Growth of potato cultivars in response to application of phosphate fertiliser

Three experiments examined the response of potato cultivars from different maturity groups to fertiliser phosphorus application under conditions of re latively low residual soil P. Initial expansion of the leaf canopy was much more rapid following P application and maximum cover was attained sooner I n the absence of applied P, maximum ground cover was reduced substantially in early-maturing cultivars but not in maincrop cultivars. At early harvest s? all cultivars showed very large growth responses to P application, but c v. Rocket grown from well-sprouted seed showed a significantly larger respo nse than cv. Desiree. In the absence of applied P, ground cover was in some cases higher at later growth stages allowing a substantial degree of growt h compensation so that final harvests showed only small effects of P applic ation on dry matter yields. At final harvests, no significant interactions between cultivar and phosphorus fertiliser level were found for either dry matter production or P uptake despite some apparent effects. Phosphorus app lication increased dry matter production through increased interception of solar radiation with no effect on efficiency of utilisation.