Weed control and irrigation alter soil microbial processes and N availability in a peach orchard

Background/Question/Methods

Orchard management practices such as weed control and irrigation are primarily aimed at maximizing fruit yields and economic profits. However, the effects of these practices on soil fertility and soil microbiology are often overlooked. A long-term experiment examining the impact of two major management practices (weed control and irrigation) on peach tree growth and productivity was conducted on a low-fertility sandy soil at the Sandhills Research Station, North Carolina. We examined soil microbiology and nutrient dynamics after the third and eighth growing seasons. An array of soil physical, chemical and microbiological parameters were examined, including soil pH, salinity, contents of soil N, P and cation nutrients, microbial biomass and activities, and arbuscular mycorrhizal (AM) fungi.

Results/Conclusions

Our results showed that irrigation facilitated peach tree growth and mycorrhizal infection of peach roots. Weed control promoted peach tree growth but reduced mycorrhizal root infection, organic C inputs to soil, microbial biomass and activities as well as the labile nutrient pool. Weed control increased soil N availability after the third growth season, but significantly decreased it after the eighth growth season. Together, these results suggest that weed plants play a significant role in nutrient retention and effective soil management strategies are needed to maintain the nutrient supplies and microbial activities in many orchards on sandy soils in the southeastern United States.