The use of low-rate sprinkler application systems for applying farm dairy effluent toland to reduce contaminant transfers

Abstract

Runoff of farm dairy effluent (FDE) isa major concern in New Zealand water management. To improve handling and applying FDE, thiswork evaluated the performance of a low-rate(K-line) sprinkler application system compared with that of a travelling irrigator. The volumes of FDE discharged in either mole-pipe drainage or overland flow were monitored at two sites, as were nutrient concentrationsand loads(and Escherichia coli (E. coli ) at one site). The low-rate sprinkler decreased overland flow losses of applied FDE compared tothe travelling irrigator. The relative concentrationsof E. coli, total P and ammonium-N (presented as C/Co, the measured concentration in drain flow divided by the concentration in applied effluent) in overland flow at South Otago and mole-pipe drainage at West Otagowere also consistently less for the low-rate sprinkler. There were significant and positive correlations between drainage C/Co valuesand effluent application rate for E. coli, total P and turbidity. Modelling predicted potentially large contamination with E. coli, total P and ammonium-N in mole-pipe drainage with no pond storage when using a travelling irrigator. Modelled loads were considerably less for FDE application to mole-pipe drained land using a low-rate sprinkler. Practical implications are that: (i) effluent pond storage is important for decreasing FDE losses in overland flow and molepipe drainage when soils are wet; (ii) a low-rate sprinkler application system requires less pond storage; (iii) a low-rate low-depth management system can decrease mole-pipe drainage discharges of pollutants when soils are wet. © 2010 The Royal Society of New Zealand.