Leguminous Vegetable Cultivation and Seed Production S ...

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36 4 GREEN MANURE IN RICE FARMING quality seed. Since the price of seed is generally higher than the price of grain, extra management inputs are justified. Preharvest factors Seed longevity and field weathering. At the Asian Vegetable Research and Development Center ( AVRDC ) , soybean can be planted in the February, July, and Scptonuberseasons. TbcFebruary crop encounters rain at harvest (Fig.|).The July rainy season crop may be exposed to typhoons. Field weathering of seed is a common problem in both seasons. Therefore, the seed quality of February and July season crops generally is not dependable. The September season CrOp produces the best quality seed (Sb0000ugasuoduranuaod Tsou 1987 ) . The seed quality of rainy season crops, in general, is poor in ' Indonesia, Thailand, Philippines, Sri Lanka, and Nigeria(Arulnaudhy 1987, Nau uut al 1978, Potan 1987, Sumarno 1987). One of the best ways to prolong seed longevity and combat field weathering of soybean is through genetics. At the International Institute of Tropical Agriculture /llT/\\ and at AVRDC, obtaining good seed quality is a key breeding objective. Varietal differences in seed deterioration in storage a*c was vo observed ' ino soybean (Wien and Kucocnouo1981). Freshly harvested seeds of /\[}S 2, a pure line from an Indonesian introduction; [`&/ from India; and /\[}S 29 from AVRDC maintained about 80% germination for about 6 . mo at ambient room temperature in Bangladesh. Locally grown variety Bragg and /\[}S 66 from AVRDC can be stored for only 2-3 mo (Fig. 2). Small-seeded varieties from Indonesia and black seed coat varieties deteriorate more slowly than large-seeded varieties. However, reports on the role of large and small seeds in seed longevity, germination, emergence, and yields have Temperature (OC) Precipitation (mm) 40 1 1700 600 30 500 20 400 300 10 200 100 0 J F M A M J J A S 0 N D Month I. Maximum and minimum temperature and rainfall pattern at AVR DC in 1984 and time of planting and harvest. 0
SEED PRODUCTION AND MANAGEMENT OF MUNGBEAN AND SOYBEAN 365 been contradictory (Edwards and Hartwig 1971, Fontes and Ohlrogge 1972, Green et al 1965, Johnson and Luedders 1974, Ndunguru and Summerfield 1975). Some changes associated with seed deterioration are reduced protein synthesis, reduced ability to utilize labeled glucose, reduced respiration, and increased respiration quotient (A. Knapp, pers. comm.). Although small seeds are associated with better seed longevity, the reasons are not yet understood. Seed vigor is an elusive and complex concept.Vigorous seeds are "likely to .. . perform particularly well in the field, better than others which may be equally satisfactory in the laboratory test" (Heydecker 1972). Loss of seed vigor due to weathering precedes loss of seed viability. Assessing seed vigor is problematic for seedmen (Kuenernan 1982). The concept of seed vigor and its importance to seed production were described by Heydecker (1972) and Perry (1978). A modified accelerated aging and hot water stress test were used to screen for seed longevity and vigor. In the accelerated aging stress test, seeds are kept at 42 °C and 100% relative humidity (RH) for 48 h, followed by a laboratory germination test (Byrd and Delouche 1971). To distinguish cultivars with good and pOOr seed storability, Wien and Kueneman (1981) used a modified accelerated aging stress technique. After pods dried, they threshed the seeds and subjected them to 75% RH at 40 °C for 6 wk, followed by a laboratory germination test. Germination (%) 100 - 80 60 40 0 AGS 2 AGS 29 V AGS 66 V AGS 129 0 Pb-l(check) Bragg (check) 20 1 Jan 1 Mar 1 Apr 1 May 15 May 1 Jun 15 Jun 1 Jul Date of germination test 2. Germination percentage of 6 soybean varieties evaluated at different intervals after storage at ambient temperature. Bangladesh, 1985.
Page 1 and 2: Leguminous Vegetable Cultivation an
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Page 9 and 10: At the seedling stage, the crop is
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Page 19 and 20: staking of the vines. In some place
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