Effects of Rainfall Events on Soil inOrchard Field underHerbicide Treatment. 1. Temporal Characteristics in Soil Physical and Chemical Properties

Abstract

The periodic application effects of two different herbicides on soil physical properties were observed in a slightly hilly orchard of pear tree located on the southestern flank of the Palbong Mountain in Gongju Chungnam : (1) bare surface vegetation; (2) glyphosate-treated plot; (3) paraquat-treated plot. The slope of experimental plots ranged from5.5%to 10.2%at an altitude of 125 mand 896 m2 (28mx 32m) inarea.The total respective rainfall events were 47, 52, 52 times during experimental period from 2006 to 2008, while approximately 65 percent of daily rainfall intensity from2006 to 2008 was less than 20mma day. The organic matter contents on the surface 15 cm soil ranging from1.23%to 1.84%in 2006 were changed into from1.35%to 2.28%in 2008 in the order of control > glyphosate > paraquat > bare plot in 2008, indicating that the herbicide treatment influenced the accumulation organic matter in soil. The changes in soil particle contents showed that the loss of soil particles in top 5 cm soil depth was greater in a bare soil than in other treatments such as control, glyphosate, and paraquat-treated plot. The net changes in the bulk densities showed that there were little variations betweenMay of 2006 and Nov. of 2008 even though there were some losses of the soil particles. The soil strength of the glyphosate-treated bare plots wasmuch greaterthan those of otherplots such as control, glyphosate, and paraquat plots. Howeverthe soil strengths in control plots were lowerthan those in the plots of glyphosate and paraquat treated ones.