Transition from deficit-irrigated to dryland crop production

Authors: Lascano, Robert

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Other
Publication Acceptance Date: 5/31/2021
Publication Date: 6/30/2021
Citation: Lascano, R.J. 2021. Transition from deficit-irrigated to dryland crop production. Frontiers in Sustainable Food Systems. 5. Article 707782. https://doi.org/10.3389/fsufs.2021.707782.
DOI: https://doi.org/10.3389/fsufs.2021.707782

Interpretive Summary: A series of six papers on the topic of the transition from deficit-irrigated to dry-land production in the Texas High Plains were published in the journal Frontiers in Sustainable Food Systems. This was a collaborative effort of scientists from Texas A&M AgriLife, ARS in Lubbock and Bushland, and economists from Texas Tech University. In four of the six papers, simulation models were used to evaluate different management options for dry-land production in the semiarid Texas High Plains. Results show that early planting date at a low planting density with no Nitrogen was the best option for cotton. For sorghum, the best grain yield was obtained in the latest planting date, lowest planting density and no nitrogen was the most profitable. Field experiments in Bushland show the importance of capturing rainfall and of increasing storage of rainwater in the soil. A final paper is a statistical optimization of a 50-year simulation showing that center-pivots can be converted to only irrigate 25 or 50% of the area. This practice would extend the longevity of the Ogallala aquifer and fostering a sustainable and profitable farm enterprise.

Technical Abstract: The Texas High Plains (THP) covers an area of approximately 3.25 million ha and is subject to different rainfall regimes and soil types resulting in several cropping systems. In this semi-arid region, rain decreases from east to west with an annual average long-term rainfall of less than 500 mm. There are three main soil series (Olton, Pullman and Amarillo) and soils tend to be sandier in the south with finer-textured soils more common in the north. The topography is relatively flat with an average elevation of 1.1 km and hence the name High Plains. The combination of different soils and rain patterns results in diverse production systems. The northern region is mainly a grain-based system with wheat, corn and grain sorghum as the main crops and in the southern region, cotton is the main crop. Given the semi-arid climate where the average annual potential evapotranspiration is greater than approximately 2400 mm with highly variable monthly and annual rainfall, irrigated agriculture was introduced and adopted. Large-scale irrigation started in the 1920’s and was an established practice by the end of the 1930’s due to the development of the internal combustion engine for pumping ground water. The source of nearly all the irrigation-water is the Ogallala aquifer, which covers eight states across the US. However, in this region, the aquifer is predominantly a closed system where extractions exceed recharge and thus over the years the water table has declined to the point that producers adopted deficit-irrigation strategies. Deficit-irrigation practices deliver less water than that required by the crop for maximum yield. As the water table continues to decline and water pumping costs rise, producers come to the realization that dryland production is the best economic option, while also conserving the remaining irrigation-water. No irrigation leads to dryland production systems, which we define as crop production without irrigation and with less than 500 mm of annual rainfall in a semiarid climate. This is the backdrop of the series of papers that address the transition from deficit-irrigated to dryland crop production in the THP. Agricultural production in the THP is in a unique position in that the transition from deficit-irrigation to dryland production has been gradual. This has provided valuable time for research scientists to address and develop economically viable dryland production systems. Agriculture production in this dryland region is challenged by frequent droughts and high climatic variability that can lead to land degradation and threaten the agricultural sustainability of the region. Further, the environmental complexity of dryland crop production requires an integrated and multi-disciplinary research approach to address the uncertainty associated with rainfall variability. To this end, in this collection of six papers, agronomists, soil scientists, plant physiologists and breeders, agricultural engineers, climatologist and economists have come together to answer questions concerning management practices that could increase crop yields and minimize production risks. A common denominator in four of the six papers is the use of models, i.e., crop and economic, to evaluate how a management practice such as seeding rate affects dryland crop yield over multiple years and locations. Simulation models are powerful tools and the results they provide are essential to develop best management practices for producers in this region. Problems associated with dryland agriculture can be formulated and addressed with simulation models. However, these simulated solutions are site-specific and results obtained with a model must be verified with measured data gathered from field experiments. In practice, simulation models can be used to identify knowledge gaps and to design specific experiments to test hypotheses. Field experiments con