21. Keogh said he has no immediate plans to patent fire or crop rotation . 22. The island is divided into six sectors or suyus for crop rotation purposes. 23. Crop rotation and fertility by alternating deep-rooted and shallow-rooted plants.24. They practised biennial crop rotation , alternating from year to year between fallow and cultivated. 25. Jones probably would continue his experiment in crop rotation regardless of what Congress does. 26. There is evidence that New Guinea gardeners invented crop rotation well before western Europeans. 27. He also studied effect of crop rotation on soil quality. 28. Many challenges exist within the practices associated with crop rotation . 29. Even with mobile crop rotation , southern villages were necessarily less mobile than northern ones. 30. The third principle is the practice of crop rotation with more than two species.
