(ShareCast News) - Shares in African Potash surged on Monday after the company said it has signed a memorandum of understanding to supply a Zambian fertiliser group with in excess of 50,000 metric tonnes of fertiliser.This marked the first MOU since African Potash's landmark trading agreement with Comesa, which is a free trade union of 20 African countries.The first delivery with the Zambian supply company that was not named is expected to occur in September 2015.Chairman Chris Cleverly said: "The signing of this trading MOU is a landmark for African Potash in its strategy to become a vertically integrated African focused fertiliser business. It is also a significant leap for agriculture in the Comesa region.James Magai, director of trade and markets of Comesa, said: "This agreement is the beginning of Africa's green revolution and marks the arrival of African Potash's vertical market on the continent."At 1209 BST, African Potash shares were up 53.2% at 1.6090p.