Under protective irrigation, tankers are used to transport water from the local village tank to farms during critical dry spells. — By Lakshmi Pranuti, Surabhi Singh, Veena Srinivasan Sustaining soil moisture is the biggest bottleneck to improving agricultural productivity in India. In much of India, it rains for only a few months a year, during the monsoons. For the rest of the year, the soil is too dry to grow anything…