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Weather and climate for agriculture         

Weather plays an important role from germination of a seed to the maturity of the crop

By Dr. Syed Manzoor Alam NIA, 
Aug  20 - 26 , 2001

Agricultural productivity is very sensitive to climate and weather conditions. An agricultural decision-maker can either be at the mercy of these natural factors or try to benefit from them. The only way to profit from natural factors is to take them into account and learn to know them as well as possible. Agrometeorological information, in practice mainly climatological data, is essential in planning agricultural production. The following decisions should not be made without knowing climatic conditions: land use and management, selecting plants and breeds of animals and crop production practices such as irrigation, pest and disease control and crop-weather relationships. The specific climate-related information needed is presented below: before giving recommendations about land use it is necessary to know the environmental conditions.

Parameters required to quantify these conditions are the monthly solar radiation, temperature and frosts, hail etc. In order to select plant species or varieties, a prior agroclimatologic characterization is required. This is determined using weekly, daily and hourly temperature, rainfall, solar radiation, evaporation, wind speed, evapotranspiration and relative humidity. To assess the suitability of an environment to animal production knowledge of the effects of radiation, wind, precipitation, temperature and relative humidity is essential. For pest management and plant diseases the minimum weather data set required should consist of temperature and humidity or derived parameters such as accumulated heat or degree-days. Moisture (relative humidity, rainfall and wetness duration) is an essential variable in most plant disease prediction schemes and also for predicting outbreaks of some insect pests. Real time meteorological information can also be effectively used in agricultural production process.

Plant growth and development are primarily governed by environmental conditions of the soil and climate of a country. The success and failure of agricultural farming is generally related to the prevailing weather conditions. Weather plays an important role from germination of a seed to the maturity of the crop. Timing of sowing of the seed of a crop, transplanting, scheduling of irrigation water application, timing of fertilization application, using of pesticides to control the diseases and pests of the crops all depend on weather condition of the area. The weather changes lead to excessive rain then it may affect at least 15-20 per cent crop yield in the country. The growth of any crop depends on the climatic country of the area cropped.

The climatic changes are undoubtedly the most important factors in the agricultural productivity on a year to year basis. Interestingly, the most important fact about climate is that it changes on every scale of time and space, every year, decade, century and in every region of the world. The causes of climatic changes are still poorly understood. Harshly variable climate leads to erratic food supplies particularly in developing countries like Pakistan, which lacks their financial, institutional and technological means to cope with weather-induced food shortfalls. Climate thus contributes fundamentally to malnutrition and an ever-pressure threat of famine. It follows that climate-agriculture interactions must be understood and to be dealth with at the national food system level, as well as directly in agricultural production itself. The green revolution has made a tremendous contribution to food production by prevailing weather condition, but does not move forward as per expectation.

The global 2000 report transpires that world food production will barely manage to keep pace with the burgeoning population and demand from present to the year 2000 and onwards. According to the agricultural weather experts, the last 40 years were exceptionally stable climatically, which have contributed towards the greatest food expansion all over the world. This situation is highly unlikely to continue in the future due to rapid environmental degradation. Most of the third world countries that were virtually self sufficient on food production in 1960's are now highly dependent on the impact of cereal grains, to fulfil the food requirements of the population. The change in weather fluctuation have been largely responsible for slowing down the production momentum of the green revolution of early 1960. The earlier high yielding varieties of cereal crops have become sensitive to weather vagaries and thus the yield of such varieties have gone down substantially.

The atmosphere is becoming warmer day by day due to increase in pollutants such as CO2, CO, SO4, CH4, nitrous oxides and particulate in the atmosphere. Among them, the most important pollutant is carbon dioxide and its content is increasing rapidly due to burning of fossil fuels. The blanketing effect of carbon dioxide causes the climate warming, because carbon dioxide allow, sunlight to penetrate the atmosphere. Presence of CO2 also changes the distribution of rainfall, a process on which crops are highly dependent. Such changes in the rainfall due definitely alter the agricultural productivity. Hail storms flood, severe winds and frosts are also expected under such conditions, which ultimately affects the growth of plants. There is a general upset in the planting of crops under such situations. The International Food Policy Research Institute (IFPRI) has made detailed studies on the amount of food that must be grown above present production levels to meet the food requirements of the world population in 2002. According to IFPRI, the present food requirement is over 100 million tons, which is in deficit condition.

In the year 2002, a person will need about 450 kg of gram of food grain per year for over six billion people, this means that present world grain production would have to be more than double in the year 2002. The success will depend on development and utilization of modern technology. It has been observed that the environmental constraints in grain production are the primarily limited or stressed resources essential to agriculture land, water, plant inhibits and energy. Man-made general constraints—political, economical and cultural are imposed by Government, landowners, waderas, farmers and consumers. These are the major essential resources used for necessary food production and their distribution. There are numerous segments which farmers and agricultural planners can take directly to reduce the vulnerability of crops and agricultural systems. To climate, mostly requiring new scientific insight and technology in their application. The appropriate agricultural technology is mono-crop farming genetics to suit climate. Integrated systems using chemical fertilizers—organic matter and biological technique are most important, which will be used in crop production. There is a need to record of climatological data for its application in agriculture.

The timing of different activities, e.g. sowing, ploughing, fertilizing and pest and disease control should be done when weather conditions are most favourable. For example the spreading of pesticide will succeed if weather is moist and warm (not hot) and not very rainy or windy. Hay should be made before a period of several dry days so that the hay enough time to, dry. The harvesting of wheat is also most effective during a dry period. If the wheat is threshed while it is damp it becomes predisposed to damages. Although, these examples concern agriculture in mild climates, the meaning of real-time meteorological information can be broadened to activities in the tropics as well. Because climate conditions are different around the world, the importance of climatological information and real-time meteorological information is emphasized differently. In Finland, for example, real-time weather information is more important than in central parts of Africa because the weather in Finland is less predictable.

In fact, it is sometimes difficult to appreciate the importance of climatological in Finland because this information is considered self-evident. On the other hand, the climatological knowledge, is often insufficient in the developing countries. The importance of climate, as an agricultural aspect, is even more crucial if the geographic situation of the developing countries and the global warming of the atmosphere are taken into account. If the climate of these regions becomes even more warm and dry, food production can be a tremendous problem. This is why climate-related knowledge should also be promoted in developing countries. Agrometeorological information can increase agricultural yield. In this way, the quality and quantity of agricultural production can be increased and production costs substantially can be reduced.