Effect of Cattle Manure on Young Plants of Khaya senegalensis Submitted to Different Irrigation Intervals

This study aimed to evaluate the effect of cattle manure on young plants of Khaya senegalensis submitted to different irrigation intervals. A greenhouse experiment was carried out during 2017 cold season, based in a 5x3 factorial arrangement – cattle manure fertilizing with 0, 10, 20, 30 and 40% doses, and 3-day, 6-day and 12-day irrigation intervals. Water potential, relative water content (RWC), water consumption (WC), water use efficiency (WUE), chlorophyll content estimation (SPAD index), plant height, stem diameter, plant total dry mass and free amino acid and proline content were measured. Irrigation intervals had no significant effect on physiological traits and plant water relationships, except for WUE, which was higher under 12-day irrigation interval. This was assumed as an indication of non-occurrence of water stress, even under the longest irrigation interval. Cattle manure, in turn, played a significant effect on these traits, except for water potential, irrespective of irrigation intervals. Increasing cattle manure doses improved RWC (just doses up to 20%), reduced WC and increased WUE, SPAD index, and both free amino acid and proline contents. On the other hand, growth-related parameters were not affected by cattle manure, but a significant effect of irrigation intervals was observed. Both plant height and total dry mass were lower under 3-day and 6-day irrigation intervals. We suspect a possibly low evapotranspiration, given the relatively low temperatures of that season (14-16 oC), which may have reduced the demand for irrigation in the experimental period. Thus, soil moisture under the shorter irrigation intervals may have increased until reach to a close to saturation level, limiting the amount of soil oxygen and hampers nutrient uptake.