Intensifying dryland wheat systems by integrating guar increased production and profitability

Abstract

Guar [Cyamopsis tetragonoloba (L.) Taub.], is a summer legume with heat- and drought-tolerance properties that is produced in the U.S. Southern Great Plains, but is often restricted to a catch crop or substitute crop following cotton failures. This is despite the large domestic market for guar gum and the opportunity to diversify regional cropping systems with guar, potentially adding ecosystem benefits like biological N fixation (BNF). To address this, a systems research study was conducted near Chillicothe, TX from 2018 to 2021 to evaluate the integration of guar into no-till dryland winter wheat (Triticum aestivum L.) systems. Treatments included integrated wheat-guar systems differing in cropping intensity, 1.33 crops yr−1 (WG1.3) and 2 crops yr−1 (WG2), plus guar (G1) and wheat (W1) monocrop systems with 1.0 crop yr−1. Results showed that crop rotation sequence influenced seasonal guar yields, with negative yield impacts when guar immediately followed wheat. Consequently, the average seasonal guar yield was greatest in G1 and WG1.3 (1.01 and 0.96 Mg ha−1, respectively), followed by WG2 (0.64 Mg ha−1). Seasonal wheat yield averaged 2.31 Mg ha−1 across years, with no differences among systems. Across years, cumulative system yield was greatest for WG2, followed by W1 and WG1.3, then G1. Similarly, average annual net income followed the trend of G1 < W1 < WG1.3 < WG2, with values ranging from US$ 62.7–213.0 ha−1 year−1. Although overall production and net income were somewhat greater for WG2 than WG1.3, seasonal risks of crop failure and economic loss were lower for the WG1.3 system under the regional climate. There was no direct evidence of guar BNF benefits on subsequent wheat yield and quality, though inclusion of guar enhanced soil NO3-N at varying levels among systems, particularly following wet growing seasons and in less intensive systems.