TECHNICAL
Precision agriculture for plant nutrition Precision Agriculture is a term used to describe fine-tuning of land management with the use of the Global Positioning System (GPS) where growers can mark and measure crop harvest variances within a particular field and try and determine the cause of these variations. By Robin Boom The United States National Research Council defined Precision Agriculture as: the application of modern information technologies to provide, process and analyse multisource data of high spatial and temporal resolution for decision making and operations in the management of crop production. In the past it has mainly been used in large, broad acre cropping farms in North America and Australia for grain and oil seed crops where a field can often be hundreds of hectares in size and the harvester records yield variations via GPS. Growers, agronomists and other rural professionals can then GPS map soil tests from the better and poorer areas and compare them. Sometimes the yield differences may have nothing to do with soil chemistry and may be related to soil physics, 70
The ORCHARDIST : OCTOBER 2021
drainage or some other factor. But more often than not, the differences are fertility related. Historically the field would have had the same fertiliser inputs blanket applied at the same rate. All too often, all the fields on large farms are treated with the same fertiliser mix and rate. Precision agriculture refines the nutrient inputs to specific areas to address known deficiencies, and ensures that nutrients are not applied to those areas within a field that do not require them. For instance, there may be a certain section that requires lime, whereas other parts of a field may have good pH (acidity/ alkalinity) and calcium levels. Applying lime to these areas would not only be a waste of money and effort but could do more harm than good, as too high pH levels can impact on the soil’s ability to retain other elements such as magnesium and potassium; and micro-nutrients –
