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126 History of the International Rice Research Institutevariety. The yield of IR8 under the same treatment was 4,796 kg/ha and thatof Palawan 3,644 kg/ha.In 1967, IRRI agronomists conducted other experiments on dryland rice,including varietal trials, rate of seeding, row spacing, and mechanized seeding.On IRRI’s experimental fields, these studies (and those in 1966) showedthat the Institute’s short-strawed, heavy-tillering varieties outyielded therecommended Philippine dryland varieties such as Palawan, Azucena, andMilfor 6(2).Multiple croppingAlthough IRRI received its first recognition for multiple cropping researchafter Bradfield launched his program in 1965, the earliest work at the Institutewith crops other than rice was done by Moomaw in 1962-64. He had studieddryland crops on tropical soils in Hawaii and believed that for the well-beingof the rice crop alone, some crop rotation should be practiced. Therefore, heimmediately started looking for legumes that could be rotated with rice (inconnection with the maximum yield experiment already described) andsimultaneously sought species that could stand flooding for short periods.He established a legume nursery in 1962, planting seeds that he hadobtained from the Philippines, Taiwan, Cambodia, and the US. He found thatspecies of the genera Sesbania and Crotolaria were the most promising as greenmanure crops and that only Sesbania sesban and Phaseolus lathyroides couldstand extended periods of flooding.In 1963, Moomaw grew mungbean, soybean, and cowpea at differentspacings to determine the optimum for seed production and tested 15 leguminousspecies for yield and nitrogen content as green manure crops.In 1964, he continued those studies and screened a group of sorghumvarieties from the College of Agriculture and from the Rockefeller Foundation’sprogram in India. It was Moomaw who first reported at IRRI thatsorghum could stand flooding far better than maize and that higher yieldscould be obtained in the ratoon crop than in the first crop from seed.By 1967, Bradfield had worked out a system of multiple cropping, combinedwith intercropping, so that — in a 12-month period on a given tract of land —one crop of rice, followed by a crop of soybean, then of sweet potato, anothercrop of soybean, and a final crop of sweet maize, could be grown. Heexperimented on crop timing (always starting with rice at the beginning of therainy season), on bed preparation, on fertilizer application, and on weed andinsect control. All of this was done on about 2 ha of land, which seems smallin comparison to that available for such research at IRRI today. Nevertheless,Bradfield laid an excellent foundation for the greatly expanded program thatIRRI developed after his retirement. Furthermore, his enthusiasm for thecropping systems he worked out and his belief in their validity attracted theattention of Canada’s International Development Research Centre, whichprovided substantial support for the enlarged multiple cropping program.(Bradfield’s early work had been funded largely by a grant from theRockefeller Foundation.)
Early research and training results 127SOIL CHEMISTRYDuring his first 5 years at IRRI, Ponnamperuma conducted literally hundredsof fundamental studies on the chemistry of flooded soils. His work embracedsuch investigations as the influence of flooding on the redox (oxidationreduction)potential, on pH, and on the amounts of ferrous iron, ammonia,phosphorus, silicon, molybdenum, zinc, and copper in the soil solution. Hestudied the losses of nitrogen by denitrification, the formation of toxic substancesfrom the decomposition of organic matter, and the influence ofsubmergence on carbon dioxide levels. He examined the chemistry of the acidsulfate clays that are so extensive in Southeast Asia and that occur also in othertropical rice-growing regions. Using large metal drums in which water levelscould be accurately controlled, he investigated the impact of various waterregimes on the chemical properties of soils.Most of Ponnamperuma’s basic studies were conducted in pots in thegreenhouse, although in 1963 he ran a field experiment, in cooperation withMoomaw, studying the effect on yield of the duration of submergence prior toplanting, with and without added organic matter. He found that 2 weeks ofsubmergence were optimum, even when as much as 7.4 t of a mixture of ricestraw and fresh leaves of Leucaena glauca per hectare was incorporated duringland preparation. Interestingly, no significant differences in yield were obtainedwhen an equal amount of nitrogen was applied as ammonium sulfate,indicating that amount of nitrogen, not source, is the important factor.Ponnamperuma’s thorough and complex studies of the chemistry offlooded rice soils cannot even be touched upon adequately here. In brief,however, his work revealed that when a dry soil is flooded, the followingchanges occur during the first 3 to 4 weeks:• The oxygen supply decreases almost to zero except in a thin layer at thesoil surface.• The pH of acid soils increases, whereas that of calcareous soils decreases,thus tending to bring most soils to harmless degrees of either acidity oralkalinity.• Iron is reduced from the ferric to the ferrous form, and large amounts ofsoluble iron are released into the soil solution.• The supply of available nitrogen, phosphorus, silicon, and molybdenumincreases.• The availability of zinc and copper decreases.• Harmful quantities of toxins, such as organic acids, ethylene, and hydrogensulfide may be produced, and under certain conditions the solubleiron quantities may build up to toxic levels.The findings showed that most of the changes that take place after floodingare beneficial to the growth of rice. This information helped develop thethinking of other IRRI scientists, for several of them questioned the need tofollow the time-honored practice of flooding and even thought it might beharmful.
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An Adventurein Applied Science:A HI
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ContentsDedication viiAbout this pu
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About this publication . . .In 20 y
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xiname, and release varieties. Thus
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PrefaceThe International Rice Resea
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CHAPTER 1An international institute
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An international institute for rice
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CHAPTER 2Developing and staffingthe
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Developing and staffing the program
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Page 100 and 101: 86 History of the International Ric
Page 107 and 108: Princess (now Queen)Beatrix of theN
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Page 117 and 118: Chapter 4Early Researchand training
Page 119 and 120: Early research and training results
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Page 161 and 162: CHAPTER 5Financing of IRRIThe purpo
Page 163 and 164: Financing of IRRI 149foreign assist
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Page 175 and 176: Creation of other international cen
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Page 181 and 182: Aerial view of IRRI in1981.However,
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IRRI today 181neering Department: K
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IRRI today 183In spite of this high
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IRRI today 185turn, received geneti
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IRRI today 1871. Research to assist
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Appendices 189materials could readi
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Appendix 2OVERSEAS DEVELOPMENTINTER
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Appendices 193ate to concentrate on
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Appendices 195estimates for buildin
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Appendices 197(4) Development of pr
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Appendices 199was approved for the
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Appendices 201association, or perso
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Appendices 203b. To pass upon the b
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Appendices 205Article VIIMISCELLANE
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208 History of the International Ri
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