Cartogram, Agrochemical

a map that shows the extent to which soil is supplied with nutrient elements that can be assimilated by plants—phosphorus, potassium, nitrogen, magnesium, and trace elements—or the need for lime and gypsum. There are large-scale, medium-scale, and small-scale agro-chemical cartograms. In the USSR, large-scale cartograms are used to determine the total fertilizer requirements in the economy and to establish the correct amounts and types of fertilizers for individual fields. They are also used in developing plans for the liming and gypsuming of soils in kolkhozes and sov-khozes. Cartograms showing the supply of available phosphorus and potassium are the most common; those showing the supply of nitrogen, magnesium, and the trace elements are less common.

Medium-scale agrochemical cartograms have been prepared for certain oblasts and agricultural zones of the USSR and small-scale ones for some republics and economic regions. The V. V. Dokuchaev Soil Institute has compiled an agrochemical cartogram for the entire USSR. The cartogram identifies the soil-agrochemical zones and regions with similar agronomic, soil, and climatic conditions, which determine the effectiveness of fertilizers and the lime and gypsum requirements of the soil. Small- and medium-scale agrochemical cartograms are needed for preparing scientifically based plans for the production of mineral fertilizers and their distribution among the various regions of the USSR.

Abroad, agrochemical cartograms are called agrochemical maps. They are classified and compiled by methods similar to those used in the USSR.