Alfalfa water productivity and yield gaps in the U.S. central Great Plains

Yield gap (Yg) analyses using farmer-reported yield and management data have been performed for a number of annual grain crops, but it lacks perennial forages. The U.S. accounts 21 % the global alfalfa production with large rainfed area located in central Great Plains, serving as an interesting case-study Yg Most existing quantified magnitude failed to identify associated practices reduce it. Challenging this analysis, systematic benchmark water productivity [WP, kg dry matter per mm evapotranspiration (ETc)] that allows quantification farmer fields does not exist. Our objectives were (i) WP, (ii) quantify fields, (iii) opportunities improve yield. We conducted review literature compiled database on ETc (n = 68 papers 1027 treatment means) from which WP boundary function was derived. collected 394 commercial during 2016–2019 Kansas. then used satellite imagery define growing season (and corresponding supply) each field. calculate field, conditional inference trees (CIT) explored impact increased suggested 34 ha-1 mm-1. Farmer-reported ranged 0.9 19.0 Mg ha-1, averaging 7.6 ha-1. Alfalfa water-limited potential (Yw) 11.1 23.2 resulting average 54–60 Yw. Row spacing, seeding rates, phosphorus fertilizer major agronomic explaining yields followed by surrogate variables sowing season, stand age, soil pH. study provided first analysis estimating attainable ETc, suggesting exist Plains. also identified key here derived can be future studies aiming at quantifying across globe. This initial step its causes we highlight limitations directions forages analyses.