11.   Nitrogen fertilizers are made from natural gas.

12.   So we can learn, for instance, how to apply nitrogen fertilizer at the proper times and doses, to limit the runoff that endangers ecosystems.

13.   Since the disease agent cannot thrive in acid soils, use an acidifying nitrogen fertilizer and elemental sulfur.

14.   The groundskeeper was probably just using nitrogen fertilizer mixed with water.

15.   The worst hit are those that were heavily fertilized with high nitrogen fertilizers.

16.   Tripp uses a slow-release type of nitrogen fertilizer only once every two years for aging trees.

17.   You can apply a nitrogen fertilizer monthly March through August.

18.   You can apply a nitrogen fertilizer monthly from March through August on young trees.

19.   David Tilman has been studying the long-term effects of nitrogen fertilizer on plots he and colleagues have tended north of the Twin Cities near Bethel for nearly two decades.

20.   Nitrogen fertilizer is made from natural gas.