The Effect of Silica on Cane Growth

have low base saturation and pH values with high A pot experiment was carried out to study the concentrations d soluble aluminium and ]OW conceneffect of carbonate and various silica-contrations of silica. A pot experiment was therefore taining materials on cane growth and to compare designed to test the effect of silica on soils from this the relative efficiencies of calcium carbonate and area and also to compare the relative efficiency of rnetasilicate slag on three acid soils. ~ 1 1 treatments different silicate materials with that of calcium caused a substantial reduction in exchangeable aluminium in the soil and in manganese uptake by the plant. With treatments containing silica an inExperimental crease in yield was associated with an increase in the silica concentration in the plant. With the calcium The following amendments where applied, as carbonate treatments, however, increasing yields were replicated treatments, at levels squivalent to 4.5, 9 accompanied by a decrease in silica concentration. and 18 metric tons per hectare to a topsoil of the Treatments containing silica proved superior to calBalgowan soil series (Van der Eyk, Macvicar and cium carbonate treatments on all three soils. De Villiers, 1969). This soil sample is referred to as Balgowan (A). Hntroduction Even though silica is not regarded as an essential (a) Silene F (pure calcium metasilicate CaSiO,). element for plant growth it occurs in sugarcane in (b) Amcor slag (a blast furnace slag). high concentrations, varying from 0.14% in very (c) Sodium metasilicate (Na,SiO,). young leaves to 6.7% in the stalks and older leaf (d) Hawaiian slag (a metasilicate slag from the sheaths according to Fox, Silva, Plucknett and same source as that used by CIements, PutTeranishi (1969). Recently it has been shown by man and Wilson, 1967). Vlamis and Williams (1967) that silica plays an important role in the elimination of minor element (e) Portland cement. toxicities in the Gramineae. It would therefore seem (f) Calcium carbonate (CaCO,). possible that-silicon might also play a beneficial role in sugarcane nutrition. Because Clements et 01. (1967) reported that the One of the first instances of the use of silicate particle size of the slag was important, all materials materials as a soil amendment was in Mauritius used were ground to pass a 100-mesh sieve. All pots where J J ' H ~ ~ ~ ~ ~ de villiers (1947) described imreceived a basic dressing of N, P and K equivalent proved yields due to application of finely ground to 112 kg N y 167 kg and 112 kg * per hectare as basalt. However, the large quantities used (up to 210 well as sufficient calcium chloride to raise the soil metric tons per hectare) precluded its widespread level to between lSo and 170 PPm. The use. In recent years a number of reports have critical level for calcium in soil accepted by the appeared describing the beneficial dect of silica on Fertilizer Advisory Services laboratory of the Expericane growth. Clements (1965) reported the results of ment Station is 150 ppm. four experiments on an aluminous ferruginous latosol T o another topsoil sample of the Balgowan soil and hydro1 humic latosols in Hawaii, and Ayres series (sample B) collected in a different locality from (1966) also described substantial yield increases in the first, and a topsoil sample of the Trevanian soil sugarcane due to a silicate slag applied to the same series (Beater, 1957) only Hawaiian metasilicate slag soil types. and calcium carbonate were applied. The levels of These Hawaiian soils are very similar to the ferapplication and the basic dressing were the same as ralitic soils occurring in the Natal Midlands. They above.