ABSTRACT
Agroecosystems are in constant confluence with atmosphere. The crop and soil phase interact with atmosphere in terms of water, gaseous exchange, dust and particle distribution. Atmosphere is a source of water. Precipitation events add to soil water. Precipitation from atmosphere that accumulates in soil profile is then absorbed into crops. Precipitation carries a certain amount of dissolved nutrients, dust and small particles depending on the geographic location. Atmospheric deposits and dusts may carry relatively more nutrients, if the location is nearer to industries that emanate large amounts particulate/gaseous material into atmosphere. For example, industries that emanate carbonaceous and sulfur containing fumes/particles may pollute atmosphere. The rainfall events that occur in such areas will obviously add more of sulfur into agricultural fields located nearby. Generally, cropping belts closer to seacoast receive greater amounts of nutrients through atmospheric deposits. There are geographic locations, such as in West African Sahel, or dusty plains in North Africa, West Asia or North West India. In these regions, dust storms (e.g., Harmattan in Sahel, Lu in Gangetic Plains) shift sand particles and nutrient attached along with it, from one place to another. Atmosphere aids shift of nutrients through storms. In the general course, in most locations if not all, morning dew carries a certain amount of water and dissolved nutrients into crop phase. The atmospheric deposits of nutrients may not be conspicuous in many regions, yet it occurs and affects nutrient dynamics of individual field. The extent of nutrients added may be small. It may often range from 5-10 kg N, 0.3-0.5 kg P and 2-3 kg K/ha annually. Atmospheric deposits may also contain S and Zn, rather regularly. It is a sizeable amount of nutrients shifted into soil and crop phase, if large agroecosystems are considered. Even marginal reductions in nutrient received from atmosphere may become perceptible in few years. Yet, many of the fertilizer schedules prescribed for individual crop/field and even large expanses grossly neglect the nutrients added from atmosphere. Let us consider a few specific examples that relate to nutrients received from atmosphere.
