Environmentally sound phosphorus management for sugarcane soils : final report on SRDC Project no CSS3S

Abstract

A field and laboratory-based survey of the behaviour of phosphorus (P) was carried out on the soils of the lower Herbert River catchment, and sediments derived from them. The aim was to explore the factors governing P sorption or desorption in Herbert soils, and in suspended sediments in associated riverine and estuarine waters, so that the extent of any problem associated with sugarcane and soil-derived inputs to streamwaters could be defined. With this information, advice on the development of best management practices for P fertilizer could be provided to the sugar industry. The results of the study of P behaviour in Herbert soils suggests that there is scope for refining the management of P fertilizer in the sugar industry based on a knowledge of particular soil properties and the behaviour of P in specific soils. Sorption of P in soils was found to be closely correlated with soil particle size, organic matter content and oxalate-extractable aluminium (Al). The results of this part of the project suggest that: • in refining P fertilizer management, both for more efficient crop production and improvec\ environmental stewardship, the utility of oxalate-extractable aluminium (Alo,) as a predictor of P fertilizer requirement should be investigated; and • clustering soils with similar physical and chemical properties is useful as a basis for identifying soils of similar potential P sorption/desorption characteristics so that, when coupled with a knowledge of the soil P content measured using normal soil testing procedures, they may' also form a basis for delivery of improved fe~tilizer advice. Further research is therefore warranted on both of these issues with a view to the developme!1t of specific guidelines for best-practice P fertilizer management.