5. M. TUAN.cdr Abstract To m a t o ( M i l l . )L y c o p e r s i c o n e s c u l e n t u m (Solanaceae) is one of the most economically important vegetable crops in the Red River Delta ( ) of Northern Vietnam. The recent marketRRD demands for tomatoes in both domestic and overseas markets have led to an increasing cultivated area for the crop in the . To supportRRD growers in producing healthy and quality produce, this paper presents in detail the agronomic requirements of tomatoes regarding temperatures, light, water, suitable soil type and nutrients. Cultivation techniques are discussed to provide a g e n e r a l g u i d e f o r d e v e l o p i n g a p p r o p r i a t e management strategies, depending on speci�c soil types, cropping seasons, cultivars and availability of resources. In addition, six major pests have been i d e n t i � e d , p r o v i d i n g u s e f u l i n f o r m a t i o n f o r developing an integrated pest management ( )IPM program for tomato production in the region. Keywords: Agronomic requirements, cultivation techniques, management strategies, market d e m a n d s , p e s t i d e n t i � c a t i o n , s u s t a i n a b l e production. Introduction Vegetable production provides major livelihoods of many people in rural and peri-urban areas of Vietnam (Ha and Nguyen, 2013; Ha et al., 2015c). To m a t o ( M i l l . )L y c o p e r s i c o n e s c u l e n t u m (Solanaceae) is among the most commercially important vegetable crops for both domestic and export markets in Vietnam (Johnson et al., 2008; Tran, 2005; Van Wijk, 2008). Compared to rice, tomato production could generate double economic ef�ciency (Tran et al., 2008) which helps to create more job opportunities for farmers (Tran, 2005). The Red River Delta ( ), a subtropical plainRRD region in northern Vietnam, is the main vegetable production area where tomato cultivated area accounts for a signi�cant proportion (Pham et al., 2002; Van Wijk, 2008). The recent increasing market demands have led to high percentage of growers shifting from rice to tomato production (Van Wijk, 2008). This paper introduces agronomic requirements, cultivation methods and major pests on tomatoes in the . These would be used as a general guide toRRD support production and de�ne appropriate pest management strategies. Tomato Agronomic Requirements Tomatoes can adapt to various climatic conditions, however the optimum temperatures for their growth and development lie between 21 and 27 C (Hanson, o 2001; Shankara et al., 2005). In addition, tomatoes are day-length neutral plants (Nuruddin, 2001). Light intensity of 400-500 μmol.m s is optimal for growth -2 -1 . and development. High light intensity may cause fruit cracking, sunscald and green shoulders (Jones, 1999). Though tomatoes have high water requirement (Peet, 2008) water surplus may cause fruit rot (Jones, 1999) and bacterial wilt (Nuruddin, 2001). According to Jones (1999) tomato is most sensitive to water de�cit at the �owering stage. Bud and �ower drops might occur under a prolonged dry period. Various soil types can be used for tomato production, preferably well-drained sandy loam soil (Hanson, 2001; Jones, 1999; Nuruddin, 2001; Peet, 2008). Suitable soil pH is between 6.0-7.0. If the pH is less than 5.5, plant disorders such as blossom-end-rot may occur (Hanson, 2001). Tuan M. Ha* Thai Nguyen University of Agriculture and Forestry, Thai Nguyen City, Vietnam Corresponding author; email haminhtuan@tuaf.edu.vn* : 33 SHORT COMMUNICATION Agronomic Requirements and Production Methods of Tomatoes in the Red River Delta of Vietnam J 2 1 Februaryournal of Tropical Crop Science Vol. No. , 2015 www.j-tropical-crops.com Due to their rapid growth in a long production period, tomatoes have high requirements of nutrients. For instance, to produce 1 ton of fruits the crop requires 1.36 - 3.63 kg N; 0.23 - 1.36 kg P O ; 2.27 - 5.45 kg2 5 K O (Peet, 2008)2 Production Methods Cropping Calendar Three traditional growing seasons in the wereRRD reported by Tran (2005) (Table 1): Table 1. Winter – spring cropping seasons for tomatoes in the Red River Delta, Vietnam Seasons Early season Main season Late season Sowing seeds July/ August Mid-September - End of October November Planting August/September November December Harvesting End of October or December (depending on cultivars) February or March March or April Due to the recent high market demands for tomatoes, growers have started two additional seasons, spring to summer (sowing from early January to February), and summer to autumn (sowing from July to August) seasons with the harvesting times of May/June and October/ November, respectively. Special attention however needs to be paid to pest management in these seasons since hot temperatures and high humidity are favorable for development of pests and diseases (Tran, 2005). Cultivar Selection There is a range of varieties used for the winter- spring season crop such as local varieties, Indian cultivars, 3 and some exotic F1 hybrids such asSB S902, Delta, 2000, 5 and S901. Some cultivarsVL HP are suitable for hot and rainy seasons such as 4,KBT SO SB12, 2, S901 (Nguyen, 2004), and virus- resistant such as VL VL DV3500, 642, 2926, Kim Cuong, Savior, Trang Nong-05 (Le, 2013). Six new cultivars produced by the Fruits and Vegetables Research Institute are also recommended, depending on the market demands including Lai 09 and 10 for main and late seasons, 2, 20,HPT VR FM and 29 for early and late seasons, and 5 forFM XH early season ( , 2009).VISTA Soil Preparation and Planting Density Seed-bed preparation: prepare raised seedbeds (15 cm high) with a 3-4 cm rice straw layer to improve drainage and to avoid soil-borne disease problems. Sow seeds in rows (750-900 seeds.m or a 6 cm -2 distance between seeds). Cover seedbeds with a thin compost or a rice straw mulch layer to conserve moisture (Hanson et al., 2001). Field preparation: prepare raised beds (1 m wide) with furrows (50 cm wide) in between. Bed height may range from 20 cm (in dry seasons) to 35 cm (in wet seasons). Mulching materials such as rice straw can be used to prevent weed development, keep moisture and reduce leaching of fertilizers (Hanson et al., 2001). Planting density: depending on plant growth habit, the Asian Vegetable Research and Development Center ( ) recommended the followingAVRDC spacing: Plant habit Spacing Plant density (number of plants per ha) Table 2. Tomato plant spacing according to plant habits (Hanson et al., 2001). 33,333 16,666 2 rows per bed (1 m wide); 40 cm between plants One row per bed (1 m wide); 40 cm between plants Indeterminate (pruned) Determinate (not pruned) J 2 1 Februaryournal of Tropical Crop Science Vol. No. , 2015 www.j-tropical-crops.com 34 Tuan M. Ha Fertilization and Irrigation Depending on soil conditions, the amount of fertilizers applied per hectare are N, P O and K O of2 5 2 60 – 120 kg; 60 -140 kg and 60 – 120 kg, respectively, as recommended by the whereAVRDC half of each element is applied at planting as the basal fertilizer. The second half is applied after the �rst fruit-set. Further, combination of organic matter (farmyard manure) and chemical fertilizers is recommended (Hanson et al., 2001). Tran (2005) recommends the following fertilizer formula for tomatoes in the :RRD Irrigation should be provided on regular basis to maintain �eld moisture at around 60% (Tran, 2005). In dry seasons, weekly watering is needed for the �rst month after transplanting and then every 10 days until the end of the crop season. Water-logging should be avoided in rainy seasons (Hanson et al., 2001). Staking & pruning Bamboo poles or wooden stakes (1.2 m) can be used for staking tomatoes to keep foliage off the ground (Hanson et al., 2001; Tran, 2005). Staking is provided when the plants reach 30 cm tall. Plants should be rebound every 5-7 days. Moreover, old and damaged leaves should be removed to maximize light interception (Peet and Welles, 2005), air circulation (Hochmuth, 2008; Koske et al., 2008) and to decrease disease incidence (Navarrete, 2000). Shoot topping (pruning) should also be carried out 5-8 weeks prior to harvest (Peet and Welles, 2005). Harvesting Timing of harvesting is important as it affects fruit nutritional composition and quality. Fruit maturity can be categorized into four stages (Table 4), and harvesting at stages 3 and 4 is recommended to obtain quality fruits (Shankara et al., 2005). However, for long distance markets, fruits can be harvested at earlier stages where less than 10% of fruit surface is tannish-yellow, pink or red (Hanson et al., 2001). Identi�cation of Major Pests on Tomatoes in the Red River Delta, Vietnam Pest management is an integral component in agricultural production to reduce crop losses due to pest damages. Pests are de�ned as “organisms such as weeds, insects, bacteria, fungi, viruses and animals which unfavorably in�uence human lifestyles” (Ha, 2014e). The insects, diseases and weeds that have been reported as the major pests that caused serious problems in tomato production in the ofRRD Vietnam are presented in Table 5. J 2 1 Februaryournal of Tropical Crop Science Vol. No. , 2015 www.j-tropical-crops.com Table 3. Fertilization method for tomatoes in the Red River Delta, Vietnam Method of fertilizer application Amount of fertilizer applied per hectare Remarks Mix the fertilizers then apply into holes, cover with a soil layer before transplanting seedlings into the holes. Additional fertilizer is applied when roots have developed, at �owering, and at fruit setting stage. 15-20 tons of decomposed manure; 400-500 kg of ; 195-200 kg ofSSP ;Potassium 70 kg of Urea. 10 tons of decomposed manure; 130-200 kg Urea. Basal (applied once) Top-dressing (4 - 5 times) Table 4. Maturity stages of tomato fruits (Shankara et al., 2005) Stage Description Seeds are white in color (immature) and can be cut when fruits are sliced. There is no juice inside the fruits. Seeds have tanned color (mature) and some juice present. Seeds are pushed aside when cut. The color inside is still green. Juice color becomes red. 1 2 3 4 35A ..........gronomic Requirements and Production Methods of Recently, eco-friendly production practices have been embraced as one of the appropriate strategies in agriculture (Bosch et al., 2015; Ha, 2007, 2014b; Ha et al., 2015a, 2015b) particularly in Vietnam vegetable production (Ha, 2011, 2014a, 2014c, 2014d) in which is an essential part in cropIPM protection towards sustainable production systems (Ha, 2014e). Therefore, developing an programIPM for tomatoes in the is of crucial importance toRRD ensure high product yields and quality in addressing the market demands, particularly in terms of food safety, and other bene�ts such as improved environment, human health, more secure income and livelihoods for smallholder farmers in the region. Details of the program for tomatoes will beIPM described in the forthcoming paper. Conclusion This paper has presented an overview of the agronomic requirements of tomatoes, which include temperatures, light intensity, water, soil types and nutrients. Special attention should be paid to its high water requirement at �owering time, and balanced amount of fertilisers to warrant plants' healthy growth, high yield and quality. Suitable cultivars should be selected in hot seasons to reduce fruit sunscald and cracking. In addition, a general guide on cultivation techniques for tomatoes to support tomato producers having appropriate management strategies, depending on their soil types, cropping seasons, cultivars and availability of resources. This paper has described six major pests of tomato crops in the region. Speci�c advice on productionRRD guidelines of new cultivars, and forecast of weather condition and emergence of potential pests should be updated from local departments of plant protection and extension stations. 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