Growth, yield, water use and crop quality responses of lettuce to different irrigation quantities in a semi-arid region of high altitude

Abstract: Water stress under reduced irrigation conditions affect plant physiology and hence yield and crop quality. Moreover, high altitude climatic conditions can significantly influence plant physiology. Therefore, a two year field study was conducted to determine the effects of different irrigation quantities on plant growth (leaf number, stem diameter, plant diameter and height), marketable yield, water use and crop quality attributes (mineral content, total phenolics and antioxidant activity) of drip-irrigated lettuce in a semi-arid region with a high altitude. A randomized complete block design was used for testing of different irrigation quantities replicated three times. Different irrigation quantities were adjusted considering 100 (I1), 85 (I2) and 70% (I3) of evaporated water from a Class A pan. Lettuce evapotranspiration was the highest in the I1 treatment (214.1 mm) considering the two year average values. Therefore, the I1 treatment provided the maximum growth and marketable yield (2.17 kg m^-2). Water use efficiency was also the highest in the I1 treatment (10.2 kg m^-3) because the lettuce yield decreased significantly with the decreasing irrigation quantity. However, total phenolic content and antioxidant activity in lettuce leaves were the highest in the I3 treatment. Moreover, I2 and I3 treatments provided higher mineral contents. While the potassium content in leaves was the most abundant among macro minerals (N, P, K, Ca, Mg, S, and Na), manganese content was the highest among micro minerals (Fe, Cu, Mn, Zn, and B). It could be said that lettuce can be irrigated with less irrigation quantities for obtaining higher mineral contents, total phenolic contents and antioxidant activity. This application can also provide water saving but cannot induce water productivity.