A comparison of nutrient losses to waters following pasture renewal by cultivation or direct-drilling
DOI:
https://doi.org/10.33584/jnzg.2016.78.524Abstract
Agricultural soils enriched in phosphorus (P) have been linked to increases in P losses and declining water quality. Cultivation of pastures near sensitive waterways lowers surface soil P and therefore the concentration of P in surface runoff. However, such a practise can increase the mineralisation of organic nitrogen (N), negating this as a mitigation option for N sensitive catchments. A field trial was set up to compare pasture renewal using either direct-drilling or cultivation (which mixed the plough layer to 150 mm) on hydraulically-isolated runoff plots at Tussock Creek near Invercargill, Southland. The trial ran from March to December 2015. Soil P concentrations (0-150 mm depth) decreased in the cultivated plots by about 20%, 8 months after cultivation. Concentrations of nitrate-N in surface runoff and shallow drainage, and P in shallow drainage only, were not different between directdrilling and cultivation treatments. Cultivation reduced filterable reactive P (FRP) losses in surface runoff by 69% (P=0.047) compared to direct-drilled plots. This study showed that mixing P within the plough layer decreased P loss over the 10 months of measurement. Conventional tillage that inverts the plough layer may result in even larger decreases in soil P concentrations. Tillage can therefore be used as a strategy to decrease P loss in small areas where surface runoff is likely, with little risk of increasing catchment-scale N loss. This includes near stream areas, but care must be taken to leave an adequate buffer strip to prevent sediment (and P) loss via erosion of bare soil. Keywords: phosphorus-enriched soil, cultivation, direct-drilling, runoff, drainageDownloads
Downloads
Published
How to Cite
Issue
Section
License
Copyright
This work is licensed under a Creative Commons Attribution-Non Commercial-NoDerivatives 4.0 International License. Rights granted to the New Zealand Grassland Association through this agreement are non-exclusive. You are free to publish the work(s) elsewhere and no ownership is assumed by the NZGA when storing or curating an electronic version of the work(s). The author(s) will receive no monetary return from the Association for the use of material contained in the manuscript. If I am one of several co-authors, I hereby confirm that I am authorized by my co-authors to grant this Licence as their agent on their behalf. For the avoidance of doubt, this includes the rights to supply the article in electronic and online forms and systems.