Bad weather, such as the heavy summer rains, after drouth, which saturate ploughed soil, reduce soil shear strength, facilitate masse soil movement, and instigate gullying.
A control program might involve early preplant tillage to encourage germination of the weed seeds, followed by shallow tillage prior to planting to kill the emerged weeds.
As a whole the variation trend was that the area of cultivated land, forest, town (city) was increased greatly, the water area was enlarged, but the grassland and badland was decreased.
All the firstling males that come of thy herd and of thy flock thou shalt sanctify unto the LORD thy God: thou shalt do no work with the firstling of thy bullock, nor shear the firstling of thy sheep.