Here is the layout of our initial prototype:

We have chosen the Particle Electron to be center of our project connected to various peripherals like a GPS module, OLED. The device has two external JST connectors to connect the Leaf Chlorophyll clip sensor and a soil moisture sensor probe.

Here is a sketch of our proposed design, The device would be a rugged chunky device with a low power display and large battery with wireless connectivity and GPS.


Usage:
The farmer would periodically go around the feild and sample various leafs of the crop, All this data is stored with a time&location stamp from the GPS device.
This makes it possible for multiple farmers to share the same device using geofencing of their farm land. The measurements are to be taken twice a week.
The data goes to a cloud server where the data is compared with a nominal database for the same crop varitey along with the date from sowing. The divergence in leaf chlorophyll is extracted from the mean statistic and thus using a detailed fertilizer application plan is obtained and this along with a local weather reported is provided to the farmer using Interative Voice Response (IVRS) on his normal phone in the farmer's local language. The farmer would thus be able to correct any crop nutrition problems in the start.