Modeling the Risk of Phosphorus Runoff Following Single and Split Phosphorus Fertilizer Applications in Two Contrasting Catchments

Abstract

The potential loss of P in runoff is a function of the combined effects of fertilizer-soil interactions and climatic characteristics. In this study, we applied a Bayesian approach to experimental data to model the annualized long-term risk of P runoff following single and split P fertilizer applications using two example catchments with contrasting rainfall/runoff patterns. Split P fertilizer strategies are commonly used in intensive pasture production in Australia and our results showed that three applications of 13.3 kg P ha(-1) resulted in a greater risk of P runoff compared with a single application of 40 kg P ha(-1) when long-term surface runoff data were incorporated into a Bayesian P risk model. Splitting P fertilizer applications increased the likelihood of a coincidence of fertilizer application and runoff occurring. We found that the overall risk of P runoff is also increased in catchments where the rainfall/runoff pattern is less predictable, compared with catchments where rainfall/runoff is winter dominant. The findings of our study also question the effectiveness of current recommendations to avoid applying fertilizer if runoff is likely to occur in the next few days, as we found that total P concentrations at the half-life were still very high (18.2 and 8.2 mg P L(-1)) following single and split P treatments, respectively. Data from the current study also highlight that omitting P fertilizer on soils that already have adequate soil test P concentrations is an effective method of reducing P loss in surface runoff. If P fertilizer must be applied, we recommend less frequent applications and only during periods of the year when the risk of surface P runoff is low.

Phosphorus requirements of some selected soil types in the Fiji sugarcane belt

“…In addition, reducing the P losses to watercourses can be achieved by improving fertilizer recommendations, water infiltration through healthier soil structure, and the careful ploughing of top soil (Burkitt et al, 2011). Major losses of nutrients occur from the fields through runoff during the rainy season just after harvest and losses are generally lower during the growing period (Puustinen et al, 2005) as fertilizer applied during rainy seasons gets washed away into rivers, lakes and oceans.…”

“…Major losses of nutrients occur from the fields through runoff during the rainy season just after harvest and losses are generally lower during the growing period (Puustinen et al, 2005) as fertilizer applied during rainy seasons gets washed away into rivers, lakes and oceans. Burkitt et al (2011) noted that the runoff could be prevented by avoiding P fertilizer application on soil types which have satisfactory soil P levels and also if fertilizer is to be applied, it should be applied when the risk of surface runoff is low. assistance, the University of the South Pacific Institute of Applied Science (IAS) for total nitrogen and aluminium analyses and Koronivia Research Station (Fiji Ministry of Primary Industries) for particle size analyses.…”

A GIS‐based Upscaling Estimation of Nutrient Runoff Losses from Rice Paddy Fields to a Regional Level

“…If we set the fertilizer reduction rate as X , through mathematical deduction, the exports reduction ratio could be calculated as: the value of which would be linearly related to but never larger than X . Therefore, the longer risk period and greater runoff of nutrients, caused by splitting fertilizer application (fertilizer is split into multiple doses and applied in different growing stages of crops) over a single application (Burkitt et al, 2011), led to a significantly smaller ratio of BS:AD for TN, and thus a higher reduction ratio during the whole rice season compared with that for TP.…”

Estimating dissolved phosphorus losses from legacy sources in pastures: The limits of soil tests and small‐scale rainfall simulators

“…Hydrological variability associated with small-scale rainfall simulation experiments has been used to justify prewetting soils shortly (i.e., ∼1-2 d.) before both tray-based F I G U R E 4 Cross-sectional profiles of possible hydrology in (a) trays and (b) plots used in small-scale rainfall simulation experiments (Burkitt et al, 2011) and plot-based experiments commence (Pote et al, 1996) (Table 2). Prewetting is expected to move P from the mixing zone into subsoil storage.…”