SOIL, TREE, AND FRUIT RESPONSE TO LIME AND TYPE 

 OF NITROGENOUS FERTILIZER APPLIED AT TWO TIMINGS 

 UNDER STURDEESPUR DELICIOUS TREES 



William J. Lord, John Baker and Richard A. Damon, Jr. 

 University of Massachusetts, Amherst 01003 



A number of fertilizers are used in orchards to supply nitro- 

 gen (N) . They may contain only an N carrier, or the N carrier may 

 be mixed with carriers of other elements. N carriers contain 

 nitrate N, ammonia N, a combination of both, or urea. 



Apple trees usually absorb N in the nitrate form because 

 ammonium N after fixation in the surface soil is rapdily converted 

 to nitrate N under most soil conditions. However, under some con- 

 ditions amm.onia N may persist for considerable time. Urea is 

 rapidly hydrolyzed to ammonia N and then behaves like ammonia. 

 Nevertheless, apple trees can absorb urea and ammonia N if they 

 are in solution. 



N sources have been compared frequently in apple orchards in 

 the past. Differential responses have been obtained on acid soils 

 from N carriers supplying either ammonium or nitrate N because of 

 slower availability of ammonium N following spring application. 

 Fixation of ammonia can influence timing of fertilization in irri- 

 gation water during the growing season, and sodium nitrate could be 

 harmful on soils with high sodium content. However, these are 

 unusual situations and it is generally suggested that price per 

 unit of actual N should determine choice of nitrogenous fertilizer 

 for orchards. 



These studies preceded the concern with low calcium (Ca) levels 

 in apple fruits and their association with cork spot, bitter pit, 

 and breakdown of apples. Dr. Shear in 1971 reported that apple 

 fruits had more severe Ca deficiency symptoms when nytrient-culture- 

 grown trees received low Ca and 3/4 of their N as NH . , than when 

 they received all NO3-N. He concluded that the effect of N -source 

 on the differential movement of Ca into fruit and leaves could be 

 an important consideration when determining the type of nitrogenous 

 fertilizer for apple orchards and timing of application. Shear and 

 Faust suggested that apple growers concerned with low flesh Ca in 

 apples should not use ammonium N before or soon after bloom because 

 the absorption of this element may be reduced if ammonium N is present 



Calcium nitrate [Ca(N03)2] was suggested as a replacement for 

 ammonium nitrate by Eggert _et__al . in New Hampshire because it does 

 not affect soil pH and it supplies a highly water soluble source of 

 Ca which moves readily into the soil. 



To investigate the soil, tree and fruit response to lime, type 

 of nitrogenous fertilizer, and/or time of application we initiated 

 an experiment in 1972 with Sturdeespur Delicious trees at the Horti- 

 cultural Research Center, Belchertown. The trees were planted in a 



