Effect of deep placement of lime on soil properties, root growth, water availability, and crop production in acid upland soils of Sitiung, West Sumatra Indonesia

Effects of deep placement of lime on root growth, water and nutrient availability, and crop production were evaluated in a field study in an acid upland soil of Sitiung from October 1987 to February 1989. Rooting density and rooting depth for corn showed a remarkable improvement with increasing depth of incorporation of lime. Rooting depth in no-lime plots was around 20 cm whereas roots grew to 60 cm depth where lime was applied to 50 cm depth. Most of the roots (73 to 95 percent) grew in the surface 10 cm of the soil. However, the small fraction of the total (5 percent in the case of no-lime plots and 27 percent in the case of deep-line plots) that grew in the subsoil, influenced water and nutrient availability and crop growth in a significant way. Extraction of water from the subsoil, as indicated by soil water pressures, increased as the depth of liming increased. Plants in the deep-lime plots never showed visible symptoms of water stress whereas those in no-lime or shallow-lime plots exhibited water stress frequently. On an average, maximum yields of 5 to 6 t/ha were obtained from plots which were limed to 30 to 50 cm depth. Grain yields from no-lime plots ranged from 0.5 to 2 t/ha. A given amount of lime, deep incorporated, produced higher yields than when the same amount of lime was incorporated in the surface. Increases in the grain yield obtained from deep liming depended on the amount of lime and the depth of incorporation. Although liming to 50 cm depth with 10 t/ha lime gave the maximum yield, data indicated that liming to 30 or 40 cm depth with 3 to 4 t/ha lime was nearly as good. Most of the benefits appeared to be related to subsoil root growth. Biomass yields showed a very definite relationship to the root mass below the 10 cm depth. No relationship existed between biomass and the root mass in the top 10 cm of the soil, although topsoil root mass accounted for 73 to 95 percent of the total root mass. Lime application to varying depths increased calcium content as expected, but distribution patterns before planting and after harvest were too variable to draw conclusion with respect to downward movement of lime. Soil potassium data were also quite variable. There were indications of distribution of both Ca and K within the root zone