Impact of Sands and Gravels on Root Growth : Implications for Maize Seedlings.
Jayraju Nadimikeri, S.V.Univ, Tirupati, India
The sand and gravelly sand media in rigid cylinders with different proportions and sizes of gravels and sands at various water tensions was prepared. For comparison, cores of forest topsoil was used. The growth of pre germinated maize seedlings of 72 hours after transplanting them in to these media was measured. Compared with growth in forest topsoil ,root lengths averaged over sand and gravelly sand media were 27% less , depth of penetration was 65% less, and primary seminal root diameter was 36% greater. Further, primary seminal roots were significantly shorter and shallower and penetrometer resistance was greater with the higher proportions of gravel , the smaller sizes of gravel and sand and the lower soil water tension. Penetration resistance increased nearly six fold as the volumetric percentage of gravel increased from 0 - 45 with a corresponding reduction in depths of root penetration below the seed of 30 %. The resistance of close packed sands to root penetration and the further hardening effect of gravel highlight the importance of promoting root-size pores to bypass mechanical resistance.