Determination of potassium and magnesium status of soils using different soil extraction procedures in the upper part of Mesopotamia (in the Harran Plain)

It is a common belief that most of the Turkish soils are rich in potassium (K) and magnesium (Mg) for crop production and that there is no crop respon se to fertilization of these nutrients. However, it is currently a common a gricultural practice by farmers to use an excess amount of K and, in some i nstances, Mg fertilizers especially for horticultural cash crops. Two biolo gical (pot and Neubauer experiments) and four chemical extraction methods ( 0.3 N HCl, 0.5 N HCl, 1 N NH4OAc, and 0.5 N NaHCO3) were employed to measur e the amounts of extractable K and Mg in the selected ten soil series of Ha rran Plain (Fertile Crescent) in the upper part of the Mesopotamia area. It alian grass (Lolium italicum) and barley (Hordeum vulgare L.) were used as test plants in the pot and Neubauer experiments, respectively. The amount o f slowly available K extracted using four chemical extraction methods were much higher in two soil series (Ekinyazi and Akcakale) than that of the oth er soil series. The Akcakale series had more slowly available Mg than the o ther soil series. Total amounts of slowly available K extracted with both o f the biological, and 0.3 N HCl and 1 N NH4OAc chemical extraction methods were found statistically significant at 1% level. Correlation coefficients between the biological and chemical methods were calculated. As the number of grass harvests increased, percentage of K content decreased and Mg conte nt increased in plant dry matter. At the last harvest, K content of the soi ls depleted, whereas Mg content nearly did not change. According to index g rouping, Italian grass grown in the pots did not need K and Mg fertilizatio n.