Untitled - IRRI books - International Rice Research Institute

REMOVING SOIL CONSTRAINTS TO CROP PRODUCTION 17future, as are organisms genetically-altered so as to be able to form agronomicallysignificant biocoenoses with non-legumes such as cereals". Beringerand Day (1981) reviewed the improvement of legumes, reporting annual fixationranging up to 550 kg/ha of N by beans, 460 kg/ha by alfalfa, and 670 kg/ha byclover. Improved clovers have fixed up to 470 kg/ha of N in English experiments.Such work points to the path that must be taken in developing countries where thebadly-needed improvement of pasture cannot afford to rely on the treatment ofgrass with fertilizer-N, the practice which is so common in Europe. The use ofclover to fix N will also become more important in much pasture land of temperatecountries where the high cost of N-fertilizer deters its use on grasslands. Otherpossibilities are the transfer of genes for nitrogen fixation to other organismswhich may form new symbioses with plants. Work on nitrogen-fixing bacteria shouldbe encouraged; some of these have already been show to be associated with theroots of grasses and cereals; others fix N while decomposing organic matter addedto soil.CONCLUDING REMARKSIncreased food production will depend on our success in providing informationon the working materials of cropping systems – soil, plant, water and nutrients.This demands research on soils and crops, and on the fertilizers essential toincrease soil fertility. This information must be used to guide both the adviceon using fertilizers in cropping systems that is given to farmers, and also theadvice that is given to fertilizer manufacturers. The high efficiency which is soessential to repay the cost of inputs will come from the right fertilizers,applied in the right place and at the right time.In developing countries many farmers still need to be introduced tofertilizers as vital aids to higher crop yields. The most serious problems willbe in formulating and manufacturing materials to suit the constraints set by soil,crop and climate, and by the farmer's capabilities and equipment. The fertilizersthat suit agriculture in temperate developed countries may not fit theserequirements; modification of their physical form and chemical composition may berequired to suit methods of application that secure high efficiency. Full useshould be made of indigenous raw materials, notably mineral rock phosphates whichmay prove superior in the long-term to the water-soluble and citrate-soluble formsof phosphate used in temperate countries. These are challenges which should besolved by the soil chemists and the chemical engineers working together.In planning to increase food production by agricultural developmentgovernments must establish the financial incentives that encourage farmers tomodernize and intensify their systems, and give full support to research anddevelopment programs to support these changes. The most rewarding investment thatgovernments can make will be to support scientific investigations of theconstraints to yield under local conditions; the information acquired will haveimmediate practical application and it will also be of permanent value to thecountry's agriculture. Lines of communication must also be examined to ensurethat all the information acquired from investigations on the efficient use ofinputs is transferred smoothly from research workers to advisers, and then tofarmers. Advice based on sound scientific knowledge must not be set aside to suitsome temporary economic advantage.The farming systems of the future, which will ensure freedom from hunger forthe world's expanding population, will be based on the results of scientificinvestigations, and will be controlled by scientific methods. The magnitude ofthe work that must be done should not be under-estimated. The sequence willalways be, firstly to identify the constraints in the production systems, and