. Proceedings of the American Society of Agronomy . ween each reading being indicated on the graduated hygrometer. Fig 41 illustrates three types of large jars which have been used atthe Nebraska Experiment Station, a is a 5-gallon water jar filledwith soil. In the bottom an inverted flowerpot is placed, with twoglass tubes, through one of which the water is poured. The surfaceof the soil around the plant is covered with several layers of paraffinpaper, to prevent evaporation. One difficulty with growing plantsto maturity in jars covered with paraffin is that no aeration is secured 266 PROCEED
. Proceedings of the American Society of Agronomy . ween each reading being indicated on the graduated hygrometer. Fig 41 illustrates three types of large jars which have been used atthe Nebraska Experiment Station, a is a 5-gallon water jar filledwith soil. In the bottom an inverted flowerpot is placed, with twoglass tubes, through one of which the water is poured. The surfaceof the soil around the plant is covered with several layers of paraffinpaper, to prevent evaporation. One difficulty with growing plantsto maturity in jars covered with paraffin is that no aeration is secured 266 PROCEEDINGS OF THE AMERICAN SOCIETY OF AGRONOMY. and the plant does not grow normally. The roots also tend to collectaround the outside of the jar. By having the inverted flowerpot inthe center, complete aeration is secured, with only a small loss byevaporation, and the roots are distributed normally, h illustrates alarge can, 36 inches in depth, to be used in the field. Gravel is placedat the bottom and the water is supplied continuously from a 5-gallon. Fig. 41.—Three types of evaporimeters, for growing plants to maturity. jar placed beside it. After the plant is well started, gravel is placedon the surface to prevent the rise of water by capillarity, and thewhole is covered with a metal lid. In the case of large plants likemaize, the water is prevented from running down the stalk of theplant into the can by the use of sculptors clay,^ which is quite adhe-sive and is plastered around the base of the plant and over the lid,as illustrated in Fig. 47. Plate III, Fig. i, shows one of the 5-gallonjar evaporimeters in section with the apparatus necessary for makingwater determinations. This apparatus has been used for growingcorn plants almost to maturity, with very good success. Field Methods for Determining the Loss of Water from Field Crops. Fig. 42 illustrates the method used by King at the Wisconsin Sta-tion. At first, vinegar barrels were sunk into the midst of the fields ^ Compos
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