Agriculture Reference
In-Depth Information
The early-broccoli system was harvested on August 4 and August 3,
while the late-broccoli system was harvested on August 31 and September
20, in 2009 and 2010, respectively. Heads were hand harvested from the
entire trial, and broccoli yield was estimated by recording head counts
and weights in a 3 m harvest row from three random plots per replicate.
Broccoli leaf, stem, and head samples were collected from a composite of
three plants in each of three random plots per replicate for dry matter and
N content determination.
Treatments were applied 1 to 2 d after harvest with plots 9 m long by
3 m wide. The control treatment representing the typical grower practice
was the incorporation of broccoli crop residue (CR-control), and was es-
tablished by mechanically mulching then disking the broccoli crop resi-
due. The crop residue removal (CR-removal) treatment was established by
hand-removing all the above-ground biomass from the plots prior to disk-
ing. An oat (
Avena sativa
L.) cover crop (CC-oat) was established by drill-
ing seeds at a rate of 108 kg ha
-1
after the broccoli residue was mulched
and incorporated. The OCA treatments were established by uniformly
hand-applying either wheat straw (OCA-straw, C:N ratio ≈ 65:1), yard
waste (OCA-yard, C:N ratio ≈ 56:1), or used cooking oil (OCA-oil, C:N
ratio > 1000:1), at a fresh rate of 5 Mg ha
-1`
onto mulched broccoli crop
residue (C:N ratio ≈ 11:1), followed by disking. In addition to samples
at broccoli harvest, post-harvest soil samples in autumn were taken for
mineral N analysis from a composite of four soil cores per plot at depths
of 0-30 and 30-60 cm on August 21, September 18, and October 22 for
the early system in 2009, on August 20, September 1, September 22, and
October 25 for the early system in 2010, on October 26 for the late system
in 2009, and on October 6 and October 25 for the late system in 2010.
In the subsequent growing season, the entire trial area was cultivated
and spring wheat seed was drilled at 154 kg ha
-1
, without N fertilization.
A broccoli residue incorporated treatment with pre-plant urea applied at
103 kg N ha
-1
(CRN-control) was also established as the treatment rep-
resenting the typical grower practice. Usual management practices were
followed for spring wheat production [33]. Grain was mechanically har-
vested from the center area of 6 by 1 m, and grain and straw were col-
lected to assess the above-ground plant biomass (grain + straw) and grain
yield (Mg ha
-1
), N content (kg N ha
-1
), and N harvest index (%). Harvest
