantages in the markets of the EU, especially Italian and Greece markets, making it possible to sustain Egypt's share in both markets, and take advantage from the price competition in the Greece market. Necessity follows flexible price policies for the Egyptian potatoes exports to Greece, which could increase its exports to this market and take advantage of price competition in this market. Necessity continue studying the ratio between export prices of Egyptian potatoes to the markets of the EU, and the export price for countries competing in these markets in general, and each of the Italian and Greece market in particular. So as to achieve the continuity and stability of this ratio, or at least achieve the stability of the quantities exported of Egyptian potatoes to both markets at the same time. Studying the prices of potatoes and seed special analytical study as Shafik in a study. Abolition of government intervention and control of prices, as Wali pointed out in the study of the abolition of control of prices and reduce supply. Abdul Rahim also mentioned in this study the effects of the liberalization of the prices of agricultural inputs and outputs on crop composition. Find alternatives to price policies for the development of Egyptian potatoes as a strong competitor in the European market with a competitive advantage price, as indicated by Azza in the study of alternatives to agricultural price policy and the effects of the Egyptian economic. Put the potatoes in the composition of a crop compatible with contemporary economic variables as explained Abdel-Maksoud

Late blight caused by Phytophthora infestans is one of the most destructive dis-eases potato in Egypt and world wide. Stability of resistance to late blight was eva-luated in twenty five potato cultivars during 2003 and 2004 successive seasons un-der heavy natural infection. Data showed that the potato cultivars Altesse, Occania, Safrane and Soleia highly resistant while cultivars Daisy, Hermine and Isabel rec-orded the highest susceptibility to late blight. Application different fungicide against potato late blight revealed that Aquagen Bro and Previcur-N were the best effective fungicides in reducing disease severity and progress of late blight. Data showed also that the losses of tubers due to late blight in season 2003 ranged from 11.75 Kg/plot (cultivar Hermes) to 18.0 Kg/plot (cultivar Lady Roseta) while in season 2004, yield losses ranged from 11.25 Kg/plot (cultivar Hermes) to 23.75 Kg/plot (cultivar Spun-ta). The results demonstrate that integration of Previcur-N treatment with host resis-tance was effective in reducing late blight and tuber yield loss of potato.