Effects of urea on the germination and early growth of kale,barley, and wheat

Summary Kale was grown in pots in the glasshouse and barley and wheat in bottomless boxes in the open with increasing amounts of urea applied to the soils maintained at various moisture contents. Two sandy soils and two clay soils (one of each containing much and little organic matter) were used in both pots and boxes; in addition four calcareous soils (two developed over chalk, and two over hard limestone) were used in the boxes to compare the effects of the applied urea on the germination and early growth of crops on different soils.The greatest amount of urea applied to the soils containing little organic matter decreased growth of kale in pots, particularly on drier soils, but did not affect growth on soils containing much organic matter; in contrast, with barley and wheat grown in boxes, urea was more damaging in the soils containing much than in those with little organic matter.The various soils used could be grouped according to the amount of urea giving maximum yield. On a soil containing much free calcium carbonate derived from chalk, urea either did not affect yield or depressed it below that of the unfertilised crop.