NITRIFICATION UNDER AND AFTER ALFALFA, BROME, TIMOTHY, AND WESTERN RYE GRASS: I. NITROGEN ABSORPTION OF HAY CROPS AND SUCCEEDING WHEAT CROPS

Abstract

The mean annual nitrogen absorption (lb./acre) of hay crops (excluding roots and stubble) was: alfalfa, 94.9; timothy, 39.5; western rye, 62.9; brome, 61.1. For entire hay plants to plow depth, based on sods one and three years old, the corresponding figures were: 241.8, 152.2, 137.8, 154.2. For entire wheat plants following one-, three-, and five-year-old sods of these hay crops for six, four, and two successive years, respectively, the mean values were: 63.4, 58.6, 56.3, 51.9. These figures are taken to indicate roughly the relative rates of soil nitrification under and after the crops in question, except under alfalfa, a legume.The roots and stubble of the hay plants contained about 71% of the dry matter and 68% of the nitrogen of these plants, whereas the wheat roots and stubble contained only 19% of the dry matter and 9% of the nitrogen of these plants.Preceding crops and seasonal conditions, especially the latter, affected the protein content and hardness of the wheat grain. Protein content of grain was generally, though not invariably, in the same relative order as indicated rates of soil nitrification after the four hay crops. Protein content was related quantitatively to hardness of grain and to loaf volume of bread, but there was no evidence of qualitative differences in the protein following the various hay crops.