Searching for synergism in dryland cropping systems in the central Great Plains

Previously published research reported a “synergistic effect” of corn (Zea mays L.) on winter wheat (Triticum aestivum L.) and proso millet (Panicum miliaceum L.) water use efficiency (WUE) when corn (C) was the preceding crop for dryland cropping systems in the central Great Plains, i.e., less water was required to grow a unit of wheat (W) or proso millet (M) when corn was the preceding crop. A similar synergistic effect of field pea (Pisum sativum L.) for seed (P) or forage (FrP) on winter wheat water use and yield has also been reported. The purpose of this study was to examine a long-term cropping systems yield and water use data set in order to determine if WUE is altered by rotational sequence (i.e., previous crop). Yield and water use data (computed by water balance using neutron probe and time-domain reflectometry measurements) were acquired from a crop rotation study conducted at Akron, CO from 1996 to 2011 using the following rotation sequences: W–fallow (F), W–C–F, W–M–F, W–C–M, W–M, W–W–C–M,W–C–M–F, W–C–M–P, W–C–M–FrP and W–M–Sunflower (S, Helianthus annuus L.)–F. Water use efficiency was computed as grain yield divided by water use. Changes in WUE due to crop rotation were also evaluated based on slopes of water use/yield production functions. The analysis of these data did not support a conclusion that corn has a synergistic effect of improving WUE of wheat or millet production nor the conclusion that pea has a synergistic effect on wheat. Published by Elsevier B.V. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD) To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. ∗ Corresponding author. E-mail addresses: [email protected], [email protected] (D.C. Nielsen).