The blame for the agricultural mistakes that led to Ireland’s drastic susceptibility to the blight should not be placed primarily at the feet of the Irish people, but instead with British policies that regulated and limited trade in and out of its territories, including Ireland. In 1846, in response to the ongoing famine in Ireland, British parliament repealed the Corn Laws, which had ensured that the price of imported grains would always remain higher than home grown grains. While in effect, the Corn Laws had effectively blocked the ability to feed the starving Irish population on grain.
During the years of the Famine, the Irish potato crop failed four times, according to David Nally in the abstract to his paper "'That Coming Storm': The Irish Poor Law, Colonial Biopolitics, and the Great Famine" (714). Though it is hard to debate that these crop failures, which ruined the staple food and product of a large swath of the Irish populace, were a natural disaster in a very concrete sense, it is equally difficult to argue that the Famine, in its full extent, was not ultimately the equal product of English colonial policies toward Ireland that were either negligent or over-invasive both during and prior to the Famine. The crop failures that triggered the Famine were natural (though perhaps preventable), but the exceptional nature of the Famine was man-made.
Nally, David. "'That Coming Storm': The Irish Poor Law, Colonial Biopolitics, and the Great Famine." Annals of the Association of American Geographers. Vol. 98. No. 3. pp. 714-741. Oxfordshire: Taylor & Francis, 2008.
Reader, John. Potato: A History of the Propitious Esculent. Conneticut: Yale UP, 2009.
Salaman, Redcliffe. The History and Social Influence of the Potato. Cambridge UP, 1949.