Drip fertigation regime for potato on sandy soil

To establish the optimum fertilizer rate and propose an appropriate drip fertigation regime for potato (Solanum tuberosum L.) on sandy soil, a two-year field experiment comparing different fertigation levels on potato yield, irrigation water productivity (IWP) and partial fertilizer productivity (PFP) was carried out during 2012-2013. The treatments included five fertigation levels: 10%, 30%, 50%, 70% and 90% of the recommended fertilizer dose of 420:105:495 of N:P: K in kg ha(-1) year(-1) in 2012; and 10%, 35%, 60%, 85% and 110% of the recommended dose of 390: 150: 465 of N: P: K in kg ha(-1) year(-1) in 2013. The recommended fertilizer dose was estimated based on the method of nutrient balance for a target yield of 45.0 Mg ha(-1). The soil matric potential at 20 cm depth beneath the emitters was controlled above -25 kPa for drip fertigation. Results showed the highest tuber yield was 38.0 Mg ha(-1) for 90% NPK in 2012 and 45.8 Mg ha(-1) for 60% NPK in 2013, which was significantly higher than that for 10% NPK. The highest IWP was for 70% NPK in 2012 and 60% NPK in 2013. The highest PFP values were 255.5 kg kg(-1) in 2012 and 316.4 kg kg(-1) in 2013, recorded in the 10% NPK plots and were significantly higher than for other fertigation treatments. High yield levels of potatoes and both high IWP and PFP could be reached by drip fertigation with 72% of the recommended fertilization dose. Compared with the recommended fertilizer dose, the yield and IWP of 72% NPK increased by 5.9% and 4.7%, respectively. It was possible to make average savings in one season alone of 136, 36 and 152 kg ha(-1) N, P2O5 and K2O, respectively. In conclusion, drip fertigation with 72% NPK should be considered optimum for potato production on sandy soils. Each fertilizer amount based on irrigation interval was applied with irrigation quota at 5-6 mm when soil matric potential at soil depths of 20 cm immediately under drip emitters reached -25 kPa. Furthermore, drip fertigation was triggered when 10 consecutive days were without fertigation or rainfall in 24 h exceeded 10 mm.