O Estado atual dos solos do município de Itapecerica, SP

Abstract

 Average physical and chemical characteristics o/ typical soils are presented for all of the 13 eluvium and colluvium soil types recognized in the county (23• 36' to 24•03 s latit., 46•46' to 47• 12' W longit., 11000 km•, 14,300 inhabs. in 1940). Methods used for classification and evaluation of possibilities of rational utilization of soils are explained. Description of local factors of soil formation explains its nature and analytical results. The meaning of the latter is fully discussed. Due to strong acidity of the soils (pH mostly from 4.4 to 5.3), special attention is given to the evaluation of need of liming. Processes of its calculation are discussed. Yearly losses of CaO are assumed to vary between 225 and 360 kg/ha, while assimilation capacity of the soils varies between 1/2 and 2 tons/ha, total need varies between 3.4 and 8. 6 tons/ha, and the number of years of consecutive maximum liming vary between 5 and 20 in order to reach pH= 6.

            Climate, geology, geomorphology, topography, vegetation and human utilization of soils are described as factors of soil formation and evolution 'til the present status, with inferences on probable future of different kinds of soils.

            Two dozen of mean physical and chemical characteristics, given for 13 typical soils, establish a quantitative background tor the factors of soil formation.

            Acid massive rocks, mountainous topography, and mild humid to super humid climate formed luxurious dense forests over shallow chemically poor and acid soils. The man eliminated virgin forest promoting strong erosion, leaching of soils, and their depletion from organic matter by means of yearly burning of all vegetation in occupied areas. Now poor fields cannot teed cattle satisfactory. The soils cannot be used today without liming, manuring, fertilizing and controlling erosion. Although fertilizers are not needed in strong amounts, they cannot yield good results without previous strong liming and manuring, besides expensive erosion control. Since such practices are absent from agricultural routine, the productivity of land is very low, and performed at expenses of remnants of soil fertility.