Effect of sustained deficit irrigation on hay and oil yield of native spearmint (Mentha spicata)

Abstract

An experiment was conducted to quantify the local yield and crop water requirement responses of spearmint to different levels of water deficit in a Pacific Northwest arid environment. A line source sprinkler system was used to apply water to the test plots where the applied water varied nearly linearly with distance from the sprinkler line. This resulted in the application of varying irrigation amounts from full irrigation to 100% water deficit. The 100% irrigation amounts were controlled by neutron probe soil moisture measurements and irrigation scheduled to refill the soil water deficit to field capacity on a weekly basis. The varying irrigation amounts were confirmed with catch cans at each of five different irrigation levels and were read after all the irrigations to verify the amounts of applied water. The hay and oil yields at different water deficit levels were thereafter evaluated. The total oil content that was distilled from the mint hay samples stayed fairly constant despite significantly decreased mint hay yields with increased water deficit. The mint oil quality indicators improved with deficit irrigation. This study indicates that spearmint is a suitable crop for a sustained deficit irrigation management strategy that would reduce farm operation technicalities of regulated deficit irrigation while considerably conserving irrigation water and power.