Irrigated and Nonirrigated Soybean, Corn, and Grain Sorghum Root Systems1

Abstract

AbstractKnowledge of rooting patterns of various crops is important in designing irrigation systems and assessing water extraction capabilities. We investigated root depth and distribution under irrigated and nonirrigated conditions for soybeans [Glycine max (L.) Merr. ‘Williams’], corn [Zea mays (L.) ‘Prairie Valley 82S’], and grain sorghum [Sorghum bicolor (L.) Moench, ‘Pioneer 846’].Soil cores 6.7 cm in diam. were taken to 180 cm deep in the crop row, ¼ row, and ½ row (furrow) for each crop at physiological maturity. The cores were sectioned in 30‐cm increments and washed through 35‐mesh screen (0.73 mm opening), and the roots oven dried. The study soil was deep, barrier‐free, Muir silt loam (fine‐silty, mixed, mesic, Pachic Haplustoll).Approximately 71, 64, and 86% of the total root dry matter were in the upper 30 cm for irrigated soybeans, corn, and grain sorghum, respectively. Approximately 67, 39, and 79% of the total root dry matter were in the upper 30 cm for nonirrigated soybeans, corn, and grain sorghum, respectively. Only corn did not have roots in the 150 to 180‐cm zone. Seasonal water uses under irrigated conditions (neglecting water flux into or from the root zone) were 65 cm, 65 cm, and 53 cm in soybeans, corn, and grain sorghum, respectively. Seasonal water use was approximately 44 cm by each of the three crops under nonirrigated conditions.