The parched landscape of Sudan, on the southern edge of the Sahara desert, is among the world’s driest regions, with a nine-month dry season and a highly unreliable rainy season. Large-scale farmers there manage to grow about half of the impoverished nation’s food production with the help of motorized irrigation pumps, but for individual subsistence farmers and their families — about two-thirds of the nation’s 40 million people — growing crops mostly means hauling water by hand in buckets.