Rice samples were picked from each treatment and control
plots after rice maturing. Random sampling could not sufficiently
reflect production because the growth of ricewas quite uneven and
some plots even showed no output. Thus, crop samples were
collected according to the grades of rice growth conditions, and
area percentage was regarded as a weighting coefficient to
calculate the yield of rice using the weighted average method.
The detailed calculations were as follows. First, based on careful
observation of rice growth vigor, including leaf color, spikelet,
plant height, and biomass, plants in each experimental plot were
divided into the following grades: good, medium, and poor.
Thereafter, the area of each grade in a single plot was measured,
and 1-m2 quadrants were set up for each grade. The yield
components, including panicle number per square meter, grain
number per panicle, percentage of filled grains, and 1000-kernel
weight, were determined to calculate the rice yield of each grade.
The grain yield of each plot was calculated as the sum of the grade
yield multiplied by its area percentage.