Root System Spatial Variability of Coffee Plants Under Water Deficit.

The capability of plants to survive in limited conditions of water supply will largely depend on the uniformity and depth of its root system. Data in literature show that plants can leave an appreciable amount of water in the soil without being extracted even in conditions of water deficit. This means that plants will become dormant or die even when a supply of water still available in the soil. If roots are not present in some soil regions, these regions will not be adequately explored and an incomplete extraction may occur. The aim of this work was to map the spatial variability of Siriema coffee plants roots, an inter-specific hybrid between Coffea Arabica and C.racemosa, under water deficit. Twelve undisturbed soil cores (2x10⁵.cm^-3) were collected and cultivated with 18 months old coffee plants during 12 and 18 months. Two water conditions were imposed, with and without deficit for each period. The soil was classified as Red-Yellow Latosol. Forty four soil samples were taken in a grid pattern at depths of 10, 30, 50 and 70 cm for each core. These soil samples were washed and sieved in order to separate the roots, which were analyzed by using the STD 1600 WhinRhizo system. With the obtained data it were prepared RLD (root length density, cm.cm^-3) maps for each soil layer. Based on these results one can say that, for the two periods the RLD was always higher in the second soil layer for plants under no water deficit. However, for the third layer, the condition was contrary to the second one, with total RLD being higher for plants under water deficit. This means that roots went deeper into the soil layers to find water. Results also showed that roots were uneven distributed for all soil layers in both periods and treatments.