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Vegetable Production UnderProtective StructuresManuel C. Palada, Visiting ScientistProgram 2: Year-Round Vegetable Production SystemsAVRDC, Shanhua, Tainan, Taiwan
Off-season vegetable production under protective structures
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
Outline of topics and subtopics Cooling system Micro-climate and environmental determinants Problems and prospects Yield of vegetables under protective structures Costs and returns
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
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
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.
Global statusProtective cultivation for off-season vegetable production under hot, wet climate in the tropics is becoming important and popular.
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
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.
Simple qounset (arch) type plastic house at AVRDC
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.
PE clipsPlastic belt PE clips Connecting and fastening accessories
Construction of protectivestructures Main point to consider in the construction of protective structures is strength. Structure should withstand against strength of heavy rainfall or wind.
Construction of simple single bed rain shelter
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.
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.
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.
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.
Microclimate and environmental determinants Solar radiation Temperature Water Wind Carbon dioxide
Problems and prospects of vegetable production underprotected 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.
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.
Yield of vegetables under protectivestructures Tomato Hot peppers Leafy vegetables Cucumber Snow peas Okra Yardlong bean
Fig. 1. Yield of two tomato cultivars grown in bag and soil culture under open and protected rain shelters.
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 widthWith 51.2 20 cm 61.2 1.0 m 58.3Without 68.1 40 cm 58.1 1.5 m 60.9SED (23 df) 3.4 NS NS
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 MktableTreatment 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 aSubplot 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 aPest and disease incidence rating at last harvest: 0=none; 1=light; 2=medium; 3=severeMean separation in columns by Duncans multiple range test (P=0.05)Seed sown: 22 Sept 1997Date transplanted: 20 Oct 1997Date harvested: 6 Jan-23 Feb 1998
Table 3. Effect of cultural practices on fruit yield of tomato under protective structure. AVRDC, 1998Fertilizer Netting Pesticide Fruit no. Mktable Mktable (no/12m2) yield fruit (%) (t/ha)Organic - - 606 52 bc 87Inorganic - - 528 46 c 90Organic + - 619 42 c 70Inorganic + - 756 57 bc 86Organic - + 748 70 ab 91Inorganic - + 830 72 ab 91Organic + + 864 79 a 97Inorganic + + 876 85 a 98Mean separation in columns by Duncans multiple range test (P=0.05)
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-MeanNon-grafted 61.8 66.6 63.8 64.1 bGrafted onto tomato, H7996 79.6 71.5 75.1 75.4 aGrafted onto eggplant, EG203 59.0 57.3 61.5 59.2 bS-Mean 66.8 a 65.1 a 66.8 aIn a row or column, means followed by the same letter are not significantly differentat P<0.05 by least significant difference.
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 shelterNon-grafted 7.5 c 63.3 ab 3.5 c 7.6 cHawaii 7996 3.3 c 26.7 bc 0.8 c 2.1 cEG203 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 Duncans multiple range test.
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 shelterNon-grafted 36.7 b 51.7 ab 7.2 b 5.5 bHawaii 7996 50.0 ab 20.0 b 10.9 b 4.4 bEG203 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 Duncans multiple range test.
Table 7. Effects of cultural practices on pest incidence and yield of Pai-tsai grown under protective structures. AVRDC 1998. Diamond Cabbage Flea YieldTreatment 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 aSubplot 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 aPest indidence: 0=none; 1=light; 2=medium; 3=severeMean separation in columns by Duncans multiple range test (P=0.05)Seed sown: 11 Nov 1997Date transplanted: 27 Nov 1997Date harvested: 23 Dec 1997
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 SeasonLeafy 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 18.9Pak-choi 17 36.3 37.6 36.9 32.5 58.0 54.7 24.8 18.9Choy sum 19 34.8 36.8 35.8 28.8 47.2 31.5 14.7 15.6Chinese kale 18 24.8 31.7 28.3 17.3 30.0 26.9 13.7 10.1Indian mustard 19 31.7 36.2 33.9 28.4 38.4 33.6 28.3 16.4Mean 33 36.1 34.5 27.5 42.1 35.9 19.4 15.9
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 LettuceShelter 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 26.77Open 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
Chinese kale and lettuce under open field and double bed rain shelter
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 SnowpeasShelter 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 5.63Open 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
Cucumber and snow pea under double bed rain shelter
Table 11. Yield of okra and yardlong bean in high and low bed under rain shelters a open field. AVRDC 2001. Okra Yardlong beanBed 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 38.645 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 37.2RS=Rainshelter; RS+N=Rainshelter+Net
Okra and yard long bean trial under rain shelters
Grafted tomato under rain shelter, Philippines
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/ 1.75a/ Price/kg is P40.00b/ 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 yearsd/ BEV = total expenses/price per kge/ BEP = total expenses/yieldf/ RTE – net income/total expenses
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.
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.
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.