Analysis of potential benefits of precision irrigation for variable soils at five pastoral and arable production sites in New Zealand

摘要

The potential benefits of modifying irrigation according to soil differences under one irrigation system have been assessed for five production sites for the period 2004-2008. A simulated analysis used a soil water balance to compare hypothetical uniform rate irrigation (URI) with variable rate irrigation (VRI) scheduling for four irrigation seasons (2004-2008). URI applies irrigation to the whole area when the most droughty soil zone reaches a critical soil moisture deficit, whereas VRI only appliesirrigation to the soil zone that has reached its critical soil moisture deficit. The method has developed digital soil water status maps from spatially located soil apparent electrical conductivity (EC_a) data regressed against soil available water-holding capacity (AWC) (R~2 > 0.8 at 4 sites), with a daily time step added using a soil water balance model (Hedley and Yule 2009). These maps are available for upload to a fully automated variable rate irrigation system (Bradbury 2009). Water-use efficiency indicators show that potential water savings with VRI are 8-21%; drainage and runoff was reduced 19-55%, and cost savings were estimated at NZ$51-NZ$150 per hectare.