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Effect of dense, stratified sandy soil on crop roots

SUMMARY A study was conducted to determine root development in a stratified and mixed sandy soil in the Sahara sands of Libya. Lucerne (Medicaqo sativa L.), millet (Pennisetum typhoides Burn.)> wheat (Triticum activumL.), grain sorghum (Sorghum bicolor L.), and several other crops were grown on soil that varied in depth to the stratified layers. Root depth and growth were measured by excavating along a representative root at intervals until the crop was mature or until no further root penetration into the subsoil occurred. Trial plantings showed that none of the root systems of the plants tested could penetrate the stratified layers to any important extent, even with the application of adequate water and fertilizer, although all the layers were sufficiently porous to allow surplus water to drain through them freely. However, a few roots of lucerne, sudangrass, grain sorghum, and millet penetrated 2—3 cm into these layers, and many roots, especially of lucerne, grew into any natural cracks that occurred in these layers. If the compacted layer was loosened by cultivation, all the crops tested rooted normally in the loosened zone.