Cultivators in which part of India did not adopt the iron ploughshare until the twentieth century?

Semi-arid regions, such as parts of Punjab and Rajasthan

During the sixth century BCE, a significant strategy to enhance agricultural production involved the adoption of plough agriculture, particularly in fertile alluvial river valleys such as those of the Ganga and the Kaveri. The iron-tipped ploughshare proved instrumental in turning the alluvial soil, especially in regions with abundant rainfall. The introduction of transplantation techniques further boosted paddy production in some parts of the Ganga valley, although it entailed strenuous labor for the cultivators.

Although the iron ploughshare led to increased agricultural productivity, its implementation was limited to specific regions of the subcontinent. Semi-arid areas like parts of Punjab and Rajasthan did not adopt it until the twentieth century, while hilly tracts in the northeastern and central parts of the subcontinent preferred hoe agriculture, which was better suited to the terrain.