A field experiment was conducted at the Botanical Gardens Research Department Land, Hort. Res. Inst. Alex., Egypt,
during 2011-2012 and 2012-2013 seasons to study the effect of Kfeldspar rock fertilizer on growth and mineral content of Moringa seedlings. Feldspar grinded rock and potassium sulphate were used as fertilizer sources of K fertilizer to Moringa plants. Fertilizer treatments consisted of three rates of K-feldspar (0, 200, 400 g /tree) and three rates of K-sulphate (0, 100, 200 g /tree), besides six combinations prepared from K-feldspar and K-sulphate. These amounts were added
as a soil drench in two equal doses, the first one was applied immediately after planting (on April, 15th.), while the other after 3 months from the first (on July, 15th.). In addition, all Moringa seedlings received phosphate (50 g P2O5/ tree), organic manure (3kg/tree) and N (50 g / tree) at processing and preparing the soil to planting seedlings. Also, in the second season, Moringa seedlings were cultivated at the same age and height as well as the same agricultural practices as in the first one. The obtained results indicated that all treatments increased plant height and stem diameter with various significant differences compared to the control at the different determinations assessed in the two seasons. However, the superiority in the two seasons was for the combination of 200g K-F + 100g K-S, which gave the tallest plants
and widest stems, as well as K mineral content of either soil or plant. In general, connecting between K-F and K-S recorded better results than the individual application of each in most determinations registered in both seasons. Also, increasing the rate of either K-F or KS, individually or in combination caused an addition improvement in all previous characters measured in different stages of the two seasons. Moreover, treatments that involved K-feldspar gave better results in the second period of each season than that included K-sulphate alone, indicating its ability to provide plants with K+ ions for a long period. So, it can be recommended to fertilize Moringa seedlings with 200g K-feldspar grinded rock + 100g of K-sulphate for to obtain the best growth with the least cost.