Effects of peat moss and sawdust compost applications on N 2 O emission and N leaching in blueberry cultivating soils.

Upland blueberry (Vaccinium ashei Read.) requires acidic and organic matter rich soils for its cultivation. Recently, the raised bed cultivation system has widely been used for blueberry cultivation, but it has a potential to cause nitrogen (N) losses via leaching and nitrous oxide (N2O) emission especially with high rate of N application. We investigated the effects of organic amendments on N losses; via leaching ammonium ( ) and nitrate ( ) and N2O emission under acid soil conditions. The treatments were (i) ammonium sulfate application (AS), (ii) AS with peat moss (AS + PM), and (iii) AS with sawdust compost (AS + SD). A container (surface area: 47 cm × 40 cm = 0.188 m2) experiment to simulate raised bed cultivation system using an ochric Cambisol was conducted at Chiba University, Japan, during 2008 and 2009. A blueberry plant in each container received N fertilizer three times: 14.8, 23.8, and 14.8 g N m−2 in July 2008, March, and July 2009, respectively. Incorporation of peat moss and sawdust compost with ferrous sulfate effectively decreased soil pH to its optimal ranges (4.0–5.2) and resulted in increased growth and yield of blueberry (berry yield of 2009: 93, 285, and 348 g plant−1 in AS, AS + PM, and AS + SD treatment, respectively) due to increased soil porosity and consequently enhanced plant root biomass. Concurrently, the AS + SD treatment resulted in the least N losses, followed by AS + PM and AS treatment both through leaching and N2O emission. The emitted N2O amount over about two-year blueberry cultivation were 1.28, 0.80, and 0.58 g N m−2 for AS, AS + PM, and AS + SD treatments, respectively. These results indicated that application of organic amendments decreased N losses to the environment most likely due to increased plant N uptake, microbial N immobilization, and consequent reduction in nitrification, denitrification, and leaching. [ABSTRACT FROM PUBLISHER]