Evaluating Growth of Baby Leaf Spinach with Respect to Water and Salt Balance in the Arid Southwest United States

Abstract

Current literature for the irrigation management of spinach focuses on full season bunching spinach with little consideration given to the much shorter season baby leaf spinach. Baby leaf spinach represents an economically valuable crop in the desert Southwest US, and therefore would benefit from greater research into data driven management strategies. To overcome the challenge of the relatively short growing season of baby leaf spinach in plotting a crop coefficient (Kc) curve, the Kc curve is plotted instead as a function of both heat units after planting (HUAP) and Normalized Difference Vegetation Index (NDVI) as opposed to days after planting (DAP) as proposed in FAO56. Utilizing in-field measurements across 9 trial sites spanning 5 years, an initial Kc (Kc-INI) value of 0.90 and a mid-season Kc (Kc-MID) value of 1.00 were calculated. Due to the rapid growth of baby leaf spinach in such a short time, further investigations with greater temporal frequency will be needed to refine the capability of utilizing NDVI as a proxy to crop evapotranspiration (ETc). Additional work in this study looked at the water and salt balance of baby leaf spinach, with it being demonstrated that diminished yields occur in soils with salinity levels in excess of 7 dS/m. Irrigation management in baby leaf spinach has many opportunities for further research, but conclusions drawn in this study demonstrated that leaching salts during the baby leaf spinach cropping season are unnecessary and could be instead deferred to other times of the year.