. Proceedings of the American Society of Agronomy . , and through the plant the rest of the watercan be charged to evaporation from the soil. MONTGOMERY: WATER REQUIREMENTS OF CROPS. 2/3 A number of experimenters have attempted to determine the waterrequirements of crops by sampling the soil to a depth supposed to bebelow the root depth of the growing crop. King, of Wisconsin, laidoff his field as shown in Fig. 48, and sampled to a depth of 6 feet, tak-ing samples in foot sections. The soil was carefully sampled beforethe crop was planted, a record was made of the amount of water re-ceived by
. Proceedings of the American Society of Agronomy . , and through the plant the rest of the watercan be charged to evaporation from the soil. MONTGOMERY: WATER REQUIREMENTS OF CROPS. 2/3 A number of experimenters have attempted to determine the waterrequirements of crops by sampling the soil to a depth supposed to bebelow the root depth of the growing crop. King, of Wisconsin, laidoff his field as shown in Fig. 48, and sampled to a depth of 6 feet, tak-ing samples in foot sections. The soil was carefully sampled beforethe crop was planted, a record was made of the amount of water re-ceived by rainfall, and after the crop had been harvested the totalamount of water in the soil was again determined by course this method is open to a great deal of error in cases wherethere is much runoff or seepage, but approximate results could besecured under conditions where the runoff or seepage during thegrowing season of the crop was small enough to be negligible or couldbe determined. Leather,^ at Pusa, India, has used a similar method,. Fig. 48.—Method of laying out plats and method of sampling used by King* atthe Wisconsin Experiment Station. (Wis. Sta. Rpt. 1901, p. 92.) sampling to the depth of 9 feet. In his case, very little rainfall comesduring the growing season and he is able to get quite reliable resultsby this method. Here, however, the great difficulty has been to sepa-rate the water lost by evaporation from the soil surface and that lostthrough evaporation from the plants. Leather used a system offallow plats alternating with his crop plats to determine the loss byevaporation from the surface. Results Secured in Determining the Water Requirements of Crop. Results secured as to the amount or ratio of water required to pro-duce a unit of dry weight have been quite variable. Most of thisvariation is probably due to the difference in amount of experimentalerror, as in almost every case evaporation lost from the surface ofthe soil has been added to that los
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