Analyses of accumulation of silica in the growth of two tropical forages using simple equations

The present study was conducted, using simple equations, to analyze the acc umulation rate of silica [ARSi], that of minerals [ARM] and silica content changes with growth of Rhodes grass [Rg] and Greenleaf desmodium [Gd]. The following two equations were suggested for analyses: (A) ARSi = 1/W . d(si)/dt = (1/W . dM/dt) . d(Si)/dM, Changes silica content = 1/1000 . ((Si)(2)/W-z -(Si)(1)/W-1) (B) = (1 - W1/W2) . {1/1000 . (<(ARSi)over bar>/(RGR) over bar - (Si)(1)/W- 1)} where W=forage dry weight (g/m(2)), Si=amount of silica in the forage (mg/m (2)), M=amount of minerals in the forage (mg/m(2)), (1/W).(d(Si)/dt)=ARSi, (1.W).(dM/dt)=ARM, (d(Si)/dM)=accumulation of silica per unit accumulation of M[ASiAM], RGR=mean relative growth rate [RGR] of forages over the interv al t(1) to t(2), <(ARSi)over bar>=mean ARSi over the interval t(1) to t(2), (1-W-1/W-2)=forage growth index [FG index], {ARSi/RGR-(Si)(1)/W-1}/1000=an index for forage growth dependent silica accumulation [FGDSiA index]. Anal yses using equation (A) suggested that Rg showed a higher selection of sili ca in the accumulation of minerals, when compared with Gd. Analyses using equation (B) suggested that Rg showed less active silica acc umulation than forage growth, in contrast to more active silica accumulatio n than forage growth in Gd. It was suggested that the present methods accou nted analytically for the accumulation characteristics of silica and its co ntent changes with growth of forages.