Application
frequency ranged from one to four applications in 2013, but the
number of applications was reduced in 2014 based on ambient
weed populations and 2013 results. A hand-weeded weed-free
control and a weedy control plot were included in each replicate
block. This design resulted in 72 plots in 2013 (4 grit types  4
application frequencies þ 2 controls in 4 blocks) and 44 plots in
2014 (3 grit types  2 possible application frequencies þ 2 controls
in 4 blocks [the experiment was originally designed for 3 application
frequencies, but crop canopy cover and low ambient weed
seedbank abundance eliminated the need for a third application;
thus, 3 plots were pooled with 2 plots resulting in twice as many
2 experimental units compared with the 1 and control treatments]).
Each plot was 3.72 m2 (1.22 m wide  3.05 m long) and
included five tomato plants spaced 0.61 m apart or nine pepper
plants spaced 0.33 m apart. Experimental plot size was limited in
part by the amount of abrasive grit available because greensand
fertilizer and soybean meal had to be hand-sieved to remove particles
greater than 0.85 mm.