Effectiveness of fall versus spring soil fertilization of field-grown peach trees

Marginally nitrogen (N)-deficient, field-grown peach trees [Prunus persica (L.) Batsch (Peach Group) 'O' Henry'] were used to evaluate seasonal patter ns of tree N uptake, vegetative growth, and yield following fall or spring fertilization. Sequential tree excavations and determinations of tree bioma ss and N contents in Feb. and Aug. allowed estimation of N uptake by fall-f ertilized trees between September 1993 and mid-February 1994. Total N uptak e (by difference) by spring-fertilized trees as well as additional N uptake by fall-fertilized trees over the spring-summer period was also determined . In fall-fertilized trees, only 24% of tree N accumulation between Septemb er 1993 and August 1994 occurred during the fall/dormancy period. Spring- a nd fall-fertilized trees exhibited comparable vegetative growth, fruit size , and yield despite lower dormant tree N contents and tissue N concentratio ns in the spring-fertilized trees. Fifty percent of tree leaf N content was available for resorption from leaves for storage in woody tree parts. This amount (N at approximate to 30 kg.ha(-1)) was calculated to represent more than 80% of the N storage capacity in perennial tree parts of fertilized p each trees. Our data suggest that leaf N resorption, even without fall soil N application, can provide sufficient N from storage to initiate normal gr owth until plant-available soil N is accessed in spring.