Alternative fertilisers and management to decrease incidental phosphorus loss

Abstract

Incidental phosphorus loss is a concern for surface water quality. Here we showed that the risk of incidental P loss can be minimised, even from highly soluble superphosphate fertiliser, by timing application when overland flow is unlikely. Moreover, we demonstrated that the risk of incidental P loss can be estimated from water solubility, decreasing the need for expensive field trials. As such, we suggest that slowly available fertilisers such as reactive phosphate rock or serpentine super could be used in situations where incidental losses need to be decreased and conditions are suitable e.g., soil pH less than 6 and rainfall greater than 800 mm for reactive phosphate rock.

Prioritisation of farm scale remediation efforts for reducing losses of nutrients and faecal indicator organisms to waterways: A case study of New Zealand dairy farming

“…An exception is in systems that have large volumes of overland flow, such as irrigation-wash exiting border dyke-irrigated pastures, where P losses from soluble P fertilisers can be potentially substantial (McDowell et al, 2003b). In these situations, the use of low solubility P fertilisers (McDowell and Catto, 2005) and improved bunding (dykes around the perimeter of a paddock to prevent excess irrigation water leaving the paddock) of the border dyke land could reduce P losses in overland flow from grazed pastures ( Table 2). In other situations soil and sediment losses from high P fertility soils can make a substantial contribution to P loss (McDowell et al, 2003a;Morton et al, 2003).…”

Managing agricultural phosphorus for water quality protection: principles for progress

“…Referred to as "wash-off" or "incidental transfer", P transfer associated with surface applied sources is at maximum potential in the first runoff events after application (Austin et al 1996), generally returning to near background levels over several months (McDowell and Catto 2005;Preedy et al 2001). High rates of P applied to soils prone to runoff during periods of high rainfall or shortly before flood irrigation events produce the greatest potential for acute transfers of applied P to water bodies Nash et al 2000;Withers et al 2003).…”

Nutrient management in New Zealand pastures— recent developments and future issues

“…Constraining P inputs to achieve economic optimum soil test levels can reduce the risk of P loss from soils. if best practice is followed, direct losses of P from fertiliser are generally less than 10% of the total P lost from pastures (McDowell & Catto 2005). Best practice implies that fertiliser is not spread too close to waterways and is applied more than 2 weeks before irrigation or at a time of year when P losses are unlikely-usually summer months when rainfall and overland flow are less.…”

“…The risk of P loss following fertiliser application depends on the solubility of the fertiliser applied, with superphosphate > serpentine Research, 2007, Vol. 50 super > reactive phosphate rock (McDowell & Catto 2005). If superphosphate cannot be applied at a time when P loss is unlikely, or if soils are hydrophobic, consideration should be given to applying a lower solubility P fertiliser to minimise losses.…”