|
Shortened day
length and cooling night temperatures affected spinach growth
so that days between planting and first harvest were vastly
different for spinach planted in early October compared to
November (Fig. 1 and Fig. 2). Autumn and winter harvests
were possible with spinach planted in early October.
March harvest was possible with spinach planted at all dates
in October and November. Harvest dates for each high
tunnel planting are indicated in Table 1.
Table 1. Harvest dates of spinach
planted in high tunnels in autumn 2005.
|
Planting date
|
Harvest dates – Avenger cultivar |
|
6
October
|
17
Nov |
1 Dec |
31 Jan |
27 Mar |
|
11 October |
1 Dec |
19 Jan |
7 Feb |
27 Mar |
|
25 October |
24 Jan |
16 Feb |
27 Mar |
|
|
3 November |
8 Feb |
27 Mar |
|
|
|
8 November |
16 Feb |
27 Mar |
|
|
|
17 November |
16 Feb |
27 Mar |
|
|
|
Planting date
|
Harvest dates – PVO172 cultivar |
|
6
October
|
24
Nov |
19 Jan |
16 Feb |
27 Mar |
|
11 October |
24 Nov |
24 Jan |
16 Feb |
27 Mar |
|
25 October |
24 Jan |
16 Feb |
27 Mar |
|
|
3 November |
8 Feb |
27 Mar |
|
|
|
8 November |
16 Feb |
27 Mar |
|
|
|
17 November |
16 Feb |
27 Mar |
|
|

Figure 1.
Intervals from planting until harvest of Avenger spinach.
Successive harvests are indicated by change in crosshatch
patterns, with final harvest on 27 March 2006.

Figure 2.
Intervals from planting until harvest of PVO172 spinach.
Successive harvests are indicated by change incrosshatch
patterns, with final harvest on 27 March 2006.
Table 2. Analysis of variance of the
effects of planting date and management (conventional or
organic) on total spinach yield in trials at Olathe, Kansas,
planted in autumn 2005.
|
Effect |
df |
P-value |
|
|
|
Cultivar |
|
|
|
Avenger |
PVO172 |
|
Planting
date |
5 |
0.0001 |
0.0001 |
|
Management |
1 |
0.8760 |
0.6898 |
|
Planting
date x Management |
5 |
0.1949 |
0.6586 |
Planting date affected total harvest yield mainly because of
differences in autumn harvests. It can probably be assumed
that the crops with reduced spring yield were less established
or had fewer reserves, going into winter. Spinach planted in
November was not harvestable until February. Yield data are
presented for Avenger (Fig. 3) and PVO172 (Fig. 4) in organic
and conventionally managed plots. Yield in organic and
conventional high tunnels differed somewhat in individual
harvests, but there was not an overall statistically
significant difference between spinach yield in organic and
conventionally managed high tunnels (Table 2). Harvest trends
due to planting date were similar in organic and
conventionally managed high tunnels (i.e. no interaction
between planting date and management).
Early planting of Avenger spinach increased the cumulative
harvest. Avenger spinach planted on 6 and 11 October had
significantly greater total yield than spinach planted on 17
November in organically managed high tunnels, and greater than
that planted on 8 and 17 November in conventionally managed
high tunnels (Table 3).
Spring harvest may be reduced spinach planted after the first
week of November. Delayed planting in the month of November
did not significantly reduce the February-March yield in
organic high tunnels, but in conventional high tunnels 17
November planting resulted in significant yield reduction
compared to 3 and 8 November plantings (Table 4). October
planting date did not affect spring harvest (February-March)
in organic high tunnels. In conventionally managed high
tunnels, spinach planted on 11 and 25 October did not have a
reduced total yield (Table 3), but because of differences in
harvest dates the spring yield was statistically similar to
the low yields of the 17 November planting, and less than the
3 and 6 November plantings (Table 4).

Figure 3. Fresh
weight yield of successive harvests of Avenger spinach from
plantings in autumn 2005, in organic or conventionally
managed high tunnels, stacked with final harvest on top.

Figure 4. Fresh
weight yield of successive harvests of PVO172 spinach from
plantings in autumn 2005, in organic or conventionally managed
high tunnels, stacked with final harvest on top.
Table 3. Total fresh weight yield of
spinach cultivars Avenger and PVO172 planted on six dates in
the autumn
of 2005 and harvested through March 2006, in conventional and
organically managed high tunnels at Olathe,Kansas. Values in a column
followed by the same letter are not significantly different (a
= 0.05).
|
Planting date |
Total yieldZ |
|
|
lb / 10 ft2 |
|
|
Avenger |
|
PVO172 |
|
|
Conventional |
Organic |
|
Conventional |
Organic |
|
6 Oct |
8.52 |
a |
9.38 |
a |
|
9.36 |
a |
9.49 |
a |
|
11 Oct |
8.74 |
a |
9.78 |
a |
|
8.74 |
a |
8.39 |
ab |
|
25 Oct |
6.85 |
ab |
8.40 |
ab |
|
7.33 |
ab |
6.87 |
abc |
|
3 Nov |
7.90 |
ab |
5.70 |
ab |
|
5.80 |
b |
6.60 |
bcd |
|
8 Nov |
5.07 |
bc |
5.60 |
ab |
|
5.42 |
b |
5.77 |
cd |
|
17 Nov |
3.53 |
c |
4.57 |
b |
|
3.00 |
c |
3.35 |
d |
ZMean of three replicates
Table 4. Fresh weight yield from the
final two cuttings of spinach cultivars Avenger and PVO172
planted on six
dates in the autumn of 2005 and harvested through March 2006,
in conventional and organically managed hightunnels at Olathe, Kansas.
Values in a column followed by the same letter are not
significantly different (a
= 0.05).
|
Planting date |
Spring yieldZ |
|
|
lb / 10 ft2 |
|
|
Avenger |
|
PVO172 |
|
|
Conventional |
Organic |
|
Conventional |
Organic |
|
6 Oct |
6.70 |
a |
7.38 |
a |
|
4.95 |
a |
5.50 |
a |
|
11 Oct |
3.68 |
b |
5.30 |
b |
|
4.92 |
a |
6.40 |
a |
|
25 Oct |
4.02 |
b |
5.63 |
ab |
|
4.63 |
ab |
5.23 |
a |
|
3 Nov |
7.90 |
a |
5.70 |
ab |
|
5.80 |
a |
6.60 |
a |
|
8 Nov |
5.07 |
a |
5.60 |
ab |
|
5.42 |
a |
5.77 |
a |
|
17 Nov |
3.53 |
b |
4.57 |
b |
|
3.00 |
b |
3.35 |
b |
ZMean of three replicates
Early planting of PVO172 spinach resulted in greater yields.
PVO172 spinach planted on 6 October had a significantly
greater total yield than that planted in November in organic
and conventionally managed high tunnels (Table 3). Plantings
on 11 November resulted in significantly greater yield than
the 3 and 17 November plantings in organic high tunnels, and
in conventional high tunnels greater yield than all November
plantings (Table 3). Each week of planting delay in November
reduced yield. Spinach planted on 17 November produced
significantly less spinach for spring harvest (February-March)
than earlier plantings (Table 4). All other plantings in
organic and conventionally managed high tunnels had
statistically similar spring spinach yields.
|