Effect of fertiliser nitrogen and irrigation on root growth and extension, and water uptake of post-rainy season sorghum uri icon


  • Effects of fertilizer nitrogen (N) and irrigation on root development are discussed by collating theobservations in published reports with those in our study using field-grown sorghum (Sorghumbiocolor (L.) Moench) on a deep Vertisol in semi-arid tropical India. In our study, the total rootbiomass was affected by fertilizer-N and irrigation and by their interaction. It is the top soil layersthat contribute largely to increased root biomass due to fertilizer-N and irrigation. Theseobservations agree with those in other reports. The total root length was not significantly affected byfertilizer-N, but was consistently higher under dry conditions than under irrigated conditions.Spatial distribution of root length did not fit a simple mathematical model such as linear, exponentialor logistic curve, except at very young growth stages under irrigated conditions. Except the top 16-cm layer, the depth at which root length density zvas maximum shifted to deeper layers as sorghumgrew. This may indicate that some roots die after water extraction and that new roots grow at the soillayers where water zvas available. This specific feature would contribute to the complexity ofmodeling of root development. Rooting depth was not affected by fertilizer-N, but it was consistentlygreater under dry conditions than under irrigated conditions. The root depth had a linearrelationship with time under dry and irrigated conditions up to the physiological maturity stage.Water uptake by sorghum was determined as the difference between measured evapotranspirationand estimated soil evaporation. In non-irrigated treatment, the differences in water uptake among Ntreatments were not significant. In the irrigated treatment, the rates of 30 to 150 kg N ha (30 Nand 150 N, respectively) resulted in significantly higher water uptake than no fertilizer-N. Thefertilizer-N effect in our study zvas not as clear-cut as that in other reports

publication date

  • 1996