Soil Variability and Sugarcane (Saccharum officinarum L.) Biomass along Ultisol Toposequences

Uniforming sugarcane management without any knowledge of soil variability could result in some parts of a sugarcane field receiving insufficient inputs, while other parts receive an excessive input. The research aimed at assessing the soil variability and sugarcane biomass along Ultisol toposequences in Central Lampung, Indonesia. Two sugarcane catenas and one forest catena were fully described in the fields. Soil horizons are represented by Ap/Ah/M, E, B, Cc and Cg with dominant clay translocation. The gleying symptom was found only in the lower slope to depression. The concretion depths can be used as an erosion indicator if the soil parent material is well characterized. Soil P has a maximum value of Ap horizon and decreases with the depth and no effect of internal erosion in the form of soil P accumulation in subsoils can be observed, except for the colluviated horizon. Kaolinite clay is dominantly found to buffer the changes in pH, except Ap horizon of sugarcane. The organic C depends on the pedogenesis and catena form. Al saturation indicates that the dominant soil weathering is intensive. Al saturation in the Ap horizon (Catena G1; G2) was reduced from 80% to 20–40% caused by liming and fertilization. The catena position was the main factor causing the increasing soil variability, which was responsible for the variability of sugarcane biomass. The sugarcane biomass increased with decreasing slopes. The highest biomass was found in the depression (105 tones/ha) if the sedimentation process is characterized by the formation horizon M and accompanied by the nutrient accumulation from the hilltops.