REQUIREMENTS AND EFFECTS OF DRIP IRRIGATION OF MID-EARLY POTATO ON A VERY LIGHT SOIL IN MODERATE CLIMATE

The purpose of the study was to determine the needs and the results of the surface drip irrigation for medium-early potato crop grown on the very light soil in moderate climate in the Centre of Poland. Field experiments were carried out in 2008-2010 on the soil of the weak rye complex in Kuyavian Pomeranian province. Nitrogen fertilization was uniform (120 kg N.ha(-1)) on the all plots of experiment. The field water consumption (FWC) of the potato crop in the period of irrigation (June-August) ranged from 213 to 236 mm in the years of the study. Crop coefficients (k(o)) calculated on the base of the FWC for medium-early potato crop equalled 0.5 for June and 0.7 for July and August for Grabarczyk formula, and 0.4 for June and 0.6 for July and August for Hargreaves(DA) formula, respectively. Water needs in the period of irrigation (ETp) of the dripirrigated potato crop calculated with the use of crop coefficients (k(c)) and reducing coefficients (k(r)) - amounted 212 mm and 214 mm, for Grabarczyk and HargreavesDA formula, respectively. Drip irrigation significantly increased the marketable potato yields from 17.4 to 36.3 t.ha(-1) (109 %), the weight of a tuber and the number of tubers per 1 plant. Fertigation of the nitrogen fertilizer with drip system increased potato crop by 5.9 t-ha(-1) (25 %). Irrigation water use efficiency increased from 171 kg-he(-1) mm(-1) (drip irrigation and broadcasting of nitrogen fertilizer) to 284 kg.ha(-1).mm(-1) (drip irrigation and fertigation of nitrogen fertilizer).