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Vegetable production under cover
1. Vegetable Production Under
Protective Structures
Manuel C. Palada, Visiting Scientist
Program 2: Year-Round Vegetable Production Systems
AVRDC, Shanhua, Tainan, Taiwan
3. Outline of topics and subtopics
Introduction
Global status of protective cultivation
Types of protective structures
Components of protective structures
Construction of protective structures
Orientation of structure
4. Outline of topics and subtopics
Cooling system
Micro-climate and environmental
determinants
Problems and prospects
Yield of vegetables under protective
structures
Costs and returns
5. Protective structures
Facilities that provide protection to vegetable crops
against biotic and abiotic stresses during the off-
season.
Covered with materials such as plastic films, glass
and nylon nets
6. Benefits of protective structures
Protection against the impact of heavy
rainfall
Provide protection against temperature
extremes
Protection against biotic stresses due to
pests and diseases
7. Global status
Predominantly common in temperate
regions
Leading countries are Japan and South
Korea
Vegetable crops occupy a major portion
of protective cultivation
Plastic houses are most common
structures.
8. Global status
Protective cultivation for off-season vegetable
production under hot, wet climate in the tropics
is becoming important and popular.
10. Greenhouses
Structure made of steel or aluminum
frames covered with transparent rigid
plates
Greenhouse roof or covering is made of
rigid plastic plates such as fiberglass,
acrylic plate or polycarbonate plate
14. Plastic house
A plastic house is a relatively simple structure made
of iron pipes or wooden frames covered with soft
plastic films or plastic nets. Characteristics which
distinguish a plastic house from a greenhouse are
flexible plastic covering materials on the structure
without overall footing.
17. Screen house/net house
Similar to a plastic house, however, plastic film is
replaced by a nylon net for top and side covers.
The net comes in several mesh-sizes. The net acts
as a physical barrier for most insect pests.
23. Rain shelter
Simple plastic houses are built using iron pipes,
bamboo or wooden frames. Rain shelters are almost
similar to high plastic tunnels, sometimes called hoop
houses.
27. Tunnels
A tunnel refers to an arched structure figured by
inserting both ends of the rod into the ground.
It is the simplest structure to support the covering
materials.
38. Construction of protective
structures
Main point to consider in the construction of protective
structures is strength. Structure should withstand against
strength of heavy rainfall or wind.
40. Orientation of structure
Orientation with respect to angle, solar radiation, and
latitude is an important factor to be considered in the
construction of protective structures. Generally,
east-west direction is more preferable than north-
south direction for lighting as the latitude becomes
higher, and single structure is more suitable for
light penetration than multiple ride and furrow
structure.
41. Cooling system
High temperature in the summer is one of the major
constrains in vegetable production under protective
structures. Temperature inside a greenhouse or
enclosed plastic net house can go up to more than 40 oC
in the summer. The passive measure for cooling the
protective structure is by shading. The active measure is
by the use of pad and fan system or by mist cooling
system.
42. Pad and fan cooling system
The principle of this system is the latent heat loss when
the liquid water changes its phase into vapor (latent heat
loss is 540 cal/g of water). One side of the structure is
padded with dripping water and the ventilating fan on
the other side of the wall does the suction of air inside
the structure. As the water flows with air movement, it
changes to vapor robbing latent hat. This systems works
effectively during daytime when dynamic evaporation
occurs.
43. Fog and fan (mist) cooling system
The principle involved in this system is similar to that
of the pad and fan system. Mist is generated from the
position of duct and the fan on the other side sucks the
air in the greenhouse. Ventilation fan turned on at 8:00 a.m.
and turned off at 6:00 p.m. with mist generated at 10:00 a.m.
can bring temperature down to as much as 2oC initially
and 4oC finally.
46. Problems and prospects of vegetable production under
protected structures
Design of protective structure suitable for the
tropics.
High cost of structures and covering
materials.
Running cost is high and the need for saving
resources and energy input.
Uncertainty of market prices for vegetables
and expected profit.
47. Problems and prospects:
Adaptability of production system to market
demands.
Technology improvement to enhance yield
and quality.
Proper disposal of waste materials, especially
plastic films.
48. Yield of vegetables under protective
structures
Tomato
Hot peppers
Leafy vegetables
Cucumber
Snow peas
Okra
Yardlong bean
49. Fig. 1. Yield of two tomato cultivars grown in bag and
soil culture under open and protected rain shelters.
50. Table 1. Main effects of rain shelter, raised beds
and bed width on fruit yields (t/ha) of
tomato planted at end of summer season
in Taiwan (AVRDC 1993).
Rain shelter Bed height Bed width
With 51.2 20 cm 61.2 1.0 m 58.3
Without 68.1 40 cm 58.1 1.5 m 60.9
SED (23 df) 3.4 NS NS
51. Table 2. Effects of cultural practices on the pest and disease incidence and yield of tomato
grown under protective structures. AVRDC 1998
Leaf Bacterial TYLCV Gray Mktable
Treatment miner spot (% ) mold yield
(t/ha)
Main plot
Chemical spray 0.08 a 0.00 b 8.34 b 0.42 a 63.39 a
No chemical spray 1.58 a 1.92 a 12.50 a 0.83 a 35.96 a
Subplot
No netting (ck) 1.75 a 1.25 a 6.23 ab 0.00 51.71 a
House netting 0.25 b 0.75 ab 10.43 ab 1.75 a 52.84 a
House open 1.50 a 1.00 ab 18.75 a 0.25 b 47.07 a
Tunnel netting 0.25 b 1.00 ab 0.00 b 1.25 a 53.96 a
Tunnel open 0.75 b 1.25 a 8.35 ab 0.25 b 47.98 a
Direct netting 0.50 b 0.50 b 18.78 a 0.25 b 44.49 a
Pest and disease incidence rating at last harvest: 0=none; 1=light; 2=medium; 3=severe
Mean separation in columns by Duncan's multiple range test (P=0.05)
Seed sown: 22 Sept 1997
Date transplanted: 20 Oct 1997
Date harvested: 6 Jan-23 Feb 1998
52. Table 3. Effect of cultural practices on fruit yield of tomato under
protective structure. AVRDC, 1998
Fertilizer Netting Pesticide Fruit no. Mktable Mktable
(no/12m2) yield fruit (%)
(t/ha)
Organic - - 606 52 bc 87
Inorganic - - 528 46 c 90
Organic + - 619 42 c 70
Inorganic + - 756 57 bc 86
Organic - + 748 70 ab 91
Inorganic - + 830 72 ab 91
Organic + + 864 79 a 97
Inorganic + + 876 85 a 98
Mean separation in columns by Duncan's multiple range test (P=0.05)
53. Table 4. Effects of rain shelters and grafting on yield of tomatoes transplanted in late
summer 1999, AVRDC headquarters (AVRDC 1999).
Marketable yield (t/ha)
Grafting (G) Rain shelter
No shelter Open-side Closed-side G-Mean
Non-grafted 61.8 66.6 63.8 64.1 b
Grafted onto tomato, H7996 79.6 71.5 75.1 75.4 a
Grafted onto eggplant, EG203 59.0 57.3 61.5 59.2 b
S-Mean 66.8 a 65.1 a 66.8 a
In a row or column, means followed by the same letter are not significantly different
at P<0.05 by least significant difference.
56. Table 5. Effects of grafting and rain shelters on plant survival and yield
summer tomato transplanted 15 July 2000 (AVRDC 2001).
Plant survival* (%) Marketable yield** (t/ha)
Rootstock Shelter No shelter Shelter No shelter
Non-grafted 7.5 c 63.3 ab 3.5 c 7.6 c
Hawaii 7996 3.3 c 26.7 bc 0.8 c 2.1 c
EG203 90.0 a 65.0 ab 26.2 a 6.0 c
*Outliers excluded from analysis: trt4 (rep 1)
**Outliers excluded from analysis: trt3 (rep 1), trt4 (rep 1)
Mean separation in a row and column at P<0.05 by Duncan's multiple range test.
64. Table 6. Effects of grafting and rain shelters on plant survival and yield of summer
tomato transplanted 12 August 2000 (AVRDC 2001).
Plant survival* (% ) Marketable yield (t/ha)
Rootstock Shelter No shelter Shelter No shelter
Non-grafted 36.7 b 51.7 ab 7.2 b 5.5 b
Hawaii 7996 50.0 ab 20.0 b 10.9 b 4.4 b
EG203 95.0 a 96.7 a 28.8 a 25.4 a
*Outliers excluded from analysis: trt4 (rep 1)
Mean separation in a row and column at P<0.05 by Duncan's multiple range test.
66. Table 7. Effects of cultural practices on pest incidence and yield
of Pai-tsai grown under protective structures. AVRDC 1998.
Diamond Cabbage Flea Yield
Treatment back moth worm beetle (t/ha)
Main plot
Chemical spray 1.58 a 1.67 a 1.92 a 13.8 b
No chemical spray 0.92 b 2.58 a 1.50 a 15.8 a
Subplot
No netting (ck) 2.50 a 1.25 b 3.00 a 13.2 b
House netting 1.00 bc 2.25 a 1.25 c 14.7 ab
House open 1.75 ab 2.50 a 1.50 bc 13.3 b
Tunnel netting 0.25 c 2.25 a 1.25 c 15.3 ab
Tunnel open 2.00 ab 2.25 a 2.50 ab 12.9 b
Direct netting 0.00 c 2.25 a 0.75 c 19.5 a
Pest indidence: 0=none; 1=light; 2=medium; 3=severe
Mean separation in columns by Duncan's multiple range test (P=0.05)
Seed sown: 11 Nov 1997
Date transplanted: 27 Nov 1997
Date harvested: 23 Dec 1997
68. Table 8. Yields (t/ha) of leafy vegetables under open field and net house from different field (AVRDC 2001)
Hot Dry Season Cool Dry Season Hot Wet Season
Leafy Vegetable No. of Sept. 1999 Nov. 1999 Open Sept. 1999 Feb. 2000 July, 2000
Acc. Open Open Field Nethouse Open Nethouse Open Nethouse
Field Field Mean (32-mesh) Field (32-mesh) Field (32-mesh)
NH Chinese cabbage 17 37.6 38.1 37.5 30.6 36.9 32.7 15.6 18.9
Pak-choi 17 36.3 37.6 36.9 32.5 58.0 54.7 24.8 18.9
Choy sum 19 34.8 36.8 35.8 28.8 47.2 31.5 14.7 15.6
Chinese kale 18 24.8 31.7 28.3 17.3 30.0 26.9 13.7 10.1
Indian mustard 19 31.7 36.2 33.9 28.4 38.4 33.6 28.3 16.4
Mean 33 36.1 34.5 27.5 42.1 35.9 19.4 15.9
69. Table 9. Yield of Chinese kale and lettuce under double bed rain shelters and open field
with drip and furrow irrigation. Cool-dry season, AVRDC 2000-2001.
Chinese kale Lettuce
Shelter Irrigation Marketable Total plant wt Marketable
yield (kg/plot) (kg/plot) yield (kg/plot)
Rainshelter Drip 23.25 45.37 23.72
(RS) Furrow 27.01 47.07 29.82
RS mean 25.13 46.22 26.77
Open field Drip 29.60 43.43 22.63
(OF) Furrow 27.93 39.87 21.05
OF mean 28.77 41.65 21.84
Drip mean 26.55 44.40 23.18
Furrow mean 27.47 43.47 25.44
70. Chinese kale and lettuce under open field and
double bed rain shelter
71. Table 10. Yield of cucumber and snow peas under double bed rain shelters and open field
with drip and furrow irrigation. Cool-dry season, AVRDC 2000-2001.
Cucumber Snowpeas
Shelter Irrigation Total no. of Total wt of Wt of 20 Total pod
fruits/plot fruits (kg/plot) pods (g) wt (kg/plot)
Rainshelter Drip 568 54.38 341.3 4.68
(RS) Furrow 594 58.53 375.3 6.57
RS mean 581 56.36 358.3 5.63
Open field Drip 595 56.29 412.1 8.5
(OF) Furrow 599 58.53 440.7 8.05
OF mean 597 57.11 426.4 8.28
Drip mean 582 55.34 376.7 6.59
Furrow mean 597 58.53 408.0 7.31
73. Table 11. Yield of okra and yardlong bean in high and low bed under rain shelters a
open field. AVRDC 2001.
Okra Yardlong bean
Bed Shelter Total no. Total wt of No. of mkt Wt of mktble
of fruits fruits (kg) pods pods (kg)
30 cm RS 768 8.02 1187 32.1
RS+N 994 11.65 1567 44.2
Open 853 9.36 1513 39.6
Bed mean 872 9.68 1422 38.6
45 cm RS 780 10.17 967 25.9
RS+N 1060 14.24 1286 34.7
Open 879 9.71 1181 34.7
Bed mean 906 11.37 1151 31.8
Shelter mean
RS 774 9.10 1077 29.0
RS+N 1087 12.95 1427 39.5
Open 866 9.53 1347 37.2
RS=Rainshelter; RS+N=Rainshelter+Net
76. Table 1. Cost and return per 1,000 sq.m. for off-season grafted tomato under rain shelter, CLSU site, wet season 2000.
ITEM QUANTITY VALUE (P)
Gross Income
Sales P2,260kga/ 90,400
Total Cost
Labor cost 15,249.60
Material inputs and irrigation cost 7,118.85
Rain shelter materialsb/ 8,887.27
Grafting and hardening chamberc/ 1,612.25
Total Expenses 32,867.96
Net Income 57,532.04
Financial Ratios
Breakeven volume (kg)d/ 821.70
Breakeven price (P) e/ 14.54
Return on total expenses f/ 1.75
a/
Price/kg is P40.00
b/
Cost is distributed over the life span of the materials, e.g. net is for 6 cropping, GI pipe frame is for 20 croppings, etc.
c/
P 19,347 last for 12 years
d/
BEV = total expenses/price per kg
e/
BEP = total expenses/yield
f/
RTE – net income/total expenses
77. Summary
Vegetable production under protective
structures is gaining importance in the
lowland tropics of Southeast Asia.
Protective structures provide protection to
vegetable crops against biotic and abiotic
stresses.
Vegetable production under protective
structures insures year-round supply of
vegetables and helps stabilize market price.
78. Summary
Protective structures include greenhouses,
plastic houses, net or screen houses, tunnels
and plastic rain shelters.
Main benefit of protective structures is
protection against the impact of heavy rainfall
and strong winds in the tropics.
Yields of vegetables such as tomatoes have
been improved under protective structures
during the off-season.
79. Summary
Yield responses of other vegetables grown
under protective structures vary depending
on species, season and environmental
conditions.
Economic benefits from vegetable production
production under protective structures are
not well defined and studied.
There is a great challenge for more research
to address the problems of vegetable
production under protective structures.
