Water use efficiency and nitrogen use efficiency of apical rooted cuttings of potato grown in a mollic Andosol

Abstract

Water and nitrogen (N) are key interacting factors that control plant growth. The objective of the study was to determine the effect of N rates and drip irrigation regimes on water use efficiency (WUE) and N use efficiency (NUE) of apical rooted cuttings of potato (Solanum tuberosum L.) grown in a mollic Andosol. The treatments comprised four drip irrigation regimes of 50%, 75%, 85% and 100% of the crop evapotranspiration (ETC), where ETC100% was irrigated according to the soil water depletion 2 d after full irrigation and four N rates: 0 (N0), 60 (N1), 90 (N2) and 130 kg N ha −1 (N3). The results showed that potato tuber yield, WUE, and NUE were significantly (P < .001) affected by irrigation regimes, N rates, and the interaction of both factors. The highest potato tuber yield, 58.29 Mg ha −1 , was obtained under ETC100% with N3, whereas the highest WUE, 17.5 kg m −3 , was found under ETC50% with N3. The apical rooted cuttings of potato grown under ETC100% with N2 produced the maximum NUE, 208.30 kg kg −1 . The correlation coefficient (r = 0.31; P < .01) obtained between WUE and NUE was weak. It was also observed that an increase in irrigation amount decreased WUE and increased NUE, whereas a high N dosage increased WUE and decreased NUE of potato grown in a mollic Andosol. This study suggests that if the farmers aim to maximize NUE of apical rooted cuttings in a mollic Andosol, then they will do so at the expense of potato WUE, and yield will be looked at as a secondary factor. INTRODUCTIONPotato (Solanum tuberosum L.) is one of the major root and tuber food crops for many people around the world (FAO-STAT, 2017). Globally, 368 Tg of potato were produced in 2018 on an estimated area of 17.58 million ha (FAOSTAT, 2020). In Kenya, it is the second staple food and cash crop