Research Bulletin - Agricultural Experiment Station, Iowa State College Volume 1-15 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...three times as great, and that receiving the three ton amount, a power about five times as great as the check soil; this increased nitrogen fixing power occurring coincident with smaller moisture content in the limed soils. July 6, a smaller nitrogen fixing power was noted in the cheek soil, but the limed soils showed greater power, 2.34 mgs. X., 16.66 mgs. N., and 30.19 mgs. N. being the amounts fixed. Evidently here the decrease in moisture reduced the nitrogen fixing power of the check soils, but the fixing power of the limed soils continued to increase notwithstanding less favorable moisture conditions. September 14, the nitrogen fixing power of all the soils was greater, 11.89 mgs. N., 25.41 mgs. N., and 38.93 mgs. N. being fixed. The drought which occurred between this and the previous date of sampling and which undoubtedly decreased the fixing power of the soils, had evidently been followed by a much quicker recovery of this power than was the case with the ammonifying and nitrifying powers, and the possibility presents itself that the drought so altered conditions in the soils that they were more favorable for the nitrogen fixing species than previously. TABLE XIV. NITROGEN FIXATION EXPERIMENTS. (IV) OCT. 24. October 24, practically identical nitrogen fixing powers of the soils were observed: 11.09 mgs. N., 27.00 mgs. N., and 37.34 mgs. N. being found. These gains in nitrogen fixing power at this date occurred notwithstanding the lower moisture content in the limed soils, and are just as great as the gains at the previous date when the moisture conditions were practically uniform. No depression in nitrogen fixing power corresponding to observed depressions in ammonifying and nitrifying powers were found here and if the lower...