DAR ES SALAAM, Oct. 3 -- ACROSS Tanzanias fields, a quiet agricultural revolution is taking shape in the palm of a farmers hand. The tool may not be a drone, a tractor or an expensive automated machine. It may simply be a mobile phone.

With it, a farmer can receive weather information before planting, search for advice when crops show signs of pests or disease, check market information, make digital payments and, in some cases, connect directly with buyers. What once required a physical visit to an extension officer, market or financial service can increasingly begin with a few taps or messages.

This is the promise of digital agriculture, a transformation that is reshaping how farmers access information, finance, markets and agricultura...