2.4. Weed density, biomass, and yield
Weed density was quantified one time per season in each plot
on 26 July 2013 and 23 June 2014, which was 37 and 25 days after
the first grit application, respectively. All grit applications (1e4)
were complete at the time of sampling. Emerged weeds growing
within all planting holes in an experimental unit were identified as
broadleaf or grass and counted. End-of-season weed biomass was
destructively sampled from each plot on 18 Oct. 2013 and 20 Oct.
2014.Weeds growing within all planting holes in a plot were cut at
the soil surface, dried to constant mass, and weighed. Ripe tomato
and pepper fruit was harvested regularly, graded as marketable or
cull (e.g., non-marketable; insect-infested, rotten, or scabbed),
counted, and weighed. Marketable, cull, and total (the sum of
and grits were siphoned from different buckets in the cart (Fig. 1).
The siphon line was removed from each bucket and cleared between
different abrasive grit treatments. One person drove the
tractor approximately 1.6 km h1 and a second person walked
behind the cart and aimed the blasting nozzle at weeds growing
within each planting hole of the plastic mulch. This speed allowed a
maximum application time of 4 s per planting hole. The tip of the
nozzlewas maintained between 30 and 60 cm from the soil surface.
Grits were applied continuously within each plot and the application
rate varied by abrasive grit type (Table 1).