Published 2009-12-01
Abstract
Two fi eld trials were conducted to determine effects of preplant N sources on strawberry (Fragaria ×ananassa Duch.) growth and yield. The preplant N rate was 50 lb/acre and the N sources were ammonium nitrate (AN; 34% N), ammonium sulfate (AS; 21% N and 24% S), ammonium sulfate nitrate (ASN; 26% N and 14% S), and polymer-coated AS (PCAS; 20% N and 23% S). A no-preplant N control was added. Strawberry plant canopy diameters at 12 weeks after transplanting were not significantly affected by N sources. Preplant N sources signifi cantly affected early and total fruit weight. The highest early yields were found in plots treated with ASN, PCAS, and AS, whereas the lowest early yield was found in the nontreated plots. Total marketable fruit weights were the highest when either AS, ASN, or PCAS were used, which were approximately 12% higher than those of plots treated with AN and the nontreated control. The results indicated that the tested fertilizer sources caused different strawberry yield responses, which might be due to the presence of S, an essential plant nutrient, in AS, ASN and PCAS in the preplant fertilization at rates between 27 and 57 lb/acre. This total marketable response was not observed in plots treated with AN, which does not contain S, and in the nontreated control. Although a total yield difference was not found in plots treated with AN and the nontreated control, adding preplant AN increased early yield by 12%. It appears that there was an early effect of N sources on fruit production, followed by a long term effect of S nutrition on the crop.