Alternative Fertility Management for Establishing New Apple Orchards in the Mid-Atlantic

In the Mid-Atlantic, mineral nitrogen (N) fertilizers are applied in high-density
apple (Malus 3domestica Borkh.) orchards to increase tree vegetative growth and
achieve earlier fruiting. However, when applied in excess of plant needs, N fertilizer
applications are an unnecessary expense and may lead to N leaching and groundwater
pollution. Therefore, it is necessary to develop orchard fertilization programs that
simultaneously provide adequate crop nutrition and minimize N loss into the environment.
Nitrogen was applied in each of 3 years to newly planted ‘Red Delicious cv Schlect’/
‘M.26’ trees at 67 kg N/ha/year in six fertilizer treatments: 1) two equal applications of
granular calcium nitrate [Ca(NO3)2]; 2) chicken litter compost; 3) yardwaste compost;
4) a combination of chicken litter compost and granularCa(NO3)2 with equal amounts ofN
from each fertilizer; 5) a combination of yardwaste compost and granular Ca(NO3)2 with
equal amounts of N from each fertilizer; and 6) fertigation which consisted of eight
weekly applications of solubilized Ca(NO3)2. Nonfertilized trees served as the control. In
the third year of this experiment, the two chicken litter compost treatments had the
greatest soil extractable P, the yardwaste compost treatment had the greatest soil
extractable K, both full-rate compost treatments had greater soil extractable Mg than the
other treatments, and all four compost treatments had greater soil extractable Mn than
the treatments without compost. The four compost treatments also had greater soil
extractable Ca and B than treatments without compost. By the third year of the
experiment, the four compost treatments also had greater soil organic matter (OM) and
soil C (with the integrated chicken litter compost treatment having similar soil C to the
other treatments). Potentially mineralizable nitrogen and soil microbial biomass were
similar among the treatments over the course of this experiment. The full rate chicken
litter compost treatment and both yardwaste compost treatments had greater soil
microbial respiration in 2015. The fertigation treatment performed similarly to the
treatment where Ca(NO3)2 was applied as a granular product to the soil. Treatment
differences found for the soil properties did not translate to increased tree size or leaf N
content, suggesting that the trees were able to acquire sufficient N from the soil under all
of the treatments. Our results suggest that applying fertilizers to fine textured soil with
relatively high OM may not increase apple tree growth or productivity within the first
3 years after planting. In addition, compost applications can improve many soil properties,
but these differences may not result in improved orchard productivity within 3 years.