Yield and size of deficit irrigated potatoes

Controlled deficit irrigation (CDI) has been studied in a potato crop culti vated in a semi-arid zone (Albacete, Spain). Ten drip irrigation treatments were differentiated by the level of fulfilment of the water requirements. The effect of deficit irrigation at three crop stages (growth, tuber bulkin g and ripening) has been studied. Tuber yield and its components were highl y influenced by the total volume of irrigation water. The treatments with d eficit during the last part of the cycle have had the lowest productions. T he larger potatoes were obtained in the treatments which had not undergone deficit in the ripening period. Against this, the smallest potatoes were ob tained in the treatments with deficit in growth period due to a higher numb er of tubers per plant. The effect of water on tuber size relies on the com bination of deficits during the growth and the ripening stages, through the influence of the number of tubers per plant. The mathematical function tha t better fits the production obtained with the water volume received is a s econd-degree polynomial. The irrigation regime that leads to moderate defic it in the beginning of the season (growth and tuber bulking periods) can ac hieve production results of the order of those obtained by the test treatme nt, well irrigated along the whole cycle, it being a clearly advisable regi me. On the other hand, the least advisable regimes are those that lead to d eficit in the ripening stage as well as at growth or tuber bulking. (C) 200 1 Elsevier Science B.V. All rights reserved.