INTRODUCTION

Plant breeders have been criticized for selecting varieties which respond well to increasing levels of inputs, especially fertilizers and irrigation. It is implicit in this criticism that these varieties do not perform as well as their contemporaries at lower input levels and that profitability for the farmer depends on continuing use of high-input husbandry. A trial was grown in 1985 to start to examine these assertions. Only data from early-maturing varieties are reported here although more extensive trials of maincrop varieties were also grown.

MATERIALS AND METHODS

Seed tubers of the old varieties Puritan and Early Rose (both grown before 1850), British Queen (1884), Great Scot (1909) and King George (1911) were obtained from the Department of Agriculture and Fisheries for Scotland. In 1984 the seed of these varieties was multiplied using stem cuttings in an aphid-proof glasshouse at Cambridge along with seed of the newer varieties Pentland Javelin (1968), Wilja (1972), Maris Bard (1974), Marfona (1977), Ukama (1980), Provost (1981) and a new variety from the Plant Breeding Institute, Rocket (1986).

Four replicates of a split-plot field trial were grown in 1985. The whole plots comprised three fertilizer treatments: (1) the normal fertilizer rate used on potato trials at Cambridge (1.76 t/ha of a 10:10:15 compound fertilizer), (2) half the normal rate and (3) no fertilizer at all. Because of shortage of seed, only four tubers were planted per plot. Planting was on 17 April and harvest on 1 August.