An adventure in applied science - IRRI books - International Rice ...

Early research and training results 125compared with a yield of only 1,079 kg/ha from an unweeded plot. Since then,De Datta has obtained excellent results with new and less expensive materials.Even today, however, weed control in dryland rice needs further improvement.Studies of management systems for riceMoomaw and De Datta were aware that a total management system for ricewas necessary for high yields. After analyzing their earlier results withspacing, seeding methods, time of planting, fertilizer responses, and watermanagement, they decided to impose, on the optimum soil and water managementmethods, three levels of insecticide and herbicide application. Thestudies of these chemical treatments used three varieties and five levels ofnitrogen. Costs and returns were analyzed for several combinations of variables.Although the highest yields were obtained with IR8 under the most intensemanagement, the greatest net profit was obtained with high nitrogen applicationsbut with the lowest amounts of insecticide and herbicide. These firstexperiments in developing total management systems, although preliminary,are of historical interest because they paved the way for more comprehensiveresearch (as described in Chapter 7) to be conducted later by agronomists,agricultural economists, and statisticians.Experiments with dryland riceIRRI has often been criticized for concentrating its early research on wetland,irrigated rice. It did so because the quickest and largest gains in productioncould be realized under that type of management. The point must be made,however, that research with dryland rice definitely did take place at IRRI from1963 onwards, although at a low level compared to that with wetland rice.The work with dryland rice in 1963 was limited to studies (mentionedpreviously in this chapter) of the effect of herbicides on weed control, theconclusion being that no chemical herbicide existed that could control weedsadequately in dryland rice seeds without at least one hand weeding. In 1964and 1965, the work was expanded to include studies of row spacing, variety,and the timing of chemical sprays, including the use of directed spray techniques.In 1966, 4 years after his arrival, De Datta ran his first field experimentstudying the time of nitrogen application on dryland rice. He used Palawan (aPhilippine dryland rice variety), IR52-18-2 (a line from IRRI’s breeding program),and IR8. A drought occurred at the panicle initiation stage and bacterialblight attacked the plants. Consequently, yields were low (mostly between 1and 2 t/ha) and it was impossible to reach firm conclusions as to the properway to split applications of nitrogen fertilizer for dryland rice. Similar experimentscarried out in 1967 had better results. The newly named IR5 variety wassubstituted for IR52-18-2, but the two other varieties were the same as in the1966 studies. The remarkable yield of 6,191 kg/ha was obtained with IR5 when60 kg nitrogen/ha was applied between the panicle initiation and bootingstages. This was the first evidence IRRI had of the value of IR5 as a dryland