Nitrogen and Phosphorus runoff from agriculture is a problem that was first identified in the 1960s by Canadian scientist Professor David Schindler. Although the cause and effect of runoff is now well understood, it continues to be a prevalent issue, with algal blooms causing the degradation of waterways.
Lake Erie in the U.S. is one of the most well known examples globally, and here in Australia we have the same problem happening in the Swan-Canning Estuary in W.A. and the Gippsland Lakes in Victoria. In the 1990s, NSW experienced algal blooms which caused harmful bacterial infections in bivalves in Ballina and Newcastle, as well as adversely affecting the oyster industry of Narooma.
Scientists hope that technology may have the answer to the problem of phosphorus and nitrogen runoff. Soil sample testing is one way farmers can measure nitrogen levels and then apply ferterilser precisely, without the excess that would cause runoff. This method has been proven effective but can be time consuming and costly for farmers.
A new device which may make measurement easier is the N-sensor ALS, developed by UK company, Yara. It’s a unit which can be fitted to tractors and measures nitrogen levels in individual plants, using light detectors. Light reflectance of plants directly correlates to nitrogen levels and because the sensor can detect levels in specific plants, the farmer can address their needs individually, rather than applying the same amount to the entire field.
A similar technique is being used in Australia, though not at the ground level, with airborne multi-spectral imaging of rice and grapevines in NSW. This has led to more precise application of fertiliser, better yields and subsequently less runoff.
No one solution offers the best solution of reducing runoff that may affect aquaculture farms and other ocean dependent industries, but technology is leading the way to a more precise and low-impact compromise through advanced monitoring techniques.