Abd-Elrahman, Shaimaa H.  <br/><br/>
Comparison between organic and mineral sources of potassium and their effects on potassium fractions in clay soil                                                          and productivity of potato plants under water stress conditions<br/>  [electronic resource]. 
 مقارنة بين المصادر العضوية والمعدنية للبوتاسيوم وتأثيرها على صور البوتاسيوم في أرض طينية وإنتاجية نباتات البطاطس تحت ظروف الإجهاد المائي 

 - p. 193-206. 
<br/><br/>Includes bibliographic reference. 
<br/><br/> Potassium (K) is an essential element for plant growth that maintains water balance within its cells. Different forms of K were <br/>investigated for their effects on potato (Solanum tuberosum, cv. Spunta) plants grown under water stress conditions as a kind of <br/>adaptation to the climatic changes and water shortage under Egyptian soil conditions. Also, knowledge of different K fractions <br/>in the studied clay soil is important to achieve the sustainability in agriculture. Therefore, a field experiment was conducted during <br/>the two tested seasons of years 2014 and 2015 at the Faculty of Agriculture, Ain Shams University, Qalubia governorate, Egypt. Two sources <br/>of K were tested under three levels of irrigation water in a split-plot design. Results indicated that K fractions in soil were in order <br/>of total K > non-exchangeable/ fixed > exchangeable > water soluble. The 50% irrigation level of irrigation requirements (IR) combined with <br/>K-humate as ground application increased water soluble and exchangeable K in the studied soil. While there was hardly no changes observed due <br/>to the applied treatments on fixed and total amounts of K in the soil. Regarding the studied vegetative growth and yield parameters of the <br/>growing potato plants, the treatment 100% of IR combined with K-humate as soil application caused significant increases. The specific gravity <br/>of tuber, as an important indicator of potato tuber quality, recorded the highest value by applying 50% of IR combined with K-humate as ground <br/>addition, compared to mineral addition which came in the second order. Regarding the nutrient concentrations in potato haulm, results revealed <br/>that the 50% of IR combined with K-humate gave the highest content of N, while the same irrigation level with K-humate plus foliar spray gave <br/>the highest content of P and K, during the two tested seasons. In tubers, 50% of IR combined with K-humate as soil application gave the highest <br/>concentration of N and P during the two tested seasons, while 75% of IR in the first season and 50% of IR in the second season combined with <br/>K-humate plus foliar spray gave the highest values of K content. The calculated water use efficiency (WUE) showed that the highest value was <br/>obtained by 50% irrigation level of IR combined with soil application of K-humate.<br/> 
<br/><br/><br/>Summary in Arabic. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Potassium fertilizers.<br/>Clay soils<br/>Potatoes--Effect of stress on<br/>Potatoes--Fertilizers<br/>Potatoes--Yields