Effects of orchard floor management on the peach rhizosphere

A preliminary study examining soil microbiology and nutrient dynamics in year three of a peach orchard at the Sandhills Research Station‎, North Carolina, USA found that maintaining a 3.6-m vegetation-free strip in the tree row reduced microbial biomass and associated activities in the soil, compared with a 0 m strip, and that the use of under tree micro-sprinkler irrigation increased peach root colonization by endomycorrhizal fungi as well as microbial biomass and associated activities. The current study was conducted in years four and five of that orchard and examined vegetation-free strip widths of 0, 1.2, 2.4, and 3.6 m, with and without irrigation, to determine their effects on endomycorrhizal fungal colonization of peach roots, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil microbial respiration (SMR), and net nitrogen mineralization (NNM). There were no significant differences between treatments for endomycorrhizal fungal colonization or MBC by year four. The 3.6 m vegetation-free strip had the lowest MBN and SMR in year four with no significant difference between strip treatments in year five. NNM decreased with greater vegetation-free strip widths in years four and five. Irrigated plots had significantly higher MBN and lower SMR in the spring of year five with no other significant differences due to irrigation. These important findings show that under standard commercial management of a bearing peach orchard there is little impairment of soil ecological function in the rhizosphere, allowing for maximum peach yield and quality while supporting the health of trees and soil.