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

Abstract

In the Mid-Atlantic, mineral nitrogen (N) fertilizers are applied in high-density apple (Malus ×domestica 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 granular Ca(NO3)2 with equal amounts of N 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.