Agriculture Reference
In-Depth Information
less frequently, but for longer periods of time than the −30/-25 and −45/-40 kPa treat-
ments (Table 1). The −45/-10 treatment irrigated the fewest number of times, but rep-
resented the longest average irrigation duration of the given treatments in 2009. The
−45/-40 kPa treatment refl ected a pulsed irrigation regime with 76 irrigation events
with an average duration of 40 min in 2009. This treatment also used the least water in
the study, with 98,500 and 85,150 gal/acre in 2009 and 2010, respectively, (Table 1).
The single-tensiometer treatment, which was set at −35 kPa in 2009, irrigated 52 times
with an average length of 91 min and was most similar to the −30/-25 kPa treatment.
This suggests that a single-tensiometer system can simulate pulsed irrigation, simpli-
fying installation of an automated-irrigation system.
There were smaller differences among the pulsed and nonpulsed irrigation treat-
ments in 2010 compared to 2009. In 2010, the number of irrigations ranged from 18 in
the −45/-40 kPa treatment to 28 in the −30/-25 kPa treatment, and 44 in the −40 kPa
treatment. In 2010, smaller plants demanding less water may have allowed suffi cient
time for greater movement of water in the plant bed through capillary action during the
day [18], resulting in less frequent irrigations. In 2010, the pattern of irrigation dura-
tion and frequency for the single-tensiometer treatment was similar to 2009, but the
other treatments were less refl ective of the 2009 treatments. Although the frequency
of irrigation in 2010 did not refl ect the pulsed treatment settings as closely as in 2009,
the amount of water applied was more representative of what would be expected in a
pulsed system [42].
Soil VWC data was recorded hourly at depths of 6 and 12 inches in 2009 and gen-
erally was representative of the irrigation treatments (Fig. 1A-E).
There were signifi cant differences in soil VWC between the different treatments
at the depths measured (Table 2). In addition, there was a signifi cant depth by treat-
ment interaction for soil VWC (Fig. 1A-E). With the exception of a period of high
rainfall in late July and early Aug., treatments had a consistent level of soil VWC in
2009 (Fig. 1A-E). In all treatments, soil VWC was greatest at a depth of 12 inches.
Excavation of a representative sample of tomato plants and intact roots after harvest
indicated that maximum rooting depth of plants ranged from 12 to 15 inches, with
80% of roots residing in the top 6 -inches of soil (data not shown). Average soil VWC
at 6 inches ranged from 19.6% to 22.5% (Table 2). At a depth of 12 inches, soil VWC
was signifi cantly different in all treatments, ranging from 24.5% to 33.4%. The soil
VWC measured at a depth of 6 inches more closely represented the applied irrigation
treatments and water applied than when measured at 12 inches. Rooting depth and soil
VWC results suggest that 6 inches may be an appropriate depth to monitor soil mois-
ture in plasticulture grown tomato.
 
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