POTATO-TUBER YIELD, MINERAL CONCENTRATION, AND QUALITY AFTER CALCIUM FERTILIZATION

In a 3-year study on a fine sandy loam soil, 'Atlantic' (1989), 'Front ier' (1990-91), and 'Russet Burbank' (1989-91) potato (Solanum tuberos um L.) response to rate and time of Ca fertilization was evaluated. Ca lcium was applied preplant at 0, 90, 180, and 270 kg.ha(-1) as CaSO4 a nd side-dressed at 0, 34, and 68 kg.ha(-1) as Ca(NO3)(2), with treatme nts combined in a complete factorial. Preplant Ca fertilization increa sed soil Ca concentration each year. Calcium fertilization did not aff ect tuber yield or grade distribution. Tuber concentrations of P, K, a nd Ca in 'Russet Burbank', Ca in 'Frontier', and S in all cultivars in creased with increasing preplant Ca rate. 'Russet Burbank' tuber P, K, Ca, and Cu concentrations and 'Frontier' tuber S concentration increa sed as side dressed Ca rate increased. Tuber concentrations of most nu trients decreased bet between midseason and harvest. The incidence of internal brown spot (IBS) was very low in 'Atlantic' and 'Russet Burl; ank' tubers and was reduced in 'Atlantic' by preplant Ca application. In 1990, IBS severity and incidence in 'Frontier' were reduced by prep lant and side dressed Ca fertilization. In 1991, after 4 months of sto rage at 7C, severity and percentage of tubers with IBS were reduced by preplant and side-dressed Ca fertilization. During storage, IBS decre ased in 'Russet Burbank'. Brown center in 'Russet Burbank' decreased a s side-dressed Ca rate increased. In 1990, 'Russet Burbank' french-fry color improved as preplant Ca rate increased.