Fate Of Granular Versus Liquid Fertilisers Applied To Soil Leaching Columns

Anecdotal reports from cane growers using a liquid fertiliser formulation at planting in North Queensland, indicate plant establishment is improved relative to granular products. However, some growers perceive liquid formulations are more prone to leaching, with insufficient residual fertiliser available to meet plant demand over the first 12 to 16 weeks prior to re-application. Soil from one of three plant cane field trials established in the Herbert and Tully regions in 2014 was selected for a glasshouse leaching trial to compare the fate of N, P and K in commercial fertilisers applied in liquid or granular formulations on Day 1 and 18 weeks later. The high concentration of muriate of potash in the granular formulation applied at planting inhibited emergence at two field sites, and inhibited nitrification in the leaching columns. Phosphorus and nitrate in the first liquid formulation were more immediately available, which may have stimulated emergence in the field. The lower concentration of N, P and K in the liquid formulation applied to the field trials at planting was sufficient to sustain plant cane for the first 12 to 16 weeks. Contrary to grower perception, the risk of nitrate leaching was greatest for the granular fertiliser treatments. This may be due to the higher concentration of N, P and K applied in the second liquid formulation, and the microbial slow release (immobilisation) of fertiliser N induced by the inclusion of molasses in the formulation.