Abstract
The area in kumara (Ipomoea batatas) in the Gisborne region is increasing, particularly in the organic sector. However, cool soil temperatures may limit yield early in the growing season. The objective of this project was to evaluate the effect of different mulches on soil temperature and kumara growth. Experiments were established on organic farms at Tikapa (2005-06) and Kiekie (2006-07) in the Gisborne region. In Experiment 1, at Tikapa, kumara cuttings (tipu) were hand planted on 7 December 2005 into raised beds covered with black polythene (P) or ryegrass-hay (H) or were planted in bare soil. In Experiment 2, at Kiekie, tipu were machine planted on 23 November 2006 into flat beds, but only the P and C treatments were used. Weeds were controlled by the mulches and regular hand weeding (Tikapa and Kiekie) and with mechanical weeding (Kiekie only) of H plots. Average daily soil temperature, prior to canopy closure, was warmest in P (24.0 and 20.1 C at Tikapa and Kiekie respectively) followed by C (21.6 and 18.6 C) and H (19.5 C; Tikapa only). Average daily air temperature (10 cm above the ground) was unaffected by the treatments. Total storage root yields were significantly higher in P (38.5 and 14.6 t ha; Tikapa and Kiekie respectively) than in C (15.2 and 7.7 t ha). Yields were lowest in H (2.4 t ha; year 1 only) because of poor weed control. Plastic mulch increased early shoot and root growth, total shoot and root biomass, and radiation interception, relative to C and H. Although a high capital outlay is required for P, gross margins in P were substantially higher than in C. Additional key words: mulch, organic production, sweet potato, yield development Introduction Kumara (Ipomoea batatas L.), or sweet potato, is an important tropical/sub-tropical crop grown in many parts of the world. It is particularly important for Gisborne’s Maori growers because of cultural ties (tikanga) dating back to pre-European times. In tropical climates sweet potatoes are often grown all year round, but in temperate climates such as in New Zealand they are strictly a summer crop. The use of polythene to control weeds and warm the soil is a common practice of Japanese growers (Steve Lewthwaite, pers. comm.). Although most of New Zealand’s kumara production is based around Dargaville (Northland), an increasing number of growers are producing kumara organically in the cooler (early and late in the season) Gisborne region. Most Gisborne kumara growers do not use chemical weed control, preferring “organic” or traditional methods involving a combination of mechanical and hand weeding. However, these growers often struggle to keep on top of weeds due to large weed seed banks, antiquated equipment, insufficient labour and, for some growers, a limited understanding of weed/crop dynamics. Mulches offer an alternative weed control option that could reduce weed infestations, alleviate labour shortfalls, and provide other benefits
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Claims 8
Claim · model-written summary
Plastic mulch warmed soil more than bare soil and hay at Tikapa and Kiekie.
- Taxon
- kumara
_Flower.jpg?width=60)
Ipomoea batatast0 - Treatment
- Pe0
- Outcome
- Average daily soil temperaturee0
- Direction
- warmeste0
- Comparator
- Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Flower.jpg?width=500)
Verbatim
e0“Average daily soil temperature, prior to canopy closure, was warmest in P (24.0 and 20.1 C at Tikapa and Kiekie respectively) followed by C (21.6 and 18.6 C) and H (19.5 C; Tikapa only).”
t0“kumara”
Claim · model-written summary
Air temperature was unaffected by mulch treatment.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- treatmentse0
- Outcome
- Average daily air temperaturee0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Average daily air temperature (10 cm above the ground) was unaffected by the treatments.”
t0“kumara”
Claim · model-written summary
Plastic mulch significantly raised storage root yield at Tikapa compared with bare soil.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- Pe0
- Outcome
- Total storage root yieldse0
- Direction
- highere0
- Value
- 38.5e0
- Comparator
- Ce0
- Setting
- Tikapae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total storage root yields were significantly higher in P (38.5 and 14.6 t ha; Tikapa and Kiekie respectively) than in C (15.2 and 7.7 t ha).”
t0“kumara”
Claim · model-written summary
Plastic mulch significantly raised storage root yield at Kiekie compared with bare soil.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- Pe0
- Outcome
- Total storage root yieldse0
- Direction
- highere0
- Value
- 14.6 t hae0
- Comparator
- Ce0
- Setting
- Kiekiee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total storage root yields were significantly higher in P (38.5 and 14.6 t ha; Tikapa and Kiekie respectively) than in C (15.2 and 7.7 t ha).”
t0“kumara”
Claim · model-written summary
Hay mulch had the lowest yield because of poor weed control.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- He0
- Outcome
- Yieldse0
- Direction
- loweste0
- Value
- 2.4 t hae0
- Qualifier
- poor weed controle0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yields were lowest in H (2.4 t ha; year 1 only) because of poor weed control.”
t0“kumara”
Claim · model-written summary
Plastic mulch increased early shoot and root growth and total shoot and root biomass relative to bare soil and hay.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- Plastic mulche0
- Outcome
- early shoot and root growth, total shoot and root biomasse0
- Direction
- increasede0
- Comparator
- C and He0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plastic mulch increased early shoot and root growth, total shoot and root biomass, and radiation interception, relative to C and H.”
t0“kumara”
Claim · model-written summary
Plastic mulch increased radiation interception relative to bare soil and hay.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- Plastic mulche0
- Outcome
- radiation interceptione0
- Direction
- increasede0
- Comparator
- C and He0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plastic mulch increased early shoot and root growth, total shoot and root biomass, and radiation interception, relative to C and H.”
t0“kumara”
Claim · model-written summary
Plastic mulch produced substantially higher gross margins than bare soil.
- Taxon
- kumaraIpomoea batatast0
- Treatment
- Pe0
- Outcome
- gross marginse0
- Direction
- substantially highere0
- Comparator
- Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Although a high capital outlay is required for P, gross margins in P were substantially higher than in C.”
t0“kumara”
The same questions in other papers
phosphorus · yield · Ipomoea batatas (sweet potato)Positive and negative results
18 papers in the same direction as this paper · 4 in the opposite direction
- no effect
- no effect
- no effect
19 papers more in this group
See all 23 papers →mulching · growth · Ipomoea batatas (sweet potato)Results agree
7 papers in the same direction as this paper
- positive
- positive
- positive
4 papers more in this group
See all 8 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.