The Effect of Weed Control and Tillage On Soil Health In Organic Vegetable Production

Conducted within a rotation of organic sweet corn and edamame from 2005 through 2007, this study measured the effects of tillage and weed control methods upon soil health indicators.  Fluorescein diacetate (FDA) hydrolysis and labile carbon measurements were the tools utilized to study the effects of weed control and tillage upon a soil’s microbial activity and active carbon content. With the exception of the 2007 August labile C measurements, the conventional (moldboard, rototill) and reciprocating spader tillage treatments had no discernable affect upon either microbial activity or labile C content.  Weed control treatments were found to have a significant (P<0.05) influence upon both microbial activity and labile C content.  In 2006 and 2007, seasonal trends indicated that reductions in microbial activity occurred from the time of planting through harvest. These reductions were particularly pronounced in the in the top 10 cm of soil in the control and rolling cultivator treatments. During this period, soil from the stale seedbed and corn gluten treatments maintained a level of microbial activity that was significantly greater than that found in the other treatments.   Similar to the FDA results, labile C measurements from 2005 through 2007, indicated that corn gluten and stale seedbed treatments were significantly greater than the other weed control treatments in the July through October samples.  Labile C analyses also indicated that samples from the rolling cultivator had significantly lower levels than what was found in the other weed control treatments.  Results indicated that heavily worked soils in the rolling cultivator and control treatments experienced significant declines of microbial activity and labile carbon from planting through harvest.  However, even with seasonal losses, weed control effects upon soil health were limited as evidenced by recovery of lost microbial activity and labile C by the following spring.