This paper presents the results obtained from the analysis of the assemblage of plant microremains recovered from profiles in agricultural terraces in the archaeological site of Yasyamayo (Santa María Valley, Tucumán, Argentina) and which correspond to the Regional Developments Period (ca. 1000-600 BP). The phytoliths were extracted by physical and chemical processing of the samples. The results showed that the phytolith assemblages in the anthropogenic profiles are characterized by having morphotypes of mainly graminoid origin (prismatic, truncated, sharp, flabellum, and bilobed cones) and by the presence of Maideas on the human occupation levels. The presence of panicoid elements and the evidence of higher humidity levels (such as the diatoms) on these levels of occupation would account for the management strategies used by the human groups of this area in the past. This paper constitutes the first approach to the phytolith study in the area. On the other hand, the differential concentration of diatoms enables the estimation of irrigation techniques by the human groups that inhabited this site.