The success or failure of farming is intimately related to the prevailing weather conditions, if weather is suitable to that particular crop production, yield would be high otherwise, the yields would be reduced. Even small changes in ambient weather conditions may affect growth rate, incidence of pest, disease in crops and ultimately the seed yield. The analysis of such trials involves weather assessments because the variation of weather from year to year and from place to place has often had more effect on yields or crop performance than all other factors put together.
The general, climate based crop management and standard agronomic practices, which may not have been tailored to weather aberrations, are no longer adequate. The farmer needs guidance for tactical decisions on daily/weekly basis round the year, whether his problem differs from normal weather conditions or those of previous year weather and so on. To make a decision for crop management they essentially require the weather information in advance along with few tips of tactical decisions as to what to do and when to do for their crop management to achieve higher yields on a sustainable basis.
In this context weather is a helpful guide to the farmers and any weather information in advance could provide the practical guidance required by the farmer regarding the management or IPM practices they need to adopt to get the best returns for his investment year after year and hence, the weather forecast becomes a necessary tool to the farmers.
In a country like India, where about 75 per cent of people are engaged in crop production, the role of weather becomes significant in crop management. An expert knowledge of past, present and future weather can also help to solve a host of other problems: Choice of crops, animals and husbandry methods that will give an immediate impetus to agricultural development and transform past farm losses into profits. Determination of favourable times to sow, make hay and gather crops. Provision of shelter from wind and drifting sand, or protection against frost. Planning of afforestation and irrigation to supplement deficient rainfall or to increase crop output and profit. Control of crop hazards as potato bight etc. which can be prevented by spraying at certain critical changes in weather.
It is possible for the farmers to modify his decision if he has advance information on the weather conditions along with proper guidelines to take tactical decisions based on weather forecast; which ultimately reduce the associated risk of his decision for sustainable agriculture. Such information can benefit the farmers if the information has some credibility in its truthfulness and its availability on real time basis.
Looking to these important aspects, Department of Science and Technology (DST) has started through National Center for Medium Range Weather Forecasting (NCMRWF), Agrometeorological Field Units (AMFUs) in the country during 1991at different centers with the objective of formulating and disseminating weather based agroadvisories to the farmers of the surrounding villages of each unit.
Till the year 2009 the MES(Previously by DST),has established 130 such units in 83 agroclimatic zones of India, the units are called Agromet Advisory Unit known as AAS unit. One such unit is located at Division of Agricultural Physics, IARI, New Delhi.
The agroadvisory expert committee members prepare this type of contingency plan throughout the year and this is supported with suitable advisory for proper crop management and is passed on to the farmers and mass media on real time basis.