Dry weights of the root systems of 5 oat varieties were determined at 4-inch intervals to a maximum depth of 24 inches. The varieties produced a differential distribution of root dry weight at the various depths sampled. Over 60 percent of the root dry weights of the Corn Belt varieties, Clinton, Marion, and Andrew, was in the upper 4 inches of soil, whereas comparable values for Craigs-afterlea and A465 were 50 percent and 35 percent, respectively. The root dry weight to a depth of 24 inches was the same at the boot stage as at maturity

Frey, K. J.

Stucker, R.

Name not available

The Root-System Distribution Patterns For Five Oat Varieties

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 67 Annual Issue Article 15 1960 The Root-System Distribution Patterns For Five Oat Varieties R. Stucker Purdue University K. J. Frey Iowa State University Let us know how access to this document benefits you Copyright ©1960 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Stucker, R. and Frey, K. J. (1960) "The Root-System Distribution Patterns For Five Oat Varieties," Proceedings of the Iowa Academy of Science, 67(1), 98-102. Available at: https://scholarworks.uni.edu/pias/vol67/iss1/15 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. The Root-System Distribution Patterns For Five Oat Varieties1 R. STUCKER and K. ]. FREY2 Abstract. Dry weights of the root systems of 5 oat varieties were determined at 4-inch intervals to a maximum depth of 24 inches. The varieties produced a differential distribution of root dry weight at the various depths sampled. Over 60 percent of the root dry weights of the Corn Belt varieties, Clinton. Marion, and Andrew, was in the upper 4 inches of soil, whereas comparable values for Craigs-afterlea and A465 were 50 percent and 3 5 per-cent, respectively. The root dry weight to a depth of 24 inches was the same at the boot stage as at maturity. Roots of plants have not been studied as extensively as above-ground parts, especially as related to genetic differences. Derick and Hamilton ( 1942) found the different crown and shallow root types among oat varieties, and Caffrey and Carroll ( 1938) related differences in root development of oat varieties to lodging resistance. These workers concluded that the root-type characteristics were controlled by genetic factors and that segregation for root type occurred. Both lodging and drought-resistance characteristics may be related to type of root system. The present study was designed to determine whether root sys-tems of oat varieties were differentially distributed in the vertical soil plane. The extent of the root-system development was deter-mined by dry-weight analyses. MATERIALS AND METHODS For the present study, 5 oat varieties--Marion, Andrew, Clinton, Craigs-afterlea, and A4653-were sown on April 24, 1959, at the agronomy farm at Ames, Iowa. They were sown at the rate of 3 bushels per acre in a split-plot design with 3 replications. Harvest stages and varieties occupied the large and split plots, respectively. The subplot size was 4 rows, each 8 feet long with a 1-foot spacing between rows. Ten days after planting, a 2-foot section in each of the center 2 rows in a plot was marked with pot labels and thinned to 50 seedlings. These row sections were used as the subsequent root-sampling sites. The root samples were taken from each variety 1 Journal Paper No. J-3823 from the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project 1176. In cooperation with the Crops Research Division, ARS. USDA. 2Graduate Assistant, Purdue University, and Professor of Agronomy, Iowa State University. 3A short oat strain obtained from W. Hartley of Australia. 98 1Stucker and Frey: The Root-System Distribution Patterns For Five Oat VarietiesPublished by UNI ScholarWorks, 19601960] ROOT-SYSTEM PATTERNS 99 at 2 developmental stages, booting and maturity. The oats were sprayed with a fungicide at weekly intervals after June 1 to keep the plants free from foliar diseases that might retard root and top growth. The techniques for root sampling developed prior to 193 7 were reviewed by Pavlychenko (1937), who also developed the soil-block washing method. More recently other techniques that allow measurement of both amount and position of the roots have been developed (de Roo, 1957; Fehrenbacher and Alexander, 1955). All of the methods for separating roots from the soil involve washing with a stream of water (de Roo). Sometimes sodium chloride has been added to aid in dispersing the soil aggregates. The soil-root samples were taken with a rectangular metal sleeve 6 x 12 x 24 inches wide, long, and deep, respectively, made from Ys-inch steel and sharpened on one end. It was marked at 4-inch intervals to facilitate measuring the 24-inch sample depth into 6 subsamples. Before a root-soil sample was taken, the tops of the plants in one 2-foot section of the plot were cut at the soil surface and dis-carded. The metal sleeve was positioned so that the soil-root core consisted of a 6-inch length of the row and an area of 6 inches on each side of the row. The sampler was driven 4 inches into the soil with a steel maul and then tipped out and the 4-inch sub-sample removed. If the soil did not break evenly, the remnants were collected with a shovel. The metal sleeve was then driven to a depth of 8 inches and the second subsample taken. This procedure was repeated until a root-soil core had been taken to a depth of 24 inches, giving 6 subsamples per core. The root-soil subsamples were put in wire baskets made from door screen and soaked in a weak salt solution for 20 minutes. After being soaked, the roots and soil were kneaded by hand until the latter was washed through the screen wire. The roots were collected in a 2-quart crock, washed to remove foreign material, dried at 138 ° F. for 48 hours, and weighed. RESULTS The mean dry weights per sample of roots were not significantly different at the boot and harvest stages (Table 1), indicating that root-system size within the sample volume was maximum at the end of the vegetative stage. However, the root system did not neces-sarily attain maximum size before the top growth, since the com-plete root system was not measured. An increase in root weight may have occurred at greater depths. The mean root weights for 2Proceedings of the Iowa Academy of Science, Vol. 67 [1960], No. 1, Art. 15https://scholarworks.uni.edu/pias/vol67/iss1/15100 IOWA ACADEMY OF SCIENCE [Vol. 67 varieties were in 3 significance groupings: Clinton and Craigs-after-lea had the highest mean root weight, Marion and Andrew were intermediate, and A465 was lowest. In every sample roots pene-trated below the 24-inch depth, but the extent of the penetration was not measured. However, with root weights as small as those in the deepest subsample (Table 2) it is very unlikely that A465 would produce enough root dry weight below 24 inches to make it equal to the total weight of the other varieties. Differential lateral root distribution of oat varieties was not variable since the root-soil core included half the distance between the row sampled and the adjacent rows. The distribution of roots in the subsamples from different depths for the 5 oat varieties are given in Table 2. The major portion of the highly significant interaction for varieties x subsample depth was caused by the differential distribution of A465 roots in com-Table 1 Mean Dry Weight of Roots Sampled From 5 Oat Varieties At the Booting and Maturity Stage at sampling Sig* Variety boot maturity Mean groups (gms) (gms) (gms) Clinton 8.03 7.90 7.96 Craigs-afterlea 7.43 8.48 7.95 Marion 7.14 7.43 7.28 Andrew 7.30 6.45 6.45 A465 5.11 5.45 5.28 Mean 7.00 7.14 *Determined by multiple-range test. Table 2 Variety Clinton Mean Dry Weights of Roots Sampled From 5 Oat Varieties At 6 Depth Intervals Below the Surface Depth (inches below soil surface) 0-4 4-8 8-12 12-16 16-20 (gms) (gms) (gms) (gms) (gms) 4.40 .131 1.04 .4 7 .38 Craigs-afterlea 3.92 1.58 1.03 .57 .43 Marion 4.30 .90 .78 .55 .40 Andrew 4.28 1.03 .64 .35 .31 A465 1.93 1.30 .80 .50 .38 20-24 (gms) .36 .43 .35 .26 .37 parison with distribution of roots of the other 4 varieties. The 3 Corn Belt varieties, Clinton, Marion, and Andrew, even though 3Stucker and Frey: The Root-System Distribution Patterns For Five Oat VarietiesPublished by UNI ScholarWorks, 19601960] ROOT-SYSTEM PATTERNS 101 unequal in total root dry weight, had about the same pattern of depth distribution. About 62 percent of the root weight was in the top 4 inches and 80 percent was located in the top 8 inches. Craigs-afterlea was similar to the Corn Belt varieties except that a somewhat smaller proportion of its roots ( 50 percent) was located in the top 4 inches of soil. The dry weights of A465 roots were sim-ilar to those of the other varieties in the subsamples between 4 and 24 inches, but the dry weight in the 0- to 4-inch level was less than half as great as that of the other varieties. The varieties used were selected to represent different areas of origin and adaptation. The Corn Belt varieties had similar pat-terns of root-depth distribution, even though no conscious effort was made to select for root characteristics. The root-distribution pattern of A465 may be related to the growing conditions characteristic of its area of origin, Australia. This strain is noted for its drought resistance, an important characteristics for successful crop produc-tion in Australia. Its root-distribution pattern would be adapted to drawing moisture from lower depths with less dependence on mois-ture derived from the top 4 inches of soil. In Iowa this pattern of root distribution would not be as advantageous as in a draughty environment, since except for occasional short dry periods the mois-ture supply in Iowa is generally adequate during the oat-growing season. The oats in this experiment were grown on a highly productive Clarion-Webster soil. Grain yields were not taken, but adjacent plots averaged over 100 bushels per acre. There did not seem to be any barriers to root penetration into the soil. Roots were found below the 24 inches in each sample, and there were no points of root concentration that suggested a blocking of root penetration by a physical barrier such as a hard plow sole. Only root dry weight was measured in this study. This attribute may or may not be related to absorption surface area or the ability of a variety to absorb moisture and nutrients efficiently. Obviously, the roots of each variety penetrated the complete depth of sampling, and, below 12 inches, the root dry weights of all varieties were approximately equal. Further studies should measure the maxi-mum depth of root penetration and possible differences in absorp-tion capacity of the oat varieties. Chandler (1958) found no rela-tion between long-time surface fertilization practices and the maxi-mum penetration depths of oat roots. Literature Cited Caffrey, M. and Carroll, P. T. 1938. Lodging in oats. Erie Dept. of Agr. Jour. 35: 25 4Proceedings of the Iowa Academy of Science, Vol. 67 [1960], No. 1, Art. 15https://scholarworks.uni.edu/pias/vol67/iss1/15102 IOWA ACADEMY OF SCIENCE [Vol. 67 Chandler, W. V. 1958. Effects of long-time surface fertilization on rooting depth and habits of oats. Agron. Jour. 50: 286. Derick, R. A. and Hamilton, D. G. 1942 Root development in oat varieties. Sci. Ag. 22: 503-508. de Roo, H. C. 1957 Root growth in Connecticut tobacco soils. The Connecti-cut Agr. Exp. Sta. Bui. 608. Fehrenbacher, J. B. and Alexander, J. D. 1955. A method for studying corn root distribution using a soil-core sampling machine and shaker-type washer. Agron. Jour. 47: 468-472. Pavlychenko, T. K. 1937. The soil block washing method in quantitative root study. Canadian Jour. Res. 15: 33-57. 5Stucker and Frey: The Root-System Distribution Patterns For Five Oat VarietiesPublished by UNI ScholarWorks, 1960

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