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 [electronic resource].

Includes bibliographic reference.

Potassium (K) is an essential element for plant growth that maintains water balance within its cells. Different forms of K were
investigated for their effects on potato (Solanum tuberosum, cv. Spunta) plants grown under water stress conditions as a kind of
adaptation to the climatic changes and water shortage under Egyptian soil conditions. Also, knowledge of different K fractions
in the studied clay soil is important to achieve the sustainability in agriculture. Therefore, a field experiment was conducted during
the two tested seasons of years 2014 and 2015 at the Faculty of Agriculture, Ain Shams University, Qalubia governorate, Egypt. Two sources
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
of total K > non-exchangeable/ fixed > exchangeable > water soluble. The 50% irrigation level of irrigation requirements (IR) combined with
K-humate as ground application increased water soluble and exchangeable K in the studied soil. While there was hardly no changes observed due
to the applied treatments on fixed and total amounts of K in the soil. Regarding the studied vegetative growth and yield parameters of the
growing potato plants, the treatment 100% of IR combined with K-humate as soil application caused significant increases. The specific gravity
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
addition, compared to mineral addition which came in the second order. Regarding the nutrient concentrations in potato haulm, results revealed
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
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
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
K-humate plus foliar spray gave the highest values of K content. The calculated water use efficiency (WUE) showed that the highest value was
obtained by 50% irrigation level of IR combined with soil application of K-humate.

Summary in Arabic.