Is my irrigation optimised?


Analysis of yield data can be tricky given the number of variables that influence yield. Agronomy, application timing, drainage, fallow management, weather, farming practices and field history just to name a few. While there are influences hard to manage, analysis of yield against base layers such as soil and terrain still build valuable knowledge about variability.

An important factor to consider is climate when it’s expected to improve yields ever year. The main contributor to overall yield being high or low is dominated by climate.  Spatially however there are optimums at the farm and field level that need to be achieved in all farming systems. Optimizing these zones on a year to year basis is a critical management methodology that should be considered and implemented.

The screenshot below has cotton yield overlaid onto soil zones derived from an EM survey. Low EM zones are typically lighter soils, lower water holding capacity and lower sub soil constraints. Higher EM values typically represent higher clay content and therefore, higher water holding capacity and increasing sub soil constraints

In the graph below the trend is – as EM increases the yield goes down. In this field soil testing has shown these areas are heavy clay, salt effected areas. The grey line indicates the area of each zone shown on the Y2-axis. The peak in the area line on the red zone indicates the irrigation management for this field suited the zone of the lowest EM as its highest yielding.

However, this isn’t spatially perfect because the next highest yield zone is the orange zone and is the zone of highest area.

The second image shows us a cost benefit analysis. There are two columns which are important. First is the Max Opportunity and the Optimal Opportunity.

Max Opportunity represents – what if I could mange to the highest yield each year with no variability (maybe possible with Variable Rate Irrigation but not likely in most cases).

Optimal Opportunity – this scenario is what if I manage the field spatially perfect. Often the results are effected by irrigation management and drainage, something which can be measured and managed for a benefit.

In this case a $50 increase in profit for no real extra work, just attention to detail. Other growers have seen results in the $200-$400/ha range. This is providing true value for an investment of less than $15/ha for one year.