Yield variability is determined by variety (genotype), variability and level of inputs (such as fertilizers, irrigation and pesticides), and variability in pests and diseases and in climatic factors (such as rainfall, frosts, and temperature). Interactions between these factors are important, although difficult to analyze. As national food-grain production has increased, especially through the introduction of improved varieties and the increased use of irrigation and fertilizers, so often has variability in yields from year to year. This leads to the perception of increased risk, which may make new technologies appear less attractive to farmers and hence slow agricultural development. It also increases instability in national and world food supplies, which may act to destabilize domestic prices, national income, and the food consumption of the poor, especially in poor agrarian countries.
The world's total production of wheat and rice increased linearly by some 150 percent from 1961 to 1993, although some variation occurred. The upward trend is attributed to technological development, and the variation is the result of climatic variability and political instability. Annual fluctuations in wheat production are larger than those for rice. This may indicate that the abundant use of water in rice-growing tempers the variations resulting from climatic fluctuations.
The Encyclopedia of World Problems and Human Potential is a unique, experimental research work of the Union of International Associations. It is currently published as a searchable online platform with profiles of world problems, action strategies, and human values that are interlinked in novel and innovative ways. These connections are based on a range of relationships such as broader and narrower scope, aggravation, relatedness and more. By concentrating on these links and relationships, the Encyclopedia is uniquely positioned to bring focus to the complex and expansive sphere of global issues and their interconnected nature.
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